TY - GEN A1 - Eckart, Sven A1 - Shrestha, Krishna P A1 - Giri, Binod R A1 - Fang, Qilong A1 - Li, Wei A1 - Mauss, Fabian A1 - Krause, Hartmut A1 - Li, Yuyang T1 - Insight into premixed diethoxymethane flames: Laminar burning velocities, temperatures, and emissions behaviour T2 - Proceedings of the Combustion Institute N2 - Diethoxymethane ((CH3CH2O)2CH2, DEM) is a promising carbon-neutral fuel. DEM is a diether or acetal with a molecular structure similar to oxymethylene ethers (CH3O–(CH2O)n–CH3, OMEn). Thus, DEM can be expected to have a similar combustion behavior to OMEs, reducing harmful emissions such as NOx and particulate matter (PM) in internal combustion engines. From both experimental and kinetic modeling, fundamental studies on DEM are scarce in the literature. More studies are required to gain a detailed insight into the oxidation kinetics of DEM. Laminar burning velocity (LBV) is a critical property that allows a detailed assessment of the potential application of DEM in combustion devices. Unfortunately, the literature on the LBV of DEM is limited. Therefore, in this study we have investigated the LBV of DEM using two reactors for the first time, namely a heat flux burner and a combustion chamber. The experimental data is reported for equivalence ratio between 0.7 and 1.7, initial temperatures of 368–423 K, and initial pressure of 1–5 bar. In addition, we developed a detailed kinetic model extending our recent work of Shrestha et al. (Combust. Flame. 246 (2022) 112,426) to characterize the combustion behavior of DEM utilizing the new experimental data from this work and the literature data. Our model performs remarkably well in capturing the newly measured LBV experimental data over various experimental conditions. We found that DEM and dimethoxy methane (DMM) have similar values of LBVs (within ±1.5 cm/s) for a given condition, which indicates that intermediate chemistry governs the flame chemistry. Despite DEM being a larger molecule that is expected to have slightly lower LBVs than DMM, its effect on the measured values of LBVs is negligible. Finally, we experimentally measured NOx formation in DEM flame for the first time. The stochiometric flame has the highest NOx formation. The proposed model predicted the equivalence ratio dependence of NOx nicely. However, it overestimates the NOx formation for stoichiometric DEM/air mixtures by ∼30 %. The model suggests that the thermal NO formation route is favored at lean and stochiometric conditions. In contrast, the prompt NO formation route is enhanced for rich mixtures. Y1 - 2024 UR - https://www.sciencedirect.com/science/article/pii/S1540748924003870 U6 - https://doi.org/10.1016/j.proci.2024.105579 VL - 40 SP - 1 EP - 7 PB - Elsevier ER - TY - GEN A1 - Eckart, Sven A1 - Shrestha, Krishna P A1 - Giri, Binod R A1 - Fang, Qilong A1 - Chen, Chen A1 - Li, Wei A1 - Krause, Hartmut A1 - Mauss, Fabian A1 - Liu, Dong A1 - Li, Yuyang T1 - Chemical insights into ethyl acetate flames from experiment and kinetic modeling: Laminar burning velocity, speciation and NOx emission T2 - Proceedings of the Combustion Institute N2 - Oxygenated fuels, such as alcohols, ethers, and esters, are promising alternatives to conventional fuels. These fuels can help reduce detrimental emissions like carbon monoxide and unburned hydrocarbons and enhance octane ratings. Among these oxygenates, ethyl acetate (EA), a small alkyl ester sourced from biomass, emerges as a clean, promising energy carrier. It serves as a surrogate fuel to facilitate investigations into the combustion behaviours of biodiesel. Despite its importance, the literature knowledge of EA combustion characteristics is limited. Therefore, this study aims to broaden the knowledge of the combustion behaviour of this type of oxygenated fuel compound. In this study, we measured the laminar burning velocities of EA by employing a heat flux burner and a closed combustion vessel over the equivalence ratios of 0.7 – 1.7, pressures of 1 – 10 bar and temperatures ranging from 353 – 423 K. Further, we also measured the NOx emissions in exhaust gas of the premixed flames fueled by EA/air for the first time over the equivalence