@misc{KurapatiBorgSeideletal., author = {Kurapati, Vinaykumar Reddy and Borg, Anders and Seidel, Lars and Mauß, Fabian}, title = {Fast CFD Diesel engine modelling using the 1-Dimentional SprayLet approach}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, number = {2024-01-2684}, issn = {0148-7191}, abstract = {In the SAE article 2023-24-0083: SprayLet: One-dimensional interactive cross-sectionally averaged spray model, we formulatet a one-dimensional Spray model in interaction with the surrounding gas phase. We could demonstrate, that the model predicted liquid and gaseous penetration length in good aggreement with ECN spray experiments. In this paper we use this model in engine CFD (CONVERGE CFD) and demonstrate a strong reduction in CPU time (50\%). We can show a strong decrease in grid dependency, which allows a further reduction of CPU time (90\%). We will present engine CFD simulations, comparing detailed spray with SpayLet simulations. This includes pressure traces, heat release, and emissions.}, language = {en} } @misc{KurapatiBorgSeideletal., author = {Kurapati, Vinaykumar Reddy and Borg, Anders and Seidel, Lars and Mauß, Fabian}, title = {SprayLet: One-Dimensional Interactive Cross-Sectionally Averaged Spray Model}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, issn = {0148-7191}, doi = {10.4271/2023-24-0083}, abstract = {Spray modeling is among the main aspects of mixture formation and combustion in internal combustion engines. It plays a major role in pollutant formation and energy efficiency although adequate modeling is still under development. Strong grid dependence is observed in the droplet-based stochastic spray model commonly used. As an alternative, an interactive model called 'SprayLet' is being developed for spray simulations based on one-dimensional integrated equations for the gas and liquid phases, resulting from cross-sectionally averaging of multi-dimensional transport equations to improve statistical convergence. The formulated one-dimensional cross-section averaged system is solved independently of the CFD program to provide source terms for mass, momentum and heat transfer between the gas and liquid phases. The transport processes take place in a given spray cone where the nozzle exit is automatically resolved. In the 1D program, the conservation equations are for droplet diameter, droplet temperature, as well as for continuity and momentum of the liquid and the gaseous phase are solved. The source terms between the phases are conservatively embedded into the spray region of the CFD program. In CFD program, the transport equations are solved for gas phase only. The SprayLet model is validated using standard Sandia sprays by comparing penetration lengths and fuel mixture fractions with experimental data.}, language = {en} } @misc{MannaSabiaShresthaetal., author = {Manna, Maria Virginia and Sabia, Pino and Shrestha, Krishna Prasad and Seidel, Lars and Ragucci, Raffaele and Mauß, Fabian and De Joannon, Mara}, title = {NH3NO interaction at low-temperatures: an experimental and modeling study}, series = {Proceedings of the Combustion Institute}, volume = {39}, journal = {Proceedings of the Combustion Institute}, number = {1}, issn = {1873-2704}, doi = {10.1016/j.proci.2022.09.027}, pages = {775 -- 784}, abstract = {The present work provides new insight into NH3single bondNO interaction under low-temperature conditions. The oxidation process of neat NH3 and NH3 doped with NO (450, 800 ppm) was experimentally investigated in a Jet Stirred Flow Reactor at atmospheric pressure for the temperature range 900-1350 K. Results showed NO concentration is entirely controlled by DeNOx reactions in the temperature range 1100-1250 K, while NH3single bondNO interaction does not develop through a sensitizing NO effect, for these operating conditions. A detailed kinetic model was developed by systematically updating rate constants of controlling reactions and declaring new reactions for N2H2 isomers (cis and trans). The proposed mechanism well captures target species as NO and H2 profiles. For NH3single bondNO mixtures, NO profiles were properly reproduced through updated DeNOx chemistry, while NH2 recombination reactions were found to be essential for predicting the formation of H2. The role of ammonia as a third-body species is implemented in the updated mechanism, with remarkable effects on species predictions. For neat NH3 mixture, the reaction H+O2(+M)=HO2(+M) was crucial to predict NO formation via the reaction NH2+HO2double bondH2NO+OH.}, language = {en} } @misc{MantePrehnTheileetal., author = {Mante, Till and Prehn, Sascha and Theile, Martin and Seidel, Lars and Mestre, Laura and Buchholz, Bert and Mauß, Fabian}, title = {Investigation of An Ammonia Diesel Dual-Fuel Combustion Process on a Heavy-Duty Single Cylinder Research Engine for the Development of Suitable Simulation Tools for Maritime Applications}, series = {Heavy-Duty-, On- und Off-Highway-Motoren 2022 : Stand der Energiewende im Heavy-Duty-Bereich}, journal = {Heavy-Duty-, On- und Off-Highway-Motoren 2022 : Stand der Energiewende im Heavy-Duty-Bereich}, editor = {Heintzel, Alexander}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41477-1}, doi = {10.1007/978-3-658-41477-1_3}, pages = {24 -- 39}, abstract = {This paper discusses the adaption of a single cylinder research engine for a retrofit application with an ammonia diesel dual-fuel combustion process