An experimental study about the vaporization, ignition and burning of multicomponent fuel droplets at elevated pressures and temperatures

Abstract

An experimental study about vaporization, ignition and burning characteristics of multicomponent fuel droplets is carried out at elevated pressures and temperatures. Kerosene, Jet A and heptane/hexadecane binary mixtures were selected as multicomponent fuels. The droplet was suspended at the tip of a fine quartz fiber and suddenly exposed to high ambient temperature by the help of falling electric furnace at desired ambient pressures under normal gravity. The evaporation/combustion process and the autoignition delay times were recorded by the use of high-speed photography. Evaporation/combustion constants were calculated from the linear regression time histories of droplet diameter squared. And the effects of ambient pressure and temperature on the evaporation/combustion rate constant and autoignition delay were investigated. The effect of droplet initial diameter on droplet vaporization regimes was also investigated at high temperature and high-pressure environments. It was found out that the evaporation/combustion of the investigated multicomponent droplet follows d2-law under most of the ambient conditions. At higher ambient temperatures, the evaporation rate constant increases as environment pressure increases but at lower ambient temperatures, the result of increasing ambient pressure was a decrease in the evaporation rate constant. The evaporation/combustion of the binary droplet at very low ambient pressures leads to extremely distortion and fragmentation of the droplet. But at higher environment pressures, droplet fragmentation does not appear. The evaporation/combustion history shows three-staged behavior. An increase in the droplet initial diameter results in an increase in heating time as well as evaporation rate constant. The heating time decreases as the ambient temperature increases and increases with an increase in ambient pressure. The ignition delay time of droplet decreases with an increase in ambient temperature and pressure and can be expres...