@misc{ShresthaMaiGirietal., author = {Shrestha, Krishna Prasad and Mai, Tam V.-T. and Giri, Sushant and Reddy, V. Mahendra and Szőri, Mil{\´a}n and Verma, Rakhi and Mauss, Fabian and Giri, Binod Raj and Huynh, Lam Kim}, title = {Reaction kinetics of NH₂ with H₂CO and CH₃CHO : modeling implications for NH₃-dual fuel blends}, series = {International journal of chemical kinetics}, volume = {57}, journal = {International journal of chemical kinetics}, number = {7}, publisher = {Wiley}, address = {New York}, issn = {0538-8066}, doi = {10.1002/kin.21781}, pages = {403 -- 416}, abstract = {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.}, language = {en} } @misc{GiriMaiShresthaetal., author = {Giri, Binod Raj and Mai, Tam V.-T. and Shrestha, Krishna Prasad and Giri, Sushant and Naik, R. Thirumaleswara and Verma, Rakhi and Mauss, Fabian and Huynh, Lam K.}, title = {Theoretical kinetic study of NH₂ reactions with dimethyl ether and diethyl ether : implications for kinetic modeling}, series = {International journal of chemical kinetics}, volume = {57}, journal = {International journal of chemical kinetics}, number = {6}, publisher = {Wiley}, address = {Hoboken, NJ}, issn = {0538-8066}, doi = {10.1002/kin.21779}, pages = {353 -- 363}, abstract = {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.}, language = {en} } @misc{WernerKimMauss, author = {Werner, Adina and Kim, Jongmin and Mauss, Fabian}, title = {Pressure and temperature dependent UNIQUAC model for methanol - water mixtures}, series = {Fluid phase equilibria : an international journal}, volume = {599}, journal = {Fluid phase equilibria : an international journal}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0378-3812}, doi = {10.1016/j.fluid.2025.114533}, pages = {1 -- 13}, abstract = {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.}, language = {en} } @misc{FrankenMaussSharmaetal., author = {Franken, Tim and Mauss, Fabian and Sharma, Saurabh and Brueger, Arnim and Lepka, Marco}, title = {Optimization of oxyfuel biogas combustion in combined heat and power plants : a multi-criteria study}, series = {32. Deutscher Flammentag - Paderborn, Germany: 15th - 17th September 2025}, journal = {32. Deutscher Flammentag - Paderborn, Germany: 15th - 17th September 2025}, abstract = {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.}, language = {en} } @misc{AsgarzadeFrankenMauss, author = {Asgarzade, Rufat and Franken, Tim and Mauss, Fabian}, title = {Experimental investigation of CH4/O2/CO2 mixtures in a single-cylinder spark ignition engine}, pages = {1}, abstract = {The Power-to-X-to-Power (P2X2P) technology involves producing synthetic methane from renewable hydrogen and captured CO2, which is then used for cogeneration of electricity and heat through oxyfuel combustion. With the P2X2P energy system demonstrator, NOx-free and carbon neutral heat and electricity generation as well as storage of excess renewable energy are realized. This work presents the experimental investigation of combustion characteristics for CH4/O2/CO2 mixtures in a single cylinder spark ignition engine that is a part of the P2X2P system.}, language = {en} } @misc{AsgarzadeFrankenMauss, author = {Asgarzade, Rufat and Franken, Tim and Mauss, Fabian}, title = {Development of an oxyfuel engine test bench for power-to-X-to-power application}, series = {12th European Combustion Meeting}, journal = {12th European Combustion Meeting}, pages = {1}, abstract = {This work presents the development of an oxyfuel engine test bench which is integrated into a Power-to-X-to-Power energy storage system demonstrator. These storage systems are considered carbon-free because they recirculate carbon without emitting it into the atmosphere.}, language = {en} } @misc{AsgarzadeFrankenMauss, author = {Asgarzade, Rufat and Franken, Tim and Mauss, Fabian}, title = {Oxyfuel combustion process development for an SI engine in a power-to-X-to-power energy system}, pages = {1}, abstract = {This work presents the development of an oxyfuel engine test bench which is to be integrated to a Power-to-X-to-Power energy storage system demonstrator. Such storage systems are considered carbon-neutral because they recirculate carbon without emitting it into the atmosphere.