Coupling Mechanism of High-Temperature Evaporation of Multi-Component Fuel Droplets

This study took a multi-component composed of high volatility ethanol and low volatility hydrogenated biodiesel and diesel as the research object and investigated the internal vapor bubble dynamics and evaporation characteristics of the individual droplet at high temperatures. The evaporation characteristics of droplet normalized square diameter and droplet lifetime of the blends of hydrogenated biodiesel, ethanol, and diesel were captured by means of the hanging droplet method and high-speed microscopic imaging in a constant temperature heating furnace. The results show that at 773 K, the evaporation is smooth and the droplet volume decreases uniformly. However, at 973 K, tiny bubbles start to form inside the droplet at 0. 093 s and gradually increase in size. Tiny bubbles were formed again at 0. 767 s and the second rupture occurs at 0. 907 s. The rise in ambient temperature contributes to increasing the evaporation rate of fuel droplets and intensifies the micro explosion during evaporation and shortens the evaporation of droplets to a certain extent; the growth of bubbles inside the droplet during evaporation is related to the Rayleigh-Taylor instability at the vapor-liquid interface, and surface tension phenomenon is observed on the surface of droplets. Compared to diesel, the inhibition effect of evaporation is stronger with the increase of hydrogenated biodiesel in binary fuels and compared with binary fuels, ethanol in ternary fuels promotes micro explosions and shortens droplet evaporation. The droplet evaporation of the ternary fuel shows three typical characteristic stages in the order of ethanol domination, ethanol and diesel co-domination and co-evaporation of all three. © 2023 South China University of Technology. All rights reserved.