TY - GEN A1 - Franken, Tim A1 - Seidel, Lars A1 - Matrisciano, Andrea A1 - Mauß, Fabian A1 - Kulzer, Andre Casal A1 - Schuerg, Frank T1 - Analysis of the Water Addition Efficiency on Knock Suppression for Different Octane Ratings T2 - SAE World Congress N2 - 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. KW - Gasoline KW - Knock KW - Water KW - Engines KW - Combustion KW - Simulation Y1 - 2020 U6 - https://doi.org/10.4271/2020-01-0551 SN - 2688-3627 SN - 0148-7191 ER - TY - GEN A1 - Franken, Tim A1 - Mauß, Fabian A1 - Seidel, Lars A1 - Gern, Maike Sophie A1 - Kauf, Malte A1 - Matrisciano, Andrea A1 - Kulzer, Andre Casal T1 - Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry T2 - International Journal of Engine Research N2 - 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. KW - Water Injection KW - Exhaust Gas Recirculation KW - Efficiency KW - Spark Ignition Engine KW - Stochastic Reactor Model KW - Emissions Y1 - 2020 UR - https://journals.sagepub.com/doi/abs/10.1177/1468087420933124 U6 - https://doi.org/10.1177/1468087420933124 SN - 2041-3149 SN - 1468-0874 VL - 21 IS - 10 SP - 1857 EP - 1877 ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Lhuillier, Charles A1 - Barbosa, Amanda Alves A1 - Brequigny, Pierre A1 - Contino, Francesco A1 - Mounaïm-Rousselle, Christine A1 - Seidel, Lars A1 - Mauß, Fabian T1 - An experimental and modeling study of ammonia with enriched oxygen content and ammonia/hydrogen laminar flame speed at elevated pressure and temperature T2 - Proceedings of the Combustion Institute N2 - 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. KW - Ammonia KW - Laminar flame speed KW - Kinetic modeling KW - Ammonia-hydrogen KW - NOx Y1 - 2020 UR - https://www.sciencedirect.com/science/article/pii/S1540748920302881#! U6 - https://doi.org/10.1016/j.proci.2020.06.197 SN - 1540-7489 VL - 2020 SP - 1 EP - 12 ER - TY - GEN A1 - Issayev, Gani A1 - Giri, Binod Raj A1 - Elbaz, Ayman M. A1 - Shrestha, Krishna Prasad A1 - Mauß, Fabian A1 - Roberts, William L. A1 - Farooq, Aamir T1 - Combustion behavior of ammonia blended with diethyl ether T2 - Proceedings of the Combustion Institute N2 - 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. KW - Ammonia KW - Diethyl ether KW - Ignition delay times KW - Laminar flame speed Y1 - 2020 U6 - https://doi.org/10.1016/j.proci.2020.06.337 SN - 1540-7489 VL - 38 (2021) IS - 1 SP - 499 EP - 506 ER - TY - GEN A1 - Elbaz, Ayman M. A1 - Giri, Binod Raj A1 - Issayev, Gani A1 - Shrestha, Krishna Prasad A1 - Mauß, Fabian A1 - Farooq, Aamir A1 - Roberts, William L. T1 - Experimental and Kinetic Modeling Study of Laminar Flame Speed of Dimethoxymethane and Ammonia Blends T2 - Energy & Fuels N2 - 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. KW - Ammonia KW - Dimethoxymethane KW - Laminar flame speed KW - Kinetic modeling Y1 - 2020 UR - https://pubs.acs.org/doi/abs/10.1021/acs.energyfuels.0c02269 U6 - https://doi.org/10.1021/acs.energyfuels.0c02269 SN - 1520-5029 VL - 34 IS - 11 SP - 14727 EP - 14740 ER - TY - GEN A1 - Van Treek, Lisa A1 - Roth, Norbert A1 - Seidel, Lars A1 - Mauß, Fabian T1 - Measurements of the laminar burning velocities of rich ethylene/air mixtures T2 - Fuel N2 - 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. KW - ethylene KW - laminar burning velocity KW - heat flux burner Y1 - 2020 UR - https://www.sciencedirect.com/science/article/pii/S0016236120309340 U6 - https://doi.org/10.1016/j.fuel.2020.117938 SN - 0016-2361 VL - 275 ER - TY - GEN A1 - Netzer, Corinna A1 - Li, Tian A1 - Seidel, Lars A1 - Mauß, Fabian A1 - Løvås, Terese T1 - Stochastic Reactor-Based Fuel Bed Model for Grate Furnaces T2 - Energy & Fuels N2 - 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. Y1 - 2020 UR - https://pubs.acs.org/doi/full/10.1021/acs.energyfuels.0c02868 U6 - https://doi.org/10.1021/acs.energyfuels.0c02868 SN - 1520-5029 VL - 34 IS - 12 SP - 16599 EP - 16612 ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Seidel, Lars A1 - Zeuch, Thomas A1 - Moréac, Gladys A1 - Dagaut, Philippe A1 - Mauß, Fabian T1 - On the implications of nitromethane – NOx chemistry interactions for combustion processes T2 - Fuel N2 - 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. KW - Nitromethane KW - NOx KW - Fuel-NOx KW - Kinetic modeling KW - EGR Y1 - 2021 UR - https://www.sciencedirect.com/science/article/pii/S001623612032857X#! U6 - https://doi.org/10.1016/j.fuel.2020.119861 SN - 0016-2361 VL - 289 ER - TY - GEN A1 - Franken, Tim A1 - Seidel, Lars A1 - Shrestha, Krishna Prasad A1 - Gonzalez Mestre, Laura Catalina A1 - Mauß, Fabian T1 - Multi-objective Optimization of Gasoline, Ethanol, and Methanol in Spark Ignition Engines N2 - 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. KW - Optimization KW - Methanol KW - Ethanol KW - Spark Ignition Engine KW - Gasoline KW - Simulation Y1 - 2021 UR - https://www.researchgate.net/publication/351688526_Multi-objective_Optimization_of_Gasoline_Ethanol_and_Methanol_in_Spark_Ignition_Engines ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Giri, Binod Raj A1 - Adil, Mohammad A1 - Seidel, Lars A1 - Zeuch, Thomas A1 - Farooq, Aamir A1 - Mauß, Fabian T1 - Detailed Chemical Kinetic Study of Acetaldehyde Oxidation and Its Interaction with NOx T2 - Energy & fuels N2 - 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. KW - NOx KW - Kinetic modeling KW - Acetaldehyde KW - Ignition delay time Y1 - 2021 UR - https://pubs.acs.org/doi/10.1021/acs.energyfuels.1c01948?ref=pdf U6 - https://doi.org/10.1021/acs.energyfuels.1c01948 SN - 1520-5029 SN - 0887-0624 VL - 35 IS - 18 SP - 14963 EP - 14983 ER - TY - GEN A1 - Issayev, Gani A1 - Giri, Binod Raj A1 - Elbaz, Ayman M. A1 - Shrestha, Krishna Prasad A1 - Mauß, Fabian A1 - Roberts, William L. A1 - Farooq, Aamir T1 - Ignition delay time and laminar flame speed measurements of ammonia blended with dimethyl ether: A promising low carbon fuel blend T2 - Renewable Energy N2 - 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%. KW - DME KW - Lamianr flame speed KW - Ignition delay time KW - Kinetic modeling KW - Ammonia Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S0960148121014440?via%3Dihub#! U6 - https://doi.org/10.1016/j.renene.2021.09.117 SN - 1879-0682 VL - 181 SP - 1353 EP - 1370 ER - TY - GEN A1 - Franken, Tim A1 - Matrisciano, Andrea A1 - Sari, Rafael A1 - Robles, Alvaro Fogue A1 - Monsalve-Serrano, Javier A1 - Pintor, Dario Lopez A1 - Pasternak, Michal A1 - Garcia, Antonio A1 - Mauß, Fabian T1 - Modeling of Reactivity Controlled Compression Ignition Combustion Using a Stochastic Reactor Model Coupled with Detailed Chemistry T2 - SAE technical papers : 15th International Conference on Engines & Vehicles N2 - 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. KW - Stochastic Reactor Models KW - RCCI KW - Chemical Kinetics KW - Low Temperature Combustion Y1 - 2021 UR - https://www.sae.org/publications/technical-papers/content/2021-24-0014/ U6 - https://doi.org/10.4271/2021-24-0014 SN - 0148-7191 SN - 2688-3627 ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Giri, Binod Raj A1 - Seidel, Lars A1 - Farooq, Aamir A1 - Mauß, Fabian T1 - A Kinetic Modeling Study for the Effect of NOx on Oxymethylene ethers (OMEn, n = 0 and 1) oxidation T2 - 10th European Combustion Meeting, Neapel N2 - 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. KW - DME KW - DMM KW - Oxymethylene ethers KW - NOx KW - Kinetic Modeling Y1 - 2021 UR - https://www.researchgate.net/publication/353620538_A_Kinetic_Modeling_Study_for_the_Effect_of_NOx_on_Oxymethylene_ethers_OMEn_n_0_and_1_oxidation CY - Neapel ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Giri, Binod Raj A1 - Elbaz, Ayman M. A1 - Issayev, Gani A1 - Roberts, William L. A1 - Seidel, Lars A1 - Mauß, Fabian A1 - Farooq, Aamir T1 - A detailed chemical insights into the kinetics of diethyl ether enhancing ammonia combustion and the importance of NOx recycling mechanism T2 - Fuel Communications N2 - 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. KW - DEE KW - Ammonia KW - Kinetic Model KW - Laminar flame speed KW - Ignition delay time Y1 - 2022 U6 - https://doi.org/10.1016/j.jfueco.2022.100051 SN - 2666-0520 VL - 10 ER - TY - GEN A1 - Fritsche, Chris A1 - Eckart, Sven A1 - Shrestha, Krishna Prasad A1 - Mauß, Fabian A1 - Krause, Hartmut T1 - 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 T2 - 10th European Combustion Meeting, Proceedings of the European Combustion Meeting N2 - 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. KW - Methane KW - Hydrogen KW - Kinetic Model KW - Laminar burning velocity KW - Constant Volume chamber Y1 - 2021 UR - https://www.researchgate.net/publication/358415279_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 ER - TY - GEN A1 - Fritsche, Chris A1 - Shrestha, Krishna Prasad A1 - Eckart, Sven A1 - Mauß, Fabian A1 - Krause, Hartmut T1 - Temperature and pressure dependency of the burning velocity in laminar premixed methanol and polyoxymethylene dimethyl ether (OME1, OME2, and OME3) flames T2 - 10th European Combustion Meeting, Proceedings of the European Combustion Meeting N2 - 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. KW - Oxymethylene ethers KW - Lamianr burning velocity KW - Kinetic Modeling KW - heat flux burne KW - constant volume chamber Y1 - 2021 UR - https://www.researchgate.net/publication/358415681_Temperature_and_pressure_dependency_of_the_burning_velocity_in_laminar_premixed_methanol_and_polyoxymethylene_dimethyl_ether_OME1_OME2_and_OME3_flames ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Seidel, Lars A1 - Zeuch, Thomas A1 - Mauß, Fabian T1 - Modeling of NOx Formation and Consumption during Oxidation of Small Alcohols T2 - 9th European