@misc{RakhiGuentherMauss, author = {Rakhi, Rakhi and G{\"u}nther, Vivien and Mauß, Fabian}, title = {A detailed surface reaction mechanism to investigate oxidation of methane over nickel catalyst}, series = {Proceedings in Applied Mathematics \& Mechanics : PAMM}, volume = {22}, journal = {Proceedings in Applied Mathematics \& Mechanics : PAMM}, number = {1}, issn = {1617-7061}, doi = {10.1002/pamm.202200055}, abstract = {We have developed a kinetically consistent detailed surface reaction mechanism for modeling the oxidation of methane over a nickel-based catalyst. A one-dimensional model, LOGEcat based on the single-channel 1D catalyst model, is used to perform the simulations. The original multi-step reaction mechanism is thermodynamically consistent and consists of 52 reactions. By thermodynamic consistency, we mean that the equilibrium is achieved with the support of the Arrhenius parameters and does not depend on the thermochemistry of the species involved in the considered reactions. The detailed mechanism developed in this investigation contains 26 reversible reactions. These reactions are obtained with the use of the thermochemistry of the species. The study focuses on ensuring kinetic consistency and this is done with the help of thermodynamic analysis by bringing the thermochemistry of the species in play in order to develop a surface reaction mechanism. The new mechanism can be used to understand the other processes, for example, steam- and dry-reforming of methane over nickel, however, the main focus of the paper is to check the performance of the detailed mechanism for catalytic partial oxidation of methane. The applicability of the mechanism is checked for various reactor conditions in terms of parameters such as temperature and pressure by comparing the results with the available reference data. The detailed mechanism developed in this study is able to accurately express oxidation of methane over the nickel catalyst for the considered reactor conditions.}, language = {en} } @misc{RakhiGuentherMauss, author = {Rakhi, Rakhi and G{\"u}nther, Vivien and Mauß, Fabian}, title = {Insights into dry reforming of methane over nickel catalyst using a thermodynamic model}, series = {Reaction Kinetics, Mechanisms and Catalysis}, journal = {Reaction Kinetics, Mechanisms and Catalysis}, issn = {1878-5204}, doi = {10.1007/s11144-023-02426-8}, pages = {14}, abstract = {A thermodynamic model is developed using a one-dimensional model, LOGEcat to understand the dry reforming of methane over nickel-based catalysts. To do so, we have extended our previously developed mechanism (Rakhi and Shrestha in React Kinet, Mech Catal 135:3059-3083, 2022) which contains 21 reversible reactions by adding 5 more reversible reactions and updating the thermochemistry of one intermediate species. The adjusted mechanism contains 26 reversible reactions obtained with the help of thermodynamic analysis. This study focuses on using the thermodynamic model for dry reforming of methane and insights into the reaction pathways and sensitivity analysis for the kinetically consistent surface reaction mechanism. The applicability of the mechanism is examined for reactor conditions in terms of parameters such as temperature by comparing the results with the available reference data. The mechanism is able to accurately express the reforming conditions of methane over the nickel catalyst for complete range of temperature and also provide useful insights into the reaction pathways established with the thermodynamic model.}, language = {en} } @misc{SiddareddyFrankenLeondeSyniawaetal., author = {Siddareddy, Reddy Babu and Franken, Tim and Leon de Syniawa, Larisa and Pasternak, Michal and Prehn, Sascha and Buchholz, Bert and Mauß, Fabian}, title = {Simulation of CNG Engine in Agriculture Vehicles. Part 1: Prediction of Cold Start Engine-Out Emissions Using Tabulated Chemistry and Stochastic Reactor Model}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, issn = {0148-7191}, doi = {10.4271/2023-24-0006}, abstract = {Worldwide, there is the demand to reduce harmful emissions from non-road vehicles to fulfill European Stage V+ and VI (2022, 2024) emission legislation. The rules require significant reductions in nitrogen oxides (NOx), methane (CH4) and formaldehyde (CH2O) emissions from non-road vehicles. Compressed natural gas (CNG) engines with appropriate exhaust aftertreatment systems such as threeway catalytic converter (TWC) can meet these regulations. An issue remains for reducing emissions during the engine cold start where the CNG engine