@misc{SeidelPerlmanFroejdetal., author = {Seidel, Lars and Perlman, Cathleen and Fr{\"o}jd, Karin and Klaus, Anna-Katharina and Laska, Timothy and Jalving, T. and Mauß, Fabian}, title = {CPU Efficient Modelling of Biomass Gasification Using a Stochastic Reactor Approach and Chemistry Guided Reduction}, pages = {1}, language = {en} } @inproceedings{RodriguezHenriquezSeidelMauss, author = {Rodriguez Henriquez, Jose Juan and Seidel, Lars and Mauß, Fabian}, title = {Plug Flow Reactor Set-up evaluation with methane decomposition at mild conditions and overpressure}, series = {Abstract book, 7th European Combustion Meeting (ECM), Budapest, Hungary, March 30-April 2}, booktitle = {Abstract book, 7th European Combustion Meeting (ECM), Budapest, Hungary, March 30-April 2}, isbn = {978-963-12-1257-0}, language = {en} } @inproceedings{MatriscianoSeidelKlaueretal., author = {Matrisciano, Andrea and Seidel, Lars and Klauer, Christian and Mauß, Fabian and Lehtiniemi, Harry}, title = {An a priori thermodynamic data analysis based on chemical lumping method for the reduction of large and multi-component chemical kinetic mechanisms}, series = {5th Annual Internation Workshop on Model Reduction in Reaction Flows (IWMRRF) L{\"u}bbenau, 28.06-01.07.2015, proceedings}, booktitle = {5th Annual Internation Workshop on Model Reduction in Reaction Flows (IWMRRF) L{\"u}bbenau, 28.06-01.07.2015, proceedings}, pages = {2}, language = {en} } @inproceedings{LehtiniemiBorgMauss, author = {Lehtiniemi, Harry and Borg, Andreas and Mauß, Fabian}, title = {Modeling of Spray Combustion under Diesel Engine Conditions}, series = {Proceedings of the 2nd Conference on Engine Processes, July 2-3, 2015, Berlin, Germany}, booktitle = {Proceedings of the 2nd Conference on Engine Processes, July 2-3, 2015, Berlin, Germany}, editor = {Sens, Marc and Baar, Roland}, publisher = {Universit{\"a}tsverlag der TU Berlin}, address = {Berlin}, isbn = {978-3-7983-2768-9}, pages = {217 -- 249}, language = {en} } @inproceedings{PasternakMaussMatrisciano, author = {Pasternak, Michal and Mauß, Fabian and Matrisciano, Andrea}, title = {Diesel Engine Performance Mapping Using Stochastic Reactor Model}, series = {Proceedings of the 2nd Conference on Engine Processes, July 2-3, 2015, Berlin, Germany}, booktitle = {Proceedings of the 2nd Conference on Engine Processes, July 2-3, 2015, Berlin, Germany}, editor = {Sens, Marc and Baar, Roland}, publisher = {Tech. Univ., Universit{\"a}tsverlag}, address = {Berlin}, isbn = {978-3-7983-2768-9}, pages = {217 -- 232}, language = {en} } @misc{MatriscianoPasternakWangetal., author = {Matrisciano, Andrea and Pasternak, Michal and Wang, Xiaoxiao and Antoshkiv, Oleksiy and Mauß, Fabian and Berg, Peter}, title = {On the Performance of Biodiesel Blends - Experimental Data and Simulations Using a Stochastic Fuel Test Bench}, series = {SAE Technical Papers}, journal = {SAE Technical Papers}, number = {2014-01-1115}, issn = {0148-7191}, doi = {10.4271/2014-01-1115}, pages = {1 -- 8}, language = {en} } @misc{SvenssonLiShamunetal., author = {Svensson, Erik and Li, Changle and Shamun, Sam and Johansson, Bengt and Tuner, Martin and Perlman, Cathleen and Lehtiniemi, Harry and Mauß, Fabian}, title = {Potential Levels of Soot, NOx , HC and CO for Methanol Combustion}, series = {SAE Technical Papers}, journal = {SAE Technical Papers}, number = {2016-01-0887}, issn = {0148-7191}, doi = {10.4271/2016-01-0887}, pages = {17 Seiten}, abstract = {Methanol is today considered a viable green fuel for combustion engines because of its low soot emissions and the possibility of it being produced in a CO2-neutral manner. Methanol as a fuel for combustion engines have attracted interest throughout history and much research was conducted during the oil crisis in the seventies. In the beginning of the eighties the oil prices began to decrease and interest in methanol declined. This paper presents the emission potential of methanol. T-Φ maps were constructed using a 0-D reactor with constant pressure, temperature and equivalence ratio to show the emission characteristics of methanol. These maps were compared with equivalent maps for diesel fuel. The maps were then complemented with engine simulations using a stochastic reactor model (SRM), which predicts end-gas emissions. The SRM was validated using experimental results from a truck engine running in Partially Premixed Combustion (PPC) mode at medium loads. The SRM was able to predict the combustion in terms of pressure trace and rate of heat release. The CO and NOx emissions were matched, however, the HC emissions were underestimated. Finally, the trajectories from the SRM simulations were superimposed on the T-Φ maps to investigate the in engine conditions. The T-Φ map analysis shows that emission of soot are non-existent, formaldehyde can be avoided and that emissions of methane are kept at, compared to diesel combustion, low levels, however CO and NOx levels are similar to diesel combustion. These results were confirmed for engine conditions by the SRM simulations and the engine experiments.}, language = {en} } @misc{FrankenMauss, author = {Franken, Tim and Mauß, Fabian}, title = {Development of Methodology for Predictive Diesel Combustion Simulation Using 0D Stochastic Reactor Model}, series = {SAE Technical Papers}, journal = {SAE Technical Papers}, number = {2016-01-0566}, issn = {0148-7191}, doi = {10.4271/2016-01-0566}, pages = {14 Seiten}, abstract = {Stringent exhaust emission limits and new vehicle test cycles require sophisticated operating strategies for future diesel engines. Therefore, a methodology for predictive combustion simulation, focused on multiple injection operating points is proposed in this paper. The model is designated for engine performance map simulations, to improve prediction of NOx, CO and HC emissions.The combustion process is calculated using a zero dimensional direct injection stochastic reactor model based on a probability density function approach. Further, the formation of exhaust emissions is described using a detailed reaction mechanism for n-heptane, which involves 56 Species and 206 reactions. The model includes the interaction between turbulence and chemistry effects by using a variable mixing time profile. Thus, one is able to capture the effects of mixture inhomogeneities on NOx, CO and HC emission formation.The mixing time model is parameterized using transfer functions for engine operating parameters, e.g., injection mass, injection duration, air fuel ratio, start of injection and speed. These functions are calibrated for nine operating points using multi objective simulated annealing optimization combined with fast running metamodels that speed up the optimization process. The calibrated transfer functions are validated for nine additional operating points. The results for the calibration and validation points show a good match of the combustion heat release rate. Especially the main injection heat release rate is well predicted by the model. The NOx and CO emissions reflect the experimental trends and are in close range to the measurements. Finally, the model is tested for triple injection operating points. The results match the measurements, which show the applicability of the stochastic reactor model in conjunction with the mixing time transfer functions for engine performance map simulations.}, language = {en} } @misc{LehtiniemiBorgMauss, author = {Lehtiniemi, Harry and Borg, Anders and Mauß, Fabian}, title = {Combustion Modeling of Diesel Sprays}, series = {SAE Technical Papers}, journal = {SAE Technical Papers}, number = {2016-01-0592}, issn = {0148-7191}, doi = {10.4271/2016-01-0592}, pages = {1 -- 11}, abstract = {Several models for ignition, combustion and emission formation under diesel engine conditions for multi-dimensional computational fluid dynamics have been proposed in the past. It has been recognized that the use of a reasonably detailed chemistry model improves the combustion and emission prediction especially under low temperature and high exhaust gas recirculation conditions.The coupling of the combustion chemistry and the turbulent flow can be achieved with different assumptions. In this paper we investigate a selection of n-heptane spray experiments published by the Engine Combustion Network (ECN spray H) with three different combustion models: well-stirred reactor model, transient interactive flamelet model and progress variable based conditional moment closure. All models cater for the use of detailed chemistry, while the turbulence-chemistry interaction modeling and the ability to consider local effects differ.The same chemical mechanism is used by all combustion models, which allows a comparison of ignition delay, flame stabilization and flame lift-off length between the experiments and the results from simulations using the different combustion models. The investigated parameters influence the predictions of computational fluid dynamics simulations of diesel engines. This study indicates that the most reasonable behavior with respect to ignition, flame stabilization and flame structure is predicted by the progress variable based conditional moment closure model.}, language = {en} } @inproceedings{MaussMatrisciano, author = {Mauß, Fabian and Matrisciano, Andrea}, title = {SRM in Engines: Performance and Emissions}, series = {3rd International Combustion Institute Summer School, June 19-23, Chania, Greece}, booktitle = {3rd International Combustion Institute Summer School, June 19-23, Chania, Greece}, language = {en} } @inproceedings{LeondeSyniawaNawdiyalSeideletal., author = {Leon de Syniawa, Larisa and Nawdiyal, A. and Seidel, Lars and Mauß, Fabian}, title = {Formation of C5 Species from iso-Butene}, series = {Book of Abstracts, SMARTCATs 2nd General Meeting \& Workshop on Smart Energy Carriers in Industry Lisbon, 14-16 November - 2016}, booktitle = {Book of Abstracts, SMARTCATs 2nd General Meeting \& Workshop on Smart Energy Carriers in Industry Lisbon, 14-16 November - 2016}, pages = {42 -- 43}, language = {en} } @inproceedings{MalliotakisBanyonCurranetal., author = {Malliotakis, Zisis and Banyon, Colin and Curran, Henry J. and Founti, Maria and Keramiotis, Christos and Vourliotakis, George and Koutmos, Panagiotis and Paterakis, George and Souflas, Konstantinos and Mauß, Fabian and Rodriguez Henriquez, Jose Juan and Skevis, George}, title = {A Comperative Study on the Oxidation of Gaseous and Liquid fuels in a Swirlstabilized Flame via Chemiluminescence Measurements}, series = {Book of abtracts, COST SMARTCATs 2nd General Meeting, Lisbon, 14-16th November}, booktitle = {Book of abtracts, COST SMARTCATs 2nd General Meeting, Lisbon, 14-16th November}, publisher = {Cost, European Cooperation in Science and Technology}, pages = {84 -- 85}, language = {en} } @inproceedings{MatriscianoBorgPerlmanetal., author = {Matrisciano, Andrea and Borg, Anders and Perlman, Cathleen and Pasternak, Michal and Seidel, Lars and Netzer, Corinna and Mauß, Fabian and Lehtiniemi, Harry}, title = {Simulation of DI-Diesel combustion using tabulated chemistry approach}, series = {1st Conference on Combustion Processes in Marine and Automotive Engines, 7th - 8th June 2016, Lund, Schweden}, booktitle = {1st Conference on Combustion Processes in Marine and Automotive Engines, 7th - 8th June 2016, Lund, Schweden}, pages = {44 -- 47}, language = {en} } @inproceedings{SeidelNetzerHilbigetal., author = {Seidel, Lars and Netzer, Corinna and Hilbig, Martin and Mauß, Fabian and Klauer, Christian and Pasternak, Michal and Matrisciano, Andrea}, title = {Systematic Reduction of Detailed Chemical Reaction Mechanisms for Engine Applications}, series = {ASME 2016 Internal Combustion Engine Division Fall Technical Conference Greenville, South Carolina, USA, October 9-12, 2016}, booktitle = {ASME 2016 Internal Combustion Engine Division Fall Technical Conference Greenville, South Carolina, USA, October 9-12, 2016}, publisher = {The American Society of Mechanical Engineers}, address = {New York, N.Y.}, isbn = {978-0-7918-5050-3}, pages = {12}, abstract = {In this work we apply a sequence of concepts for mechanism reduction on one reaction mechanism including novel quality control. We introduce a moment based accuracy rating method for species profiles. The concept is used for a necessity based mechanism reduction utilizing 0D reactors. Thereafter a stochastic reactor model (SRM) for internal combustion engines is applied to control the quality of the reduced reaction mechanism during the expansion phase of the engine. This phase is sensitive on engine out emissions, and is often not considered in mechanism reduction work. The proposed process allows to compile highly reduced reaction schemes for CFD application for internal combustion engine simulations. It is demonstrated that the resulting reduced mechanisms predict combustion and emission formation in engines with accuracies comparable to the original detailed scheme.}, language = {en} } @inproceedings{RodriguezHenriquezKeramiotisVourliotakisetal., author = {Rodriguez Henriquez, Jose Juan and Keramiotis, Christos and Vourliotakis, George and Mauß, Fabian and Founti, Maria}, title = {An Experimental Investigation of the Effect of Simulated EGR on Typical Gaseous Fuels Mixtures}, series = {1st Conference on Combustion Processes in Marine and Automotive Engines, 7th - 8th June 2016, Lund, Schweden}, booktitle = {1st Conference on Combustion Processes in Marine and Automotive Engines, 7th - 8th June 2016, Lund, Schweden}, pages = {18 -- 21}, language = {en} } @inproceedings{RodriguezHenriquezKeramiotisVourliotakisetal., author = {Rodriguez Henriquez, Jose Juan and Keramiotis, Christos and Vourliotakis, George and Mauß, Fabian and Founti, Maria}, title = {An emission characterization study on a model flame fuelled with natural gas and commercial grade propane}, series = {Proceedings, The MCAA Poster Session - ESOF 2016, EuroScience Open Forum - Manchester, United Kingdom, 24-27 July 2016}, booktitle = {Proceedings, The MCAA Poster Session - ESOF 2016, EuroScience Open Forum - Manchester, United Kingdom, 24-27 July 2016}, editor = {Krstić, Snežana and Cunningham, Paul}, publisher = {MCAA}, address = {Brussels}, isbn = {978-2-9601724-2-3}, pages = {27 -- 28}, language = {en} } @misc{NetzerSeidelPasternaketal., author = {Netzer, Corinna and Seidel, Lars and Pasternak, Michal and Klauer, Christian and Perlman, Cathleen and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Engine Knock Prediction and Evaluation Based on Detonation Theory Using a Quasi-Dimensional Stochastic Reactor Mode}, series = {SAE technical paper}, journal = {SAE technical paper}, number = {2017-01-0538}, issn = {0096-5170}, doi = {10.4271/2017-01-0538}, pages = {11 Seiten}, language = {en} } @misc{MatriscianoFrankenPerlmanetal., author = {Matrisciano, Andrea and Franken, Tim and Perlman, Cathleen and Borg, Anders and Lehtiniemi, Harry and Mauß, Fabian}, title = {Development of a Computationally Efficient Progress Variable Approach for a Direct Injection Stochastic Reactor Model}, series = {SAE technical papers}, journal = {SAE technical papers}, number = {2017-01-0512}, issn = {0148-7191}, doi = {10.4271/2017-01-0512}, pages = {18 Seiten}, language = {en} } @misc{AslanjanKlauerPerlmanetal., author = {Aslanjan, Jana and Klauer, Christian and Perlman, Cathleen and G{\"u}nther, Vivien and Mauß, Fabian}, title = {Simulation of a Three-Way Catalyst Using Transient Single and Multi-Channel Models}, series = {SAE technical paper}, journal = {SAE technical paper}, number = {2017-01-0966}, issn = {0148-7191}, doi = {10.4271/2017-01-0966}, pages = {11 Seiten}, language = {en} } @misc{FrankenSommerhoffWillemsetal., author = {Franken, Tim and Sommerhoff, Arnd and Willems, Werner and Matrisciano, Andrea and Lehtiniemi, Harry and Borg, Anders and Netzer, Corinna and Mauß, Fabian}, title = {Advanced Predictive Diesel Combustion Simulation Using Turbulence Model and Stochastic Reactor Model}, series = {SAE technical paper}, journal = {SAE technical paper}, issn = {0148-7191}, doi = {10.4271/2017-01-0516}, language = {en} } @inproceedings{NetzerSeidelPasternaketal., author = {Netzer, Corinna and Seidel, Lars and Pasternak, Michal and Mauß, Fabian and Lehtiniemi, Harry and Perlman, Cathleen and Ravet, Fr{\´e}d{\´e}ric}, title = {3D CFD Engine Knock Predication and Evaluation Based on Detailed Chemistry and Detonation Theory}, series = {Motorische Verbrennung : aktuelle Probleme und moderne L{\"o}sungsans{\"a}tze, XIII. Tagung im Haus der Technik Ludwigsburg, 16.-17. M{\"a}rz 2017}, booktitle = {Motorische Verbrennung : aktuelle Probleme und moderne L{\"o}sungsans{\"a}tze, XIII. Tagung im Haus der Technik Ludwigsburg, 16.