}, language = {en} } @misc{WernerKimMauss, author = {Werner, Adina and Kim, Jongmin and Mauss, Fabian}, title = {Excess volumes calculated from UNIQUAC model using the example of methanol - water mixtures}, series = {Fluid phase equilibria}, volume = {603}, journal = {Fluid phase equilibria}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0378-3812}, doi = {10.1016/j.fluid.2025.114650}, pages = {1 -- 13}, abstract = {Excess volumes can be calculated generally via equations of state. In this work, the excess volumes are obtained using the UNIQUAC model with two approaches of a temperature- and pressure-dependent binary interaction parameter. The pressure dependency is required as the excess volume is derived from the pressure dependency of the excess free enthalpy. Both UNIQUAC approaches are successfully able to predict the vapor-liquid equilibrium as well as the excess volume of methanol-water mixtures over a temperature range between 288.15-473 K and a pressure range between 0.1519-134 bar using a single optimized parameter set.}, language = {en} } @misc{FrankenVermaSharmaetal., author = {Franken, Tim and Verma, Rakhi and Sharma, Saurabh and Gloesslein, Tobias and Brueger, Arnim and Mauss, Fabian}, title = {Modeling of synthetic methane production using Gaussian processes regression}, series = {CYPHER Workshop on "Digital Twins for the Decarbonization of hard-to-abate industries"}, journal = {CYPHER Workshop on "Digital Twins for the Decarbonization of hard-to-abate industries"}, abstract = {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.}, language = {en} } @misc{ShresthaGiriPeleetal., author = {Shrestha, Krishna Prasad and Giri, Binod Raj and Pel{\´e}, Ronan and Aljohani, Khalid and Brequigny, Pierre and Mauss, Fabian and Halter, Fabien and Huynh, Lam K. and Mouna{\"i}m-Rousselle, Christine}, title = {A comprehensive chemical kinetic modeling and experimental study of NH₃-methanol/ethanol combustion towards net-zero CO₂ emissions}, series = {Combustion and flame}, volume = {274}, journal = {Combustion and flame}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2024.113954}, pages = {1 -- 21}, abstract = {Ammonia is gaining attention as a green fuel with the potential to reduce carbon emissions. Its versatility allows it to be used directly in combustion engines, fuel cells, and as a hydrogen carrier, making it a key candidate for sustainable energy applications. This study provides a comprehensive analysis of the oxidation kinetics of ammonia (NH3) blends with methanol (CH3OH) and ethanol (C2H5OH) under diverse conditions. We measured laminar flame speeds of different NH3-alcohol blends — varying CH3OH/C2H5OH ratios (0-100 \%) — using a constant volume combustion chamber across temperatures from 503 to 645 K and pressures of 2-11.3 bar. We also obtained the ignition delay times for NH3/C2H5OH blends with 10 \% and 30 \% (by mole) C2H5OH using a shock tube at pressures of 1, 10, and 20 bar and temperatures of 1100-1500 K. Our results show that incorporating CH3OH and C2H5OH into NH3 increases the laminar flame speed, with C2H5OH being a more effective promoter than CH3OH due to its higher contribution to the formation of reactive radicals (OH, H, and O). Our model suggests that at high temperatures, both CH3OH and C2H5OH contribute to increased NO formation, with C2H5OH being more effective in reducing N2O emissions than CH3OH. In shock tube experiments, adding C2H5OH significantly shortens ignition delay times of NH3. At low temperatures (in the rapid compression machine case), the sensitivity to ignition delay times decreases when the CH3OH/C2H5OH content exceeds 5 \% in NH3-alcohol blends. C2H5OH is a more effective combustion promoter, enhancing NH3 reactivity and reducing NOx emission more efficiently than CH3OH. We developed a detailed kinetic model, building on our previous work, and validated it against new experimental and literature data. Our model accurately predicts the combustion behavior of neat NH3 and NH3 fuel blends and serves as a base for future research on NH3 blended with higher hydrocarbons and/or oxygenated blends.