Study on the evaporation and micro-explosion characteristics of PODE-diesel blended droplets

Blending a certain proportion of PODE in diesel can significantly reduce the cold filter plugging point of diesel and improve the combustion quality of the engine, thus improving the thermal efficiency of the engine and reducing emissions. PODE₄-diesel droplet is taken as the research object in this article, a hanging drop test system is built, and research on the evaporation and micro-explosion characteristics of PODE₄-diesel droplets and their influencing factors are conducted. The research results indicate that, unlike the evaporation process of pure diesel droplets, the evaporation process of PODE diesel droplets mainly exists in the equilibrium evaporation stage, with the evaporation rate showing a fast and then slow trend, and then remaining basically unchanged until the evaporation is complete; The addition of PODE is beneficial for the evaporation of diesel droplets. The evaporation process of PODE diesel mixture droplets generally only goes through the equilibrium evaporation stage where the normalized diameter square of the droplets gradually decreases. Overall, the droplet evaporation rate is a gradually decreasing process. The influence of environmental temperature on droplet evaporation process is significant. The higher the environmental temperature, the more obvious the trend of slower evaporation rate at the end of droplet evaporation will be; At different ambient temperatures, the temperature of droplets will experience a sudden increase followed by a slow increase. The initial droplet diameter has a significant impact on the evaporation process too, with larger initial diameters leading to a sharp increase in droplet evaporation time; The trend of droplet temperature over time is approximately the same for different initial diameters, but the larger the initial diameter, the longer it takes for the droplet temperature to reach ambient temperature. An increase in PODE mass fraction can promote the evaporation of mixed droplets. The micro-explosion process of PODE diesel droplets can be divided into three stages: delayed micro-explosion stage, severe micro-explosion stage, and evaporation disappearance stage; The delayed micro-explosion stage is the process of energy absorption by the droplet, the severe micro-explosion stage is the process of repeated generation and explosion of bubbles inside the droplet, and the evaporation disappearance stage is the process of no bubbles generated and the volume of the droplet evaporates completely. The influence of environmental temperature and initial droplet diameter on droplet micro-explosion process is relatively monotonous, but when the initial droplet diameter is 1.42 mm, the equivalent evaporation rate of the droplet will appear to be 0; The influence of PODE mass fraction on droplet micro-explosion process is relatively complex. Droplets with a PODE mass fraction of 40% have the longest entry time into micro-explosion, the shortest duration of droplet micro-explosion, and the longest droplet survival time; When the PODE mass fraction is 50%, the duration of droplet micro-explosion is the longest, and its percentage of droplet survival time is also the highest. Through this study, it is beneficial to deepen the understanding of the influencing factors and laws of PODE diesel droplet evaporation and micro-explosion, thereby providing important basis for controlling the process of PODE diesel droplet evaporation and micro-explosion.