Effects of intake swirl and coolant temperature on spray structure of a high pressure multi-hole injector in a direct-injection gasoline engine

The spray characteristics of a 6-hole injector were examined in a single cylinder optical direct injection spark ignition engine. The effects of injection timing, in-cylinder charge motion, fuel injection pressure and coolant temperature were investigated using the 2-dimensional Mie scattering technique. It was confirmed that the in-cylinder charge motion played a major role in the fuel spray distribution during the induction stroke while injection timing had to be carefully considered at high injection pressures during the compression stroke to prevent spray impingement on the piston. A new approach has been applied to the processing of Mie images to analyse the effect of coolant temperature on the spray liquid phase structure. These results quantified the fraction of the liquid phase that was vaporised as a result of the increase in coolant temperature.