}, language = {en} } @misc{PasternakPrzybyłaSiddareddyetal., author = {Pasternak, Michał and Przybyła, Grzegorz and Siddareddy, Reddy and Lewandowski, Michał and Bj{\o}rgen, Karl and Mauss, Fabian and Nadimi, Ebrahim and Peczkis, Grzegorz and Zhou, Min-min and Adamczyk, Wojciech}, title = {Development of ammonia-biodiesel fueled agricultural tractor : aspects of retrofitting a compression ignition engine to direct ammonia injection}, series = {Energy}, volume = {327}, journal = {Energy}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0360-5442}, doi = {10.1016/j.energy.2025.136255}, pages = {1 -- 14}, abstract = {The automotive industry has shown growing interest in ammonia as a carbon-free fuel, which holds potential for mitigating the greenhouse effect. Nonetheless, adapting current combustion engines to use ammonia necessitates prior modifications. This paper introduces a retrofitting technique for converting an existing compression ignition engine into one powered by a direct injection of ammonia and biodiesel. The development results from collaboration between Polish and Norwegian research teams as part of the ACTIVATE project (Ammonia as carbon-free fuel for internal combustion engine-driven agricultural vehicles). The new technology is grounded on experimental and numerical research involving a single-cylinder engine installed in a small agricultural tractor. Biodiesel was directly injected to initiate ammonia combustion. Experimental activities were performed on engine test benches and a chassis dynamometer, complemented by 0D and 3D simulations using the stochastic reactor model and CFD code Converge, respectively. A comprehensive exploration of engine operating conditions and fuel injection strategies was undertaken experimentally and numerically to assess the potential benefits and drawbacks of various designs. A segment of the research focused on analyzing nitrous oxide formation, given its significant impact on global warming. The investigations resulted in a method for combusting ammonia with biodiesel as an ignition enhancer. It was determined that maintaining a stable engine operation in a tractor under real driving scenarios requires 47\% of the energy sourced from ammonia. Optimal engine performance occurs when ammonia and biodiesel are injected near the end of the compression stroke, closely followed by the ignition promoter. A prolonged interval between these injections impairs combustion efficiency and raises ammonia emissions. The integrated numerical and experimental research resulted in a demonstration tractor fueled by directly injected biodiesel and ammonia.}, language = {en} } @misc{HemaiziaVermaGuanetal., author = {Hemaizia, Abdelkader and Verma, Rakhi and Guan, Wei and Mauss, Fabian and Th{\´e}venin, Dominique}, title = {The influence of hydrocarbon additives on laminar burning velocity and NOx emissions in hydrogen-air combustion}, series = {Proceedings in applied mathematics and mechanics : PAMM}, volume = {25}, journal = {Proceedings in applied mathematics and mechanics : PAMM}, number = {4}, editor = {Mauss, Fabian}, publisher = {Wiley}, address = {Weinheim}, issn = {1617-7061}, doi = {10.1002/pamm.70028}, pages = {1 -- 13}, abstract = {Hydrogen is a promising carbon-free fuel but faces challenges due to combustion instability and nitrogen oxide () emissions during combustion. This study investigates the potential of blending hydrocarbons (methane, propane) or ammonia with hydrogen-air flames in order to minimize these challenges. Simulations were performed using a one-dimensional, freely-propagating, adiabatic premixed flame (FPPF) model in Cantera, incorporating detailed kinetic and thermodynamic modeling. Updated, detailed, and reduced reaction mechanisms were utilized to accurately represent the chemical kinetics of the selected fuel blends. We analyzed laminar flame velocity (LFV), flame structure, and emissions of and CO across a range of inlet pressures, temperatures, equivalence ratios, and blend ratios of /, /, and /. The results were validated against experimental data. Propane addition (10\% -60\% vol.) was found to be the most effective solution to reduce emissions by promoting reburning pathways that convert NO to , while moderately reducing LFV. Methane exhibits a comparable effect in suppressing thermal while slightly reducing LFV. Ammonia drastically lowers via fuel-bound nitrogen pathways but sharply increases CO emissions and destabilizes flames at high concentrations. By identifying key reaction pathways governing formation (thermal, prompt, , NNH, and reburning), propane is finally selected as the optimal additive for achieving low- hydrogen combustion, despite its trade-off with LFV, providing critical insights for designing cleaner and more stable combustion systems.