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 -