and the build of an ammonia fuel system. The gaseous ammonia will be injected in the air intake pipe and the premixed ammonia air mixture will enter the combustion chamber. The diesel injection is carried out via a high-pressure common rail system. All relevant parameters can be freely adjusted via a freely programmable control unit. With the help of experimental data from a single cylinder research engine at the chair of piston machines and internal combustion engines of the University of Rostock (LKV), a dual-fuel combustion model based on detailed chemistry will be developed and optimized. This model will be integrated in a full research engine model, which ensures the best possible representation of the real engine. The combustion model is being developed by LOGE Deutschland GmbH. The full research engine model is developed by FVTR GmbH. The analysis of the combustion process starts with pure diesel operating points and is successively substituted by ammonia in the course of the measurement campaigns. Both the combustion characteristics are relevant, as they significantly influence the resulting performance and engine operation, as well as the exhaust emissions, as the carbon emissions can be reduced, but the nitrogen oxides and ammonia slip increase significantly in relevance due to the ammonia. The results obtained will be used to derive initial recommendations for action and to estimate the potential for application in the inland waterway shipping. In addition, the development of the systematic simulation tools covers a broad spectrum of research questions and aims to increase the efficiency of the necessary R\&D.}, language = {en} } @misc{Turquandd'AuzayShapiroProuvieretal., author = {Turquand d'Auzay, Charles and Shapiro, Evgeniy and Prouvier, Matthieu and Winkler, Axel and Seidel, Lars and Borg, Anders and Mauß, Fabian}, title = {Evaluation of Fast Detailed Kinetics Calibration Methodology for 3D CFD Simulations of Spray Combustion}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, number = {2022-01-1042}, issn = {0148-7191}, doi = {10.4271/2022-01-1042}, abstract = {Meeting strict current and future emissions legislation necessitates development of computational tools capable of predicting the behaviour of combustion and emissions with an accuracy sufficient to make correct design decisions while keeping computational cost of the simulations amenable for large-scale design space exploration. While detailed kinetics modelling is increasingly seen as a necessity for accurate simulations, the computational cost can be often prohibitive, prompting interest in simplified approaches allowing fast simulation of reduced mechanisms at coarse grid resolutions appropriate for internal combustion engine simulations in design context. In this study we present a simplified Well-stirred Reactor (WSR) implementation coupled with 3D CFD Ricardo VECTIS solver. A detailed evaluation of benchmark ECN spray problem is presented demonstrating that a single point calibration of such a model using a bulk reaction multiplier approach can provide correct representation of the solution across a wide range of temperatures on grid sizes typically employed for RANS internal combustion engine simulations with tabulated kinetics or zonal combustion models.}, language = {en} } @misc{VanTreekLubranoLavaderaSeideletal., author = {Van Treek, Lisa and Lubrano Lavadera, Marco and Seidel, Lars and Mauß, Fabian and Konnov, Alexander A.}, title = {Experimental and modelling study of laminar burning velocity of aqueous ethanol}, series = {Fuel}, volume = {257}, journal = {Fuel}, issn = {1873-7153}, doi = {10.1016/j.fuel.2019.116069}, abstract = {Laminar burning velocities of ethanol-water-air mixtures have been determined using the heat flux method. Aqueous ethanol contained 0-40\% of water by mole fraction. Laminar premixed flat flames were stabilized on a perforated burner under adiabatic conditions for the equivalence ratio range from 0.7 to 1.4. Burning velocity measurements were performed for the initial gas temperature of 358 K and at atmospheric pressure. The results for ethanol-air flames are in good agreement with the previous data obtained using the same heat flux method. The present and literature experimental data were compared against predictions using four different kinetic models. All models show uniform behaviour over the range of ethanol dilution by water covered in the present study. However, model predictions significantly diverge from the experimental data obtained in spherical flames. To quantify the effect of dilution on the laminar burning velocity, an empirical dimensionless correlation has been derived from the experimental data and predictions of the models tested. Further numerical analyses were performed to identify the effects of water addition on laminar burning velocities. Results suggested that water strongly interacts with the H2/O2 and C1 oxidation/recombination routes.