Comparative study on different spark plug positions of a rotary engine with gasoline port and direct injection

This research aims to numerically investigate the combined effect of ignition position and injection method on the gasoline rotary engine. The three-dimensional dynamic model was established by CONVERGE software and validated by the experimental data. The results indicate that compared with port injection, the direct injection leads to obvious fuel stratification in the combustion chamber, and the local equivalence ratios around the two spark plugs are different. The index of in-cylinder fuel inhomogeneity corresponding to direct injection decreases linearly with the progress of the mixing process. Adopting the double spark plug can obtain a higher release heat rate and combustion efficiency than adopting the single spark plug ignition. Higher in-cylinder peak pressure and indicated thermal efficiency also can be obtained by using double spark plugs ignition. Only using leading spark plug ignition would cause a large in-cylinder unburned area, resulting in poor power performance of the rotary engine. In particular, the direct injection can obtain higher mean in-cylinder pressure than the port injection, but the indicated thermal efficiency of port injection is higher than that of direct injection. In the aspect of emissions, double spark plugs ignition would lead to higher in-cylinder temperature and NOx content than other ignition modes, but double spark plugs ignition can alleviate incomplete combustion and reduce HC emission. Under the same ignition strategy, the port injection can effectively reduce CO emission than direct injection.