Effects of Biodiesel–Ethanol–Graphene Droplet Volume and Graphene Content on Microexplosion: Distribution, Velocity and Acceleration of Secondary Droplets

Under the continuous tightening of global carbon emission policies, the search for sustainable low-emission energy sources is of great significance to reduce the reliance on the use of fossil fuels and to save energy and reduce emissions. Biodiesel–ethanol–graphene mixed fuel has high combustion efficiency and low emission characteristics, and an in-depth study of its evaporation and microexplosion characteristics during the heating process can help to better understand the characteristics of this fuel. In this paper, the evaporation, microexplosion, sub-droplet distribution and kinematic properties of biodiesel–ethanol–graphene droplets under different temperatures, volumes and mixing ratios were investigated by simulating the air atmosphere using a modified tube furnace experimental platform. It was found that the BD50E50 (1%G) droplet produced a weak microexplosion under 600 °C, and three secondary droplets were formed, with the largest secondary droplet area reaching 5.28 mm2. The BD50E50 (1%G) droplet produced strong microexplosion under 800 °C conditions, and 10 secondary droplets were formed, with the largest secondary droplet area of 3.02 mm2. Different intensities of microexplosion and ejection phenomena produced by the biodiesel–ethanol–graphene droplets during the heating process were found, and it was found that the temperature and droplet volume determine whether the microexplosion of the mixed droplets can occur or not, while the intensity of the microexplosion determines the number of secondary droplets and the speed of movement. Additionally, the velocity and acceleration of secondary droplets produced by ejection were significantly greater than those produced by microexplosion. These studies provide a theoretical basis for the application of this fuel.