ratio of 0.8 – 1.2. Additionally, we employed a non-premixed counterflow flame setup for extensive characterisation of species and their concentration under diverse conditions encompassing various strain rates and oxygen concentrations. Finally, we utilized these newly measured data to construct and validate a detailed kinetic model developed as part of this work. The newly developed model will help characterize the combustion properties of EA. Y1 - 2024 UR - https://www.sciencedirect.com/science/article/pii/S1540748924002955 U6 - https://doi.org/10.1016/j.proci.2024.105487 VL - 40 (2024) SP - 1 EP - 7 PB - Elsevier ER - TY - GEN A1 - Thomas, Daniel E A1 - Shrestha, Krishna P A1 - Mauss, Fabian A1 - Northrop, William F T1 - Extinction and NO formation of ammonia-hydrogen and air non-premixed counterflow flames T2 - Proceedings of the Combustion Institute N2 - Green ammonia, produced using renewable energy, is a promising carbon-free energy vector and fuel. This work studies combustion of ammonia-hydrogen fuel mixtures with air in counterflow diffusion flame experiments and provides an improved kinetic mechanism for modeling ammonia combustion. The extinction strain rate is measured for a range of 0 to 15% hydrogen in the fuel blend. The flame structure is also investigated with quantitative laser-induced fluorescence (LIF) measurements of nitric oxide (NO) for the same hydrogen concentrations and strain rate range from 26 to 134 s. For these conditions, NO concentration increases with both strain rate and fuel hydrogen content. The previously published kinetic model developed by the authors is used to perform one-dimensional flame simulations of the experimental setup and conditions, and results are compared to three other recently published ammonia mechanisms. None of the selected models satisfactorily predict both the measured extinction strain rate and flame NO concentration. The models mainly fail to predict extinction strain rate at higher Hfraction and NO formation at the highest experimental strain rates and H fraction. The reaction rate parameters for some of the key reactions in the published model developed by authors were updated to improve agreement with experimental results. The updated model results are closely aligned with extinction strain rate measurements, and have improved prediction of flame NO concentration. The model reveals that the reactions from the NH and NH sub-mechanism are sensitive in predicting the extinction strain rate as well as NO. In particular, the reaction NH+NO=NO+H had significant impact on NO predictions. Y1 - 2024 UR - https://www.sciencedirect.com/science/article/abs/pii/S1540748922003388 U6 - https://doi.org/10.1016/j.proci.2022.08.067 VL - 39 IS - 2 SP - 1803 EP - 1812 PB - Elsevier ER - TY - GEN A1 - Pasternak, Michał A1 - Siddareddy, Reddy Babu A1 - de Syniawa, Larisa León A1 - Guenther, Vivien A1 - Picerno, Mario A1 - Andert, Jakob A1 - Franken, Tim A1 - Mauss, Fabian A1 - Adamczyk, Wojciech T1 - Plant modelling of engine and aftertreatment systems for X-in-the-loop simulations with detailed chemistry T2 - CONAT 2024 International Congress of Automotive and Transport Engineering. N2 - Use of numerical simulations at early stage of engine and aftertreatment systems development helps in evaluating their different concepts and reducing the need for costly building of prototypes. In this work, we explore the feasibility of fully physical and chemical-based tool-chain for co-simulating engine in-cylinder and aftertreatment processes. Detailed gas-phase reaction kinetics and surface chemistry mechanisms are applied for the modeling of combustion, pollutants formation and aftertreatment, respectively. Engine in-cylinder performance parameters are simulated using a stochastic reactor model and multi-component fuel surrogate. The engine model is coupled with an aftertreatment model capable of simulating diesel oxidation catalyst (DOC), selective catalytic reduction catalyst, lean NOx trap, ammonia slip catalyst, and three-way catalyst. Both the engine and aftertreatment models are embedded within the Simulink framework. They work in co-simulation and are coupled using