Characteristics of Sub/supercritical Gasoline and Iso-octane Jets in High Temperature Environment 2019-01-0289
Based on the temperature and pressure in the cylinder of GDI (Gasoline Direct Injection) engine under com-mon operating conditions, the jet characteristics of gasoline and isooctane at different fuel temperatures under high temperature environment were studied by means of high-speed photography and striation method. The experiment provides an insight to morphological differentia between the gasoline and isooctane. It was found that the gas-liquid composition and distribution of the jets are different as the fuel temperature increases, result-ing in the appearance of collapse and convergence of the gasoline jet, but not of the isooctane jet. Meanwhile, a strong effect of air-convergence and the collapse of the jet center are the main reason that affects its penetra-tion and cone angle. In the subcritical stage, rising the fuel temperature will increase the projected area of the jet, but vary the contour circumference of the jet. In the supercritical stage, the diffusion effect dominated by the thermal motion of the fuel molecules will led the projected area and the circumference of the contour to change regularly. This study reveals that fuel temperature has a significant impact on the jet characteristics, and the degree of influence varies between gasoline and isooctane at high ambient temperature.