Effect of composition and temperature on the puffing and microexplosion of diesel-ethanol-jatropha oil ternary fuel blend droplets

The reliance on fossil fuels as well as engine emissions can be curbed by adopting low-carbon alternative fuels, which, when blended with diesel, may require minimal engine modifications. Fuels derived from plant and biological sources such as ethanol and jatropha oil are considered some of the low-carbon fuels. The blended fuel droplets may undergo smooth burning, puffing, and micro-explosions based on their composition and the surrounding environment. The current study focuses on the effect of composition and temperature on blended fuel droplet combustion and correlates the observations with the microstructure of the blend. Droplet combustion behaviour at three different temperatures, viz. 500, 600, and 700 °C, that are relevant to combustion engines were tested. The ethanol concentration in the blends varied between 10 and 50 % by volume, while the jatropha oil concentration changed between 10 and 40 %. As the temperature increased from 500 to 700 °C, the burning characteristics of the droplets changed from puffing to micro-explosions due to the rapid evaporation of ethanol. Puffing and explosions gave rise to secondary and tertiary droplets, which were similar in size (∼50–100 μm) to diesel spray droplets and exhibited cascaded puffing and explosions. The blends with ethanol to jatropha oil (E/J > 1) greater than 1 produced a larger dispersed phase and larger agglomerates and hence promoted micro-explosions. The findings of this study highlight the importance of blend composition and temperature for achieving micro-explosions in diesel–jatropha oil–ethanol ternary blends, which are potential alternative fuels for compression ignition (CI) engines and spray flames.