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Ammonia is considered one of the most promising fuels, and mixing ammonia with hydrogen as fuel can achieve zero carbon emissions for engines. In this study, an experimental platform for an ammonia/hydrogen rotary engine was constructed, and successful ignition combustion was performed, demonstrating the possibility of the ammonia/hydrogen rotary engine. A 3-dimensional computational model of the ammonia/hydrogen rotary engine coupled with chemical reaction mechanisms was established, and the dependability of the model was confirmed using experimental data. Using numerical simulations, the impact of hydrogen injection position and time on the distribution of the fuel-air mixture, the propagation of flames, and the emissions of NO X in the cylinder under direct hydrogen injection have been studied. The research shows that the injection position and timing of hydrogen can affect airflow movement by changing the impingement angle and cylinder swirl intensity to alter hydrogen distribution in the cylinder under the guidance of the cylinder wall. Furthermore, with a delay in hydrogen injection timing, the turbulence kinetic energy in the cylinder gradually increases and is consistently more significant than that under premixed conditions, with turbulence kinetic energy in Case B-190 approximately 60% higher than that under premixed conditions. When more hydrogen is around the spark plug, the initial flame kernel is formed faster, resulting in a notable acceleration of the fuel-air mixture's combustion rate within the cylinder. In contrast to alternative hydrogen injection strategies, the injection strategy that employs nozzle A and an injection timing of 230°CA (BTDC) can achieve the highest cylinder pressure and lower NO X emissions. • A CFD computational model of ammonia/hydrogen rotor engine was established and validated. • Hydrogen has a greater impact on the flame development compared to ammonia. • Direct injection of hydrogen enhances the turbulent kinetic energy within the cylinder. • Optimizing the direct injection method of hydrogen can effectively reduce the emission of NOx. [ABSTRACT FROM AUTHOR]

A computational model for premixed methane-air flame under the flame-wall interaction was established based on CFD software and experimentally verified. The head-on quenching process of premixed methane-air flame under different hydrogen additions was simulated. The changes in CO emission, quenching distance, and the distribution of CO near the wall under different hydrogen additions were obtained. With the increase of H 2 addition, the mass fraction of HCO and the generation of CO increase. Moreover, the consumption of OH in R79: O H + H 2 = H + H 2 O increases, resulting in the weakening of the oxidation of OH to CO in R94: O H + C O = C O 2 + H , and the EICO increases. With the increase of H 2 addition, the heat release rate increases, the quenching distance decreases, and the Peclet number (Pe) increases. With the increase of hydrogen addition, the mole fraction of CO in Region A gradually decreases, the mole fraction of CO in Region B first increases and then decreases, and the mole fraction of CO in Region C increases. The temperature drops first and then rises. Near the wall (y < 0.3 mm), the convection term and diffusion term dominate, and the heat transfer time is less than the generation time and oxidation time of CO, and the generation branch and oxidation branch of CO move to the low-temperature region. Far from the wall (y ≥ 0.3 mm), the reaction source term dominates, the heat transfer time is greater than the generation time of CO, less than the oxidation time of CO, and the oxidation branch of CO moves to low temperature. With the increase of hydrogen addition, the chemical time scale of CO decreases, and the generation branches and oxidation branches of CO move to higher temperatures. • Establish a computational model for methane/air premixed flames under wall action. • The effects of H 2 addition on emissions and thermochemical states were studied. • The variation of species transport near the wall is studied. • As H 2 addition increases, the quenching distance decreases and Pe increases. [ABSTRACT FROM AUTHOR]

• Investigating hydrogen heterogeneous reaction takes place in catalytic combustor with a blunt body. • Introducing the blunt body into the catalytic combustor enhances the hydrogen conversion ratio. • Strengthening heat and mass transfer characteristics is observed as the blockage ratio increases. • By exploring field synergy effects, the optimal performance parameters of the combustor with a blunt body are determined. A numerical investigation has been conducted to explore the effect of an inserted blunt body on the heterogeneous reaction (HTR) characteristics in a micro-catalytic combustor operating with premixed hydrogen/air. The two-dimensional numerical model incorporates a comprehensive heterogeneous reaction mechanism of hydrogen employed by experimental verification. The influences of blockage ratio at various inlet velocities have been investigated to obtain optimized design parameters of the combustor. The findings of this research highlight analysis of the positive influence of an inserted blunt body within the combustor, including enhancement of chemical reaction rate and hydrogen conversion ratio. Numerical results shows that the gaseous mixture between the blunt body and catalytic surface noticed a considerable velocity increase, leading to a greater adsorption–desorption of bulk species on the catalytic surface. At the same inlet velocity, the hydrogen conversion ratio gradually increases with higher blockage ratios. When the blockage ratio is less than or equal to 0.6, the average inner wall temperature is positively affected by the increased blockage ratio. However, the effect becomes negative at higher blockage ratios (0.8). The Pr (Prandtl number) number near the gas–solid interface adjacent to the blunt body initially decreases and then increases, while Nu/Nu0 (Nusselt number) and Pe (Peclet number) exhibit an initial increase followed by a decrease. The presence of the blunt body leads to a reduction in the cross-sectional area of the channel, causing an acceleration in fluid velocity near the blunt body and exerting an impact on the boundary layer near the gas–solid interface. This indicates that the addition of the blunt body reduces the boundary layer thickness and enhances the mass and heat transfer characteristics in the region. The study reveal that as the blockage ratio increases, the overall field synergy of the combustor initially increases and then decreases. The peak field synergy is attained at an optimal blocking ratio of 0.6. The findings of this study have important implications for the design of micro-scale combustors. [ABSTRACT FROM AUTHOR]