Functional Mock-up Interface (FMI) technology. The coupled framework acts as a virtual test bench that is developed given its application for X-in-the-Loop (XiL) simulations. The framework can be applied to engine steady state or transient operating conditions. Here, exemplary calculations are performed using a Model-in-the-Loop (MiL) approach. Simulations are conducted under transient conditions of Worldwide Harmonized Light Vehicle Test Cycle for a compression ignition engine coupled with a DOC. The presented framework is considered a first step towards complex engine plant modeling using detailed chemistry for the virtualization of the development of engine, fuels and aftertreatment systems. Y1 - 2024 SN - 978-3-031-77626-7 U6 - https://doi.org/10.1007/978-3-031-77627-4_14 SP - 151 EP - 163 PB - Springer Nature Switzerland CY - Cham ER - TY - GEN A1 - Mauss, Fabian A1 - Rakhi, Rakhi T1 - Numerical study of catalytic methanation reactions using a kinetic model T2 - SAE Technical Paper N2 - Even if huge efforts are made to push alternative mobility concepts, such as, electric cars (BEV) and fuel cell powered cars, the importance and use of liquid fuels is anticipated to stay high during the 2030s. The biomethane and synthetic natural gas (SNG) might play a major role in this context as they are raw material for chemical industry, easy to be stored via existing infrastructure, easy to distribute via existing infrastructure, and versatile energy carrier for power generation and mobile applications. Hence, biomethane and synthetic natural gas might play a major role as they are suitable for power generation as well as for mobile applications and can replace natural gas without any infrastructure changes. In this paper, we aim to understand the direct production of synthetic natural gas from CO2 and H2 in a Sabatier process based on a thermodynamic analysis as well as a multi-step kinetic approach. For this purpose, we thoroughly discuss CO2 methanation to control emission in order to maximize the methane formation and minimize the CO formation and to understand the complex methanation process. We have considered an equilibrium and kinetic modelling study on the NiO-SiO2 catalyst for methanation focusing on CO2 derived SNG. In this work, a comprehensive thermodynamic analysis of CO2 hydrogenation is preformed to define the optimum process parameters followed by the kinetic simulations. Further, the simulations can be performed at various conditions, for example, catalyst mass, mass flow, pressure, temperature etc. to optimize the methanation process. Y1 - 2024 U6 - https://doi.org/10.4271/2024-24-0022 SN - 0148-7191 IS - 2024-24-0022 ER - TY - GEN A1 - Mauss, Fabian A1 - Rakhi, Rakhi T1 - Numerical investigation of equilibrium and kinetic aspects for hydrogenation of CO2 T2 - Catalysts N2 - Even if huge efforts are made to push alternative mobility concepts, such as electric cars and fuel-cell-powered cars, the significance and use of liquid fuels is anticipated to stay high during the 2030s. Biomethane and synthetic natural gas (SNG) might play a major role in this context, as they are raw material for chemical industry that is easy to be stored and distribute via existing infrastructure, and are a versatile energy carrier for power generation and mobile applications. Since biomethane and synthetic natural gas are suitable for power generation and for mobile applications, they can therefore replace natural gas without any infrastructure changes, thus playing a major role.In this paper, we aim to comprehend the direct production of synthetic natural gas from CO2 and H2 in a Sabatier process based on a thermodynamic analysis as well as a multi-step kinetic approach. For this purpose, we thoroughly discuss CO2 methanation to control emissions in order to maximize the methane formation along with minimizing the CO formation and to understand the complex methanation process. We consider an equilibrium and kinetic modeling study on the NiO-SiO2 catalyst for methanation focusing on CO2-derived SNG. The thermodynamic analysis of CO2 hydrogenation is preformed to define the optimal process parameters followed by the kinetic