Combustion Meeting, Proceedings of the European Combustion Meeting N2 - 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). Y1 - 2019 UR - https://hal.archives-ouvertes.fr/hal-02334906 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Günther, Vivien A1 - Richter, Jana A1 - Mauß, Fabian T1 - Steam reforming of methane over nickel catalyst using a one-dimensional model T2 - International Journal of Environmental Sciences N2 - 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. Y1 - 2022 UR - https://www.iprjb.org/journals/index.php/IJES/article/view/1520/1605 U6 - https://doi.org/10.47604/ijes.1520 SN - 2519-5549 VL - 5 IS - 1 SP - 1 EP - 32 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Shrestha, Krishna Prasad A1 - Günther, Vivien A1 - Mauß, Fabian T1 - Thermodynamic analysis to develop a detailed surface reaction mechanism T2 - Fuel Science - From Production to Propulsion, Aachen, Germany, May 2022 N2 - 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. Y1 - 2022 UR - https://www.researchgate.net/publication/361279412_Thermodynamic_analysis_to_develop_a_detailed_surface_reaction_mechanism ER - TY - GEN A1 - Picerno, Mario A1 - Lee, Sung-Yong A1 - Pasternak, Michal A1 - Siddareddy, Reddy Babu A1 - Franken, Tim A1 - Mauß, Fabian A1 - Andert, Jakob T1 - Real-Time Emission Prediction with Detailed Chemistry under Transient Conditions for Hardware-in-the-Loop Simulations T2 - Energies N2 - 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%). KW - hardware-in-the-loop KW - virtual calibration KW - diesel powertrain KW - tabulated chemistry Y1 - 2022 U6 - https://doi.org/10.3390/en15010261 SN - 1996-1073 VL - 15 IS - 1 SP - 1 EP - 21 ER - TY - GEN A1 - Franken, Tim A1 - Srivastava, Vivek A1 - Lee, Sung-Yong A1 - Heuser, Benedikt A1 - Shrestha, Krishna Prasad A1 - Seidel, Lars A1 - Mauß, Fabian ED - Xandra, Margot ED - Payri, Raúl ED - Serrano, José Ramón T1 - Numerical Analysis of the Combustion of Diesel, Dimethyl Ether, and Polyoxymethylene Dimethyl Ethers (OMEn, n=1-3) Using Detailed Chemistry T2 - THIESEL 2022 : Conference on Thermo- and Fluid-Dynamics of Clean Propulsion Powerplants, 13th-16th September 2022 : conference proceedings N2 - 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. KW - Polyoxymethylene Dimethyl Ethers KW - Stochastic Reactor Model KW - Detailed Chemistry KW - Modelling KW - Emissions Y1 - 2022 UR - https://www.lalibreria.upv.es/portalEd/UpvGEStore/products/p_6328-1-1 SN - 978-84-1396-055-5 U6 - https://doi.org/10.4995/Thiesel.2022.632801 PB - Editorial Universitat Politècnica de València CY - València ER - TY - GEN A1 - Franken, Tim A1 - Shrestha, Krishna Prasad A1 - Seidel, Lars A1 - Mauß, Fabian ED - Sens, Marc T1 - Effect of Gasoline–Ethanol–Water Mixtures on Auto-Ignition in a Spark Ignition Engine T2 - International Conference on Knocking in Gasoline Engines N2 - 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. KW - Knock KW - Gasoline KW - Ethanol KW - Simulation KW - Detailed Chemistry KW - Spark Ignition Y1 - 2022 SN - 978-3-8169-3544-5 U6 - https://doi.org/10.24053/9783816985440 SP - 175 EP - 222 PB - expert CY - Tübingen ER - TY - GEN A1 - Giri, Binod Raj A1 - Shrestha, Krishna Prasad A1 - Mai, Tam V.-T. A1 - Giri, Sushant A1 - Adil, Mohammad A1 - Naik, R. Thirumaleswara A1 - Mauß, Fabian A1 - Huynh, Lam Kim T1 - A Theoretical Study of NH2 Radical Reactions with Propane and Its Kinetic Implications in NH3-Propane Blends’ Oxidation T2 - Energies N2 - 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. Y1 - 2023 U6 - https://doi.org/10.3390/en16165943 SN - 1996-1073 VL - 16 IS - 16 ER - TY - GEN A1 - Elbaz, Ayman M. A1 - Giri, Binod Raj A1 - Shrestha, Krishna Prasad A1 - Arab, Omar Z. A1 - Farooq, Aamir A1 - Mauß, Fabian A1 - Roberts, William L. T1 - A comprehensive experimental and kinetic modeling study of laminar flame propagation of ammonia blended with propene T2 - Combustion and Flame N2 - 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. Y1 - 2023 U6 - https://doi.org/10.1016/j.combustflame.2023.112791 SN - 0010-2180 VL - 253 ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Mai, Tam V.-T. A1 - Giri, Sushant A1 - Giri, Binod Raj A1 - Huynh, Lam Kim A1 - Mauss, Fabian T1 - Reaction Kinetics of NH2 Radicals with Dimethyl Ether (DME) and Diethyl Ether (DEE) and Their Implications in NH3-DME/DEE blend modeling T2 - Los Alamos National Laboratory (LANL) N2 - 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. Y1 - 2023 UR - https://www.osti.gov/biblio/1987392 IS - LA-UR-23-26969 ER - TY - GEN A1 - Giri, Binod Raj A1 - Shrestha, Krishna Prasad A1 - Mai, Tam V.