}, language = {en} } @misc{VermaGuentherGirietal., author = {Verma, Rakhi and G{\"u}nther, Vivien and Giri, Binod Raj and Hemaizia, Abdelkader and Th{\´e}venin, Dominique and Mauss, Fabian}, title = {Kinetic modeling of CO₂ methanation for methane production : a comprehensive study}, series = {IFAC-PapersOnLine}, volume = {59}, journal = {IFAC-PapersOnLine}, number = {29}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2025.12.175}, pages = {18 -- 23}, abstract = {To understand the complex methanation reaction, experiments have been conducted at various operating conditions, for instance, temperature, inlet gas dilution, and inlet composition. In addition, a detailed surface reaction mechanism is developed to conduct the study numerically by validating the simulation results with the experimental data. The kinetic model developed in this study is able to capture the experimental trends successfully for all conditions considered for the analysis.}, language = {en} } @misc{VermaGuentherGirietal., author = {Verma, Rakhi and G{\"u}nther, Vivien and Giri, Binod Raj and Mauss, Fabian}, title = {Effect of pressure and nitrogen dilution on surface species and reaction kinetics in CO₂ methanation over Ni catalyst}, series = {IFAC-PapersOnLine}, volume = {59}, journal = {IFAC-PapersOnLine}, number = {29}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2025.12.172}, pages = {1 -- 5}, abstract = {The CO2 methanation process is studied under varying pressures to support the development of efficient and sustainable technologies aligned with emission reduction and hydrogen economy goals. Experiments at two pressures, followed by pressure-dependent simulations, show strong agreement. Additionally, surface species coverage is analyzed, offering insights into catalytic behavior. These findings aid in optimizing methanation by deepening understanding of reaction mechanisms and guiding the design of improved catalysts.}, language = {en} } @misc{VermaMauss, author = {Verma, Rakhi and Mauss, Fabian}, title = {Equilibrium analysis for methanation focusing on CO₂ derived substitute natural gas}, series = {Proceedings of the Second SIMS EUROSIM Conference on Modelling and Simulation, SIMS EUROSIM 2024}, volume = {211}, journal = {Proceedings of the Second SIMS EUROSIM Conference on Modelling and Simulation, SIMS EUROSIM 2024}, publisher = {Link{\"o}ping University Electronic Press}, address = {Link{\"o}ping}, isbn = {978-91-8075-984-7}, issn = {1650-3686}, doi = {10.3384/ecp212.022}, pages = {162 -- 167}, abstract = {In this study the methanation of synthesis gas (syngas) is investigated with a focus on achieving maximum methane and minimum CO by full methanation of CO2. For this study, we have considered a comprehensive thermodynamics analysis of CO2 hydrogenation. This will help us to understand the thermodynamic behaviour of the reactions involved in the methanation process. We have discussed the behavior of the species, CO2, H2, CH4, and H2O at the equilibrium with temperature, pressure, and fuel ratio variation in order to get the desired output. The preliminary study will focus on selecting the optimum conditions (temperature, pressure, and H2/CO2 ratio) for performing the experiments and for catalyst development.}, language = {en} } @misc{HemaiziaVermaMaussetal., author = {Hemaizia, Abdelkader and Verma, Rakhi and Mauss, Fabian and Th{\´e}venin, Dominique}, title = {On the impact of swirl number on premixed C3H8/air combustion in a bluff-body burner}, series = {IFAC-PapersOnLine}, volume = {59}, journal = {IFAC-PapersOnLine}, number = {29}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2025.12.201}, pages = {174 -- 179}, abstract = {Utilizing ANSYS-Fluent 21.0, large eddy simulations (LES) of the reactive flow in the Volvo bluff-body burner under various swirl intensities were performed. The Eddy Dissipation Concept (EDC) model coupled with a reduced chemical mechanism was employed to simulate premixed combustion. Results show thatLES is able to capture the interaction between swirl strength and fame stabilization behind the bluff-body. High swirl numbers generate strong central recirculation zones (CRZ), which enhance fame anchoring and combustion efficiency through increased hot gas recirculation and improved turbulent mixing.