simulations for catalyst development. The investigation presented in this paper can also be used for developing machine learning algorithms for methanation processes. Y1 - 2024 UR - https://www.mdpi.com/2073-4344/14/9/562 U6 - https://doi.org/10.3390/catal14090562 VL - 14 SP - 1 EP - 20 PB - MDPI ER - TY - GEN A1 - Sabia, Pino A1 - Manna, M.V. A1 - Mauss, Fabian A1 - Ragucci, R. T1 - MILD Combustion stabilization issues through the analysis of hysteresis behaviors : the case of new energy carriers T2 - Applications in Energy and Combustion Science N2 - MILD combustion processes are renewed to reveal a strong resilience to extinction phenomena and/or instabilities, whereas the oxidation process is stabilized trough ignition phenomena. Under MILD conditions, igni-diffusive and/or perfectly mixed kernels, forming during the mixing process between hot products and fresh reactants, are so much diluted and pre-heated to escape classical feed-back flammable flames stabilization mechanisms, while ignition and extinction events merge in a unique condition through “anhysteretic” behaviors. So far, considering methane as reference fuel, it has been largely demonstrated the mentioned “anhysteretic” condition is very conservative and defines a sub-domain of MILD combustion processes, following Cavaliere and de Joannon's definition. Furthermore, the coincidence of ignition and extinction phenomena can occur also preserving hysteresis phenomena. In turns, this condition strongly enlarges the stabilization domain of MILD combustion processes, starting from the upper branch of the hysteresis behaviors to the real extinction, with characteristic unstable loci to consider as further/last opportunity to promote stable operative conditions through the formation of local thermo-kinetic conditions in the combustion chamber during hot products/fresh reactants mixing process (injection configuration/burner design), or by forced ignition events. The hysteresis behaviors of renewable/alternative fuels, relevant within the decarbonization policies of several energy sectors, are thoroughly discussed under MILD conditions through numerical studies in model reactors in order to shed light on common and/or different features, and outline practical rules towards the definition of stable MILD combustion domains. Results show that, as MILD combustion is a chemical kinetics-driven processes, stability issues have to be discussed in relation to fuel nature, albeit with common behavior can be derived. The coincidence between extinction/ignition phenomena is reached for extremely diluted conditions, already ascribable to MILD combustion conditions, thus defining a small sub-domain of the process. This condition can be reached through “hysteretic” or “anhysteretic” behaviors. Y1 - 2024 U6 - https://doi.org/10.1016/j.jaecs.2024.100276 VL - 19 IS - September 2024 ER - TY - GEN A1 - Vadivala, Monang A1 - Franken, Tim A1 - Thapa, Ashish A1 - Mauss, Fabian T1 - Evaluation of metamodels for prediction of species concentration and reactor outlet temperature of Sabatier reactor N2 - The production of green gases using Power-to-gas in industry and the energy sector is essential for reducing the carbon footprint. In this process, green hydrogen and carbon dioxide are converted into synthetic methane using nickel (Ni) catalysts. A one-dimensional (1D) model of a Sabatier reactor enables the simulation of transport processes in the porous medium and reaction kinetics on the Ni/Al2O3 catalyst. KW - Metamodel KW - Methane Synthesis KW - Gaussian Processes KW - Neural Network KW - Random Forest KW - Autoencoder KW - Gradient Boosting Y1 - 2025 UR - https://www.researchgate.net/publication/389675809_Evaluation_of_Metamodels_for_Prediction_of_Species_Concentration_and_Reactor_Outlet_Temperature_of_Sabatier_Reactor ER - TY - GEN A1 - Rakhi, Rakhi A1 - Shrestha, Krishna Prasad A1 - Günther, Vivien A1 - Mauß, Fabian T1 - Kinetically consistent detailed surface reaction mechanism for steam reforming of methane over nickel catalyst T2 - Reaction Kinetics, Mechanisms and Catalysis KW - Nickel-based catalyst KW - Kinetic consistency KW - Thermodynamic analysis KW - Steam