A study on direct in-cylinder methanol-reforming strategy for performance enhancement of rotary engines

Methanol, a promising low-carbon alternative fuel synthesized via CO2 hydrogenation, enhances combustion efficiency in internal combustion engines due to its high oxygen content and rapid flame propagation. To further leverage its potential, fuel reforming technology is employed to generate hydrogen-rich gas. Nevertheless, studies on in-cylinder reforming for rotary engines are notably scarce. In response, this study develops a novel in-cylinder methanol reforming method, which utilizes the high-temperature and low-oxygen conditions during the end of the combustion stroke to produce hydrogen. The hydrogen is introduced into the next working cycle through exhaust gas recirculation (EGR). This research systematically examines how reformate injection position and angle affect reforming efficiency and combustion performance. The results indicate that injection position and angle determine the distribution of methanol across different temperature-pressure regions in the cylinder, significantly influencing reforming efficiency. In addition, the distribution of reforming hydrogen in the exhaust stage significantly determines the quality of hydrogen available for the next cycle, thereby enhancing the efficiency of pure-methanol rotary engines. According to the simulation results, when applying methanol reforming technology in jet ignition methanol rotary engines, it is recommended to place the reforming fuel nozzle on the cylinder block 40 mm away from the long axis, with an injection angle of −20°.