Experimental investigation of emulsified fuels produced with a micro-channel emulsifier: Puffing and micro-explosion analyses

In this investigation, puffing and micro-explosion occurrence in emulsified fuels are studied. The emulsified fuels are formulated using a micro-channel emulsifier, a blend of rapeseed oil in diesel fuel as continuous phase, water as dispersed phase and Sorbitan Sesquioleate as surfactant. Several stable dispersed systems are obtained, classified as emulsions based on their optical appearance and dispersed droplet size. The dynamic viscosity measured as a function of shear rate indicated non-Newtonian behavior with a shear-thinning response for all emulsions. An increase of water percentage led to emulsified fuels with higher viscosity levels. Finally, puffing and micro-explosion occurrence was studied by placing emulsified fuel droplets on a heated plate leading to the Leidenfrost effect. The puffing occurrence is reported for all emulsified fuels tested. A sudden puffing is noted when the water ratio is increased. Conversely, the micro-explosion phenomenon only occurred in emulsions formulated without surfactant. However, an analysis conducted on a smaller emulsion droplet showed several ejected child droplets and micro-explosion. This fact denotes a strong relationship between the emulsion droplet size, water ratio and water droplet size with the occurrence of the puffing and micro-explosion phenomena.