Enhancement Mechanism of Jet Ignition Mode on the Combustion Performance of Rotary Engine Fueled With Pure Methanol

Abstract Methanol is a promising renewable fuel and hydrogen carrier for rotary engines, offering a sustainable solution to reduce carbon emissions. Additionally, jet ignition technology, with its advantages of high ignition energy and multipoint ignition capability, can be utilized to enhance the combustion efficiency of pure methanol rotary engines. As the core component of the jet ignition system, the structure of the prechamber determines the jet ignition intensity, thereby influencing in-cylinder flame propagation and combustion efficiency. This study focuses on the effects of shape and volume of prechamber on ignition and combustion in pure methanol rotary engines. The results demonstrate that the in-cylinder combustion process is governed by the prechamber shape, which dictates the methanol mass and turbulent kinetic energy at ignition via vortex-induced entrainment and retention of the fuel, and by directly intensifying the in-chamber turbulence through its geometric features. Meanwhile, the prechamber volume has a nonmonotonic effect on combustion performance due to a trade-off: increased volume enhances jet flame intensity but delays the entry timing of the jet flame into the cylinder. Consequently, an optimal configuration (a 0.5 cc cylindrical prechamber) is identified, which maximizes thermal efficiency by balancing these mechanisms. These findings establish a practical design framework for high-efficiency methanol rotary engines.