reforming KW - Detailed surface reaction mechanism Y1 - 2022 UR - https://link.springer.com/article/10.1007/s11144-022-02314-7 U6 - https://doi.org/10.1007/s11144-022-02314-7 SN - 1878-5204 SN - 1878-5190 VL - 135 IS - 6 SP - 3059 EP - 3083 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Mauss, Fabian T1 - Thermodynamic model : steam and oxidative reforming of methane over nickel catalyst T2 - Reaction Kinetics, Mechanisms and Catalysis N2 - In this paper, we have used a thermodynamic model for the first time to investigate the steam and oxidative reforming of methane over a nickel catalyst in a wide temperature range, i.e., 400–1200 K. The available literature focus on the kinetic models and hence, thermodynamic models require attention to understand the behaviour of the thermochemistry of the species involved in the mechanism. This study presents the comparison between the species concentration produced using the thermodynamic model against the available kinetic model to validate the results. The investigation is further extended, firstly, to perform the sensitivity analysis of the reactions involved in a thermodynamic model to figure out the most influential reactions at various temperatures and pressures. This allows us to compare the most influencing reactions in reforming process for kinetic and thermodynamic model to optimize the processes. Secondly, the reaction flow analysis is carried out for the thermodynamic model to comprehend the effect of the thermochemistry of the species and the major difference in the reaction pathways for both the models are noted. Y1 - 2024 UR - https://link.springer.com/article/10.1007/s11144-024-02571-8 U6 - https://doi.org/10.1007/s11144-024-02571-8 VL - 137 IS - 2 SP - 791 EP - 812 PB - Springer ER - TY - GEN A1 - Rakhi, A1 - Mauss, Fabian T1 - Optimising production of synthetic natural gas (SNG) from methane synthesis T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2025 U6 - https://doi.org/10.1002/pamm.202400044 SN - 1617-7061 VL - 25 IS - 1 SP - 1 EP - 5 PB - Wiley-VCH GmbH CY - Weinheim ER - TY - GEN A1 - Shrestha, Krishna Prasad A1 - Mai, Tam V.‐T. A1 - Giri, Sushant A1 - Reddy, V. Mahendra A1 - Szőri, Milán A1 - Verma, Rakhi A1 - Mauss, Fabian A1 - Giri, Binod Raj A1 - Huynh, Lam Kim T1 - Reaction kinetics of NH₂ with H₂CO and CH₃CHO : modeling implications for NH₃‐dual fuel blends T2 - International journal of chemical kinetics N2 - Carbon‐free fuels like ammonia (NH₃) and hydrogen (H₂) offer significant potential in combating global warming by reducing greenhouse gas emissions and moving toward zero carbon emissions. Over the past few years, our research has focused on understanding the combustion behavior of carbon‐neutral and carbon‐free fuels. In particular, we have explored the combustion characteristics of NH₃ when blended with various hydrocarbons and oxygenates. Our investigation revealed that carbon‐nitrogen cross‐chemistry plays a crucial role in shaping the combustion properties of NH3‐hydrocarbon/oxygenate blends. Specifically, the chemistry of amino (NH₂) radicals is vital in influencing the low‐temperature reactivity of these blends. Understanding the interactions between carbon and nitrogen is essential for optimizing combustion processes and improving the emissions profile of NH₃‐based fuels. Recognizing the significance of this cross‐chemistry, we investigated the reaction kinetics of NH₂ radicals with formaldehyde (H₂CO) and acetaldehyde (CH₃CHO) using high‐level ab initio and transition state theory calculations. We computed the potential energy profiles of these reactions at the CCSD(T)/CBS//M06‐2X/aug‐cc‐pVTZ level of theory to analyze the reactivity of NH2 radicals at various C─H bond sites. The newly derived rate constants have proven to be highly sensitive for modeling the low‐temperature oxidation of NH₃‐dual fuel blends, significantly enhancing the predictive accuracy of our previously published kinetic models. This work offers valuable insights into the role of NH₂ radicals, thereby advancing the development of NH₃‐dual fuel systems. Y1 - 2025 U6 - https://doi.org/10.1002/kin.21781 SN - 0538-8066 SN - 1097-4601 VL - 57 IS - 7 SP - 403 EP - 416 PB - Wiley CY - New York ER - TY - GEN A1 - Giri, Binod Raj A1 - Mai, Tam V.