}, language = {en} } @misc{HilbigMalliotakisSeideletal., author = {Hilbig, Martin and Malliotakis, Zisis and Seidel, Lars and Vourliotakis, George and Keramiotis, Christos and Mauß, Fabian and Founti, Maria}, title = {The effect of base chemistry choice in a generated n-hexane oxidation model using an automated mechanism generator}, series = {International Journal of Chemical Kinetics}, volume = {51}, journal = {International Journal of Chemical Kinetics}, number = {10}, issn = {1097-4601}, doi = {10.1002/kin.21309}, pages = {786 -- 798}, abstract = {The present study describes the utilization of a reaction mechanism generator for the development of chemical kinetic models. The aim of the investigation is twofold. The in-house developed mechanism generator is updated with reaction classes reported in the literature, and the effect of the lower hydrocarbon chemistry, that is, base chemistry, on the generation process is assessed. For this purpose, the algorithm is implemented on two different base chemistry mechanisms, that have previously been validated against a different range of hydrocarbons, that is, the mechanisms of the groups coauthoring the study. n-Hexane has been used as a modeling target due to its important role in combustion studies as a surrogate for engine and aviation applications. The steps of the generation process are given in detail as this is the first time the current algorithm is utilized. The two generated mechanisms are compared against speciation data, ignition delay times, and flame velocities from the literature. The overall agreement of the generated mechanisms is satisfying; discrepancies exist in the negative temperature coefficient regime. Reaction path analysis and sensitivity analysis were performed, revealing the reactions that cause the different mechanism performance. Among others, the study reveals that the generated schemes pose a fast and adequate alternative to literature mechanisms; it is however evident that the latter may include more detailed reaction paths and are therefore superior in terms of validation.}, language = {en} } @misc{RichterGuentherMauss, author = {Richter, Jana and G{\"u}nther, Vivien and Mauß, Fabian}, title = {Reaction mechanism development and investigation on the convergence influence in a 1D catalyst model for a γ-alumina stabilized three-way catalyst}, series = {The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines}, journal = {The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines}, issn = {2424-2918}, doi = {10.1299/jmsesdm.2022.10.A10-3}, abstract = {Accurate and computational cost-effective modeling tools for the optimization of processes and devices of all kinds are needed in nearly all scientific fields. While experimental optimization entails high expenses in terms of cost and time virtual optimization may be a promising alternative. In this work, the suitability and accuracy of a 1D heterogeneous catalytic model is investigated. First, the influence of cell discretization and residence time on the convergence in a 1D catalyst model are investigated. Second, the catalyst model is investigated and validated with use of a stoichiometric steady state three-way catalyst experiment. With the help of these investigations the reaction mechanism is further developed and new reaction rates for two reactions are presented. The modeling results are compared to a 2D simulation approach in terms of computational time and catalyst conversion behavior. The presented model is capable to capture the experimental results with a drastically reduced computational time in comparison to the 2D simulation presented in literature.}, language = {en} } @misc{MaiBuiNhungetal., author = {Mai, Tam V.-T. and Bui, Thanh Q. and Nhung, Nguyen Thi Ai and Quy, Phan Tu and Shrestha, Krishna Prasad and Mauß, Fabian and Giri, Binod Raj and Huynh, Lam Kim}, title = {An Ab Initio RRKM-Based Master Equation Study for Kinetics of OH-Initiated Oxidation of 2-Methyltetrahydrofuran and Its Implications in Kinetic Modeling}, series = {Energies}, volume = {16}, journal = {Energies}, number = {9}, issn = {1996-1073}, doi = {10.3390/en16093730}, abstract = {Cyclic ethers (CEs) can be promising future biofuel candidates. Most CEs possess physico-chemical and combustion indicators comparable to conventional fuels, making them suitable for internal combustion engines. This work computationally investigates the kinetic behaviors of hydrogen abstraction from 2-methyl tetrahydrofuran (2MTHF), one of the promising CEs, by hydroxyl radicals under combustion and atmospheric relevant conditions. The various reaction pathways were explored using the CCSD(T)/cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory. The Rice-Ramsperger-Kassel-Marcus-based master equation (RRKM-ME) rate model, including treatments for hindered internal rotation and tunneling, was employed to describe time-dependent species profiles and pressure and temperature-dependent rate coefficients. Our kinetic model revealed that the H-abstraction proceeds via an addition-elimination mechanism forming reaction complexes at both the entrance and exit channels. Eight different reaction channels yielding five radical products were located. The reaction exhibited complex kinetics yielding a U-shaped Arrhenius behavior. An unusual occurrence of negative temperature dependence was observed at low temperatures, owing to the negative barrier height for the hydrogen abstraction reaction from the C-H bond at the vicinity of the O-atom. A shift in the reaction mechanism was observed with the dominance of the abstraction at Cα-H of 2MTHF ring (causing negative-T dependence) and at CH3 (positive-T dependence) at low and high temperatures, respectively. Interestingly, the pressure effect was observed at low temperatures, revealing the kinetic significance of the pre-reaction complex. Under atmospheric pressure, our theoretical rate coefficients showed excellent agreement with the available literature data. Our model nicely captured the negative temperature-dependent behaviors at low temperatures. Our predicted global rate coefficients can be expressed as k (T, 760 Torr) = 3.55 × 101 × T-4.72 × exp [-340.0 K/T] + 8.21 × 10-23 × T3.49 × exp [918.8 K/T] (cm3/molecule/s). Our work provides a detailed kinetic picture of the OH-initiated oxidation kinetics of 2MTHF. Hence, this information is useful for building a kinetic me chanism for methylated cyclic ethers.