-T. A1 - Mauß, Fabian A1 - Huynh, Lam Kim T1 - A theoretical kinetic study of the reactions of NH2 radicals with methanol and ethanol and their implications in kinetic modeling T2 - International Journal of Chemical Kinetics N2 - 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. Y1 - 2023 U6 - https://doi.org/10.1002/kin.21609 SN - 0538-8066 VL - 55 IS - 1 SP - 3 EP - 14 ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Eckart, Sven A1 - Drost, Simon A1 - Fritsche, Chris A1 - Schießl, Robert A1 - Seidel, Lars A1 - Maas, Ulrich A1 - Krause, Hartmut A1 - Mauß, Fabian T1 - A comprehensive kinetic modeling of oxymethylene ethers (OMEn, n= 1–3) oxidation-laminar flame speed and ignition delay time measurements T2 - Combustion and Flame N2 - 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). Y1 - 2022 U6 - https://doi.org/10.1016/j.combustflame.2022.112426 SN - 1556-2921 SN - 0010-2180 VL - 246 ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Elbaz, Ayman M. A1 - Giri, Binod Raj A1 - Arab, Omar Z. A1 - Adil, Mohammad A1 - Seidel, Lars A1 - Roberts, William L. A1 - Farooq, Aamir A1 - Mauß, Fabian T1 - Experimental and Kinetic Modeling Study of 1, 3-Dioxolane Oxidation and Comparison with Dimethoxymethane T2 - Energy & Fuels N2 - 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. Y1 - 2022 U6 - https://doi.org/10.1021/acs.energyfuels.2c01132 SN - 1520-5029 SN - 0887-0624 VL - 36 IS - 14 SP - 7744 EP - 7754 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Giri, Binod Raj A1 - Günther, Vivien A1 - Mauss, Fabian T1 - Investigation dry reforming of methane over nickel using a one‐dimensional model T2 - PAMM N2 - 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. Y1 - 2023 UR - https://onlinelibrary.wiley.com/doi/pdf/10.1002/pamm.202300266 U6 - https://doi.org/10.1002/pamm.202300266 VL - 23 IS - 4 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Giri, Binod Raj A1 - Günther, Vivien A1 - Mauss, Fabian T1 - Insight into the thermodynamic model for reforming of methane over nickel catalyst T2 - Proceedings of the 64th International Conference of Scandinavian Simulation Society, SIMS 2023 Västerås, Sweden, September 25-28, 2023 N2 - 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. Y1 - 2023 UR - https://ecp.ep.liu.se/index.php/sims/article/view/766 U6 - https://doi.org/10.3384/ecp200025 SP - 192 EP - 197 ER - TY - GEN A1 - Fotiadis, Kyriakos A1 - Asimakopoulou, Akrivi A1 - Baltzopoulou, Penelope A1 - Kastrinaki, Georgia A1 - Koutsonikolas, Dimitrios A1 - Karagiannakis, George A1 - Skevis, George A1 - Richter, Jana A1 - Mauß, Fabian T1 - Experimental Characterization of a Novel Foam Burner Design for the Low-Excess-Enthalpy Combustion of Very Lean Syngas Mixtures T2 - Energies N2 - 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. Y1 - 2023 U6 - https://doi.org//10.3390/en16197014 SN - 1996-1073 VL - 16 IS - 19 SP - 7014 ER - TY - GEN A1 - Rossi, Edoardo A1 - Bargende, Michael A1 - Kulzer, André Casal A1 - Chiodi, Marco A1 - Massoud, Ehab A1 - Shrestha, Krishna Prasad A1 - Mauß, Fabian T1 - Analysis of the applicability of Water Injection in Combination with an eFuel for Knock Mitigation and Improved Engine Efficiency T2 - SAE Technical Paper N2 - 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. Y1 - 2022 U6 - https://doi.org/10.4271/2022-37-0019 SN - 2688-3627 SN - 0148-7191 ER - TY - GEN A1 - Dong, Shijun A1 - Aul, Christopher A1 - Gregoire, Claire A1 - Cooper, Sean P. A1 - Mathieu, Olivier A1 - Petersen, Eric L. A1 - Rodriguez, Jose A1 - Mauß, Fabian A1 - Wagnon, Scott W. A1 - Kukkadapu, Goutham A1 - Pitz, William J. A1 - Curran, Henry J. T1 - A comprehensive experimental and kinetic modeling study of 1-hexene T2 - Combustion and Flame N2 - 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. Y1 - 2021 U6 - https://doi.org/10.1016/j.combustflame.2021.111516 SN - 1556-2921 SN - 0010-2180 VL - 232 ER - TY - GEN A1 - Matrisciano, Andrea A1 - Franken, Tim A1 - Gonzalez Mestre, Laura Catalina A1 - Borg, Anders A1 - Mauß, Fabian T1 - Development of a Computationally Efficient Tabulated Chemistry Solver for Internal Combustion Engine Optimization Using Stochastic Reactor Models T2 - Applied Sciences N2 - The use of chemical kinetic mechanisms in computer aided engineering tools for internal combustion engine simulations is of high importance for studying and predicting pollutant formation of conventional and alternative fuels. However, usage of complex reaction schemes is accompanied by high computational cost in 0-D, 1-D and 3-D computational fluid dynamics frameworks. The present work aims to address this challenge and allow broader deployment of detailed chemistry-based simulations, such as in multi-objective engine optimization campaigns. A fast-running tabulated chemistry solver coupled to a 0-D probability density function-based approach for the modelling of compression and spark ignition engine combustion is proposed. A stochastic reactor engine model has been extended with a progress variable-based framework, allowing the use of pre-calculated auto-ignition tables instead