Numerical study of ammonia-hydrogen blending ratio and ignition timing on the combustion and emission characteristics of a gasoline rotary engine

This study investigates the potential of using zero-carbon fuels ammonia (NH3) and hydrogen (H2) to address the issues of high fuel consumption and carbon emissions in conventional gasoline rotary engines. By introducing an ammonia-hydrogen mixture with a 1:1 vol ratio as a gasoline substitute, significant carbon reduction is achieved while maintaining the engine's original power performance. Using three-dimensional computational fluid dynamics methods, the effects of different ammonia-hydrogen energy substitution ratios and ignition timings on the in-cylinder flow field, combustion process, and emission characteristics were systematically studied. The results demonstrate that as the ammonia-hydrogen energy substitution ratio increases, the combustion velocity of the mixture significantly accelerates, leading to higher peak in-cylinder pressure and heat release rate. At a 75 % ammonia-hydrogen energy substitution ratio, the engine maintains power performance comparable to gasoline operation while achieving lower carbon emissions. These findings provide a theoretical foundation for the application of ammonia-hydrogen mixtures in rotary engines and highlight their potential in facilitating the transition toward low-carbon internal combustion engines. When the A-HESR increases from 20 % to 75 %, ITE and IMEP rise by 41.11 % and 30.55 %, respectively. Meanwhile, NOx emissions reaching the lowest value at 75 %.In contrast, Carbon monoxide (CO) and Carbon Dioxide (CO2) emissions were significantly reduced by 74.2 % and 75.6 %. Furthermore, the ignition timing optimization study reveals that at a 75 % A-HESR, the optimal performance is achieved with an ignition timing of 30°CA before top dead center (TDC). Under this condition, the indicated thermal efficiency reaches 36.91 %, while the IMEP attains 1.04 MPa.