and TWC yet do not reach their optimum operating conditions. The resulting complexity of engine and catalyst calibration can be efficiently supported by numerical models. Hence, it is required to develop accurate simulation models which can predict cold start emissions. This work presents a real-time engine model for transient engine-out emission prediction using tabulated chemistry for CNG. The engine model is based on a stochastic reactor model (SRM) which describes the in-cylinder processes of spark ignition (SI) engines including large-scale and lowscale turbulence, convective heat transfer, turbulent flame propagation and chemistry. Chemistry is described using a tabulated chemistry model which calculates the major exhaust gas emissions of CNG engines such as CO2, NOx, CO, CH4 and CH2O. By best practice, the engine model parameters are optimized by matching the experimental cylinder pressure and engine-out emissions from steady-state operating points. The engine model is trained for a non-road transient cycle (NRTC) cold start at 25°C ambient temperature and validated for a NRTC cold start at 10°C ambient temperature. The trained model is evaluated regarding their feasibility and accuracy predicting transient engineout emissions.}, language = {en} } @misc{LeondeSyniawaSiddareddyPrehnetal., author = {Leon de Syniawa, Larisa and Siddareddy, Reddy Babu and Prehn, Sascha and G{\"u}nther, Vivien and Franken, Tim and Buchholz, Bert and Mauß, Fabian}, title = {Simulation of CNG Engine in Agriculture Vehicles. Part 2: Coupled Engine and Exhaust Gas Aftertreatment Simulations Using a Detailed TWC Model}, series = {SAE Technical Paper}, journal = {SAE Technical Paper}, issn = {0148-7191}, doi = {10.4271/2023-24-0112}, abstract = {In more or less all aspects of life and in all sectors, there is a generalized global demand to reduce greenhouse gas (GHG) emissions, leading to the tightening and expansion of existing emissions regulations. Currently, non-road engines manufacturers are facing updates such as, among others, US Tier 5 (2028), European Stage V (2019/2020), and China Non-Road Stage IV (in phases between 2023 and 2026). For on-road applications, updates of Euro VII (2025), China VI (2021), and California Low NOx Program (2024) are planned. These new laws demand significant reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions from heavy-duty vehicles. When equipped with an appropriate exhaust aftertreatment system, natural gas engines are a promising technology to meet the new emission standards. Gas engines require an appropriate aftertreatment technology to mitigate additional GHG releases as natural gas engines have challenges with methane (CH4) emissions that have 28 times more global warming potential compared to CO2. Under stoichiometric conditions a three-way catalytic converter (TWC - stoichiometric combustion) can be used to effectively reduce emissions of harmful pollutants such as nitrogen oxides and carbon monoxide (CO) as well as GHG like methane. The aim of the present study is to understand the performance of the catalytic converter in function of the engine operation and coolant temperature in order to optimize the catalyst operating conditions. Different cooling temperatures are chosen as the initial device temperature highly affects the level of warm up emissions such that low coolant temperatures entail high emissions. In order to investigate the catalyst performance, experimental and virtual transient engine emissions are coupled with a TWC model to predict tail-pipe emissions at transient operating conditions. Engine experiments are conducted at two initial engine coolant temperatures (10°C and 25°C) to study the effects on the Non-Road Transient Cycle (NRTC) emissions. Engine simulations of combustion and emissions with acceptable accuracy and with low computational effort are developed using the Stochastic Reactor Model (SRM). Catalyst simulations are performed using a 1D catalytic converter model including detailed gas and surface chemistry. The initial section covers essential aspects including the engine setup, definition of the engine test cycle, and the TWC properties and setup. Subsequently, the study introduces the transient SI-SRM, 1D catalyst model, and kinetic model for the TWC. The TWC model is used for the validation of a NRTC at different coolant temperatures (10°C and 25°C) during engine start. Moving forward, the next section includes the coupling of the TWC model with measured engine emissions. Finally, a virtual engine parameter variation has been performed