Effect of equivalence ratio on diesel direct injection spark ignition combustion

Abstract

Aviation heavy-fuel spark ignition (SI) piston engines have been paid more and more attention in the area of small aviation. Aviation heavy-fuel refers to aviation kerosene or light diesel fuel, which is safer to use and store compared to gasoline fuel. And diesel fuel is more suitable for small aviation application on land. In this study, numerical simulation was performed to evaluate the possibility of switching from gasoline direct injection spark ignition (DISI) to diesel DISI combustion. Diesel was injected into the cylinder by original DI system and ignited by spark. In the simulation, computational models were calibrated by test data from a DI engine. Based on the calibrated models, furthermore, the behavior of diesel DISI combustion was investigated. The results indicate that diesel DISI combustion is slower compared to gasoline, and the knock tendency of diesel in SI combustion is higher. For a diesel/air mixture with an equivalence ratio of 0.6 to 1.4, higher combustion pressure and faster burning rate occur when the equivalence ratios are 1.2 and 1.0, but the latter has a higher possibility of knock. In summary, the SI combustion of diesel fuel with a rich mixture can achieve better combustion performance in the engine.