}, language = {en} } @misc{SiddareddyPasternakdeSyniawaetal., author = {Siddareddy, Reddy Babu and Pasternak, Michał and de Syniawa, Larisa Le{\´o}n and Guenther, Vivien and Seidel, Lars and Mauss, Fabian and Przybyła, Grzegorz and Adamczyk, Wojciech}, title = {Simulations of the SCR catalyst in ammonia-biodiesel fuelled CI engine using virtual test bench with detailed chemistry}, series = {Renewable energy}, volume = {251}, journal = {Renewable energy}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0960-1481}, doi = {10.1016/j.renene.2025.123169}, pages = {1 -- 12}, abstract = {The use of ammonia as an alternative fuel in the automotive industry is not yet fully established. Further research and development are required to account for both engine and aftertreatment systems, as well as their integration and control to ensure the most efficient use of ammonia. In this work, we present a fully physics and chemistry-based toolchain for co-simulating an ammonia-biodiesel fuelled compression ignition engine with a selective catalytic reduction catalyst. The investigations refer to experimental data from a single-cylinder research engine. This is a direct injection engine that was retrofitted to run on ammonia and biodiesel, the latter acting as a combustion promoter. Engine in-cylinder processes were simulated using a stochastic reactor model. Detailed gas phase chemistry is used to simulate the combustion process and pollutants formation. The catalyst model employs detailed surface chemistry that is trained using available data from literature. Eventually, the co-simulation toolchain was applied to investigate numerically the impact of the properties of the catalyst on ammonia reduction under engine-relevant operating conditions}, language = {en} } @misc{WelpRudolphGirietal., author = {Welp, Alexandra and Rudolph, Charlotte and Giri, Binod Raj and Shrestha, Krishna Prasad and Verma, Rakhi and Mauss, Fabian and Atakan, Burak}, title = {Oxidation kinetics of ammonia methanol blends : an experimental and kinetic modeling study}, series = {Combustion and flame}, volume = {278}, journal = {Combustion and flame}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2025.114210}, pages = {1 -- 11}, abstract = {Ammonia is emerging as a key hydrogen energy carrier for decarbonization. However, its low reactivity necessitates blending with hydrocarbons and/or oxygenates, such as alcohols, to improve combustion properties. Understanding the oxidation kinetics of such blends is essential for evaluating ammonia's potential as a sustainable fuel. The experimental data on ammonia blended with simple alcohols like methanol remains scarce. This study investigates the oxidation kinetics of ammonia/methanol blends for the first time using a plug-flow reactor coupled with a time-of-flight mass spectrometer setup. This advanced setup enabled simultaneous quantification of temperature-dependent reactant conversion and product distribution over a temperature range of 373-973 K, a pressure of 3 bar, and equivalence ratios of 1 and 2. Adding 10 \% methanol significantly enhances radical formation, reducing oxidation onset temperature compared to neat ammonia. Interestingly, the conversion onset temperature was only slightly influenced by the mixture composition or the equivalence ratio. The temperature dependence of the product distribution as a function of the equivalence ratio was further analyzed. Experimental results were compared to simulation using selected kinetic models from the literature, revealing significant disparities in predicting capabilities. Among the kinetic models, Shrestha 2025, He 2023 and Wang 2024 performed well, capturing our experimental data for NH3/CH3OH blends. Reaction flux and sensitivity analyses highlighted some key reactions involving the reactive combustion species (OH, HO2 and NH2), such as CH3OH+HO2 ⇌ CH2OH+H2O2 and CH3OH+NH2, governing the oxidation kinetics of NH3/CH3OH blends. This combined experimental and kinetic modeling approach provides valuable insights into fundamental reaction mechanisms of NH3/CH3OH blends, aiding the development of cleaner and more efficient combustion systems.}, language = {en} } @misc{RotheBikasMauss, author = {Rothe, Paul and Bikas, Georgios and Mauss, Fabian}, title = {Investigation of the combustion process of a thermally conditioned active prechamber in monovalent operation with ammonia}, series = {SAE technical papers}, journal = {SAE technical papers}, publisher = {SAE International}, address = {Warrendale, PA}, issn = {0148-7191}, doi = {10.4271/2025-24-0028}, pages = {13}, abstract = {The debate over synthetic fuels is intense especially in sectors with a high energy demand like maritime [1, 2]. Hydrogen production from renewable sources is growing, but immediate measures for decarbonization are needed [3, 4]. In this context, the project MethMag was