TY - GEN A1 - Franken, Tim A1 - Rachow, Fabian A1 - Charlafti, Evgenia A1 - Flege, Jan Ingo A1 - Jenssen, Martin A1 - Verma, Rakhi A1 - Günther, Vivien A1 - Mauss, Fabian T1 - Numerical investigation of oxy-methane combustion for stationary engines T2 - 40th International Symposium on Combustion N2 - This work presents a numerical investigation of turbulent oxyfuel combustion of methane in a gas engine with passive pre-chamber. The experimental data of a motored operating point at 1600 rpm and natural gas fired operating point at 2450 rpm, 6 bar IMEP and λ=1.5 are provided by TU Freiberg to validate the simulation model. The performance of the detailed chemistry model of Shrestha et al. predicting laminar burning velocity of premixed methane-oxygen flames is evaluated using the experiments of Mouze-Mornettas et al. The detailed chemistry model predicts the laminar flame speed within an accuracy range of ±10% for elevated pressure, temperature, and different equivalence ratios. For predicting the turbulent combustion in the gas engine, a three-dimensional (3D) Large Eddy Simulation (LES) with G Equation model and laminar flame speed look-up tables is used. The chemistry in the unburnt and burnt gas is solved using a constant volume detailed chemistry solver. The 3D LES model shows a good match of the motored and natural gas fired in-cylinder pressure profile. Subsequently the fuel is switched to methane and oxygen is used as oxidizer. The 3D LES results show an increase of maximum cylinder pressure up to 100 bar for λ=1.5, and the turbulent flame regime is shifted towards high Damköhler numbers compared to combustion with air. Diluting the cylinder gas with 50 mole-% CO2 or 65 mole-% H2O shows a significant reduction of peak cylinder pressure, and lower Damköhler and higher Karlovitz numbers compared to methane-oxygen combustion. KW - Oxyfuel KW - Simulation KW - Engines Y1 - 2024 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 - David, William I. F. A1 - Agnew, Gerry D. A1 - Bañares-Alcántara, René A1 - Barth, James A1 - Hansen, John Bogild A1 - Bréquigny, Pierre A1 - De Joannon, Mara A1 - Fürstenberg Stott, Sofia A1 - Fürstenberg Stott, Conor A1 - Guati-Rojo, Andrea A1 - Hatzell, Marta A1 - MacFarlane, Douglas R. A1 - Makepeace, Joshua W. A1 - Mastorakos, Epaminondas A1 - Mauß, Fabian A1 - Medford, Andrew A1 - Mounaim-Rousselle, Christine A1 - Nowicki, Duncan A. A1 - Picciani, Mark A. A1 - Postma, Rolf S. A1 - Rouwenhorst, Kevin H. R. A1 - Sabia, Pino A1 - Salmon, Nicholas A1 - Simonov, Alexandr N. A1 - Smith, Collin A1 - Torrente-Murciano, Laura A1 - Valera-Medina, Augustin T1 - 2023 Roadmap on ammonia as a carbon-free fuel T2 - Journal of Physics: Energy N2 - The 15 short chapters that form this 2023 ammonia-for-energy roadmap provide a comprehensive assessment of the current worldwide ammonia landscape and the future opportunities and associated challenges facing the use of ammonia, not only in the part that it can play in terms of the future displacement of fossil-fuel reserves towards massive, long-term, carbon-free energy storage and heat and power provision, but also in its broader holistic impacts that touch all three components of the future global food-water-energy nexus. Y1 - 2024 U6 - https://doi.org/10.1088/2515-7655/ad0a3a SN - 2515-7655 VL - 6 IS - 2 ER - TY - GEN A1 - Giri, Binod Raj A1 - Palacios, Manuel Monge A1 - Thangaraj, Ravikumar A1 - Shrestha, Krishna Prasad A1 - Viskolcz, Béla A1 - Mauss, Fabian A1 - Szőri, Milán T1 - An Ab initio based OH initiated oxidation kinetics of glycerol carbonate: A promising biofuel component T2 - Proceedings of the Combustion Institute N2 - The global energy demand is steadily increasing because of the population explosion and economic growth. Fossil fuels supply around 85 % of global primary energy demand. On one hand, fulfilling the increasing energy demands is a big challenge for the next few decades. On the other hand, the continued burning of fossil fuels leads to higher CO2 emissions, severely impacting global warming. Therefore, the policymakers vow to shift from conventional fuels to renewable resources for economic, environmental, and future energy security reasons. In this context, biofuels from lignocellulosic biomass and/or carbon-neutral fuels produced in the sustainable carbon cycle can close the carbon cycle and reach net zero-carbon emission. Recently, glycerol carbonate has been proposed as a promising fuel or fuel additive for future sustainability. Therefore, we investigated the hydrogen abstraction reactions of glycerol carbonate (GC) by OH radicals using high-level ab initio and variational transition state theory calculations. We mapped out the potential energy surface using the CCSD(T)/cc-pV(D, T)Z//MP2/cc-pVTZ level of theory. We used the ab initio parameters to obtain the site-specific rate coefficients by employing the variational transition state theory. We observed that every hydrogen atom in GC displays a unique reactivity with OH radicals. We derived branching ratio of each channel that are difficult to access experimentally. The overall rate coefficients exhibit a strong non-Arrhenius behaviour, which can be represented as: This is the first reported rate data for the glycerol carbonate and OH radicals reaction. Y1 - 2024 UR - https://www.sciencedirect.com/science/article/abs/pii/S1540748924004760 U6 - https://doi.org/10.1016/j.proci.2024.105668 VL - 40 SP - 1 EP - 8 PB - Elsevier ER - 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 - 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 - Franken, Tim A1 - Verma, Rakhi A1 - Sharma, Saurabh A1 - Gloesslein, Tobias A1 - Brueger, Arnim A1 - Mauss, Fabian T1 - Modeling of synthetic methane production using Gaussian processes regression T2 - CYPHER Workshop on "Digital Twins for the Decarbonization of hard-to-abate industries" 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 catalysts. The carbon dioxide can be obtained from the environment or from point sources such as waste-to-energy plants, combined heat and power plants or industrial furnaces. A one-dimensional model of methane synthesis in the Sabatier reactor enables the simulation of transport processes in the porous medium and the reaction kinetics on the active surface of the nickel catalyst. Despite the low dimensionality, the reactor model is still computationally intensive, as it must solve the reaction mechanism of heterogeneous surface reactions and the mass and heat transport. The introduction of Gaussian processes regression can help to significantly reduce the computational effort for the prediction of species and temperature in the Sabatier reactor under different thermodynamic conditions. This allows for faster turnaround times, enables the application of advanced methods like optimization and more. The accuracy of a Gaussian processes regression is investigated in this work. KW - Gaussian Processes KW - Machine Learning KW - Reactor Y1 - 2024 UR - https://www.researchgate.net/publication/384441411_Modeling_of_synthetic_methane_production_using_Gaussian_processes_regression ER -