of solving the chemical reactions on-the-fly. As a first validation step, the tabulated chemistry-based solver is assessed against the online chemistry solver under constant pressure reactor conditions. Secondly, performance and accuracy targets of the progress variable-based solver are verified using stochastic reactor models under compression and spark ignition engine conditions. Detailed multicomponent mechanisms comprising up to 475 species are employed in both the tabulated and online chemistry simulation campaigns. The proposed progress variable-based solver proved to be in good agreement with the detailed online chemistry one in terms of combustion performance as well as engine-out emission predictions (CO, CO2, NO and unburned hydrocarbons). Concerning computational performances, the newly proposed solver delivers remarkable speed-ups (up to four orders of magnitude) when compared to the online chemistry simulations. In turn, the new solver allows the stochastic reactor model to be computationally competitive with much lower order modeling approaches (i.e., Vibe-based models). It also makes the stochastic reactor model a feasible computer aided engineering framework of choice for multi-objective engine optimization campaigns. Y1 - 2020 U6 - https://doi.org/10.3390/app10248979 SN - 2076-3417 VL - 10 IS - 24 ER - TY - GEN A1 - Franken, Tim A1 - Seidel, Lars A1 - Gonzalez Mestre, Laura Catalina A1 - Shrestha, Krishna Prasad A1 - Matrisciano, Andrea A1 - Mauss, Fabian T1 - Assessment of Auto-Ignition Tendency of Gasoline, Methanol, Toluene and Hydrogen Fuel Blends in Spark Ignition Engines T2 - THIESEL 2020 Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines N2 - State of the art spark ignited gasoline engines achieve thermal efficiencies above 46 % e.g. due to friction optimized crank trains, high in-cylinder tumble flow and direct fuel injection. Further improvements of thermal efficiency are expected from lean combustion, higher compression ratio and new knock-resistant fuel blends. One of the limitations to these improvements are set by the autoignition in the end gas, which can develop to knocking combustion and severely damage the internal combustion engine. The auto-ignition is enhanced by high cylinder gas temperatures and reactive species in the end gas composition. Quasi-dimensional Stochastic Reactor Model simulations with detailed chemistry allow to consider the thermochemistry properties of surrogates and complex end gas compositions. Based on the detailed reaction scheme and surrogate model, an innovative tabulated chemistry approach is utilized to generate dual-fuel laminar flame speed and combustion chemistry look-up tables. This reduces the simulation duration to seconds per cycle, while the loss in accuracy compared to solving the chemistry “online” is marginal. The auto-ignition events predicted by the tabulated chemistry simulation are evaluated using the Detonation Diagram developed by Bradley and co-workers. This advanced methodology for quasi-dimensional models evaluates the resonance between the shock wave and reactionfront velocity from auto-ignition in the end gas and determines if it is a harmful developing detonation or normal deflagration. The aim of this work is to evaluate the auto-ignition characteristics of different fuel blends. The Stochastic Reactor Model with tabulated chemistry is applied to perform a numerical analysis of the autoignition of the fuel blends and operating conditions. Experimental measurements of a single cylinder research engine operated with RON95 E10 fuel are used to train and validate the simulation model. The RON95 E10 fuel is blended with Methanol, Hydrogen and Toluene. The knock tendency based on the evaluation of auto-ignition events of the different fuel blends are analysed for three operating points at 1500 rpm 15 bar IMEP, 2000 rpm 20 bar IMEP and 2500 rpm 15 bar IMEP with advanced spark timings. Y1 - 2020 UR - https://hal.science/hal-03573870 ER - TY - GEN A1 - Matrisciano, Andrea A1 - Netzer, Corinna A1 - Werner, Adina A1 - Borg, Anders A1 - Seidel, Lars A1 - Mauß, Fabian T1 - A Computationally Efficient Progress Variable Approach for In-Cylinder Combustion and Emissions Simulations T2 - SAE Technical Paper N2 - The use of complex reaction schemes is accompanied by high computational cost in 3D CFD simulations but is particularly important to predict pollutant emissions in internal combustion engine simulations. One solution to tackle this problem is to solve the chemistry prior the CFD run and store the chemistry information in look-up tables. The approach presented combines pre-tabulated progress variable-based source terms for auto-ignition as well as soot and NOx source terms for emission predictions. The method is coupled to the 3D CFD code CONVERGE v2.4 via user-coding and tested over various