On the enhancement of biodiesel droplet vaporisation using electrostatic charge

An electrostatic atomiser is an energy-efficient device that can be used to promote theatomisation of highly viscous fluids, for example biodiesel. It imposes an electrical chargeonto the liquid that creates enough Coulombic repulsive force to lower the surface-tensionforce of the liquid and result in atomisation.In this study, the vaporisation of electrically charged fatty-acid methyl-ester (FAME)droplets are reported as a function of the initial charge density, ambient temperature, anddroplet Reynolds number. Existing data from a direct numerical simulation (DNS) of chargeinjection are also post-processed to better understand the physics of electro-convection as afunction of the average bulk-flow velocity and the electrical Rayleigh number.The model predictions are assessed by comparing with experimental results, and themaximum deviation in evaporation time is reported to be 13.6% for C12:0. The effectof charge increases with increasing initial charge density and decreases at high ambient temperatures, while the droplets Reynolds number shows a mixed effect. The DNS dataprocessing reveals that the developed electro-convective instabilities force the liquid into aroll-like structured motion and in a high-flow-rate atomiser, higher instability could maximisethe amount of charge in the middle of the domain.