and coupled with TWC simulations to investigate the performance of the engine beyond the experimental campaign. Various engine operating conditions (lambda variation for this paper) are virtually investigated, and the performance of the engine can be extrapolated. The presented virtual development approach allows comprehensive emission evaluations during the initial stages of engine prototype development}, language = {en} } @misc{DavidAgnewBanaresAlcantaraetal., author = {David, William I. F. and Agnew, Gerry D. and Ba{\~n}ares-Alc{\´a}ntara, Ren{\´e} and Barth, James and Hansen, John Bogild and Br{\´e}quigny, Pierre and De Joannon, Mara and F{\"u}rstenberg Stott, Sofia and F{\"u}rstenberg Stott, Conor and Guati-Rojo, Andrea and Hatzell, Marta and MacFarlane, Douglas R. and Makepeace, Joshua W. and Mastorakos, Epaminondas and Mauß, Fabian and Medford, Andrew and Mounaim-Rousselle, Christine and Nowicki, Duncan A. and Picciani, Mark A. and Postma, Rolf S. and Rouwenhorst, Kevin H. R. and Sabia, Pino and Salmon, Nicholas and Simonov, Alexandr N. and Smith, Collin and Torrente-Murciano, Laura and Valera-Medina, Augustin}, title = {2023 Roadmap on ammonia as a carbon-free fuel}, series = {Journal of Physics: Energy}, volume = {6}, journal = {Journal of Physics: Energy}, number = {2}, issn = {2515-7655}, doi = {10.1088/2515-7655/ad0a3a}, abstract = {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.}, language = {en} } @misc{GiriPalaciosThangarajetal., author = {Giri, Binod Raj and Palacios, Manuel Monge and Thangaraj, Ravikumar and Shrestha, Krishna Prasad and Viskolcz, B{\´e}la and Mauss, Fabian and Szőri, Mil{\´a}n}, title = {An Ab initio based OH initiated oxidation kinetics of glycerol carbonate: A promising biofuel component}, series = {Proceedings of the Combustion Institute}, volume = {40}, journal = {Proceedings of the Combustion Institute}, publisher = {Elsevier}, doi = {10.1016/j.proci.2024.105668}, pages = {1 -- 8}, abstract = {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.}, language = {en} } @misc{EckartShresthaGirietal., author = {Eckart, Sven and Shrestha, Krishna P and Giri, Binod R and Fang, Qilong and Li, Wei and Mauss, Fabian and Krause, Hartmut and Li, Yuyang}, title = {Insight into premixed diethoxymethane flames: Laminar burning velocities, temperatures, and emissions behaviour}, series = {Proceedings of the Combustion Institute}, volume = {40}, journal = {Proceedings of the Combustion Institute}, publisher = {Elsevier}, doi = {10.1016/j.proci.2024.105579}, pages = {1 -- 7}, abstract = {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.}, language = {en} } @misc{EckartShresthaGirietal., author = {Eckart, Sven and Shrestha, Krishna P and Giri, Binod R and Fang, Qilong and Chen, Chen and Li, Wei and Krause, Hartmut and Mauss, Fabian and Liu, Dong and Li, Yuyang}, title = {Chemical insights into ethyl acetate flames from experiment and kinetic modeling: Laminar burning velocity, speciation and NOx emission}, series = {Proceedings of the Combustion Institute}, volume = {40 (2024)}, journal = {Proceedings of the Combustion Institute}, publisher = {Elsevier}, doi = {10.1016/j.proci.2024.105487}, pages = {1 -- 7}, abstract = {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.}, language = {en} } @misc{ThomasShresthaMaussetal., author = {Thomas, Daniel E and Shrestha, Krishna P and Mauss, Fabian and Northrop, William F}, title = {Extinction and NO formation of ammonia-hydrogen and air non-premixed counterflow flames}, series = {Proceedings of the Combustion Institute}, volume = {39}, journal = {Proceedings of the Combustion Institute}, number = {2}, publisher = {Elsevier}, doi = {10.1016/j.proci.2022.08.067}, pages = {1803 -- 1812}, abstract = {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.}, language = {en} } @misc{PasternakSiddareddydeSyniawaetal., author = {Pasternak, Michał and Siddareddy, Reddy Babu and de Syniawa, Larisa Le{\´o}n and Guenther, Vivien and Picerno, Mario and Andert, Jakob and Franken, Tim and Mauss, Fabian and Adamczyk, Wojciech}, title = {Plant modelling of engine and aftertreatment systems for X-in-the-loop simulations with detailed chemistry}, series = {CONAT 2024 International Congress of Automotive and Transport Engineering.}, journal = {CONAT 2024 International Congress of Automotive and Transport Engineering.}, publisher = {Springer Nature Switzerland}, address = {Cham}, isbn = {978-3-031-77626-7}, doi = {10.1007/978-3-031-77627-4_14}, pages = {151 -- 163}, abstract = {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.}, language = {en} }