speed and load passenger-car Diesel engine conditions. This work includes the comparison between the combustion progress variable (CPV) model and the online chemistry solver in CONVERGE 2.4. Both models are compared by means of combustion and emission parameters. A detailed n-decane/α-methyl-naphthalene mechanism, comprising 189 species, is used for both online and tabulated chemistry simulations. The two chemistry solvers show very good agreement between each other and equally predict trends derived experimentally by means of engine performance parameters as well as soot and NOx engine-out emissions. The CPV model shows a factor 8 speed-up in run-time compared to the online chemistry solver without compromising the accuracy of the solution. Y1 - 2019 U6 - https://doi.org/10.4271/2019-24-0011 SN - 0148-7191 SN - 2688-3627 ER - TY - GEN A1 - Franken, Tim A1 - Duggan, Alexander A1 - Matrisciano, Andrea A1 - Lehtiniemi, Harry A1 - Borg, Anders A1 - Mauß, Fabian T1 - Multi-Objective Optimization of Fuel Consumption and NO x Emissions with Reliability Analysis Using a Stochastic Reactor Model T2 - SAE Technical Paper N2 - The introduction of a physics-based zero-dimensional stochastic reactor model combined with tabulated chemistry enables the simulation-supported development of future compression-ignited 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 the simulation-based multi-objective optimization, genetic algorithms are proven to be an effective tool. Based on an initial set of designs, the algorithm aims to evolve the designs to find the best parameters for the given constraints and objectives. The extension by response surface models improves the prediction of the best possible Pareto Front, while the time of optimization is kept low. This work presents a novel methodology to couple the stochastic reactor model and the Non-dominated Sorting Genetic Algorithm. First, the stochastic reactor model is calibrated for 10 low, medium and high load operating points at various engine speeds. Second, each operating point is optimized to find the lowest fuel consumption and specific NOx emissions. The optimization input parameters are the temperature at intake valve closure, the compression ratio, the start of injection, the injection pressure and exhaust gas recirculation rate. Additionally, it is ensured that the maximum peak cylinder pressure and turbine inlet temperature are not exceeded. This enables a safe operation of the engine and exhaust aftertreatment system under the optimized conditions. Subsequently, a reliability analysis is performed to estimate the effect of off-nominal conditions on the objectives and constraints. The novel multi-objective optimization methodology has proven to deliver reasonable results. The zero-dimensional stochastic reactor model with tabulated chemistry is a fast running physics-based model that allow to run large optimization problems in a short amount of time. The combination with the reliability analysis also strengthens the confidence in the simulation-based optimized engine operation parameters. Y1 - 2019 U6 - https://doi.org/10.4271/2019-01-1173 SN - 0148-7191 SN - 2688-3627 ER - TY - GEN A1 - Kurapati, Vinaykumar Reddy A1 - Borg, Anders A1 - Seidel, Lars A1 - Mauß, Fabian T1 - Fast CFD Diesel engine modelling using the 1-Dimentional SprayLet approach T2 - SAE Technical Paper N2 - 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. Y1 - 2024 UR - https://www.sae.org/publications/technical-papers/content/2024-01-2684/ SN - 0148-7191 SN - 2688-3627 IS - 2024-01-2684 ER - TY - GEN A1 - Kurapati, Vinaykumar Reddy A1 - Borg, Anders A1 - Seidel, Lars A1 - Mauß, Fabian T1 - SprayLet: One-Dimensional Interactive Cross-Sectionally Averaged Spray Model T2 - SAE Technical Paper N2 - 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. Y1 - 2023 U6 - https://doi.org/10.4271/2023-24-0083 SN - 0148-7191 SN - 2688-3627 ER - TY - GEN A1 - Manna, Maria Virginia A1 - Sabia, Pino A1 - Shrestha, Krishna Prasad A1 - Seidel, Lars A1 - Ragucci, Raffaele A1 - Mauß, Fabian A1 - De Joannon, Mara T1 - NH3NO interaction at low-temperatures: an experimental and modeling study T2 - Proceedings of the Combustion Institute N2 - 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. Y1 - 2023 U6 - https://doi.org/10.1016/j.proci.2022.09.027 SN - 1873-2704 VL - 39 IS - 1 SP - 775 EP - 784 ER - TY - GEN A1 - Mante, Till A1 - Prehn, Sascha A1 - Theile, Martin A1 - Seidel, Lars A1 - Mestre, Laura A1 - Buchholz, Bert A1 - Mauß, Fabian ED - Heintzel, Alexander T1 - 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 T2 - Heavy-Duty-, On- und Off-Highway-Motoren 2022 : Stand der Energiewende im Heavy-Duty-Bereich N2 - 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. Y1 - 2022 SN - 978-3-658-41477-1 SN - 978-3-658-41476-4 U6 - https://doi.org/10.1007/978-3-658-41477-1_3 