Evaporation Behavior of Fuel Droplet at High Pressures.

Abstract

Single-droplet evaporation of fuel at high pressures and high temperatures has been studied experimentally. Suspended n-heptane and n-hexadecane droplets were employed in the experiments at pressures in the range of 0.1-5.0 MPa, and temperatures varying from room temperature to 800K. The initial droplet diameter range of the experiments was 0.4-0.8 mm. Evaporation processes were observed by a CCD camera with a backlight and recorded by a video recorder. A computer-aided image analysis system was developed and applied in order to obtain precise temporal variations of the droplet diameter. The variation of the squared nondimensional droplet diameter with the corrected time is independent of the initial droplet diameter at 0.1 MPa. At high pressures, the slope of the variations tend to become steeper as the initial droplet diameter is increased. The ratio of the initial heat-up period to the evaporation lifetime increases with increased ambient temperature. At ambient temperatures sufficiently above the critical temperature of the fuel, the ratio tends to decrease gradually.