@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{GernKaufVaccaetal., author = {Gern, Maike Sophie and Kauf, Georg Malte and Vacca, Antonino and Franken, Tim and Kulzer, Andr{\´e} Casal}, title = {Ganzheitliche Methode zur Bewertung der Wassereinspritzung}, series = {MTZ - Motortechnische Zeitschrift}, volume = {80}, journal = {MTZ - Motortechnische Zeitschrift}, number = {7-8}, issn = {2192-8843}, doi = {10.1007/s35146-019-0070-x}, pages = {124 -- 129}, abstract = {Die k{\"u}nftige Effizienzsteigerung bei Ottomotoren mit Direkteinspritzung sowie die Reduktion von gas- und partikelf{\"o}rmigen Emissionen erfordern innovative Ans{\"a}tze. Durch die neue RDEGesetzgebung f{\"u}r leichte Kraftfahrzeuge verschiebt sich der Fokus hin zu dynamischen Testzyklen mit 12 \% mehr Hochlastbetriebspunkten im Vergleich zum WLTC (Worldwide harmonized Light Duty Test Cycle). Die Steigerung des Mitteldrucks bei Ottomotoren f{\"u}hrt zu einem effizienten Betrieb, der jedoch durch das Risiko irregul{\"a}rer Verbrennung und hohen Abgastemperaturen limitiert ist. Durch den Einsatz von Wassereinspritzung k{\"o}nnen sowohl die Klopfneigung als auch die Abgastemperatur reduziert werden, was den Schutz der Abgasnachbehandlungskomponenten bei gleichzeitiger Wirkungsgradsteigerung erm{\"o}glicht. Im Rahmen des FVV-Projekts „Wassereinspritzung bei Ottomotoren" wird der Einfluss der NiederdruckWassereinspritzung (NDWE) und Hochdruck-Wassereinspritzung (HDWE) untersucht. Insbesondere die Auswirkungen auf Gemischbildung, Verbrennung und Abgasnachbehandlung werden durch die Vernetzung von Experiment und Simulation analysiert.}, language = {de} } @misc{VaccaBargendeChiodietal., author = {Vacca, Antonino and Bargende, Michael and Chiodi, Marco and Netzer, Corinna and Gern, Maike Sophie and Kauf, Georg Malte and Kulzer, Andr{\´e} Casal and Franken, Tim}, title = {Analysis of Water Injection Strategies to Exploit the Thermodynamic Effects of Water in Gasoline Engines by Means of a 3D-CFD Virtual Test Bench}, publisher = {SAE International}, address = {Neapel}, doi = {10.4271/2019-24-0102}, abstract = {CO2 emission constraints taking effect from 2020 lead to further investigations of technologies to lower knock sensitivity of gasoline engines, main limiting factor to increase engine efficiency and thus reduce fuel consumption. Moreover the RDE cycle demands for higher power operation, where fuel enrichment is needed for component protection. To achieve high efficiency, the engine should be run at stoichiometric conditions in order to have better emission control and reduce fuel consumption. Among others, water injection is a promising technology to improve engine combustion efficiency, by mainly reducing knock sensitivity and to keep high conversion rates of the TWC over the whole engine map. The comprehension of multiple thermodynamic effects of water injection through 3D-CFD simulations and their exploitation to enhance the engine combustion efficiency is the main purpose of the analysis. As basis for the research a single cylinder engine derived from a 1l turbocharged 3-cylinders engine is used to evaluate indirect and direct water injection. The entire engine flow field is reproduced and analyzed with 3D-CFD simulations and numerical models are employed to separate the influence of chemical and thermodynamic properties. Measurements are performed with different injectors for indirect/direct water injection in the single-cylinder engine in order to assess water break-up, wall wetting, spray interaction and penetration. Several injection strategies, such as varying start of injection, injection pressure, and water to fuel ratio, are tested at the single-cylinder engine test bench. Detailed gas phase chemistry is employed to link flame front speed with water concentration and knocking occurrence. These results are correlated with the 3D-CFD simulation of mixture formation, in-cylinder flow and water distribution for two different operating points (part load and maximum power) in order to study water behavior, with focus on the evaporation process, in-cylinder pressure and temperature profile, as well as the combustion development, during multiple engine cycles.}, 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} }