funded, and a gas engine for methane combustion with an innovative cooling concept and a purged prechamber (PC) spark plug was virtually developed [5, 6]. Validation with data from the test bench demonstrates that the simulations accurately represent the operating conditions [7, 8]. This combustion process is adapted for ammonia, which is being considered as a climate-friendly fuel of the future, particularly in maritime transportation [4, 9]. This fuel faces significant combustion challenges and is therefore mostly considered in complex, bivalent systems [10]. In particular, the prechamber is examined regarding the ignitability of ammonia. The overarching objective is to eliminate the necessity for a secondary fuel system, thereby reducing system complexity and associated costs. The transition to ammonia highlights the need for further adjustments. The geometry of the PC cap significantly affects turbulence and mixture formation in the prechamber [11]. While swirl caps generate high turbulence, the mixture formation is inadequate. Tumble caps, on the other hand, provide advantages in mixture formation by achieving an earlier increase in turbulence, even though the maximum turbulence is lower. For ammonia combustion, PC wall conditioning is not essential, given the inherently low combustion temperatures. However, conditioning can improve cold-start behavior by accelerating PC combustion and offering greater flexibility in ignition timing [12]. Direct injection into the prechamber enhances fuel mixing and reduces sensitivity to ignition timing adjustments. This leads to higher efficiency and better combustion characteristics, particularly at lean air-fuel ratios [13, 14]. Operating with a lean ammonia-air mixture is challenging but offers benefits for non-selective catalytic reduction (non-SCR) of nitrogen oxides. Simulations show that operation with λ = 1.2 and λ = 1.4 is feasible, although efficiency decreases at leaner mixtures [15].}, language = {en} } @misc{UdaybhanuGiriLeeetal., author = {Udaybhanu, Gadi and Giri, Binod R. and Lee, Bok Jik and Shrestha, Krishna P. and Roberts, William L and Mauss, Fabian and Reddy, V. Mahendra}, title = {Investigation of staging techniques for hydrocarbon-assisted ammonia flames in a novel dual-stage combustor}, series = {Combustion and flame}, volume = {284}, journal = {Combustion and flame}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2025.114607}, pages = {1 -- 12}, abstract = {Ammonia presents itself as a high-hydrogen dense and carbon-free alternative for industrial heating, power generation, and transportation. Nevertheless, the challenges of its low flame speed and elevated NOx (nitrogen oxides) emissions pose significant challenges in combustor applications. This study investigates a novel two-stage burner employing a radial injection staging technique and explores various NOx reduction strategies for hydrocarbon-assisted ammonia flames. These strategies include premixing, fuel staging, balanced fuel staging, air staging, and sequential premixing. The focus is on LPG (liquid petroleum gas)-stabilized ammonia flames. The experiments are conducted at a constant thermal input of 20 kW (10 kW LPG + 10 kW NH3), with global equivalence ratios ranging from 0.7 to 1.4. This approach aims to provide valuable insights into the effectiveness of different staging strategies for NOx reduction in ammonia combustion. Experimental analysis is undertaken to ascertain the flame stabilization, flame temperature and its reaction zone, intermediate species and major emissions like NOx and NH3 of the burner. Staging configuration strongly influenced flame stabilization, heat release distribution, and thermal field, with downstream-shifted combustion zones lowering peak temperatures and NOx formation. Among the tested strategies, fuel staging and sequential premixing consistently achieved the greatest NOx reduction across the entire operating range compared to the premixed baseline, without compromising flame stability. Chemical kinetics analysis further reveals the dominant NO formation pathways, highlighting the key roles of HNO and NHi radicals. Additionally, this analysis helps identify dominant reaction routes and the role of intermediate species in NO formation and reduction processes. The combined experimental and kinetic insights provide a mechanistic basis for optimizing staged combustion of ammonia-hydrocarbon blends for lower NOx emissions.}, language = {en} }