Injection parameters for combustion enhancement in TJI DI Wankel engine with methanol-gasoline blend fuel

Nowadays Wankel rotary engine shows widespread application in the power sector. Therefore, it is highly essential to explore how to enhance its thermal efficiency furtherly. Turbulent Jet Ignition (TJI) coupled with direct-injection (DI) is one effective technology in engine combustion performance enhancement. DI strategy has great impact on performance of TJI-DI rotary engine. Thus, the effects of injection strategy including injector location(L_inj), injector installation angle(α_inj) and injection timing(t_inj) on combustion performance of TJI DI Wankel engine with gasoline-methanol as carbon-reducing fuel were numerically investigated at first in this paper. The results show that the adoption of injector on the side wall of the cylinder could achieve significant stratification of mixture in the combustion chamber. At the same L_inj, too large α_inj (80°) and too late t_inj (230° EA BTDC) could cause misfire, which corresponded to the values of the equivalence ratio lower than the lean ignition limit of the mixture and higher than the rich ignition limit, respectively, at ignition position. Then, multi-objective optimization analysis based on Kriging surrogate model and Non-dominated Sorting Genetic Algorithm-Ⅱ (NSGA-Ⅱ) was carried out for combustion improvement. This rotary engine owns optimal combustion performance when L_inj = -36°, α_inj = 36° and t_inj = 270°EA BTDC. The research provides basic reference for development of TJI DI Wankel engine.