SP - 24 EP - 39 PB - Springer Vieweg CY - Wiesbaden ER - TY - GEN A1 - Turquand d'Auzay, Charles A1 - Shapiro, Evgeniy A1 - Prouvier, Matthieu A1 - Winkler, Axel A1 - Seidel, Lars A1 - Borg, Anders A1 - Mauß, Fabian T1 - Evaluation of Fast Detailed Kinetics Calibration Methodology for 3D CFD Simulations of Spray Combustion T2 - SAE Technical Paper N2 - 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. Y1 - 2022 U6 - https://doi.org/10.4271/2022-01-1042 SN - 0148-7191 SN - 0096-5170 IS - 2022-01-1042 ER - TY - GEN A1 - Van Treek, Lisa A1 - Lubrano Lavadera, Marco A1 - Seidel, Lars A1 - Mauß, Fabian A1 - Konnov, Alexander A. T1 - Experimental and modelling study of laminar burning velocity of aqueous ethanol T2 - Fuel N2 - 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. Y1 - 2019 U6 - https://doi.org/10.1016/j.fuel.2019.116069 SN - 1873-7153 VL - 257 ER - TY - GEN A1 - Hilbig, Martin A1 - Malliotakis, Zisis A1 - Seidel, Lars A1 - Vourliotakis, George A1 - Keramiotis, Christos A1 - Mauß, Fabian A1 - Founti, Maria T1 - The effect of base chemistry choice in a generated n‐hexane oxidation model using an automated mechanism generator T2 - International Journal of Chemical Kinetics N2 - 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. Y1 - 2019 U6 - https://doi.org/10.1002/kin.21309 SN - 1097-4601 SN - 0538-8066 VL - 51 IS - 10 SP - 786 EP - 798 ER - TY - GEN A1 - Richter, Jana A1 - Günther, Vivien A1 - Mauß, Fabian T1 - Reaction mechanism development and investigation on the convergence influence in a 1D catalyst model for a γ-alumina stabilized three-way catalyst T2 - The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines N2 - 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. Y1 - 2022 UR - https://www.jstage.jst.go.jp/article/jmsesdm/2022.10/0/2022.10_A10-3/_article/-char/en U6 - https://doi.org/10.1299/jmsesdm.2022.10.A10-3 SN - 2424-2918 ER - TY - GEN A1 - Mai, Tam V.-T. A1 - Bui, Thanh Q. A1 - Nhung, Nguyen Thi Ai A1 - Quy, Phan Tu A1 - Shrestha, Krishna Prasad A1 - Mauß, Fabian A1 - Giri, Binod Raj A1 - Huynh, Lam Kim T1 - An Ab Initio RRKM-Based Master Equation Study for Kinetics of OH-Initiated Oxidation of 2-Methyltetrahydrofuran and Its Implications in Kinetic Modeling T2 - Energies N2 - 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. KW - ab initio KW - RRKM-ME calculations KW - 2-methyl tetrahydrofuran KW - OH radicals KW - kinetic modeling Y1 - 2023 U6 - https://doi.org/10.3390/en16093730 SN - 1996-1073 VL - 16 IS - 9 ER - TY - GEN A1 - Siddareddy, Reddy Babu A1 - Franken, Tim A1 - Pasternak, Michal A1 - Leon de Syniawa, Larisa A1 - Oder, Johannes A1 - Rottengruber, Hermann A1 - Mauß, Fabian T1 - Real-Time Simulation of CNG Engine and After-Treatment System Cold Start. Part 1: Transient Engine-Out Emission Prediction Using a Stochastic Reactor Model T2 - SAE Technical Paper N2 - 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. KW - Spark Ignition Engines KW - Gas Engines KW - Alternative Fuel Engines KW - Natural Gas KW - Nitrogen Oxides KW - Cold Start KW - Carbon Monoxide KW - Methane KW - Formaldehyde KW - Simulation KW - Stochastic Reactor Model KW - Tabulated Chemistry Y1 - 2023 U6 - https://doi.org/10.4271/2023-01-0183 SN - 2688-3627 SN - 0148-7191 ER - TY - GEN A1 - Leon de Syniawa, Larisa A1 - Siddareddy, Reddy Babu A1 - Oder, Johannes A1 - Franken, Tim A1 - Günther, Vivien A1 - Rottengruber, Hermann A1 - Mauß, Fabian T1 - 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 T2 - SAE Technical Report N2 - 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. KW - Exhaust Emissions KW - Tail Pipe Emissions KW - Three Way Catalyst KW - Gas Engines KW - Cold Start KW - Simulation KW - Detailed Chemistry KW - Methane Oxidation Catalyst KW - Methane KW - Co-Simulation KW - Catalysts Y1 - 2023 U6 - https://doi.org/10.4271/2023-01-0364 SN - 2688-3627 SN - 0148-7191 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Günther, Vivien A1 - Mauß, Fabian T1 - A detailed surface reaction mechanism to investigate oxidation of methane over nickel catalyst T2 - Proceedings in Applied Mathematics & Mechanics : PAMM N2 - We have developed a kinetically consistent detailed surface reaction mechanism for modeling the oxidation of methane over a nickel-based catalyst. A one-dimensional model, LOGEcat based on the single-channel 1D catalyst model, is used to perform the simulations. The original multi-step reaction mechanism is thermodynamically consistent and consists of 52 reactions. By thermodynamic consistency, we mean that the equilibrium is achieved with the support of the Arrhenius parameters and does not depend on the thermochemistry of the species involved in the considered reactions. The detailed mechanism developed in this investigation contains 26 reversible reactions. These reactions are obtained with the