Effect of equivalence ratio on spark ignition combustion of an air-assisted direct injection heavy-fuel two-stroke engine

In the small aviation field, the research of direct injection (DI) heavy-fuel two-stroke engines has attracted much attention. The safety and unity of aviation heavy-fuel (i.e., aviation kerosene and diesel) is better than those of gasoline, which is more suitable for small aviation engines. In this paper, the influence of air-assisted injection on the formation and combustion of aviation kerosene direct injection mixture is studied on an aviation heavy-fuel direct injection spark ignition (DISI) two-stroke engine. Firstly, the spray simulation model of three-dimensional air-assisted injector was established by Computational Fluid Dynamics (CFD) software. And the effectiveness of the spray model was verified by comparing the simulation results with the experimental data of constant volume bomb spray. The combustion system CFD model of the two-stroke engine was further established to study the heavy-fuel spark ignition combustion at different ignition timings and equivalence ratios. The results show that when the ignition advance angle is 30 degrees CA BTDC, higher combustion pressure and faster flame propagation speed can be achieved without knock. Aviation kerosene is less prone to knock than diesel and can achieve better combustion performance under the condition of rich mixture.