-17. M{\"a}rz 2017}, editor = {Leipertz, Alfred and Fr{\"o}ba, Andreas Paul}, publisher = {ESYTEC Energie- und Systemtechnik GmbH}, address = {Erlangen}, isbn = {978-3-945806-08-1}, language = {en} } @inproceedings{NetzerSeidelPasternaketal., author = {Netzer, Corinna and Seidel, Lars and Pasternak, Michal and Klauer, Christian and Perlman, Cathleen and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Impact of Gasoline Octane Rating on Engine Knock using Detailed Chemistry and a Quasi-dimensional Stochastic Reaktior Model}, series = {Digital Proceedings of the 8th European Combustion Meeting (ECM 2017), Dubrovnik, Croatia}, booktitle = {Digital Proceedings of the 8th European Combustion Meeting (ECM 2017), Dubrovnik, Croatia}, pages = {493 -- 498}, language = {en} } @inproceedings{NetzerSeidelLehtiniemietal., author = {Netzer, Corinna and Seidel, Lars and Lehtiniemi, Harry and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Efficient tracking of knock onset for a wide range of fuel surrogates}, series = {International Multidimensional Engine Modeling User's Group Meeting at the SAE Congress}, booktitle = {International Multidimensional Engine Modeling User's Group Meeting at the SAE Congress}, pages = {6}, language = {en} } @misc{PasternakMaussKlaueretal., author = {Pasternak, Michal and Mauß, Fabian and Klauer, Christian and Matrisciano, Andrea}, title = {Diesel engine performance mapping using a parametrized mixing time model}, series = {International Journal of Engine Research}, volume = {19}, journal = {International Journal of Engine Research}, number = {2}, issn = {2041-3149}, doi = {10.1177/1468087417718115}, pages = {202 -- 213}, language = {en} } @inproceedings{AslanjanKlauerGuentheretal., author = {Aslanjan, Jana and Klauer, Christian and G{\"u}nther, Vivien and Mauß, Fabian}, title = {On the Influence of Inlet Gas Variations and Gas Phase Chemistry in a Three-Way Catalyst}, series = {COMODIA - The Ninth International Conference on Modeling and Diagnostics for Advanced, July 25, 2017 - July 28, 2017}, booktitle = {COMODIA - The Ninth International Conference on Modeling and Diagnostics for Advanced, July 25, 2017 - July 28, 2017}, doi = {10.1299/jmsesdm.2017.9.A308}, abstract = {The conversion effects of a three-way catalyst are simulated in previous works using single and multiple representative channel approaches with detailed surface kinetic models. In addition, this article introduces global gas phase chemistry to the model. This allows reflecting ongoing reactions due to incomplete combustion products in low temperature regime. The 1D single-channel model representative for the catalyst is used here. Next to the comparison of the catalyst outlet emissions with and without gas phase chemistry, the transient temperature increase is simulated in order to model the catalysts light off temperature. Additionally, the transient inlet emissions are enhanced to show the influence of water and hydrogen on the modeling results. The heat transfer is modeled by wall heat losses to provide proper heat dissipation out of the catalyst. The modeling results show a good agreement to the experimental data with low computational cost.}, language = {en} } @inproceedings{FischerGuentherBergeretal., author = {Fischer, Michael and G{\"u}nther, Michael and Berger, Carsten and Troeger, Ralf and Pasternak, Michal and Mauß, Fabian}, title = {Suppressing Knocking by Using CleanEGR - Better Fuel Economy and Lower Raw Emissions Simultaneously}, series = {Knocking in Gasoline Engines, 5th International Conference, December 12-13, 2017, Berlin, Germany}, booktitle = {Knocking in Gasoline Engines, 5th International Conference, December 12-13, 2017, Berlin, Germany}, editor = {G{\"u}nther, Michael and Sens, Marc}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-319-69760-4}, doi = {10.1007/978-3-319-69760-4_21}, pages = {384}, language = {en} } @inproceedings{PasternakNetzerMaussetal., author = {Pasternak, Michal and Netzer, Corinna and Mauß, Fabian and Fischer, Michael and Sens, Marc and Riess, Michael}, title = {Simulation of the Effects of Spark Timing and External EGR on Gasoline Combustion Under Knock-Limited Operation at High Speed and Load}, series = {Knocking in Gasoline Engines, 5th International Conference, December 12-13, 2017, Berlin, Germany}, booktitle = {Knocking in Gasoline Engines, 5th International Conference, December 12-13, 2017, Berlin, Germany}, editor = {G{\"u}nther, Michael and Sens, Marc}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-319-69760-4}, doi = {10.1007/978-3-319-69760-4_8}, pages = {121 -- 142}, language = {en} } @inproceedings{AslanjanKlauerGuentheretal., author = {Aslanjan, Jana and Klauer, Christian and Guenther, Vivien and Mauß, Fabian}, title = {Simulation of a three-way catalyst using a transient multi-channel model}, series = {Digital Proceedings of the 8th European Combustion Meeting (ECM 2017), Dubrovnik, Croatia}, booktitle = {Digital Proceedings of the 8th European Combustion Meeting (ECM 2017), Dubrovnik, Croatia}, address = {Dubrovnik}, pages = {570 -- 574}, abstract = {The conversion effects of a three-way catalyst (TWC) are simulated in previous works using single-channel approaches and detailed kinetic models. In addition to the single-channel model multiple representative catalyst channels are used in this work to take heat transfer between the channels into account. Furthermore, different inlet temperature distributions are considered and tested. An experimental four-stroke engine setup with emission outputs fed into a TWC is used to validate the model. Furthermore, the temperature progress is simulated to reflect the catalyst's light off temperature. Heat conduction between the channels is modeled to provide proper heat dissipation during the catalytic process. A good agreement to the experimental data can be achieved with low computational cost.}, language = {en} } @misc{AslanjanKlauerGuentheretal., author = {Aslanjan, Jana and Klauer, Christian and G{\"u}nther, Vivien and Mauß, Fabian}, title = {Simulation of a three-way-catalyst using a transient multi-channel model}, pages = {S. 103}, abstract = {The importance to reduce automotive exhaust gas emissions is constantly increasing. Not only the country-specific laws are getting more stringent also the global increase of automobiles is requiring a responsible handling of the issue. The three-way-catalytic converter (TWC) is one of the most common catalysts for the engine exhaust gas after treatment. The reduction of CO, NO and unburned hydrocarbons is fulfilled via oxidation of carbon monoxide and hydrocarbons, and reduction of nitrogen oxides. These conversion effects were simulated in previous works using single channel approaches [e.g. Fr{\"o}jd/Mauss, SAE International 2011-01-1306] and detailed kinetic models [e.g Chatterjee et al., Faraday Discussions 119 (2001) 371-384 and Koop et al., Appl. Catal.B: Environmental 91 (2009), 47-58]. In this work multiple representative catalyst channels are used to take heat variations in between the catalyst into account. Each channel is split into a user given number of cells and each cell is treated like a perfectly stirred reactor (PSR). The simulation is validated against an experimental four-stroke engine setup with emission outputs fed into a TWC. Next to the emissions the transient temperature increase is simulated in order to model the catalyst light off temperature. The heat transfer is modelled by wall heat losses to provide a proper heat dissipation out of the catalyst. The simulation results show a good agreement to the experimental data with low computational cost.}, language = {en} } @misc{VanTreekRothSeideletal., author = {Van Treek, Lisa and Roth, Norbert and Seidel, Lars and Mauß, Fabian}, title = {Laminar burning velocities of rich ethylene / air flames}, abstract = {The laminar burning velocity SL of a given mixture of fuel and oxidizer is an important parameter to characterize premixed flames. SL is not only a fundamental parameter to calculate properties of turbulent flames, it is also an important target for the development of chemical kinetic mechanisms. Under fuel rich conditions it has relevance when simulating soot formation in burner stabilized flames. Many experiments on soot formation have been conducted in fuel-rich burner stabilized ethylene flames. Therefore an interest exists in experimental data for laminar burning velocity, in particular in fuel-rich ethylene flames. In the present work, ethylene / air flames were measured in the heat flux setup. Subsequently, the experimental data were compared against existing data and modelled using two kinetic models.}, language = {en} } @misc{HoyermannMaussOlzmannetal., author = {Hoyermann, Karlheinz and Mauß, Fabian and Olzmann, Matthias and Welz, Oliver and Zeuch, Thomas}, title = {Exploring the chemical kinetics of partially oxidized intermediates by combining experiments, theory, and kinetic modeling}, series = {Physical Chemistry Chemical Physics}, volume = {19}, journal = {Physical Chemistry Chemical Physics}, number = {28}, issn = {1463-9076}, doi = {10.1039/C7CP02759A}, pages = {18128 -- 18146}, abstract = {Partially oxidized intermediates play a central role in combustion and atmospheric chemistry. In this perspective, we focus on the chemical kinetics of alkoxy radicals, peroxy radicals, and Criegee intermediates, which are key species in both combustion and atmospheric environments. These reactive intermediates feature a broad spectrum of chemical diversity. Their reactivity is central to our understanding of how volatile organic compounds are degraded in the atmosphere and converted into secondary organic aerosol. Moreover, they sensitively determine ignition timing in internal combustion engines. The intention of this perspective article is to provide the reader with information about the general mechanisms of reactions initiated by addition of atomic and molecular oxygen to alkyl radicals and ozone to alkenes. We will focus on critical branching points in the …}, language = {en} } @misc{WeberLiLovasetal., author = {Weber, Kathrin and Li, T. and L{\o}v{\aa}s, Terese and Perlman, Cathleen and Seidel, Lars and Mauß, Fabian}, title = {Stochastic reactor modeling of biomass pyrolysis and gasification}, series = {Journal of analytical and applied pyrolysis}, volume = {124}, journal = {Journal of analytical and applied pyrolysis}, issn = {0165-2370}, doi = {10.1016/j.jaap.2017.01.003}, pages = {592 -- 601}, abstract = {Abstract In this paper, a partially stirred stochastic reactor model is presented as an alternative for the modeling of biomass pyrolysis and gasification. Instead of solving transport equations in all spatial dimensions as in CFD simulations, the description of state variables and mixing processes is based on a probability density function, making this approach computationally efficient. The virtual stochastic particles, an ensemble of flow elements consisting of porous solid biomass particles and surrounding gas, mimic the turbulent exchange of heat and mass in practical systems without the computationally expensive resolution of spatial dimensions. Each stochastic particle includes solid phase, pore gas and bulk gas interaction. The reactor model is coupled with a chemical mechanism for both surface and gas phase reactions. A Monte Carlo algorithm with operator splitting …}, language = {en} } @misc{SeidelNetzerHilbigetal., author = {Seidel, Lars and Netzer, Corinna and Hilbig, Martin and Mauß, Fabian and Klauer, Christian and Pasternak, Michal and Matrisciano, Andrea}, title = {Systematic reduction of detailed chemical reaction mechanisms for engine applications}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {139}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {9}, issn = {1528-8919}, doi = {10.1115/1.4036093}, pages = {091701-1 -- 091701-9}, abstract = {In this work, we apply a sequence of concepts for mechanism reduction on one reaction mechanism including novel quality control. We introduce a moment-based accuracy rating method for species profiles. The concept is used for a necessity-based mechanism reduction utilizing 0D reactors. Thereafter a stochastic reactor model for internal combustion engines is applied to control the quality of the reduced reaction mechanism during the expansion phase of the engine. This phase is sensitive on engine out emissions, and is often not considered in mechanism reduction work. The proposed process allows to compile highly reduced reaction schemes for computational fluid dynamics application for internal combustion engine simulations. It is demonstrated that the resulting reduced mechanisms predict combustion and emission formation in engines with accuracies comparable to the original detailed scheme.}, language = {en} } @misc{NagyMatriscianoLehtiniemietal., author = {Nagy, Imre Gergely and Matrisciano, Andrea and Lehtiniemi, Harry and Mauß, Fabian and Schmid, Andreas}, title = {Influence of nozzle eccentricity on spray structures in marine diesel sprays}, series = {SAE technical papers}, journal = {SAE technical papers}, number = {2017-24-0031}, issn = {0148-7191}, pages = {13}, abstract = {Abstract: Large two-stroke marine Diesel engines have special injector geometries, which differ substantially from the configurations used in most other Diesel engine applications. One of the major differences is that injector orifices are distributed in a highly non-symmetric fashion affecting the spray characteristics. Earlier investigations demonstrated the dependency of the spray morphology on the location of the spray orifice and therefore on the resulting flow conditions at the nozzle tip. Thus, spray structure is directly influenced by the flow formation within the orifice. Following recent Large Eddy Simulation resolved spray primary breakup studies, the present paper focuses on spray secondary breakup odelling of asymmetric spray structures in Euler-Lagrangian framework based on previously obtained droplet distributions of primary breakup. Firstly, the derived droplet distributions were …}, language = {en} } @misc{BanyonRodriguezHenriquezPaterakisetal., author = {Banyon, Colin and Rodriguez Henriquez, Jose Juan and Paterakis, George and Malliotakis, Zisis and Souflas, Konstantinos and Keramiotis, Christos and Vourliotakis, George and Mauß, Fabian and Curran, Henry J. and Skevis, George and Koutmos, Panagiotis and Founti, Maria}, title = {A comparative study of the effect of varied reaction environments on a swirl stabilized flame geometry via optical measurements}, series = {Fuel : the science and technology of fuel and energy}, volume = {216}, journal = {Fuel : the science and technology of fuel and energy}, issn = {0016-2361}, doi = {10.1016/j.fuel.2017.09.105}, pages = {826 -- 834}, abstract = {The present work is a part of a larger experimental campaign which examines the behaviour of various fuels on a swirl stabilized flame burner configuration. Overall, detailed speciation measurements and temperature measurements were combined with optical measurements. The work presented here concerns the part of the experimental campaign which deals with the optical characteristics of the examined flames. The work adds to the growing database of experimental measurements assessing engine-relevant reaction environments which shift from traditional ones in order to meet pollutant emission regulations and efficiency standards. Here, the oxidation of several commonly used fuel and fuel surrogates that are subjected to the addition of a bio-derived fuel additive (dimethyl ether) and emulated exhaust gas recirculation (EGR) is studied in a laboratory-scale swirl …}, language = {en} } @misc{MedinaMendezSchmidtMaussetal., author = {Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko and Mauß, Fabian and Jozefik, Zoltan}, title = {Constant volume n-Heptane autoignition using One-Dimensional Turbulence}, series = {Combustion and Flame}, volume = {190}, journal = {Combustion and Flame}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2017.12.015}, pages = {388 -- 401}, abstract = {Abstract Constant volume premixed lean n-Heptane/air autoignition at high pressure is investigated using the One-Dimensional Turbulence (ODT) model. The configuration consists of a 1D fixed volume domain with a prescribed velocity spectrum and temperature fluctuations superimposed on an initial uniformly elevated scalar field. The sensitivity of the heat release rate and pressure evolution to the initial temperature distribution is studied by imposing different initial temperature fields while holding the mean, RMS and integral length scale of the field constant. Three detailed chemical mechanisms are employed for the prediction of autoignition and heat release rate. To mitigate the high computational cost associated with the calculation of the chemical source terms in the stiff complex mechanisms, an approach based on the Strang-Splitting method is presented. Finally, a …}, language = {en} } @inproceedings{ShresthaSeidelMauss, author = {Shrestha, Krishna Prasad and Seidel, Lars and Mauß, Fabian}, title = {Kinetic study of methanol and ethanol oxidation in presence of NOx}, series = {Workshop on Gas-phase reaction kinetics of biofuels oxygenated molecules}, booktitle = {Workshop on Gas-phase reaction kinetics of biofuels oxygenated molecules}, language = {en} } @misc{NetzerFrankenLehtiniemietal., author = {Netzer, Corinna and Franken, Tim and Lehtiniemi, Harry and Mauß, Fabian and Seidel, Lars}, title = {Numerical Analysis of the Impact of Water Injection on Combustion and Thermodynamics in a Gasoline Engine using Detailed Chemistry}, series = {SAE technical papers}, journal = {SAE technical papers}, number = {2018-01-0200}, issn = {0148-7191}, doi = {10.4271/2018-01-0200}, pages = {14}, language = {en} } @inproceedings{NetzerSeidelLehtiniemietal., author = {Netzer, Corinna and Seidel, Lars and Lehtiniemi, Harry and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Impact of Formulation of Fuel Surrogates on Engine Knock Prediction}, series = {International Multidimensional Engine Modeling User's Group Meeting at the SAE Congress, April 9th , 2018, Detroit, USA}, booktitle = {International Multidimensional Engine Modeling User's Group Meeting at the SAE Congress, April 9th , 2018, Detroit, USA}, pages = {6}, language = {en} } @misc{AslanjanKlauerGuentheretal., author = {Aslanjan, Jana and Klauer, Christian and G{\"u}nther, Vivien and Mauß, Fabian}, title = {Development of a Physical Parameter Optimizer for 1D Catalyst Modeling on the Example of a Transient Three-Way Catalyst Experiment, 37th International Symposium on Combustion 2018, Dublin}, pages = {1}, abstract = {The importance of catalytic after-treatment for automotive emissions is not neglectable concerning current environmental protection discussions. A reasonable and time efficient catalyst model can help to reduce the necessity of time consuming experimental investigations on physical parameters for catalytic converter construction. It can further support the preparation of necessary experimental setups to analyze physical and chemical phenomena in catalysts. Physical parameter and/or chemical kinetic optimizers can be an advanced tool to support computational models in terms of adjustment to an experiment. In this work a physical parameter optimizer is developed and validated against a transient three-way catalyst experiment. The modeling results are compared to the measured data in terms of temperature and emission conversion behavior and show a good agreement.