use of the thermochemistry of the species. The study focuses on ensuring kinetic consistency and this is done with the help of thermodynamic analysis by bringing the thermochemistry of the species in play in order to develop a surface reaction mechanism. The new mechanism can be used to understand the other processes, for example, steam- and dry-reforming of methane over nickel, however, the main focus of the paper is to check the performance of the detailed mechanism for catalytic partial oxidation of methane. The applicability of the mechanism is checked for various reactor conditions in terms of parameters such as temperature and pressure by comparing the results with the available reference data. The detailed mechanism developed in this study is able to accurately express oxidation of methane over the nickel catalyst for the considered reactor conditions. Y1 - 2023 U6 - https://doi.org/10.1002/pamm.202200055 SN - 1617-7061 N1 - Special Issue: 92nd Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM) VL - 22 IS - 1 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Günther, Vivien A1 - Mauß, Fabian T1 - Insights into dry reforming of methane over nickel catalyst using a thermodynamic model T2 - Reaction Kinetics, Mechanisms and Catalysis N2 - A thermodynamic model is developed using a one-dimensional model, LOGEcat to understand the dry reforming of methane over nickel-based catalysts. To do so, we have extended our previously developed mechanism (Rakhi and Shrestha in React Kinet, Mech Catal 135:3059–3083, 2022) which contains 21 reversible reactions by adding 5 more reversible reactions and updating the thermochemistry of one intermediate species. The adjusted mechanism contains 26 reversible reactions obtained with the help of thermodynamic analysis. This study focuses on using the thermodynamic model for dry reforming of methane and insights into the reaction pathways and sensitivity analysis for the kinetically consistent surface reaction mechanism. The applicability of the mechanism is examined for reactor conditions in terms of parameters such as temperature by comparing the results with the available reference data. The mechanism is able to accurately express the reforming conditions of methane over the nickel catalyst for complete range of temperature and also provide useful insights into the reaction pathways established with the thermodynamic model. Y1 - 2023 U6 - https://doi.org/10.1007/s11144-023-02426-8 SN - 1878-5204 SN - 1878-5190 ER - TY - GEN A1 - Siddareddy, Reddy Babu A1 - Franken, Tim A1 - Leon de Syniawa, Larisa A1 - Pasternak, Michal A1 - Prehn, Sascha A1 - Buchholz, Bert A1 - Mauß, Fabian T1 - Simulation of CNG Engine in Agriculture Vehicles. Part 1: Prediction of Cold Start Engine-Out Emissions Using Tabulated Chemistry and Stochastic Reactor Model T2 - SAE Technical Paper N2 - Worldwide, there is the demand to reduce harmful emissions from non-road vehicles to fulfill European Stage V+ and VI (2022, 2024) emission legislation. The rules require significant reductions in nitrogen oxides (NOx), methane (CH4) and formaldehyde (CH2O) emissions from non-road vehicles. Compressed natural gas (CNG) engines with appropriate exhaust aftertreatment systems such as threeway catalytic converter (TWC) can meet these regulations. An issue remains for reducing emissions during the engine cold start where the CNG engine and TWC yet do not reach their optimum operating conditions. The resulting complexity of engine and catalyst calibration can be efficiently supported by numerical models. Hence, it is required to develop accurate simulation models which can predict cold start emissions. This work presents a real-time engine model for transient engine-out emission prediction using tabulated chemistry for CNG. The engine model is based on a stochastic reactor model (SRM) which describes the in-cylinder processes of spark ignition (SI) engines including large-scale and lowscale turbulence, convective heat transfer, turbulent flame propagation and chemistry. Chemistry is described using a tabulated chemistry model which calculates the major exhaust gas emissions of CNG engines such as CO2, NOx, CO, CH4 and CH2O. By best practice, the engine model parameters are optimized by matching the experimental cylinder pressure and engine-out emissions from steady-state operating points. The engine model is trained for a non-road transient cycle (NRTC) cold start at 25°C ambient temperature and validated for a NRTC cold start at 10°C ambient temperature. The trained model is evaluated regarding their feasibility and accuracy predicting transient engineout emissions. KW - CNG engine KW - Cold start KW - Stochastic reactor model KW - Tabulated chemistry KW - Natural gas KW - Driving cycle Y1 - 2023 U6 - https://doi.org/10.4271/2023-24-0006 SN - 0148-7191 SN - 2688-3627 ER -