An Insight Into Effect of Split Injection on Mixture Formation and Combustion of DI Gasoline Engines

In the previous study of the authors, it was found that some benefits for the mixture preparation of DI gasoline engines can be offered by splitting the fuel injection, such as the phenomenon of high density liquid phase fuel piling up at the leading edge of the spray can be circumvented. In a further analysis, the vapor quantity in the “stable operating” range (equivalence ratio of vapor ϕ_v in a range of 0.7≤ϕ_v≤1.3) was significantly increased by the split injection compared to the single injection.

In this work, the mechanism of the effect of the split injection on the mixture formation process was studied by combining the laser-sheet imaging, LIF-PIV and the LAS (Laser Absorption Scattering) technique. As a result, it is found that the spray-induced ambient air motion can help the formation of the more combustible mixture of the split injection whereas it played a minus role of diluting the spray by the single injection.

Finally, the experiments on a wall-guided-type DI gasoline engine were done. The engine performance and exhaust emissions were presented and discussed.