}, language = {en} } @inproceedings{FrankenDugganFengetal., author = {Franken, Tim and Duggan, Alexander and Feng, Tao and Mauß, Fabian}, title = {Multi-Objective Optimization of Fuel Consumption and NOx Emissions for a Heavy-Duty Direct Injection Diesel Engine}, series = {European ESTECO User Meeting 2018, Trieste, Italy}, booktitle = {European ESTECO User Meeting 2018, Trieste, Italy}, language = {en} } @misc{FrankenDugganFengetal., author = {Franken, Tim and Duggan, Alexander and Feng, Tao and Borg, Anders and Lehtiniemi, Harry and Matrisciano, Andrea and Mauß, Fabian}, title = {Multi-Objective Optimization of Fuel Consumption and NOx Emissions using a Stochastic Reactor Model, THIESEL 2018 Conference on Thermo- and Fluid Dynamic Processes in Direct Injection Engines}, language = {en} } @inproceedings{FrankenNetzerPasternaketal., author = {Franken, Tim and Netzer, Corinna and Pasternak, Michal and Mauß, Fabian and Seidel, Lars and Matrisciano, Andrea and Borg, Anders and Lehtiniemi, Harry and Kulzer, Andr{\´e} Casal}, title = {Assessment of Water Injection in a SI Engine using a Fast Running Detailed Chemistry Based Combustion Model}, series = {Symposium of Combustion Control 2018, Aachen}, booktitle = {Symposium of Combustion Control 2018, Aachen}, address = {Aachen}, pages = {10}, language = {en} } @misc{FrankenNetzerMauss, author = {Franken, Tim and Netzer, Corinna and Mauß, Fabian}, title = {Water Injection in Spark-Ignition Engines, FVV Autumn Conference 2018}, language = {en} } @misc{FrankenNetzerPasternaketal., author = {Franken, Tim and Netzer, Corinna and Pasternak, Michal and Mauß, Fabian and Seidel, Lars and Matrisciano, Andrea and Borg, Anders and Lehtiniemi, Harry and Kulzer, Andr{\´e} Casal}, title = {Simulation of Spark-Ignited Engines with Water Injection using the Stochastic Reactor Model, 37th International Symposium on Combustion}, language = {en} } @misc{AgbroTomlinZhangetal., author = {Agbro, Edirin and Tomlin, Alison S. and Zhang, Wankang and Burluka, Alexey and Mauß, Fabian and Alfazazi, Adamu and Sarathy, S. Mani}, title = {Chemical Kinetic Modeling Study on the Influence of n-Butanol Blending on the Combustion, Autoignition, and Knock Properties of Gasoline and Its Surrogate in a Spark-Ignition Engine}, series = {American Chemical Society}, volume = {32}, journal = {American Chemical Society}, number = {10}, issn = {1520-5029}, doi = {10.1021/acs.energyfuels.8b00962}, pages = {10065 -- 10077}, abstract = {The ability of a mechanism describing the oxidation kinetics of toluene reference fuel (TRF)/n-butanol mixtures to predict the impact of n-butanol blending at 20\% by volume on the autoignition and knock properties of gasoline has been investigated under conditions of a strongly supercharged spark-ignition (SI) engine. Simulations were performed using the LOGEengine code for stoichiometric fuel/air mixtures at intake temperature and pressure conditions of 320 K and 1.6 bar, respectively, for a range of spark timings. At the later spark timing of 6° crank angle (CA) before top dead center (BTDC), the predicted knock onsets for a gasoline surrogate (TRF) and the TRF/n-butanol blend are higher compared to the measurements, which is consistent with an earlier study of ignition delay times predicted in a rapid compression machine (RCM; Agbro, E.; Tomlin, A. S.; Lawes, M.; Park, S.; Sarathy, S. M. The influence of n …}, language = {en} } @misc{ShresthaSeidelZeuchetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Zeuch, Thomas and Mauß, Fabian}, title = {Detailed Kinetic Mechanism for the Oxidation of Ammonia Including the Formation and Reduction of Nitrogen Oxides}, series = {Energy \& Fuels}, volume = {32}, journal = {Energy \& Fuels}, number = {10}, issn = {1520-5029}, doi = {10.1021/acs.energyfuels.8b01056}, pages = {10202 -- 10217}, abstract = {This work introduces a newly developed reaction mechanism for the oxidation of ammonia in freely propagating and burner-stabilized premixed flames as well as shock-tube, jet-stirred reactor, and plug-flow reactor experiments. The paper mainly focuses on pure ammonia and ammonia-hydrogen fuel blends. The reaction mechanism also considers the formation of nitrogen oxides as well as the reduction of nitrogen oxides depending upon the conditions of the surrounding gas phase. Doping of the fuel blend with NO2 can result in acceleration of H2 autoignition via the reaction NO2 + HO2 ⇋ HONO + O2, followed by the thermal decomposition of HONO, or deceleration of H2 oxidation via NO2 + OH ⇋ NO + HO2. The concentration of HO2 is decisive for the active reaction pathway. The formation of NO in burner-stabilized premixed flames is shown to demonstrate the capability of the mechanism to be integrated …}, language = {en} } @misc{NetzerSeidelPasternaketal., author = {Netzer, Corinna and Seidel, Lars and Pasternak, Michal and Lehtiniemi, Harry and Perlman, Cathleen and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Three-dimensional computational fluid dynamics engine knock prediction and evaluation based on detailed chemistry and detonation theory}, series = {International Journal of Engine Research}, volume = {19}, journal = {International Journal of Engine Research}, number = {1}, issn = {1468-0874}, doi = {10.1177/1468087417740271}, pages = {33 -- 44}, abstract = {Engine knock is an important phenomenon that needs consideration in the development of gasoline-fueled engines. In our days, this development is supported using numerical simulation tools to further understand and predict in-cylinder processes. In this work, a model tool chain which uses a detailed chemical reaction scheme is proposed to predict the auto-ignition behavior of fuels with different octane ratings and to evaluate the transition from harmless auto-ignitive deflagration to knocking combustion. In our method, the auto-ignition characteristics and the emissions are calculated using a gasoline surrogate reaction scheme containing pathways for oxidation of ethanol, toluene, n-heptane, iso-octane and their mixtures. The combustion is predicted using a combination of the G-equation based flame propagation model utilizing tabulated laminar flame speeds and well-stirred reactors in the burned and …}, language = {en} } @misc{MoshammerSeidelWangetal., author = {Moshammer, Kai and Seidel, Lars and Wang, Yu and Selim, Hatem and Sarathy, S. Mani and Mauß, Fabian and Hansen, Nils}, title = {Aromatic ring formation in opposed-flow diffusive 1, 3-butadiene flames}, series = {Proceedings of the Combustion Institute}, volume = {36}, journal = {Proceedings of the Combustion Institute}, number = {1}, issn = {1540-7489}, doi = {10.1016/j.proci.2016.09.010}, pages = {947 -- 955}, abstract = {This paper is concerned with the formation of one-and two-ring aromatic species in near atmospheric-pressure opposed-flow diffusion flames of 1, 3-butadiene (1, 3-C 4 H 6). The chemical structures of two different 1, 3-C 4 H 6/Ar-O 2/Ar flames were explored using flame-sampling molecular-beam mass spectrometry with both electron and single-photon ionization. We provide mole fraction profiles of 47 components as function of distance from the fuel outlet and compare them to chemically detailed modeling results. To this end, the hierarchically developed model described by Seidel et al.[16] has been updated to accurately comprise the chemistry of 1, 3-butadiene. Generally a very good agreement is observed between the experimental and modeling data, allowing for a meaningful reaction path analysis. With regard to the formation of aromatic species up to naphthalene, it was essential to improve the fulvene …}, language = {en} } @inproceedings{ShresthaSeidelMaussetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Mauß, Fabian and Zeuch, Thomas}, title = {Development of a kinetic mechanism for NOx fuel interaction}, series = {Proceedings, Joint Meeting of the German and Italian Sections of the Combustion Institute, 41st Meeting on Combustion, Sorrento, May 2018}, booktitle = {Proceedings, Joint Meeting of the German and Italian Sections of the Combustion Institute, 41st Meeting on Combustion, Sorrento, May 2018}, editor = {Bockhorn, Henning and Scala, F. and Commodo, M. and Tregrossi, A.}, publisher = {Associazione Sezione Italiana del Combustion Institute}, address = {Napoli}, isbn = {978-88-88104-22-5}, pages = {6}, abstract = {This work introduces a newly developed reaction mechanism to predict fuel/NOx interaction in freely propagating, burner stabilized premixed flames, shock tubes, jet stirred reactors and plug flow reactors experiments. The study focuses on pure ammonia as fuel as well as H₂,H₂/CO, CH₄ doped with NO, NO₂ and N₂O. The kinetic scheme also focuses on the formation and consumption of nitrogen oxides at different experimental conditions. It is found that the doping with N₂O has almost no sensitivity on the H₂ chemistry, while small amount of NO₂ is enough to change the pressure dependence of H₂ auto ignition. The experiments with N₂O still show the significant influence of the chain breaking reaction H+O₂(+M)⇋HO₂(+M) on the H₂ ignition delay times, resulting in the crossing lines for the ignition delay times, which are moved at higher pressure to higher temperature. The concentration of HO₂ is decisive for the active reaction pathway in shock tube oxidation as well as in jet stirred and flow reactor. Reaction NO+HO₂⇋NO₂+OH and NO₂+H⇋NO+OH are very important because they strongly influence the inter conversion process of NO and NO₂ in jet stirred reactor and flow reactor for cases studied herein. The formation of NO in burner stabilized premixed flames is shown to demonstrate the capability of the mechanism to be integrated into mechanisms for hydrocarbon oxidation.}, language = {en} } @inproceedings{NetzerSeidelLehtiniemietal., author = {Netzer, Corinna and Seidel, Lars and Lehtiniemi, Harry and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Impact of gasoline surrogates with different fuel sensitivity (RON-MON) on knock prediction}, series = {Proceedings of the 6th European Conference on Computational Mechanics (Solids, Structures and Coupled Problems) ECCM 6 and 7th European Conference on Computational Fluid Dynamics ECFD 7, Glasgow, Scotland, UK June 11 - 15, 2018}, booktitle = {Proceedings of the 6th European Conference on Computational Mechanics (Solids, Structures and Coupled Problems) ECCM 6 and 7th European Conference on Computational Fluid Dynamics ECFD 7, Glasgow, Scotland, UK June 11 - 15, 2018}, pages = {906 -- 917}, language = {en} } @misc{FrankenDugganTaoetal., author = {Franken, Tim and Duggan, Alexander and Tao, Feng and Matrisciano, Andrea and Lehtiniemi, Harry and Borg, Anders and Mauß, Fabian}, title = {Multi-Objective Optimization of Fuel Consumption and NOx Emissions of a heavy-duty Diesel engine using a Stochastic Reactor Model}, series = {SAE technical paper}, journal = {SAE technical paper}, number = {2019-01-1173}, issn = {0096-5170}, abstract = {Highly fuel-efficient Diesel engines, combined with effective exhaust aftertreatment systems, enable an economic and low-emission operation of heavy-duty vehicles. The challenge of its development arises from the present engine complexity, which is expected to increase even more in the future. The approved method of test bench measurements is stretched to its limits, because of the high demand for large parameter variations. The introduction of a physics-based quasi-dimensional stochastic reactor model combined with tabulated chemistry enables the simulation-supported development of these Diesel engines. The stochastic reactor model mimics mixture and temperature inhomogeneities induced by turbulence, direct injection and heat transfer. Thus, it is possible to improve the prediction of NOx emissions compared to common mean-value models. To reduce the number of designs to be evaluated during …}, language = {en} } @misc{MalliotakisBanyonZhangetal., author = {Malliotakis, Zisis and Banyon, Colin and Zhang, Kuiwen and Wagnon, Scott W. and Rodriguez Henriquez, Jose Juan and Vourliotakis, George and Keramiotis, Christos and Founti, Maria and Mauß, Fabian and Pitz, William J. and Curran, Henry J.}, title = {Testing the validity of a mechanism describing the oxidation of binary n-heptane/toluene mixtures at engine operating conditions}, series = {Combustion and Flame}, volume = {199}, journal = {Combustion and Flame}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2018.10.024}, pages = {241 -- 248}, abstract = {The aim of this work is to evaluate the influence of the n-heptane/toluene ratio on the reactivity of binary toluene reference fuels (TRFs), through a combined experimental and numerical work. Novel experimental ignition delay time (IDT) data of three binary TRFs of varying n-heptane/toluene ratios have been obtained in a high-pressure shock tube and in a rapid compression machine at conditions relevant to novel engine operation. Measurements have been performed at two pressures (10 and 30 bar), and at three fuel/air equivalence ratios (0.5, 1.0 and 2.0) for TRF mixtures of 50\%, 75\% and 90\% by volume toluene concentration, over the temperature range of 650-1450 K. It was found that, increasing the n-heptane content, led to an increase in reactivity and shorter measured IDTs. Reduced sensitivity to the equivalence ratio was observed at high temperatures, especially for high toluene content mixtures. A …}, language = {en} } @misc{FrankenKlauerKienbergetal., author = {Franken, Tim and Klauer, Christian and Kienberg, Martin and Matrisciano, Andrea and Mauß, Fabian}, title = {Prediction of thermal stratification in an engine-like geometry using a zero-dimensional stochastic reactor model}, series = {International Journal of Engine Research}, journal = {International Journal of Engine Research}, isbn = {2041-3149}, issn = {1468-0874}, doi = {10.1177/1468087418824217}, pages = {14}, language = {en} } @misc{WernerMatriscianoNetzeretal., author = {Werner, Adina and Matrisciano, Andrea and Netzer, Corinna and Lehtiniemi, Harry and Borg, Anders and Seidel, Lars and Mauß, Fabian}, title = {Further Application of the Fast Tabulated CPV Approach}, doi = {10.13140/RG.2.2.18689.71529}, language = {en} } @misc{WernerNetzerLehtiniemietal., author = {Werner, Adina and Netzer, Corinna and Lehtiniemi, Harry and Borg, Anders and Matrisciano, Andrea and Seidel, Lars and Mauß, Fabian}, title = {A Computationally Efficient Combustion Progress Variable (CPV) Approach for Engine Applications}, doi = {10.13140/RG.2.2.15334.27209}, language = {en} } @misc{ShresthaSeidelZeuchetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Zeuch, Thomas and Mauß, Fabian}, title = {Kinetic Modeling of NOx Formation and Consumption during Methanol and Ethanol Oxidation}, series = {Combustion Science and Technology}, volume = {191}, journal = {Combustion Science and Technology}, number = {9}, issn = {1563-521X}, doi = {10.1080/00102202.2019.1606804}, pages = {1628 -- 1660}, language = {en} } @misc{NetzerSeidelRavetetal., author = {Netzer, Corinna and Seidel, Lars and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Impact of the surrogate formulation on 3D CFD engine knock prediction using detailed chemistry}, series = {Fuel}, volume = {Volume 254}, journal = {Fuel}, issn = {1873-7153}, doi = {10.1016/j.fuel.2019.115678}, pages = {13}, abstract = {For engine knock prediction, surrogate fuels are often composed of iso-octane and n-heptane since they are the components of the Primary Reference Fuel (PRF). By definition, a PRF has no octane sensitivity (S = RON-MON). However, for a commercial gasoline fuel holds RON > MON and therefor S > 0. More complex surrogates are Toluene Reference Fuels (TRF) and Ethanol containing Toluene Reference Fuels (ETRF). In this work, the impact of the surrogate formulation on the prediction of flame propagation and auto-ignition in the unburnt gases are investigated. The surrogates are composed such that the Research Octane Number is the same. The auto-ignition events ahead of the flame front are predicted using 3D CFD and a combustion model based on the ETRF mechanism by Seidel (2017). The strength of the auto-ignition is determined using the detonation diagram by Bradley and co-workers (2002, 2003). Applying the different surrogates, ignition kernels of different size and reactivity are predicted. The results indicate a dependency on the local temperature history and the low temperature chemistry of the fuel species. The comparison of homogenous constant volume reactor and transient simulations show that the analysis of ignition delay time and octane rating solely from homogenous simulations is not sufficient if the knock tendency of a surrogate in engine simulations needs to be characterized.