Experimental And Theoretical Study Of Fuel Dorplet Evaporation At Subnormal Pressure

In Scramjet, the evaporation of most liquid fuel occurs under the subnormal pressure condition. However, it is rarely seen in the existing documents about the study of the evaporation and combustion of the fuel droplet at subnormal pressure. This thesis gives the experimental and theoretical study about that.For the experimental study, an experimental facility was designed and built. It can be used for the study of evaporation of the hanging fuel droplet at different ambient temperature and pressure. The change of the fuel droplet radius with time was recorded by a high speed digital camera (FASTCAM-ultima APX) during the evaporation process for obtaining the evaporation rate at different ambient temperature and pressure. The results show the lower subnormal pressure and the higher ambient temperature, the shorter existing time for fuel droplet.It the theoretical study, an unsteady state model of fuel droplet evaporation at subnormal pressures was developed based on reasonable simplification and presumption. The momentum equation of the gas phase was employed for solving the velocity field around the fuel droplet. The model equations were discrete by full implicit central scheme according to the model. The evaporation rate of the fuel droplet was obtained. The results show that the Kerosene droplet evaporation rate at subnormal pressure has a sharp declination at the beginning, and then ascend quickly. This process lasts a very short time and it is a typical unsteady state. Then the evaporation rate reaches a maximum value in process. The lower subnormal pressure, the greater maximum value and the shorter time for reaching the maximum value at the same temperature. The lower ambient subnormal pressure and higher temperature, the shorter existing time for the Kerosene droplet.