Experimental investigation on evaporation characteristics of RP-3 aviation kerosene droplet above the critical temperature under various pressure conditions

Abstract

The evaporation of aviation kerosene droplets in the aeroengine combustion chamber is one of the basic processes during liquid fuel combustion, which directly affects fuel atomization, air-fuel mixture formation and the combustion quality. However, the data are rarely reported due to the difficulty of conducting experiments in high temperature and pressure conditions. In this study, a series of experiments were carried out to investigate the evaporation characteristics of RP-3 aviation kerosene droplet. The environmental pressure and temperature of droplet evaporation ranged from 1 and 20 bar and 400 and 600°C respectively. An individual RP-3 kerosene droplet with initial diameter between 0.9 and 1.1 mm was suspended at a thermocouple bead with 50 μm diameter to measure droplet temperature. Droplet diameter during the whole evaporation process was recorded simultaneously by a high-speed camera. Experimental results indicated that at lower evaporation rate, RP-3 kerosene droplet evaporation experienced two processes: transient heating and equilibrium evaporation periods. While under high evaporation rates, the droplet only underwent equilibrium evaporation period without droplet expansion. At all the studied temperatures, droplet temperature kept increasing during the entire evaporation process without reaching a stable temperature. In most cases, the transient evaporation rate (K) of RP-3 kerosene droplet first increased rapidly until reaching the peak, and then followed by a monotonous decrease. However, at 20 bar above 500°C conditions, the temporal K curve exhibited a double-peak feature. Above the critical temperature of the fuel, increasing ambient pressure and temperature both can promote the heating and evaporation. However, the promotion of increasing ambient temperature to droplet evaporation was weakened at high ambient pressure. The quantitative correlations of droplet lifetime and evaporation rate constant with pressure were proposed under different ambient temperatures.