}, language = {en} } @misc{NetzerSeidelRavetetal., author = {Netzer, Corinna and Seidel, Lars and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Assessment of the validity of RANS knock prediction using the resonance theory}, series = {International Journal of Engine Research}, volume = {21}, journal = {International Journal of Engine Research}, number = {4}, issn = {2041-3149}, doi = {10.1177/1468087419846032}, pages = {610 -- 621}, abstract = {Following the resonance theory by Bradley and co-workers, engine knock is a consequence of an auto-ignition in the developing detonation regime. Their detonation diagram was developed using direct numerical simulations and was applied in the literature to engine knock assessment using large eddy simulations. In this work, it is analyzed if the detonation diagram can be applied for post-processing and evaluation of predicted auto-ignitions in Reynolds-averaged Navier-Stokes simulations even though the Reynolds-averaged Navier-Stokes approach cannot resolve the fine structures resolved in direct numerical simulations and large eddy simulations that lead to the prediction of a developing detonation. For this purpose, an engine operating point at the knock limit spark advance is simulated using Reynolds-averaged Navier-Stokes and large eddy simulations. The combustion is predicted using the G-equation and the well-stirred reactor model in the unburnt gases based on a detailed gasoline surrogate reaction scheme. All the predicted ignition kernels are evaluated using the resonance theory in a post-processing step. According to the different turbulence models, the predicted pressure rise rates and gradients differ. However, the predicted ignition kernel sizes and imposed gas velocities by the auto-ignition event are similar, which suggests that the auto-ignitions predicted by Reynolds-averaged Navier-Stokes simulations can be given a meaningful interpretation within the detonation diagram.}, language = {en} } @misc{NetzerPasternakSeideletal., author = {Netzer, Corinna and Pasternak, Michal and Seidel, Lars and Ravet, Fr{\´e}d{\´e}ric and Mauß, Fabian}, title = {Computationally efficient prediction of cycle-to-cycle variations in spark-ignition engines}, series = {International Journal of Engine Research}, volume = {21}, journal = {International Journal of Engine Research}, number = {4}, issn = {2041-3149}, doi = {10.1177/1468087419856493}, pages = {649 -- 663}, abstract = {Cycle-to-cycle variations are important to consider in the development of spark-ignition engines to further increase fuel conversion efficiency. Direct numerical simulation and large eddy simulation can predict the stochastics of flows and therefore cycle-to-cycle variations. However, the computational costs are too high for engineering purposes if detailed chemistry is applied. Detailed chemistry can predict the fuels' tendency to auto-ignite for different octane ratings as well as locally changing thermodynamic and chemical conditions which is a prerequisite for the analysis of knocking combustion. In this work, the joint use of unsteady Reynolds-averaged Navier-Stokes simulations for the analysis of the average engine cycle and the spark-ignition stochastic reactor model for the analysis of cycle-to-cycle variations is proposed. Thanks to the stochastic approach for the modeling of mixing and heat transfer, the spark-ignition stochastic reactor model can mimic the randomness of turbulent flows that is missing in the Reynolds-averaged Navier-Stokes modeling framework. The capability to predict cycle-to-cycle variations by the spark-ignition stochastic reactor model is extended by imposing two probability density functions. The probability density function for the scalar mixing time constant introduces a variation in the turbulent mixing time that is extracted from the unsteady Reynolds-averaged Navier-Stokes simulations and leads to variations in the overall mixing process. The probability density function for the inflammation time accounts for the delay or advancement of the early flame development. The combination of unsteady Reynolds-averaged Navier-Stokes and spark-ignition stochastic reactor model enables one to predict cycle-to-cycle variations using detailed chemistry in a fraction of computational time needed for a single large eddy simulation cycle.}, language = {en} } @misc{FrankenNetzerMaussetal., author = {Franken, Tim and Netzer, Corinna and Mauß, Fabian and Pasternak, Michal and Seidel, Lars and Borg, Anders and Lehtiniemi, Harry and Matrisciano, Andrea and Kulzer, Andr{\´e} Casal}, title = {Multi-objective optimization of water injection in spark-ignition engines using the stochastic reactor model with tabulated chemistry}, series = {International Journal of Engine Research}, volume = {20}, journal = {International Journal of Engine Research}, number = {10}, issn = {2041-3149}, doi = {10.1177/1468087419857602}, pages = {1089 -- 1100}, abstract = {Water injection is investigated for turbocharged spark-ignition engines to reduce knock probability and enable higher engine efficiency. The novel approach of this work is the development of a simulation-based optimization process combining the advantages of detailed chemistry, the stochastic reactor model and genetic optimization to assess water injection. The fast running quasi-dimensional stochastic reactor model with tabulated chemistry accounts for water effects on laminar flame speed and combustion chemistry. The stochastic reactor model is coupled with the Non-dominated Sorting Genetic Algorithm to find an optimum set of operating conditions for high engine efficiency. Subsequently, the feasibility of the simulation-based optimization process is tested for a three-dimensional computational fluid dynamic numerical test case. The newly proposed optimization method predicts a trade-off between fuel efficiency and low knock probability, which highlights the present target conflict for spark-ignition engine development. Overall, the optimization shows that water injection is beneficial to decrease fuel consumption and knock probability at the same time. The application of the fast running quasi-dimensional stochastic reactor model allows to run large optimization problems with low computational costs. The incorporation with the Non-dominated Sorting Genetic Algorithm shows a well performing multi-objective optimization and an optimized set of engine operating parameters with water injection and high compression ratio is found.}, language = {en} } @misc{ShresthaVinHerbinetetal., author = {Shrestha, Krishna Prasad and Vin, Nicolas and Herbinet, Olivier and Seidel, Lars and Battin-Leclerc, Fr{\´e}d{\´e}rique and Zeuch, Thomas and Mauß, Fabian}, title = {Insights into nitromethane combustion from detailed kinetic modeling - Pyrolysis experiments in jet-stirred and flow reactors}, series = {Fuel}, volume = {261}, journal = {Fuel}, issn = {0016-2361}, doi = {https://doi.org/10.1016/j.fuel.2019.116349}, pages = {19}, abstract = {The pyrolysis of nitromethane highly diluted in helium was studied in a plug flow reactor and in a jet-stirred reactor at 1.07 bar and over the temperature range from 500 to 1100 K. Mole fraction profiles of major products and of intermediates were identified with gas chromatography and Fourier transform infrared spectroscopy. Using these experimental data, as well as published ones, we have developed a newly compiled model for the prediction of the pyrolysis and of the oxidation of nitromethane in jet-stirred and flow reactors, freely propagating, and burner-stabilized premixed flames, as well as in shock-tubes. The experimental results from the present work and from the literature are interpreted with the help of the kinetic model derived here. This study mainly focuses on the analysis of speciation in different reactors. Among the nitrogenous species, NO is found to be a major product for pyrolysis and oxidation. The model suggests that for nitromethane pyrolysis and oxidation the thermal dissociation channel to CH3 and NO2 is the main reaction path for the nitromethane degradation followed by the H-atom abstraction channel. The most sensitive reactions for nitromethane pyrolysis in a flow reactor and during pyrolysis and oxidation in a jet-stirred reactor are found to be CH3NO2(+M) ⇋ CH3 + NO2(+M) and CH3 + NO2 ⇋ CH3O + NO. The reaction CH3 + NO2 ⇋ CH3O + NO is found to be the most important reaction for all conditions studied. In a burner-stabilized premixed flame, as the mixture gets richer, the thermal dissociation channel CH3NO2(+M) ⇋ CH3 + NO2(+M) becomes more important as the contribution of the H-atom abstraction channel is decreased. Furthermore, in the burner-stabilized premixed flames, it was found that NO is mainly formed via NO2: NO2 + H ⇋ NO + OH, NO2 + CH3 ⇋ CH3O + NO. The model provided an overall reasonable agreement with the experimental data. However, for pyrolysis conditions, future work is desirable to improve predictions of intermediate species. This work extends the kinetic database and helps to improve the understanding of nitromethane chemistry. The kinetic model presented in this work can serve as a base model for hydrocarbons and oxygenated fuels higher than C2 and nitrogen-containing compounds higher than C1 as well as for pure nitrogen compounds.}, language = {en} } @misc{VanTreekLubranoLavaderaKonnovetal., author = {Van Treek, Lisa and Lubrano Lavadera, Marco and Konnov, Alexander A. and Seidel, Lars and Mauß, Fabian}, title = {Measurements of the laminar burning velocities of ethanol-water-air flames}, abstract = {The laminar burning velocity of ethanol-water-air flames at atmospheric pressure and initial gas temperatures of T = 358 K was measured with the heat flux method. The mixture of ethanol-water-air contained 0\%, 10\%, 20\%, 30\% and 40\% water by mole and the equivalence ratio (ϕ) range was varied from 0.7 to 1.4. The experiments were compared against predictions using three different kinetic models.}, language = {en} } @misc{ShresthaSeidelZeuchetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Zeuch, Thomas and Mauß, Fabian}, title = {Modeling for Nitromethane oxidation}, series = {1st International Conference on Smart Energy Carriers Napoli, 2019}, journal = {1st International Conference on Smart Energy Carriers Napoli, 2019}, abstract = {The diminishing availability of conventional fuels and stricter regulations on pollution control and CO2 emission targets have led scientist and engineers to look for alternative fuels. Recently nitromethane has slowly gained interest as alternative fuel over conventional fuel for internal combustion engines. In the past, it was mostly used as rocket propellant or as an explosives [1,2]. Nitromethane is an energetic compound with a wide variety of applications, including its use as a monopropellant, a liquid explosive, a solvent for chemical processing and analysis, and a highperformance fuel additive for internal combustion engines and pulsed detonation engines [3]. The chemical formula of nitromethane is CH3NO2. As the name suggests, the molecule is essentially methane with one of the four hydrogens replaced by a nitro group. In essence, it is the simplest of possible energetic CHON molecules that contain nitro groups, which is why it is often used in reaction studies as a prototype for more complex energetic materials. There is no reliable kinetic model for nitromethane combustion, which is validated over a wide range of experimental conditions. There are a few published studies [4-8] both numerically and experimentally focusing often on a single reactor at very specific conditions. The aim of the present work is to extend our recently published mechanism [9] for syngas, methane and ammonia oxidation to include CH3NO2 as fuel and validate against the available experimental data from the literature. The development and compilation strategy for our mechanism is described in our recent work [9] and this study is conducted in a similar manner. Rates are taken mainly from [7,10-16]. This makes the kinetic model more robust and reliable for combustion modelling.}, language = {en} } @misc{ShresthaSeidelMaussetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Mauß, Fabian and Zeuch, Thomas}, title = {Kinetic Modeling for NOx prediction with improved base Chemistry}, series = {COST 1404, SMARTCATs, Chemistry of smart energy carriers and technologies, 3rd General Meeting and Workshop on SECs in Industry of SMARTCATs Action}, journal = {COST 1404, SMARTCATs, Chemistry of smart energy carriers and technologies, 3rd General Meeting and Workshop on SECs in Industry of SMARTCATs Action}, language = {en} } @misc{LeonRuweMoshammeretal., author = {Le{\´o}n, Larisa and Ruwe, Lena and Moshammer, Kai and Seidel, Lars and Shrestha, Krishna Prasad and Wang, Xiaoxiao and Mauß, Fabian and Kohse-H{\"o}inghaus, Katharina and Hansen, Nils}, title = {Chemical insights into the larger sooting tendency of 2-methyl-2-butene compared to n-pentane}, series = {Combustion and Flame}, volume = {208}, journal = {Combustion and Flame}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2019.06.029}, pages = {182 -- 197}, abstract = {A comprehensive, chemically detailed mechanism for the combustion of 2-methyl-2-butene and n-pentane is presented to provide insights into the different sooting tendencies of these two structurally different C5 hydrocarbons. A hierarchically assembled mechanism has been developed to specifically target speciation data from low-pressure premixed flames of 2-methyl-2-butene [Ruwe et al., Combust. Flame, 175, 34-46, 2017] and newly measured mole fraction data for a fuel-rich (ɸ=1.8) n-pentane flame, in which species profiles up to phenol were quantified. The partially isomer-resolved chemical composition of this flame was determined using flame-sampling molecular-beam mass spectrometry with single-photon ionization by tunable, synchrotron-generated vacuum-ultraviolet radiation. The presented model, which includes a newly determined, consistent set of the thermochemistry data for the C5 species, presents overall satisfactory capabilities to predict the mole fraction profiles of common combustion intermediates. The analysis of the model predictions revealed the fuel-structure dependencies (i.e. saturated vs. unsaturated and linear vs. branched) of the formation of small aromatic species that are considered as soot precursors. The propensity of the 2-methyl-2-butene flame to form larger concentrations of aromatic species was traced back to the readily available formation routes of several small precursor molecules and the efficient formation of "first aromatic rings" beyond benzene.}, language = {en} } @misc{ShresthaEckartElbazetal., author = {Shrestha, Krishna Prasad and Eckart, Sven and Elbaz, Ayman M. and Giri, Binod Raj and Fritsche, Chris and Seidel, Lars and Roberts, William L. and Krause, Hartmut and Mauß, Fabian}, title = {A comprehensive kinetic model for dimethyl ether and dimethoxymethane oxidation and NOx interaction utilizing experimental laminar flame speed measurements at elevated pressure and temperature}, series = {Combustion and Flame}, volume = {218}, journal = {Combustion and Flame}, issn = {1556-2921}, doi = {10.1016/j.combustflame.2020.04.016}, pages = {57 -- 74}, abstract = {Laminar flame speeds of dimethyl ether and dimethoxymethane at pressures from 1 to 5 bar and initial temperatures from 298 to 373 K were determined experimentally using a constant volume spherical vessel and a heat flux burner setup. This study is the first to report dimethoxymethane laminar flame speeds at a pressure higher than 1 bar. Using these experimental data along with data available in the literature, a new kinetic model for the prediction of the oxidation behavior of dimethyl ether and dimethoxymethane in freely propagating and burner stabilized premixed flames, in shock tubes, rapid compression machines, flow reactors, and a jet-stirred reactor has been developed. The experimental results from the present work and literature are interpreted with the help of the derived kinetic model. This newly developed reaction mechanism considers the redox chemistry of NOx to accommodate the influence of the oxygen level on the onset of fuel conversion and interconversion of NO and NO2. The current model suggests that an increased O2 level promotes the HO2 production, which in turn leads to the formation of OH radicals, which promotes the combustion of the fuel/air mixture under lean conditions. The increase of OH radical concentrations is mainly via the NO/NO2 interconversion reaction channel, NO+HO2=NO2+OH, NO2+H=NO+OH, CH3OCH3+NO2=CH3OCH2+HONO, followed by the thermal decomposition of HONO. This work extends the kinetic database and helps to improve the understanding of dimethyl ether and dimethoxymethane combustion behavior. The kinetic model presented in this work can serve as a base model for hydrocarbons and oxygenated fuels higher than C2.