Experimental analysis of the near-nozzle direct injection spray for gasoline and ethanol-gasoline blended fuels

Abstract

The current work analyses the spray during the early stage of development in the near-nozzle region using a single-hole gasoline direct injection system for gasoline (G100) and ethanol-gasoline (E85) blended fuels. The present work combined a Galilean-type beam expander with an achromatic lens, using an LED light and a high-speed camera to visualize a magnified view of the near-nozzle microscopic aspect of the emerged jet. Three different shapes, spheroids, cylindrical, and steeple, were visualized experimentally during the evolution of the fuel jet under different fuel injection and chamber pressures. A transition in shape from the steeple-to-spheroid shape was detected. It was observed that the velocity of the emerged jet is affected by its evolved shapes, attributing to differences in the initial breakup characteristics and shot-to-shot variation in the spray at a given condition. The velocity of the cylindrical-shaped jet was 14% and 42% higher than the steeple and spheroid-shaped jets, respectively. The Rayleigh-Plesset equation describes the reason for an increase in the spheroidal-shaped jet velocity by 84% when the chamber pressure is reduced from 0.6 to 0.1 MPa. The Ohnesorge and Reynolds number of the emerged liquid jets were estimated to describe the breakup regime of the jet during the initial stage. It was observed that the cylindrical and the steeple-shaped jets pertain to a higher tendency to atomize during the initial stage of evolution compared to the spheroidal jet. The average jet velocities and liquid penetrations in the near-nozzle region for E85 and G100 were estimated.