Comparative assessment of mixture formation and combustion characteristics of a hydrogen/n-butanol rotary engine with various rotor recess designs

The application of clean alternative fuels and the optimization of combustion chamber structures constitute key technical pathways for the sustainable development of high-efficiency, low-carbon rotary engines. N-Butanol has become a focus of researchers due to its combustion characteristics and physicochemical properties being highly similar to those of gasoline, while hydrogen is regarded as the cleanest fuel. Therefore, the mixed combustion of hydrogen and n-butanol in rotary engines holds significant research value. In this study, a three-dimensional computational fluid dynamics model was established to conduct in-depth research and analysis on the formation of the mixture, the combustion process, and the generation laws of emissions from three aspects: compression ratio, hydrogen blending volume fraction, and combustion chamber shape optimization. The results show that hydrogen blending can effectively enhance the turbulence intensity of the mixture and reduce hydrocarbon emissions. Increasing the compression ratio can improve the combustion process, thereby enhancing the thermal efficiency and total work of the engine. In addition, the research on the influence of rotor recess shape on engine ignition and combustion characteristics indicates that narrow rotor recesses have significant advantages in both mixture combustion and emission generation, and from the perspective of rotor recess optimization, this helps to improve the performance of rotary engines. This study clarifies the intrinsic mechanism of n-butanol-hydrogen blended combustion and provides a theoretical reference for the optimization direction of combustion chamber structures.