}, language = {en} } @misc{FrankenSeidelMatriscianoetal., author = {Franken, Tim and Seidel, Lars and Matrisciano, Andrea and Mauß, Fabian and Kulzer, Andre Casal and Schuerg, Frank}, title = {Analysis of the Water Addition Efficiency on Knock Suppression for Different Octane Ratings}, series = {SAE World Congress}, journal = {SAE World Congress}, issn = {2688-3627}, doi = {10.4271/2020-01-0551}, pages = {5}, abstract = {Water injection can be applied to spark ignited gasoline engines to increase the Knock Limit Spark Advance and improve the thermal efficiency. The Knock Limit Spark Advance potential of 6 °CA to 11 °CA is shown by many research groups for EN228 gasoline fuel using experimental and simulation methods. The influence of water is multi-layered since it reduces the in-cylinder temperature by vaporization and higher heat capacity of the fresh gas, it changes the chemical equilibrium in the end gas and increases the ignition delay and decreases the laminar flame speed. The aim of this work is to extend the analysis of water addition to different octane ratings. The simulation method used for the analysis consists of a detailed reaction scheme for gasoline fuels, the Quasi-Dimensional Stochastic Reactor Model and the Detonation Diagram. The detailed reaction scheme is used to create the dual fuel laminar flame speed and combustion chemistry look-up tables. The Detonation Diagram is used as a novel approach in the Quasi-Dimensional Stochastic Reactor Model to evaluate the auto-ignition characteristic in the end gas and determine if it is a harmless deflagration or developing detonation. First, the Quasi-Dimensional Stochastic Reactor Model is trained for three engine operating points and a RON95 E10 fuel. Its performance is evaluated based on experimental results of a single cylinder research engine. Subsequently, different spark timings and water-fuel ratios are investigated for different Primary Reference Fuels. The results outline that water addition can effectively reduce the strength of auto-ignition in the end gas for different Primary Reference Fuels. Thereby, it can be stated that the reduction of the auto-ignition strength through water addition by 50 - 80 \% water-fuel ratio for high octane number fuels corresponds to the spark timing delay of 6 °CA or an increase of research octane number by 10 points.}, language = {en} } @misc{FrankenMaussSeideletal., author = {Franken, Tim and Mauß, Fabian and Seidel, Lars and Gern, Maike Sophie and Kauf, Malte and Matrisciano, Andrea and Kulzer, Andre Casal}, title = {Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry}, series = {International Journal of Engine Research}, volume = {21}, journal = {International Journal of Engine Research}, number = {10}, issn = {2041-3149}, doi = {10.1177/1468087420933124}, pages = {1857 -- 1877}, abstract = {This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and coworkers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at l = 1 at full load using water-fuel ratios of up to 60\% or cooled low-pressure exhaust gas recirculation rates of up to 30\%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air-fuel ratio and water injection, the indicated efficiency is improved to 40\% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air-fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43\% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30\% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions.}, language = {en} } @misc{ShresthaLhuillierBarbosaetal., author = {Shrestha, Krishna Prasad and Lhuillier, Charles and Barbosa, Amanda Alves and Brequigny, Pierre and Contino, Francesco and Mouna{\"i}m-Rousselle, Christine and Seidel, Lars and Mauß, Fabian}, title = {An experimental and modeling study of ammonia with enriched oxygen content and ammonia/hydrogen laminar flame speed at elevated pressure and temperature}, series = {Proceedings of the Combustion Institute}, volume = {2020}, journal = {Proceedings of the Combustion Institute}, issn = {1540-7489}, doi = {10.1016/j.proci.2020.06.197}, pages = {1 -- 12}, abstract = {Laminar flame speeds of ammonia with oxygen-enriched air (oxygen content varying from 21 to 30 vol.\%) and ammonia-hydrogen-air mixtures (fuel hydrogen content varying from 0 to 30 vol.\%) at elevated pressure (1-10 bar) and temperature (298-473 K) were determined experimentally using a constant volume combustion chamber. Moreover, ammonia laminar flame speeds with helium as an inert were measured for the first time. Using these experimental data along with published ones, we have developed a newly compiled kinetic model for the prediction of the oxidation of ammonia and ammonia-hydrogen blends in freely propagating and burner stabilized premixed flames, as well as in shock tubes, rapid compression machines and a jet-stirred reactor. The reaction mechanism also considers the formation of nitrogen oxides, as well as the reduction of nitrogen oxides depending on the conditions of the surrounding gas phase. The experimental results from the present work and the literature are interpreted with the help of the kinetic model derived here. The experiments show that increasing the initial temperature, fuel hydrogen content, or oxidizer oxygen content causes the laminar flame speed to increase, while it decreases when increasing the initial pressure. The proposed kinetic model predicts the same trends than experiments and a good agreement is found with measurements for a wide range of conditions. The model suggests that under rich conditions the N2H2 formation path is favored compared to stoichiometric condition. The most important reactions under rich conditions are: NH2+NH=N2H2+H, NH2+NH2=N2H2+H2, N2H2+H=NNH+H2 and N2H2+M=NNH+H+M. These reactions were also found to be among the most sensitive reactions for predicting the laminar flame speed for all the cases investigated.}, language = {en} } @misc{IssayevGiriElbazetal., author = {Issayev, Gani and Giri, Binod Raj and Elbaz, Ayman M. and Shrestha, Krishna Prasad and Mauß, Fabian and Roberts, William L. and Farooq, Aamir}, title = {Combustion behavior of ammonia blended with diethyl ether}, series = {Proceedings of the Combustion Institute}, volume = {38 (2021)}, journal = {Proceedings of the Combustion Institute}, number = {1}, issn = {1540-7489}, doi = {10.1016/j.proci.2020.06.337}, pages = {499 -- 506}, abstract = {Ammonia (NH3) is recognized as a carbon-free hydrogen-carrier fuel with a high content of hydrogen atoms per unit volume. Recently, ammonia has received increasing attention as a promising alternative fuel for internal combustion engine and gas turbine applications. However, the viability of ammonia fueling future combustion devices has several barriers to overcome. To overcome the challenge of its low reactivity, it is proposed to blend it with a high-reactivity fuel. In this work, we have investigated the combustion characteristics of ammonia/diethyl ether (NH3/DEE) blends using a rapid compression machine (RCM) and a constant volume spherical reactor (CVSR). Ignition delay times (IDTs) of NH3/DEE blends were measured using the RCM over a temperature range of 620 to 942 K, pressures near 20 and 40 bar, equivalence ratios (Φ) of 1 and 0.5, and a range of mole fractions of DEE, χDEE, from 0.05 to 0.2 (DEE/NH3 = 5 - 20\%). Laminar burning velocities of NH3/DEE premixed flames were measured using the CVSR at 298 K, 1 bar, Φ of 0.9 to 1.3, and χDEE from 0.1 to 0.4. Our results indicate that DEE promotes the reactivity of fuel blends resulting in significant shortening of the ignition delay times of ammonia under RCM conditions. IDTs expectedly exhibited strong dependence on pressure and equivalence ratio for a given blend. Laminar burning velocity was found to increase with increasing fraction of DEE. The burnt gas Markstein length increased with equivalence ratio for χDEE = 0.1 as seen in NH3-air flames, while the opposite evolution of Markstein length was observed with Φ for 0.1 < χDEE ≤ 0.4, as observed in isooctane-air flames. A detailed chemical kinetics model was assembled to analyze and understand the combustion characteristics of NH3/DEE blends.}, language = {en} } @misc{ElbazGiriIssayevetal., author = {Elbaz, Ayman M. and Giri, Binod Raj and Issayev, Gani and Shrestha, Krishna Prasad and Mauß, Fabian and Farooq, Aamir and Roberts, William L.}, title = {Experimental and Kinetic Modeling Study of Laminar Flame Speed of Dimethoxymethane and Ammonia Blends}, series = {Energy \& Fuels}, volume = {34}, journal = {Energy \& Fuels}, number = {11}, issn = {1520-5029}, doi = {10.1021/acs.energyfuels.0c02269}, pages = {14727 -- 14740}, abstract = {Ammonia (NH3) is considered a promising carbon-neutral fuel, with a high hydrogen content, that can diversify the global energy system. Blending ammonia with a highly reactive fuel is one possible strategy to enhance its combustion characteristics. Here, an investigation of blends of NH3 and dimethoxymethane (DMM), a biofuel with high fuel-born oxygen content and no carbon-carbon bonds, is reported. Unstretched laminar burning velocity (SL) and Markstein length of different NH3/DMM blends were experimentally determined using spherically propagating premixed flames. The DMM mole fraction was varied from 0.2 to 0.6 while measuring SL at 298 K, 0.1 MPa, and equivalence ratios (Φ) over the range of 0.8-1.3. The addition of DMM was found to immensely enhance the combustion characteristics of ammonia. DMM 20\% (by mole fraction) in the NH3/DMM blend increased SL by more than a factor of 3 over neat ammonia; such enhancement was found to be comparable to 60\% CH4 in NH3 (Φ = 0.9-1.1) blends. Increasing Φ was found to significantly decrease the burned gas Markstein length for lean cases, whereas a negligible effect was observed for rich mixtures. A composite chemical kinetic model of DMM/NH3, aimed at interpreting the high-temperature combustion chemistry, was able to reliably predict SL for neat NH3 and DMM flames. Also, the predictive capability of the kinetic model to describe SL for DMM/NH3 blends is reasonably good. Sensitivity analysis and reaction path analysis indicated that the NH3/DMM blends could be understood as dual oxidation processes of the individual fuels that are competing for the same radical pool.}, language = {en} } @misc{VanTreekRothSeideletal., author = {Van Treek, Lisa and Roth, Norbert and Seidel, Lars and Mauß, Fabian}, title = {Measurements of the laminar burning velocities of rich ethylene/air mixtures}, series = {Fuel}, volume = {275}, journal = {Fuel}, issn = {0016-2361}, doi = {10.1016/j.fuel.2020.117938}, pages = {9}, abstract = {Laminar burning velocities of premixed ethylene/air flames were investigated under fuel lean and rich conditions. The laminar burning velocities were measured with the heat flux method at atmospheric pressure and unburnt gas temperatures of 298 K. The measurements have been performed for the equivalence ratio range of Φ = 0.7-2.5 using stabilized and flat flames on a perforated burner plate under adiabatic conditions. This is the first time that experimental measurements with the heat flux method of the ethylene/air flames under super fuel rich conditions are performed. The experimental data were compared against predictions using three different kinetic models and published flame speed. The measured flame speeds agree with other published data within the error margin. The experimental and predicted laminar flames do agree at fuel lean conditions, but there are some notable discrepancies under fuel rich conditions.}, language = {en} } @misc{NetzerLiSeideletal., author = {Netzer, Corinna and Li, Tian and Seidel, Lars and Mauß, Fabian and L{\o}v{\aa}s, Terese}, title = {Stochastic Reactor-Based Fuel Bed Model for Grate Furnaces}, series = {Energy \& Fuels}, volume = {34}, journal = {Energy \& Fuels}, number = {12}, issn = {1520-5029}, doi = {10.1021/acs.energyfuels.0c02868}, pages = {16599 -- 16612}, abstract = {Biomass devolatilization and incineration in grate-fired plants are characterized by heterogeneous fuel mixtures, often incompletely mixed, dynamical processes in the fuel bed and on the particle scale, as well as heterogeneous and homogeneous chemistry. This makes modeling using detailed kinetics favorable but computationally expensive. Therefore, a computationally efficient model based on zero-dimensional stochastic reactors and reduced chemistry schemes, consisting of 83 gas-phase species and 18 species for surface reactions, is developed. Each reactor is enabled to account for the three phases: the solid phase, pore gas surrounding the solid, and the bulk gas. The stochastic reactors are connected to build a reactor network that represents the fuel bed in grate-fired furnaces. The use of stochastic reactors allows us to account for incompletely mixed fuel feeds, distributions of local temperature and local equivalence ratio within each reactor and the fuel bed. This allows us to predict the released gases and emission precursors more accurately than if a homogeneous reactor network approach was employed. The model approach is demonstrated by predicting pyrolysis conditions and two fuel beds of grate-fired plants from the literature. The developed approach can predict global operating parameters, such as the fuel bed length, species release to the freeboard, and species distributions within the fuel bed to a high degree of accuracy when compared to experiments.}, language = {en} } @misc{ShresthaSeidelZeuchetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Zeuch, Thomas and Mor{\´e}ac, Gladys and Dagaut, Philippe and Mauß, Fabian}, title = {On the implications of nitromethane - NOx chemistry interactions for combustion processes}, series = {Fuel}, volume = {289}, journal = {Fuel}, issn = {0016-2361}, doi = {10.1016/j.fuel.2020.119861}, pages = {8}, abstract = {In this work, we report a detailed investigation of the CH3NO2 chemistry effect on fuel-NO interactions for the fuels methane and n-heptane using a recently developed and extensively validated H2/O2/CO/NOx/NH3/CH3NO2 baseline chemistry. In general, the model predictions show good agreement with temperature profiles of major and intermediate species in jet-stirred reactor experiments and they capture the subtle effect of NO addition. For both fuels, the CH3NO2 kinetics retard the system reactivity in the low temperature range by delaying the production of key radicals like OH and HO2. This explains the retarding effect of NO for n-heptane low temperature ignition and the overprediction of reactivity enhancement by NO in earlier studies on methane combustion. For methane, the recently explored roaming mediated dissociation channel of CH3NO2 to CH3O + NO is a major reaction pathway for CH3NO2 consumption. Our analysis suggests that at higher pressure, relevant to engine conditions, the two key intermediate species HONO and CH3NO2 feature strongly increased concentrations during n-heptane combustion and they may be detectable under such conditions in combustion experiments of this fuel-NOx system. The results of this work call for detailed future investigations of the CH3NO2 chemistry effect in the context of exhaust gas recirculation, also with regard to the suppression of engine knock.}, language = {en} } @misc{FrankenSeidelShresthaetal., author = {Franken, Tim and Seidel, Lars and Shrestha, Krishna Prasad and Gonzalez Mestre, Laura Catalina and Mauß, Fabian}, title = {Multi-objective Optimization of Gasoline, Ethanol, and Methanol in Spark Ignition Engines}, abstract = {In this study, an engine and fuel co-optimization is performed to improve the efficiency and emissions of a spark ignition engine utilizing detailed reaction mechanisms and stochastic combustion modelling. The reaction mechanism for gasoline surrogates (Seidel 2017), ethanol, and methanol (Shrestha et al. 2019) is validated for experiments at different thermodynamic conditions. Liquid thermophysical properties of the RON95E10 surrogate (iso-octane, n-heptane, toluene, and ethanol mixture), ethanol, and methanol are determined using the NIST standard reference database (NIST 2018) and Yaws database (Yaws 2014). The combustion chemistry, laminar flame speed, and thermophysical data are pre-compiled in look-up tables to speed up the simulations (tabulated chemistry). The auto-ignition in the stochastic reactor model is predicted by the detailed chemistry and subsequently evaluated using the Bradley Detonation Diagram (Bradley et al. 2002, Gu et al. 2003, Neter 2019), which assigns two dimensionless parameters (resonance parameter and reactivity parameter). According to the defined developing detonation limits, the auto-ignition is either in deflagration, sub-sonic auto-ignition, or developing detonation mode. Ethanol and methanol show a knock-reducing characteristic, which is mainly due to the high heat of vaporization. The multi-objective optimization process includes mathematical algorithms for design space exploration with Uniform Latin Hypercube, pareto front convergence with Non-dominated Sorting Genetic Algorithm II (NSGA-II), and multi-criteria decision making (Deb et al. 2002). The optimization input parameter ranges are selected according to the previous sensitivity analysis, and the objectives are to minimize specific CO2 and specific CO and maximize indicated efficiency. The performance study of different optimization algorithms shows that the incorporation of metamodels is beneficial to improve the design space exploration, while keeping the optimization duration low. The comparison of different reaction mechanisms, which are applied in the optimization process, shows a strong impact on the pareto front solutions. This is due to differences in the emission formation and auto-ignition between the different reaction schemes. Overall, the engine efficiency is increased by 3.5 \% points, and specific CO2 emissions are reduced by 99 g/kWh for ethanol and 142 g/kWh for methanol combustion compared to the base case. This is achieved by advanced spark timing, lean combustion, and reduced C:H ratio of ethanol and methanol in relation to RON95E10.