}, language = {en} } @misc{SiddareddyFrankenPasternaketal., author = {Siddareddy, Reddy Babu and Franken, Tim and Pasternak, Michal and Leon de Syniawa, Larisa and Oder, Johannes and Rottengruber, Hermann and Mauß, Fabian}, title = {Real-Time Simulation of CNG Engine and After-Treatment System Cold Start. Part 1: Transient Engine-Out Emission Prediction Using a Stochastic Reactor Model}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, issn = {2688-3627}, doi = {10.4271/2023-01-0183}, abstract = {During cold start of natural gas engines, increased methane and formaldehyde emissions can be released due to flame quenching on cold cylinder walls, misfiring and the catalyst not being fully active at low temperatures. Euro 6 legislation does not regulate methane and formaldehyde emissions. New limits for these two pollutants have been proposed by CLOVE consortium for Euro 7 scenarios. These proposals indicate tougher requirements for aftertreatment systems of natural gas engines. In the present study, a zero-dimensional model for real-time engine-out emission prediction for transient engine cold start is presented. The model incorporates the stochastic reactor model for spark ignition engines and tabulated chemistry. The tabulated chemistry approach allows to account for the physical and chemical properties of natural gas fuels in detail by using a-priori generated laminar flame speed and combustion chemistry look-up tables. The turbulence-chemistry interaction within the combustion chamber is predicted using a K-k turbulence model. The optimum turbulence model parameters are trained by matching the experimental cylinder pressure and engine-out emissions of nine steady-state operating points. Subsequently, the trained engine model is applied for predicting engine-out emissions of a WLTP passenger car engine cold start. The predicted engine-out emissions comprise nitrogen oxide, carbon monoxide, carbon dioxide, unburnt methane, formaldehyde, and hydrogen. The simulation results are validated by comparing to transient engine measurements at different ambient temperatures (-7°C, 0°C, 8°C and 20°C). Additionally, the sensitivity of engine-out emissions towards air-fuel-ratio (λ=1.0 and λ=1.3) and natural gas quality (H-Gas and L-Gas) is investigated.}, language = {en} } @misc{LeondeSyniawaSiddareddyOderetal., author = {Leon de Syniawa, Larisa and Siddareddy, Reddy Babu and Oder, Johannes and Franken, Tim and G{\"u}nther, Vivien and Rottengruber, Hermann and Mauß, Fabian}, title = {Real-Time Simulation of CNG Engine and After-Treatment System Cold Start. Part 2: Tail-Pipe Emissions Prediction Using a Detailed Chemistry Based MOC Model}, series = {SAE Technical Report}, journal = {SAE Technical Report}, issn = {2688-3627}, doi = {10.4271/2023-01-0364}, abstract = {In contrast to the currently primarily used liquid fuels (diesel and gasoline), methane (CH4) as a fuel offers a high potential for a significant reduction of greenhouse gas emissions (GHG). This advantage can only be used if tailpipe CH4 emissions are reduced to a minimum, since the GHG impact of CH4 in the atmosphere is higher than that of carbon dioxide (CO2). Three-way catalysts (TWC - stoichiometric combustion) and methane oxidation catalysts (MOC - lean combustion) can be used for post-engine CH4 oxidation. Both technologies allow for a nearly complete CH4 conversion to CO2 and water at sufficiently high exhaust temperatures (above the light-off temperature of the catalysts). However, CH4 combustion is facing a huge challenge with the planned introduction of Euro VII emissions standard, where stricter CH4 emission limits and a decrease of the cold start starting temperatures are discussed. The aim of the present study is to develop a reliable kinetic catalyst model for MOC conversion prediction in order to optimize the catalyst design in function of engine operation conditions, by combining the outputs from the predicted transient engine simulations as inputs to the catalyst model. Model development and training has been performed using experimental engine test bench data at stoichiometric conditions as well as engine simulation data and is able to reliably predict the major emissions under a broad range of operating conditions. Cold start (-7°C and +20°C) experiments were performed for a simplified worldwide light vehicle test procedure (WLTP) driving cycle using a prototype gas engine together with a MOC. For the catalyst simulations, a 1-D catalytic converter model was used. The model includes detailed gas and surface chemistry that are computed together with catalyst heat up. In a further step, a virtual transient engine cold start cycle is combined with the MOC model to predict tail-pipe emissions at transient operating conditions. This method allows to perform detailed emission investigations in an early stage of engine prototype development.}, language = {en} }