Spray and mixture properties of evaporating fuel spray injected by hole-type direct injection diesel injector

Abstract

The spray and mixture properties are the vital factors that control the fuel—air mixing formation, subsequent combustion, and exhaust emission processes in direct injection (DI) diesel engines. In the current study, by means of the ultraviolet-visible laser absorption-scattering (LAS) technique, the spray and mixture properties of the evaporating fuel spray injected by hole-type DI diesel injector are quantitatively investigated under various injection conditions in terms of spray tip penetration, spray cone angle, equivalence ratio distributions of liquid/vapour phases, mass of ambient gas entrained, and evaporation ratio etc. The principle and imaging procedures of the LAS technique are first summarized and discussed. Then, the effects of injection pressure and nozzle hole diameter on the spray and mixture properties are examined in particular. The results show that — for the injection system and ambient conditions in this study — increasing the injection pressure from 90 MPa to 120 MPa results in approximately 40 per cent more ambient gas being entrained into the spray on average, and the effect of nozzle hole diameter on the mixture properties shows two contrasting trends.