Parametric Study on the Evaporation Characteristics of Biodiesel-Diesel-Methanol Microemulsion Droplets

Abstract

ABSTRACT In order to investigate the evaporation characteristics of biodiesel-diesel-methanol microemulsions, an experimental method of droplet evaporation with post processing techniques is established. The droplet normalized square diameter (NSD), droplet temperature and images during evaporation process are used to analyze the evaporation characteristics at different ambient temperatures. The results indicate that the methanol volume percentage, initial volume of droplet and ambient temperature have evident influence on the evaporation characteristics of droplets. When the initial volume of droplet is 0.5 μL, BD95M5 (biodiesel-diesel blend (95%)+methanol (5%)) and BD85M15 (biodiesel-diesel blend (85%)+methanol (15%)) droplets do not show the puffing and micro-explosion phenomena during evaporation process, but BD75M25 (biodiesel-diesel blend (75%)+methanol (25%)) droplet exhibits micro-explosion evidently at ambient temperature of 573K. Puffing is observed for BD85M15 droplet, and micro-explosion is for BD75M25 droplet at ambient temperature of 773K. The droplet lifetime is decreased and the mean evaporation rate (MER) is increased with the increase of ambient temperature and methanol volume percentage in microemulsion. The evaporation process ends at 5.938 s/mm2, 5.417 s/mm2 and 4.792 s/mm2 for BD95M5, BD85M15 and BD75M25, respectively, and MERs of them are 0.087 mm3/s, 0.095 mm3/s and 0.108 mm3/s at ambient temperature of 573K. The MERs of BD95M5, BD85M15 and BD75M25 are 0.225 mm3/s, 0.244 mm3/s and 0.309 mm3/s, respectively, at ambient temperature of 773K. With the increase of initial volume of droplet, the occurrence of puffing and micro-explosion is strengthened. The MER of droplets with initial volume of 0.6 μL is the largest, which increases by 13.1% and 12.8% compared with 0.4 μL droplets and 0.5 μL droplets, respectively.