Atomisation and combustion characteristics of high-vapour pressure nanofuel droplets

The presented experimental investigation encompasses the atomisation and combustion dynamics of pure and nanoparticle (cerium dioxide, CeO2) laden Ethanol-Water (EW) droplets. The nanoparticle loading rate is maintained dilute, varying between 0 to 1.5 by weight. Inclusion of nanoceria enhances the internal ebullition in the burning droplets although it also results in the increased droplet combustion lifetime. The mechanism of secondary atomisation for pure EW droplets is attributed to the imbalance between vapour thrust and surface tension. This disintegration mechanism is quantified using a modified Weber number for EW droplets. On the other hand, bubble expulsion is the sole mechanism of atomization for nanofuel droplets. For both cases, formation of surface openings is evident, although due to separate mechanisms, i.e. vapour thrust for EW droplets and bubble ejection for NP laden droplets. These surface openings result in the formation of high-speed ligaments which undergoes Rayleigh-Plateau tip break-up. Further, using the technique of proper orthogonal decomposition (POD) we decipher the causality between the droplet deformation and heat release.