Time evolution of composite fuel/water droplet radii before the start of puffing/micro-explosion

Puffing and micro-explosion processes in composite water/fuel (kerosene, Diesel fuel and rapeseed oil) droplets are investigated experimentally and numerically, using the recently developed model of the phenomena. The experiments were performed in quiescent air at atmospheric pressure in the presence of natural convection. The model uses the assumption that a spherical water subdroplet is located exactly in the centre of a spherical fuel droplet; the start of the puffing/micro-explosion process is identified as the time instant when the temperature at the water/fuel interface reaches the water nucleation temperature. Both experimentally observed and predicted times to puffing/micro-explosion tau(p) are shown to decrease with increasing ambient temperature and increase with increasing initial droplet radii for all three fuels. The longer observed tau(p) compared with those predicted for rapeseed oil droplets is attributed to the time required for bubble formation. This time is not considered in the model used in the analysis. The observed and predicted time evolutions of droplet radii before the start of puffing/micro-explosion are shown to be close. (c) 2022 The Authors. Published by Elsevier Ltd.

Automated summary

This study investigates the puffing and micro-explosion processes in composite water/fuel droplets (kerosene, Diesel fuel, and rapeseed oil) through experimental and numerical methods. The experiments were conducted in quiescent air at atmospheric pressure with natural convection. The results show that the time to puffing/micro-explosion decreases with increasing ambient temperature and increases with increasing initial droplet radii for all three fuels. The observed longer time for rapeseed oil droplets compared to the predicted time is attributed to the formation of bubbles, which is not considered in the model used in the analysis.