‐T. A1 - Shrestha, Krishna Prasad A1 - Giri, Sushant A1 - Naik, R. Thirumaleswara A1 - Verma, Rakhi A1 - Mauss, Fabian A1 - Huynh, Lam K. T1 - Theoretical kinetic study of NH₂ reactions with dimethyl ether and diethyl ether : implications for kinetic modeling T2 - International journal of chemical kinetics N2 - Ammonia (NH₃) and hydrogen (H₂) have emerged as promising carbon‐free fuels to help mitigate global warming by reducing greenhouse gas emissions. Our ongoing research currently focuses on understanding the combustion characteristics of NH₃ blends with oxygenates and hydrocarbons, uncovering the critical role of carbon–nitrogen cross‐reactions in accurately modeling their combustion behavior. Amino (NH₂) radicals, which are abundant in ammonia and nitrogen‐rich environments, strongly influence the low‐temperature reactivity of NH₃‐hydrocarbon/oxygenate mixtures, affecting overall reactivity and emission characteristics. Recognizing the importance of NH₂ radicals, we investigated the reaction kinetics of NH₂ with dimethyl ether (DME, CH₃OCH₃) and diethyl ether (DEE, CH₃CH₂OCH₂CH₃) using appropriate high‐level ab initio and statistical rate theory methods. We computed the potential energy profiles at the CCSD(T)/cc‐pV(T, Q)Z//M06‐2X/aug‐cc‐pVTZ level of theory, analyzing the reactivity of NH₂ radicals at various C─H sites of these diethers. Incorporating these newly derived rate parameters, our updated kinetic model successfully captures previous experimental data, addressing the modeling challenges encountered in our earlier studies. Our findings, including insights into the impact of NH₂ radicals, contribute to an understanding of ammonia combustion and its potential in achieving carbon‐neutral energy systems. KW - Diethyl ether KW - Dimethyl ether KW - Kinetic modeling KW - NH Y1 - 2025 U6 - https://doi.org/10.1002/kin.21779 SN - 0538-8066 SN - 1097-4601 VL - 57 IS - 6 SP - 353 EP - 363 PB - Wiley CY - Hoboken, NJ ER - TY - GEN A1 - Werner, Adina A1 - Kim, Jongmin A1 - Mauss, Fabian T1 - Pressure and temperature dependent UNIQUAC model for methanol - water mixtures T2 - Fluid phase equilibria : an international journal N2 - A pressure dependency is included in a quadratic temperature dependent binary interaction parameter of the UNIQUAC model. The obtained activity coefficients for methanol-water mixtures are compared with only temperature dependent UNIQUAC and UNIFAC, and with calculated activity coefficients based on experimental data between 298.15 - 373.15 K and 0.1519 - 1.01325 bar produced with vapor-liquid equilibrium calculations and Wilson method. This model exhibits an overall good agreement. The predicted activity coefficients are more adaptable than those from models without pressure dependence, indicating potential for further improvement. Y1 - 2026 U6 - https://doi.org/10.1016/j.fluid.2025.114533 SN - 0378-3812 VL - 599 SP - 1 EP - 13 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Franken, Tim A1 - Mauss, Fabian A1 - Sharma, Saurabh A1 - Brueger, Arnim A1 - Lepka, Marco T1 - Optimization of oxyfuel biogas combustion in combined heat and power plants : a multi-criteria study T2 - 32. Deutscher Flammentag – Paderborn, Germany: 15th – 17th September 2025 N2 - This paper investigates the influence of oxygen addition on the combustion of biogas and biomethane in a combined heat and power plant using numerical methods. A multi-objective optimization platform was established, employing a stochastic engine model with detailed chemistry to predict oxyfuel combustion and emission formation. Additionally, a hybrid optimization algorithm, combining NSGA-II and metamodels, was utilized to conduct the optimization. The optimization results indicate that the lowest indicated specific fuel consumption was achieved with biomethane, while the lowest NOx emissions were attained with biogas. An increase in oxygen addition proved beneficial for reducing specific fuel consumption. However, higher oxygen addition rates resulted in increased NOx emissions. KW - Biogas KW - Optimization KW - Oxyfuel Y1 - 2025 ER -