}, language = {en} } @misc{ShresthaGiriAdiletal., author = {Shrestha, Krishna Prasad and Giri, Binod Raj and Adil, Mohammad and Seidel, Lars and Zeuch, Thomas and Farooq, Aamir and Mauß, Fabian}, title = {Detailed Chemical Kinetic Study of Acetaldehyde Oxidation and Its Interaction with NOx}, series = {Energy \& fuels}, volume = {35}, journal = {Energy \& fuels}, number = {18}, issn = {1520-5029}, doi = {10.1021/acs.energyfuels.1c01948}, pages = {14963 -- 14983}, abstract = {This work entails a detailed modeling and experimental study for the oxidation kinetics of acetaldehyde (CH3CHO) and its interaction with NOx. The ignition behavior of CH3CHO/O2/Ar has been investigated in a shock tube over the temperature range of 1149 to 1542 K, with equivalence ratios of 0.5 and 1.0 and pressures near 1.2 bar. Absorbance-time profiles of acetaldehyde were recorded using a mid-IR laser during the autoignition measurements. A comprehensive kinetic model has been developed to quantitatively predict the oxidation of acetaldehyde and its interaction with NOx. The kinetic model has been validated using experimental data of this work and available literature data from shock tube, plug flow, and jet-stirred reactors, freely propagating, and burner-stabilized premixed flames. For better accuracy of the kinetic model, the thermochemistry of 14 important species in the acetaldehyde submechanism was calculated using ab initio methods. The heat of formation of these species was computed using atomization and isodesmic reaction schemes. For the first time, this modeling study examines the effect of NO on acetaldehyde oxidation behavior over a wide range of experimental conditions. In most cases, the proposed kinetic model captures the experimental trends remarkably well. Interestingly, the doping of NO in CH3CHO did not perturb the NTC behavior of CH3CHO in contrast to other fuels, such as n-heptane and dimethyl ether. However, for flow reactor conditions at 1 atm, doping with 504 ppm of NO was found to promote the reactivity of acetaldehyde by lowering the onset temperature for CH3CHO oxidation by ∼140 K. The hydroxyl radical is the main cause of this shift, which originates from the NO + HO2 = OH + NO2 reaction. Further evolution of hydroxyl radicals occurs via the "NO-NO2" looping mechanism and expedites the reactivity of the system. This experimental and modeling work sheds new light on acetaldehyde oxidation behavior and its interaction with NOx under combustion-relevant conditions.}, language = {en} } @misc{IssayevGiriElbazetal., author = {Issayev, Gani and Giri, Binod Raj and Elbaz, Ayman M. and Shrestha, Krishna Prasad and Mauß, Fabian and Roberts, William L. and Farooq, Aamir}, title = {Ignition delay time and laminar flame speed measurements of ammonia blended with dimethyl ether: A promising low carbon fuel blend}, series = {Renewable Energy}, volume = {181}, journal = {Renewable Energy}, issn = {1879-0682}, doi = {10.1016/j.renene.2021.09.117}, pages = {1353 -- 1370}, abstract = {Ammonia (NH3) has recently received much attention as a promising future fuel for mobility and power generation. The use of ammonia as a fueling vector can help curb global warming by cutting CO2 emissions because it is a carbon-free fuel and a hydrogen carrier with a high percentage of hydrogen atoms per unit volume. Liquid ammonia contains a higher volumetric density of hydrogen than liquid hydrogen. The low reactivity of ammonia, however, hinders its direct usage as a combustible fuel. One feasible way to boost the reactivity of ammonia is to target a dual-fuel system comprising of ammonia and a suitable combustion promoter. In this work, combustion properties of ammonia were investigated by blending it with various proportions of dimethyl ether (DME) using a rapid compression machine (RCM) and a constant volume spherical reactor (CVSR) over a wide range of experimental conditions. DME is a highly reactive fuel that may be produced in a sustainable carbon cycle with a net zero-carbon emission. Ignition delay times (IDTs) of NH3/DME blends were measured over a temperature (T) range of 649e950 K, pressures (P) of 20 and 40 bar, equivalence ratios (F) of 0.5 and 1 for a range of DME mole fractions (cDME) of 0.05e0.5 in the blends. In addition, the laminar burning velocities of NH3/DME blends were measured at P ¼ 1, 3 and 5 bar, F ¼ 0.8e1.3 and T ¼ 300 K for cDME ranging from 0.18 to 0.47. Our results suggest that DME is a good ignition promoter, resulting in a significant shortening of IDTs and an increase of flame speeds of NH3. A detailed chemical model has been developed and validated against the experimental data. Overall, our kinetic model offered reasonable predictive capabilities capturing the experimental trends over a wide range of conditions. In the worst-case scenario, our model underpredicted IDTs by a factor of ~2.5 while overpredicting laminar flame speed by ~20\%.}, language = {en} } @misc{FrankenMatriscianoSarietal., author = {Franken, Tim and Matrisciano, Andrea and Sari, Rafael and Robles, Alvaro Fogue and Monsalve-Serrano, Javier and Pintor, Dario Lopez and Pasternak, Michal and Garcia, Antonio and Mauß, Fabian}, title = {Modeling of Reactivity Controlled Compression Ignition Combustion Using a Stochastic Reactor Model Coupled with Detailed Chemistry}, series = {SAE technical papers : 15th International Conference on Engines \& Vehicles}, journal = {SAE technical papers : 15th International Conference on Engines \& Vehicles}, issn = {0148-7191}, doi = {10.4271/2021-24-0014}, pages = {18}, abstract = {Advanced combustion concepts such as reactivity controlled compression ignition (RCCI) have been proven to be capable of fundamentally improve the conventional Diesel combustion by mitigating or avoiding the soot-NOx trade-off, while delivering comparable or better thermal efficiency. To further facilitate the development of the RCCI technology, a robust and possibly computationally efficient simulation framework is needed. While many successful studies have been published using 3D-CFD coupled with detailed combustion chemistry solvers, the maturity level of the 0D/1D based software solution offerings is relatively limited. The close interaction between physical and chemical processes challenges the development of predictive numerical tools, particularly when spatial information is not available. The present work discusses a novel stochastic reactor model (SRM) based modeling framework capable of predicting the combustion process and the emission formation in a heavy-duty engine running under RCCI combustion mode. The combination of physical turbulence models, detailed emission formation sub-models and stateof-the-art chemical kinetic mechanisms enables the model to be computationally inexpensive compared to the 3D-CFD approaches. A chemical kinetic mechanism composed of 248 species and 1428 reactions was used to describe the oxidation of gasoline and diesel using a primary reference fuel (PRF)mixture and n-heptane, respectively. The model is compared to operating conditions from a single-cylinder research engine featuring different loads, speeds, EGR and gasoline fuel fractions. The model was found to be capable of reproducing the combustion phasing as well as the emission trends measured on the test bench, at some extent. The proposed modeling approach represents a promising basis towards establishing a comprehensive modeling framework capable of simulating transient operation as well as fuel property sweeps with acceptable accuracy.}, language = {en} } @misc{ShresthaGiriSeideletal., author = {Shrestha, Krishna Prasad and Giri, Binod Raj and Seidel, Lars and Farooq, Aamir and Mauß, Fabian}, title = {A Kinetic Modeling Study for the Effect of NOx on Oxymethylene ethers (OMEn, n = 0 and 1) oxidation}, series = {10th European Combustion Meeting, Neapel}, journal = {10th European Combustion Meeting, Neapel}, address = {Neapel}, abstract = {We present a detailed kinetic model for the oxidation of dimethyl ether (OME0) and dimethoxymethane (OME1) in presence of NOx. We further explored the effect of NOx chemistry on the oxidation kinetics of the two OMEs. Our kinetic model is validated against the recent flow reactor data from Zhang et al. (Combust. Flame. 224 (2021) 94- 107). The results indicated that NO doping severely alters the oxidation kinetics of both fuels. The onset temperature for total fuel consumption is significantly shifted to lower temperatures for both fuels, which is in line with the experimental observation. We found that the addition of NO significantly inhibited the NTC behaviour of dimethyl ether. This inhibiting effect appears to stem from the competition between CH3OCH2O2 radical consumption by NO directly and the isomerization/dissociation reactions of CH3OCH2O2. Unlike dimethyl ether, dimethoxymethane does not exhibit a strong NTC behavior, and NO addition completely inhibited its weak NTC behavior.}, language = {en} } @misc{ShresthaGiriElbazetal., author = {Shrestha, Krishna Prasad and Giri, Binod Raj and Elbaz, Ayman M. and Issayev, Gani and Roberts, William L. and Seidel, Lars and Mauß, Fabian and Farooq, Aamir}, title = {A detailed chemical insights into the kinetics of diethyl ether enhancing ammonia combustion and the importance of NOx recycling mechanism}, series = {Fuel Communications}, volume = {10}, journal = {Fuel Communications}, issn = {2666-0520}, doi = {10.1016/j.jfueco.2022.100051}, pages = {18}, abstract = {In this work, we investigated the combustion characteristics of ammonia (NH3) by blending it with various proportions of diethyl ether (DEE). We measured laminar flame speed of various NH3/DEE blends (DEE, 10-40\% by mole) using a constant volume spherical vessel at Ti = 298 K and Pi = 3 and 5 bar and Φ = 0.8-1.3. We developed a detailed kinetic model to describe the trends of the current and previously published experimental data. For the robustness of the model, we first developed a comprehensive diethyl ether kinetic mechanism to accurately characterize neat DEE oxidation behavior. We validated the kinetic model using a large pool of experimental data comprising shock tube, rapid compression machine, jet-stirred and flow reactors, freely propagating, and burner-stabilized premixed flames. The developed kinetic model performs remarkably in capturing the combustion behavior of pure DEE and NH3. Importantly, our model captures the experimental data of laminar flame speed and ignition delay times of various NH3/DEE blends over a wide range of conditions. We found that DEE is a promising candidate to promote the combustion characteristics of NH3. A small portion of DEE (10\%) enhances the laminar flame speed of NH3 by a factor of 2 at Pi = 1 bar, Ti = 298 K, and Φ = 1.0. A further doubling of the DEE mole fraction to 20\% did not enhance the laminar flame speed of NH3 with the same propensity. At low temperatures, adding 5\% DEE in NH3 blend has significantly expedited the system reactivity by lowering the autoignition temperature. A further 5\% increment of DEE (i.e., 10\% DEE in NH3) lowers the autoignition temperature by ∼120 K to achieve the same ignition delay time. The "NOsingle bondNO2" looping mechanism predominantly drives such reactivity accelerating effect. Here, the reactions, NO + HO2 = NO2 + OH and NO2 + H = NO + OH, appear to enhance the reactive radical pool by generating OH radicals. We observed that the HNO path is favored more with increasing DEE content which eventually liberates NO. Other key reactions in "NOsingle bondNO2" looping mechanism are: CH3 + NO2 = CH3O + NO, CH3O2 + NO = CH3O + NO2, C2H5 + NO2 = C2H5O + NO, C2H5O2 + NO = C2H5O + NO2. In addition, CH3 + NH2(+M) = CH3NH2(+M) reaction is also one of the important cross-reactions which leads to the formation of HCN. Therefore, cross-reactions between the nitrogen and carbon family are crucial in accurately predicting autoignition timing. This work provides a detailed chemical insight into the NH3 and DEE interaction, which could be applied to other fuel blends of NH3. The kinetic model is also validated for several C1single bondC3 fuels including their interaction with NOx.}, language = {en} } @misc{FritscheEckartShresthaetal., author = {Fritsche, Chris and Eckart, Sven and Shrestha, Krishna Prasad and Mauß, Fabian and Krause, Hartmut}, title = {Methane flames with a substitution of 50 to 100 percent hydrogen: Experimental and numerical investigation of the temperature and pressure dependence of the laminar burning velocities}, series = {10th European Combustion Meeting, Proceedings of the European Combustion Meeting}, journal = {10th European Combustion Meeting, Proceedings of the European Combustion Meeting}, abstract = {This work reports the laminar burning velocities for CH4/H2 blends in mixtures with air utilizing the constant volume chamber at temperatures from 300 to 423 K, pressures from 2 to 10 bar and equivalence ratios from 0.7 to 2.4. A detailed chemical kinetic model based on our previous work is used to reproduce the experimental data. The chemical kinetic model can reproduce the experimental data better at lean conditions compared to rich conditions. It is observed that with an increase in H2 fraction in fuel blend, laminar burning velocities increase. Model reveals that with increasing H2 fraction in the fuel blend, formation of key radicals H, OH and O are promoted leading to higher laminar burning velocities. The most sensitive reactions are O2+H=OH+O, CO+OH=CO2+H, CH4+H=CH3+H2 and CH4+OH=CH3+H2O. It is found that as initial mixture temperature increases, the laminar burning velocity increases and shows a linear trend whereas this trend is reversed as the initial pressure increases.}, language = {en} } @misc{FritscheShresthaEckartetal., author = {Fritsche, Chris and Shrestha, Krishna Prasad and Eckart, Sven and Mauß, Fabian and Krause, Hartmut}, title = {Temperature and pressure dependency of the burning velocity in laminar premixed methanol and polyoxymethylene dimethyl ether (OME1, OME2, and OME3) flames}, series = {10th European Combustion Meeting, Proceedings of the European Combustion Meeting}, journal = {10th European Combustion Meeting, Proceedings of the European Combustion Meeting}, abstract = {This work reports the laminar burning velocities (LBV) for the liquid fuels methanol, and polyoxymethylene dimethyl ethers (OMEn, n = 1-3) in mixtures with air utilizing the heat flux burner and constant volume chamber at temperature 393 to 443 K, pressure 1 to 10 bar, and equivalence ratio 0.6 to 1.9. Laminar burning velocities for OME2 and OME3 higher than 1 bar are reported for the first time. A detailed chemical kinetic model for OME2 and OME3 was developed based on our previous work utilizing experimental data from this work. Overall, model predictions are in good agreement with the experimental data. It is previously shown that with increases in unburned gas temperature laminar burning velocity increases and shows a linear trend with respect to temperature. Further, laminar burning velocity decreases with an increase of initial pressure. The dependence of burning velocity is not linear for all the fuels investigated. For comparable temperature and pressure conditions, it was found that with an additional CH2O group the laminar burning velocities increase marginally and there is no shift of maximum laminar burning velocity with respect to equivalence ratio.}, language = {en} } @misc{ShresthaSeidelZeuchetal., author = {Shrestha, Krishna Prasad and Seidel, Lars and Zeuch, Thomas and Mauß, Fabian}, title = {Modeling of NOx Formation and Consumption during Oxidation of Small Alcohols}, series = {9th European Combustion Meeting, Proceedings of the European Combustion Meeting}, journal = {9th European Combustion Meeting, Proceedings of the European Combustion Meeting}, pages = {6}, abstract = {This work presents a newly developed kinetic mechanism extending our recent work (Shrestha et al. [1]) for the oxidation of methanol and ethanol and their fuel interaction with NO x chemistry in jet-stirred reactors, flow reactors, and burner-stabilized premixed flames. The work mainly focuses on fuel interaction with nitrogen chemistry and NO formation in laminar premixed flames. It is found that for methanol oxidation in jet-stirred reactor doping of the fuel blends with NO increase the reactivity of the system by increasing the net production of OH radicals. The increased amount of OH is formed via NO/NO 2 interconversion reaction channels NO+HO 2 ⇋NO 2 +OH, NO 2 +H⇋NO+OH, NO 2 +HO 2 ⇋HONO+O 2, followed by the thermal decomposition of HONO producing NO and OH. In burner-stabilized premixed flames studied here for methanol/air and ethanol/air, NO is mainly formed via the NCN route (CH+N 2 ⇋NCN+H) and minor contribution comes from the NNH route (NNN⇋N 2 +H).