Study on combustion and micro-explosion characteristics of biodiesel and ethanol mixture droplets under different oxygen concentrations and temperatures

An experimental platform for measuring droplet combustion and micro-explosion characteristics based on a tube furnace was established. Through this experimental platform, the BD60E40 droplets involving a mixture of 60?vol. % biodiesel and 40?vol. % ethanol was tested. Instantaneous gray images were obtained by means of high-speed photography during the BD60E40 droplets heating or combustion cycle. The expansion, ejection, micro-explosion, and combustion characteristics of mixed droplets under different temperatures and oxygen concentrations were studied by using the platform. The study found that the BD60E40 droplets produced high intensity primary and secondary micro-explosions when the oxygen concentration in the tube furnace was 0% and 30%. However, when the oxygen concentration was 50%, the BD60E40 droplet showed a weak micro-explosion phenomenon. The temperature was an important condition for the occurrence of micro-explosions. The BD60E40 droplet was not subject to micro-explosions during heating under 300?°C ambient temperature, but the micro-explosion occurred under 400 and 500?°C. According to the different experimental phenomena, the equation for calculating the micro-explosion intensity was established and the micro-explosion intensity of BD60E40 droplets under different oxygen concentration was calculated, and the reason for the different micro-explosion behavior of BD60E40 droplets under different oxygen concentration was established.