}, language = {en} } @misc{RakhiGuentherRichteretal., author = {Rakhi, Rakhi and G{\"u}nther, Vivien and Richter, Jana and Mauß, Fabian}, title = {Steam reforming of methane over nickel catalyst using a one-dimensional model}, series = {International Journal of Environmental Sciences}, volume = {5}, journal = {International Journal of Environmental Sciences}, number = {1}, issn = {2519-5549}, doi = {10.47604/ijes.1520}, pages = {1 -- 32}, abstract = {Steam reforming of hydrocarbons is a well established chemical process which provides synthesis gas (H2 and CO). These synthesis products can hence be converted to numerous valuable basic chemicals. For the industrial application of steam reforming, a detailed understanding of the process is a prerequisite. Models that capture the detailed homogeneous and heterogeneous reaction kinetics and the comprehensive transport processes as well as their interaction have the potential to optimize the catalytic process without expensive experimental campaigns. In this paper, a detailed investigation has been done using a multi-step reaction mechanism for modeling steam reforming of methane over nickel-based catalyst using a one-dimensional (1D) model, LOGEcat [1]. The model is applicable to the simulation of all standard after-treatment catalytic processes of combustion exhaust gas along with other chemical processes involving heterogeneous catalysis, such as, the Sabatier process [27]. It is a 1D tool, thus is computationally cost effective and is based on a series of perfectly stirred reactors (PSR). The model is used to perform the simulations for various reactor conditions in terms of temperature, pressure, flow rates and steam-to-carbon (S/C) ratio. Several chemical reaction terms, such as, selectivity, yield, conversion, and mole fraction have been shown with respect to the varied parameters and the results are compared with 2D simulations and experimental reference data. We report a very good agreement of the various profiles produced with 1D model as compared to the reference data. Note that the main aim of this study is to check how far the 1D model can capture the basic chemistry for modeling steam reforming of methane over nickel-based catalysts. It is interesting to note that the cost effective reduced order model is capable to capture the physics and chemistry involved with a multi-step reaction mechanism showing the predictive capability of the model. This study forms the basis for further analysis towards the thermochemistry of the species to develop a kinetically consistent reaction mechanism.}, language = {en} } @misc{RakhiShresthaGuentheretal., author = {Rakhi, Rakhi and Shrestha, Krishna Prasad and G{\"u}nther, Vivien and Mauß, Fabian}, title = {Thermodynamic analysis to develop a detailed surface reaction mechanism}, series = {Fuel Science - From Production to Propulsion, Aachen, Germany, May 2022}, journal = {Fuel Science - From Production to Propulsion, Aachen, Germany, May 2022}, pages = {2}, abstract = {The reduction of greenhouse gasses such as CO2 and CH4 is becoming necessary due to global environmental problems. The reforming of light hydrocarbons is a particularly efficient process for producing synthesis gas, H2 and CO, from greenhouse gasses [1]. The steam reforming of methane is the most important method to produce syngas in industry by using a nickel catalyst. Nickel-based catalysts are the conventional catalysts in industrial applications due to their fast turnover rates, good availability, and low costs, however, limited by their tendency towards coke formation. In this study, a detailed surface reaction mechanism is developed for steam reform-ing of methane over nickel and results are compared with the reference data.}, language = {en} } @misc{PicernoLeePasternaketal., author = {Picerno, Mario and Lee, Sung-Yong and Pasternak, Michal and Siddareddy, Reddy Babu and Franken, Tim and Mauß, Fabian and Andert, Jakob}, title = {Real-Time Emission Prediction with Detailed Chemistry under Transient Conditions for Hardware-in-the-Loop Simulations}, series = {Energies}, volume = {15}, journal = {Energies}, number = {1}, issn = {1996-1073}, doi = {10.3390/en15010261}, pages = {1 -- 21}, abstract = {The increasing requirements to further reduce pollutant emissions, particularly with regard to the upcoming Euro 7 (EU7) legislation, cause further technical and economic challenges for the development of internal combustion engines. All the emission reduction technologies lead to an increasing complexity not only of the hardware, but also of the control functions to be deployed in engine control units (ECUs). Virtualization has become a necessity in the development process in order to be able to handle the increasing complexity. The virtual development and calibration of ECUs using hardware-in-the-loop (HiL) systems with accurate engine models is an effective method to achieve cost and quality targets. In particular, the selection of the best-practice engine model to fulfil accuracy and time targets is essential to success. In this context, this paper presents a physically- and chemically-based stochastic reactor model (SRM) with tabulated chemistry for the prediction of engine raw emissions for real-time (RT) applications. First, an efficient approach for a time-optimal parametrization of the models in steady-state conditions is developed. The co-simulation of both engine model domains is then established via a functional mock-up interface (FMI) and deployed to a simulation platform. Finally, the proposed RT platform demonstrates its prediction and extrapolation capabilities in transient driving scenarios. A comparative evaluation with engine test dynamometer and vehicle measurement data from worldwide harmonized light vehicles test cycle (WLTC) and real driving emissions (RDE) tests depicts the accuracy of the platform in terms of fuel consumption (within 4\% deviation in the WLTC cycle) as well as NOx and soot emissions (both within 20\%).}, language = {en} } @misc{FrankenSrivastavaLeeetal., author = {Franken, Tim and Srivastava, Vivek and Lee, Sung-Yong and Heuser, Benedikt and Shrestha, Krishna Prasad and Seidel, Lars and Mauß, Fabian}, title = {Numerical Analysis of the Combustion of Diesel, Dimethyl Ether, and Polyoxymethylene Dimethyl Ethers (OMEn, n=1-3) Using Detailed Chemistry}, series = {THIESEL 2022 : Conference on Thermo- and Fluid-Dynamics of Clean Propulsion Powerplants, 13th-16th September 2022 : conference proceedings}, journal = {THIESEL 2022 : Conference on Thermo- and Fluid-Dynamics of Clean Propulsion Powerplants, 13th-16th September 2022 : conference proceedings}, editor = {Xandra, Margot and Payri, Ra{\´u}l and Serrano, Jos{\´e} Ram{\´o}n}, publisher = {Editorial Universitat Polit{\`e}cnica de Val{\`e}ncia}, address = {Val{\`e}ncia}, isbn = {978-84-1396-055-5}, doi = {10.4995/Thiesel.2022.632801}, abstract = {New types of synthetic fuels are introduced in internal combustion engine applications to achieve carbon-neutral and ultra-low emission combustion. Dimethyl Ether (DME) and Polyoxymethylene Dimethyl Ethers (OMEn) belong to such kind of synthetic fuels. Recently, Shrestha et al. (2022) have developed a novel detailed chemistry model for OMEn (n=1-3) to predict the ignition delay time, laminar flame speed and species formation for various thermodynamic conditions. The detailed chemistry model is applied in the zero dimensional (0D) stochastic reactor model (DI-SRM) to investigate the non-premixed combustion in a 2-liter diesel engine. Further insights in the formation of unburned hydrocarbons (HC), carbon monoxide and nitrogen oxides during the combustion of OMEn fuels are obtained in this work. The combustion and emission formation of DME and OMEn (n=1-3) are investigated and compared to conventional Diesel combustion. The mixture formation is governed by an earlier vaporization of the DME and OMEn fuels, faster homogenization of the respective air-fuel mixture and higher reactivity. At the same injection pressure, the OMEn fuels obtain higher NOx but lower CO and HC emissions. High amounts of aromatics, ethene, methane formaldehyde and formic acid are found within the Diesel exhaust gas. The DME and OMEn exhaust gas contains higher fractions of formaldehyde and formic acid, and fractions of methane, methyl formate and nitromethane.}, language = {en} } @misc{FrankenShresthaSeideletal., author = {Franken, Tim and Shrestha, Krishna Prasad and Seidel, Lars and Mauß, Fabian}, title = {Effect of Gasoline-Ethanol-Water Mixtures on Auto-Ignition in a Spark Ignition Engine}, series = {International Conference on Knocking in Gasoline Engines}, journal = {International Conference on Knocking in Gasoline Engines}, editor = {Sens, Marc}, publisher = {expert}, address = {T{\"u}bingen}, isbn = {978-3-8169-3544-5}, doi = {10.24053/9783816985440}, pages = {175 -- 222}, abstract = {The climate protection plan of the European Union requires a significant reduction of CO2 emissions from the transportation sector by 2030. Today ethanol is already blended by 10vol-\% in gasoline and further increase of the ethanol content to 20vol-\% is discussed. During the ethanol production process, distillation and molecular sieving is required to remove the water concentration to achieve high-purity ethanol. However, hydrous ethanol can be beneficial to suppress knock of spark ignition engines. The hygroscopic nature of ethanol can allow to increase the water content in gasoline - water emulsions even more, without adding additional surfactants, and improve the thermal efficiency by optimized combustion phasing, while keeping the system complexity low. Hence, the effect of gasoline - ethanol - water mixtures on the auto-ignition in a single-cylinder spark ignition engine is investigated by using multi-dimensional simulation and detailed chemistry. The gasoline - ethanol mixtures are defined to keep the Research Octane Number constant, while the Motored Octane Number is decreasing. In total five surrogates are defined and investigated: E10 (10vol-\% ethanol-in-gasoline), E20, E30, E70 and E100. The water content is determined according to experimentally defined ternary diagrams that evaluated stable gasoline - ethanol - water emulsion at different gasoline - ethanol blending ratios. The auto-ignition modes of the surrogates are analyzed using the diagram, which determines if hotspots are within harmless deflagration or harmful developing detonation regime. The strongest auto-ignition is observed for the E10 surrogate, while increasing ethanol content reduces the surrogate reactivity and increases the resonance parameter. No auto-ignition of the unburnt mixture is observed for the E70 and E100 surrogates. The addition of hydrous ethanol decreased the excitation time of the surrogates, especially at low ethanol content, wherefor the reactivity parameter is significantly increased. The hotspots for E10, E20 and E30 surrogates with hydrous ethanol are found within the developing detonation regime, while hotspots of the E70 surrogate with hydrous ethanol are found in the transition regime. For the hydrous E100 surrogate no auto-ignition is predicted because of reduced temperature of the unburnt mixture due to water vaporization, which outweighs the increased reactivity due to water vapor addition.}, language = {en} } @misc{GiriShresthaMaietal., author = {Giri, Binod Raj and Shrestha, Krishna Prasad and Mai, Tam V.-T. and Giri, Sushant and Adil, Mohammad and Naik, R. Thirumaleswara and Mauß, Fabian and Huynh, Lam Kim}, title = {A Theoretical Study of NH2 Radical Reactions with Propane and Its Kinetic Implications in NH3-Propane Blends' Oxidation}, series = {Energies}, volume = {16}, journal = {Energies}, number = {16}, issn = {1996-1073}, doi = {10.3390/en16165943}, abstract = {The reaction of NH2 radicals with C3H8 is crucial for understanding the combustion behavior of NH3/C3H8 blends. In this study, we investigated the temperature dependence of the rate coefficients for the hydrogen abstraction reactions of C3H8 by NH2 radicals using high-level theoretical approaches. The potential energy surface was constructed at the CCSD(T)/cc-pV(T, Q)//M06-2X/aug-cc-pVTZ level of theory, and the rate coefficients were computed using conventional transition state theory, incorporating the corrections for quantum tunneling and hindered internal rotors (HIR). The computed rate coefficients showed a strong curvature in the Arrhenius behavior, capturing the experimental literature data well at low temperatures. However, at T > 1500 K, the theory severely overpredicted the experimental data. The available theoretical studies did not align with the experiment at high temperatures, and the possible reasons for this discrepancy are discussed. At 300 K, the reaction of NH2 with C3H8 predominantly occurs at the secondary C-H site, which accounts for approximately 95\% of the total reaction flux. However, the hydrogen abstraction reaction at the primary C-H site becomes the dominant reaction above 1700 K. A composite kinetic model was built, which incorporated the computed rate coefficients for NH2 + C3H8 reactions. The importance of NH2 + C3H8 reactions in predicting the combustion behavior of NH3/C3H8 blends was demonstrated by kinetic modeling.}, language = {en} } @misc{ElbazGiriShresthaetal., author = {Elbaz, Ayman M. and Giri, Binod Raj and Shrestha, Krishna Prasad and Arab, Omar Z. and Farooq, Aamir and Mauß, Fabian and Roberts, William L.}, title = {A comprehensive experimental and kinetic modeling study of laminar flame propagation of ammonia blended with propene}, series = {Combustion and Flame}, volume = {253}, journal = {Combustion and Flame}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2023.112791}, abstract = {Enhancement of ammonia reactivity is crucial for potential applications of ammonia as an engine and gas turbine fuel. A common strategy for improving ammonia's poor reactivity is blending it with more reactive fuels like hydrogen and methane. However, fundamental studies of ammonia combustion with higher hydrocarbons and key intermediate oxidation species of higher alkanes such as propene do not exist. Thus, this work presents an effort to study the laminar flame propagation of ammonia blended with propene. Laminar burning velocity (SL) of NH3/C3H6/air mixtures was measured at 298 K, pressures up to 5 bar, equivalence ratios of 0.7 to 1.3, and various propene to ammonia ratios (i.e.,\% propene to ammonia mole fraction, xC3H6 = 10 to 50) in a high-pressure spherical propagating flame vessel. A kinetic model was developed based on our previous work to characterize the combustion behavior of NH3/C3H6/air mixture. The model reasonably agrees with the experimental data and follows the observed trends very well. The results showed that blending NH3 with C3H6 positively enhanced SL of NH3 by promoting the formation of key radicals e.g., O, OH, and H. Relative to a neat ammonia/air mixture, co-firing ammonia with propene leads to a reduced pressure dependence of the laminar burning velocity. However, the reaction H + O2(+M)=HO2(+M) leads to strong pressure dependency of lean NH3/C3H6 mixtures compared to rich mixtures. The model reveals that besides fuel-NO coming from NH3, prompt NO also actively contributes to NO formation. It is seen that N2O formation is significantly suppressed with increasing pressure or increasing C3H6 content in the fuel blend. In contrast to NO and N2O, NO2 concentration increases slightly with an increase in pressure. The reported experimental data and model will be useful in understanding the interaction between NH3 and alkenes.}, language = {en} } @misc{ShresthaMaiGirietal., author = {Shrestha, Krishna Prasad and Mai, Tam V.-T. and Giri, Sushant and Giri, Binod Raj and Huynh, Lam Kim and Mauss, Fabian}, title = {Reaction Kinetics of NH2 Radicals with Dimethyl Ether (DME) and Diethyl Ether (DEE) and Their Implications in NH3-DME/DEE blend modeling}, series = {Los Alamos National Laboratory (LANL)}, journal = {Los Alamos National Laboratory (LANL)}, number = {LA-UR-23-26969}, abstract = {The reactions of amino radicals (NH2) play a vital role in governing the combustion behaviour of various nitrogen-rich chemical systems such as ammonia, coal nitrogen gasification, and biomass. Ammonia has recently gained considerable attention in the combustion community. Since it is a carbon-free fuel, it can help combat global warming by decarbonizing the energy sectors. However, several reports in the literature highlight the importance of the NH3-dual fuel approach to boost the combustion properties of neat ammonia. For combustion modeling of NH3-dual fuel systems, accurate knowledge of the cross-reactions between the nitrogen and carbon family is very critical. Several earlier studies have shown the influence of NH2 radical reactions with the fuel (combustion promoter) in accurately predicting the low- temperature combustion behaviour of NH3-dual fuels (see Giri et al. and references cited therein). The reactions of NH2 radicals are not only important in the combustion environment but also, they are relevant to the chemistry of planetary atmospheres. In this work, we investigated the hydrogen abstraction reactions of NH2 radials with dimethyl ether (DME) and diethyl ether (DEE) using a high-level quantum method combined with the statistical rate theory. We implemented the derived rate coefficients in our kinetic model to identify its effect in the combustion modeling of NH3-DME/DEE blends.}, language = {en} } @misc{GiriShresthaMaietal., author = {Giri, Binod Raj and Shrestha, Krishna Prasad and Mai, Tam V.-T. and Mauß, Fabian and Huynh, Lam Kim}, title = {A theoretical kinetic study of the reactions of NH2 radicals with methanol and ethanol and their implications in kinetic modeling}, series = {International Journal of Chemical Kinetics}, volume = {55}, journal = {International Journal of Chemical Kinetics}, number = {1}, issn = {0538-8066}, doi = {10.1002/kin.21609}, pages = {3 -- 14}, abstract = {Amino (NH2) radicals play a central role in the pyrolysis and oxidation of ammonia. Several reports in the literature highlight the importance of the reactions of NH2 radicals with fuel in NH3-dual-fuel combustion. Therefore, we investigated the reactions of NH2 radicals with methanol (CH3OH) and ethanol (C2H5OH) theoretically. We explored the various reaction pathways by exploiting CCSD(T)/cc-pV(T, Q)Z//M06-2X/aug-cc-pVTZ level of theory. The reaction proceeds via complex formation at the entrance and exit channels in an overall exothermic process. We used canonical transition state theory to obtain the high-pressure limiting rate coefficients for various channels over the temperature range of 300-2000 K. We discerned the role of various channels in the potential energy surface (PES) of NH2 + CH3OH/C2H5OH reactions. For both reactions, the hydrogen abstraction pathway at the OH-site of alcohols plays a minor role in the entire T-range investigated. By including the title reactions into an extensive kinetic model, we demonstrated that the reaction of NH2 radicals with alcohols plays a paramount role in accurately predicting the low-temperature oxidation kinetics of NH3-alcohols dual fuel systems (e.g., shortening the ignition delay time). On the contrary, these reactions have negligible importance for high-temperature oxidation kinetics of NH3-alcohol blends (e.g., not affecting the laminar flame speed). In addition, we calculated the rate coefficients for NH2 + CH4 = CH3 + NH3 reaction that are in excellent agreement with the experimental data.}, language = {en} } @misc{ShresthaEckartDrostetal., author = {Shrestha, Krishna Prasad and Eckart, Sven and Drost, Simon and Fritsche, Chris and Schießl, Robert and Seidel, Lars and Maas, Ulrich and Krause, Hartmut and Mauß, Fabian}, title = {A comprehensive kinetic modeling of oxymethylene ethers (OMEn, n= 1-3) oxidation-laminar flame speed and ignition delay time measurements}, series = {Combustion and Flame}, volume = {246}, journal = {Combustion and Flame}, issn = {1556-2921}, doi = {10.1016/j.combustflame.2022.112426}, abstract = {This work reports on the development and experimental validation of a detailed reaction mechanism for the oxidation of polyoxymethylene dimethyl ethers (OMEn, n = 1-3). The validation is done by constant-volume chamber laminar flame speeds (393 K and 443 K, 1 to 5 bar, and equivalence ratio 0.8 to 1.6) and Rapid Compression Machine ignition delay times (550-680 K, 10 and 15 bar, equivalence ratios of 0.5-2.0) in OMEn/air mixtures. Using our new experimental and published data, the validation basis for the new kinetic model comprises the pyrolysis and oxidation of OMEn (n = 1-3) in freely propagating flames, auto-ignition in rapid compression machines and shock tubes, and speciation in jet-stirred and flow reactors as well as burner-stabilized premixed flames. The model provides a reasonable agreement with the experimental data for a broad range of conditions investigated. The performance of the developed model is compared against the recent literature models. OMEn (n = 1-3) all have the same laminar flame speed. The model suggests that the chemistry of OME0 (DME) and CH3OCHO (methyl formate) is the one that dictates the flame chemistry. Under the same pressure and equivalence ratio conditions, ignition delay times of OME2 and OME3 are similar for the investigated temperature range. This work helps to improve the understanding of OMEs chemistry. The model developed in this work will serve as the base mechanism for higher chain length OMEs (n>3).}, language = {en} } @misc{ShresthaElbazGirietal., author = {Shrestha, Krishna Prasad and Elbaz, Ayman M. and Giri, Binod Raj and Arab, Omar Z. and Adil, Mohammad and Seidel, Lars and Roberts, William L. and Farooq, Aamir and Mauß, Fabian}, title = {Experimental and Kinetic Modeling Study of 1, 3-Dioxolane Oxidation and Comparison with Dimethoxymethane}, series = {Energy \& Fuels}, volume = {36}, journal = {Energy \& Fuels}, number = {14}, issn = {1520-5029}, doi = {10.1021/acs.energyfuels.2c01132}, pages = {7744 -- 7754}, abstract = {This work reports laminar flame speeds and ignition delay times of 1,3-dioxolane/O2/inert gases over a wide range of conditions. Laminar flame speeds were determined experimentally at pressures of 1 and 3 bar, the temperature of 300 K, and equivalence ratios ranging from 0.7 to 1.4 using a constant-volume spherical chamber, whereas ignition delay times were measured in a shock tube at a pressure of 1 bar, the temperature range of 1000-1265 K, and equivalence ratios of 0.5 and 1.0. A detailed kinetic model is developed to predict the oxidation of 1,3-dioxolane utilizing our new experimental data and published datasets on the oxidation of 1,3-dioxolane in freely propagating flames, autoignition in rapid compression machines and shock tubes, and speciation in a jet-stirred reactor. Model predictions are in reasonable agreement with the experimental data. Laminar flame speeds and ignition delay times of 1,3-dioxolane (cyclic ether) are compared with those of dimethoxymethane (acyclic ether). It is found that 1,3-dioxolane has a higher laminar flame speed than that of dimethoxymethane, which may be attributed to the formation of C2H4, C2H2, and the H atom from 1,3-dioxolane. On the contrary, ignition delay times of 1,3-dioxolane are longer than those of dimethoxymethane below 1000 K and shorter above 1000 K for the same dilution level. The reaction ȮCHO = CO2 + H is critical for accurately predicting 1,3-dioxolane oxidation, and it significantly influences model predictions under low-pressure conditions. The model developed in this work will serve as the base mechanism for higher cyclic and acyclic ethers.}, language = {en} } @misc{RakhiGiriGuentheretal., author = {Rakhi, Rakhi and Giri, Binod Raj and G{\"u}nther, Vivien and Mauss, Fabian}, title = {Investigation dry reforming of methane over nickel using a one-dimensional model}, series = {PAMM}, volume = {23}, journal = {PAMM}, number = {4}, doi = {10.1002/pamm.202300266}, pages = {8}, abstract = {In the field of catalysis, dry reforming, that is, methane reforming with CO2, is in the focus due to growing environmental concerns about oil depletion and global warming with a desire to produce synthesis gas. However, this process can lead to the formation of carbon, which can cause catalyst deactivation, especially at industrial conditions. Nevertheless, the key to develop a more coke-resistant catalyst is a better comprehension of the reforming process at a molecular level. Regardless of all the investigations available in literature, the detailed path for the conversion of methane to syngas and carbon remains a controversial issue. Another problem in setting up a reaction mechanism is the difficulty to define the thermodynamic data for intermediate surface species and this leads to the development of thermodynamic consistent surface reaction mechanisms in literature where the thermodynamic data are not used to calculate the rate coefficients of the reverse reactions. Rather the Arrhenius parameters for the forward as well as backward reactions are explicitly given in the reaction mechanism to establish thermodynamic equilibrium. In this investigation, a kinetically consistent detailed surface reaction mechanism is developed which consists of 26 reversible reactions with the help of a one-dimensional model, LOGEcat. Our previous work constructs the basis of the present investigation. Further, a detailed sensitivity analysis of reversible reactions and reaction pathways is performed to understand the mechanism better. The mechanism is validated for dry reforming of methane over nickel catalyst, however, it can also be used for other processes, such as, steam reforming and partial oxidation. The mechanism is tested by comparing the simulation results with the literature experiments and simulations in a wide range of temperature. The new developed kinetically consistent surface reaction mechanism is able to accurately express the dry reforming of methane over the nickel catalyst for complete range of temperature and also provide a useful insight into the key rate determining steps.}, language = {en} } @misc{RakhiGiriGuentheretal., author = {Rakhi, Rakhi and Giri, Binod Raj and G{\"u}nther, Vivien and Mauss, Fabian}, title = {Insight into the thermodynamic model for reforming of methane over nickel catalyst}, series = {Proceedings of the 64th International Conference of Scandinavian Simulation Society, SIMS 2023 V{\"a}ster{\aa}s, Sweden, September 25-28, 2023}, journal = {Proceedings of the 64th International Conference of Scandinavian Simulation Society, SIMS 2023 V{\"a}ster{\aa}s, Sweden, September 25-28, 2023}, doi = {10.3384/ecp200025}, pages = {192 -- 197}, abstract = {The reforming of light hydrocarbons to produce synthesis gas, H2 and CO, is an important intermediate for manufacturing valuable basic chemicals and synthesis fuels. In order to understand these reforming processes better, elementary step reaction mechanisms are developed. In the available literature, the surface reaction mechanisms are usually achieved with the help of reaction kinetic parameters without using the thermochemistry of the species referred to kinetic models due to the unavailability of the thermochemistry of the intermediate species involved in the multi-step reaction mechanism. In this work, investigations are made to obtain the thermochemistry of the intermediate species to establish thermodynamic equilibrium in order to develop a thermodynamic model for steam reforming of methane over nickel. The thermochemistry of the surface bound species is taken from different sources available in the literature and after that a detailed sensitivity analysis is performed to match the results with experiments. The simulation set up is adapted from the literature experiments given in [1]. The results produced with the one-dimensional tool using the thermodynamic model developed in the present investigation consisting of 21 reversible reactions are compared with the kinetic scheme with 42 irreversible reactions from reference simulation along with their experimental results. Both the models show some major differences in the reaction pathways which provides a useful insight into the key rate determining steps and needs further investigations.}, language = {en} } @misc{FotiadisAsimakopoulouBaltzopoulouetal., author = {Fotiadis, Kyriakos and Asimakopoulou, Akrivi and Baltzopoulou, Penelope and Kastrinaki, Georgia and Koutsonikolas, Dimitrios and Karagiannakis, George and Skevis, George and Richter, Jana and Mauß, Fabian}, title = {Experimental Characterization of a Novel Foam Burner Design for the Low-Excess-Enthalpy Combustion of Very Lean Syngas Mixtures}, series = {Energies}, volume = {16}, journal = {Energies}, number = {19}, issn = {1996-1073}, doi = {/10.3390/en16197014}, pages = {7014}, abstract = {In the present work, a novel foam burner design is proposed and experimentally evaluated for operation with highly diluted syngas mixtures. The lab-scale burner consists of a purpose-built, square-shaped, high-temperature-grade stainless steel tubular reactor filled with square-sectioned siliconized silico carbide (SiSiC) foams. The assembly was installed in an electrical furnace. Spatially resolved temperature measurements were obtained along the reactor axis, while simultaneous measurements of CO, CO2, H2, O2, and N2 were taken at the burner exit and the water levels were recorded upstream and downstream of the reactor. The results clearly show that flames can be stabilized along the reactor for a range of foam characteristics and operating conditions. Hydrogen conversion efficiencies in excess of 98\%, and overall thermal efficiencies close to 95\% were achieved for the selected operating conditions. Overall, the denser 10 ppi foam demonstrated superior combustion characteristics in terms of stability, lower enthalpy rises, and a wider operating range at the expense of a very modest pressure drop penalty. Finally, scanning electron microscopy, coupled with energy dispersion spectroscopy (SEM/EDS) and Raman spectroscopy analyses, was used to determine the morphological and compositional characteristics of the pristine and aged foams. After more than 100 h of operation, no significant performance degradation was observed, even though the burner design was subjected to considerable thermal stress.}, language = {en} } @misc{RossiBargendeKulzeretal., author = {Rossi, Edoardo and Bargende, Michael and Kulzer, Andr{\´e} Casal and Chiodi, Marco and Massoud, Ehab and Shrestha, Krishna Prasad and Mauß, Fabian}, title = {Analysis of the applicability of Water Injection in Combination with an eFuel for Knock Mitigation and Improved Engine Efficiency}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, issn = {2688-3627}, doi = {10.4271/2022-37-0019}, abstract = {The development of future gasoline engines is dominated by the study of new technologies aimed at reducing the engine negative environmental impact and increase its thermal efficiency. One common trend is to develop smaller engines able to operate in stoichiometric conditions across the whole engine map for better efficiency, lower fuel consumption, and optimal conversion rate of the three-way catalyst (TWC). Water injection is one promising technique, as it significantly reduces the engine knock tendency and avoids fuel enrichment for exhaust temperature mitigation at high power operation. With the focus on reducing the carbon footprint of the automotive sector, another vital topic of research is the investigation of new alternative CO2-neutral fuels or so-called eFuels. Several studies have already shown how these new synthetic fuels can be produced by exploiting renewable energy sources and can significantly reduce engine emissions. This work is part of the FVV project number 1367, "Water Injection in Spark-Ignition Engines II", which investigates the coexistence of two different engine technologies that heads towards the same direction of sustainability of the internal combustion engine: water injection and eFuels. The goal is to assess the advantages that the adoption of an eFuel in combination with water injection strategies can bring, with respect to the same strategies applied in combination with commercial gasoline. Several water injection strategies, including direct water injection, indirect water injection, injection timing, and pressure variations, are considered for a better understanding of the benefits brought by the combination of an eFuel with water injection. For this purpose, experimental tests and 3D-CFD engine simulations have been performed. The physical properties of the investigated eFuel have been experimentally measured for accurate modelling in the simulation environment, and the thermodynamic properties have been evaluated utilizing detailed chemistry calculations.}, language = {en} } @misc{DongAulGregoireetal., author = {Dong, Shijun and Aul, Christopher and Gregoire, Claire and Cooper, Sean P. and Mathieu, Olivier and Petersen, Eric L. and Rodriguez, Jose and Mauß, Fabian and Wagnon, Scott W. and Kukkadapu, Goutham and Pitz, William J. and Curran, Henry J.}, title = {A comprehensive experimental and kinetic modeling study of 1-hexene}, series = {Combustion and Flame}, volume = {232}, journal = {Combustion and Flame}, issn = {1556-2921}, doi = {10.1016/j.combustflame.2021.111516}, abstract = {It is important to understand the low-temperature chemistry of 1-hexene as it is used as a representative alkene component in gasoline surrogate fuels. Ignition delay times (IDTs) of 1-hexene measured in rapid compression machines (RCMs) can be used to validate its low-temperature chemistry. However, volume history profiles are not available for published RCM IDT data. This has restricted the validation of the low-temperature chemistry of 1-hexene at engine-relevant conditions (i.e. at low temperatures and high pressures). Thus, new RCM IDT data with associated volume history profiles are needed. In this study, both an RCM and a high-pressure shock tube (ST) are employed to measure IDTs of 1-hexene at equivalence ratios of 0.5, 1.0 and 2.0 in 'air' and at pressures of 15 and 30 atm. A cool-flame (first stage) and total (second stage) ignition was observed in the RCM experiments. Moreover, carbon monoxide and water versus time histories produced during 1-hexene oxidation at highly diluted conditions were measured in a ST. A new detailed chemical kinetic model describing 1-hexene oxidation is proposed and validated using these new measured data together with various experimental data available in the literature. The kinetic model can predict well the auto-ignition behavior and oxidation processes of 1-hexene at various conditions. The rate constants and branching ratio for hydroxyl radical addition to the double bond of 1-hexene are particularly important and discussed based on the experimental and theoretically calculated results from previous studies as well as validation results from jet-stirred reactor (JSR) species profiles. Flux and sensitivity analyses are performed to determine the important reaction classes for 1-hexene oxidation and show that the reactions associated with hydroxy radical addition to the double bond contribute most to the low-temperature reactivity of 1-hexene. In the negative temperature coefficient (NTC) regime, the isomerization of hexenyl-peroxy radicals promotes fuel reactivity due to its associated chain branching pathways.}, language = {en} }