Combustion Characteristics of Multicomponent Fuel Droplets

Abstract

The present study investigates the combustion characteristics of the multicomponent diesel-water (D-W) emulsion fuel droplets. The stable blends obtained by using Surfactant, Span-80 (s) and three different fuels viz., WD1 (D-95%, W-3%, S-2%), WD2 (D-94%, W-4%, S-2%) and WD3 (D-96%, W-3%, S-1%) are subjected to the pendant mode of droplet combustion in the ambient conditions. The blend's stability depends on surfactant and water compositions. WD1 exhibited a higher viscosity W/s ≥ 1 at near-boiling point of the dispersed fluid. The higher viscosity droplets resulted in fewer secondary atomization. WD3 with lower viscosity (W/s >1.5) exhibited multiple cycles of the micro-explosion events. The cycles of micro-explosion depend on water to surfactant concentration. The blend with lesser surfactant exhibited the lesser cycles of explosion events. The regression rate of the droplets was fitted using d2-law. WD1 possesses the least burn time. The vapors of low volatile fluid, i.e., water vapor were trapped inside emulsion the droplets. Upon receiving the constant heat from flame surface, the surface of the droplets gets highly corrugated due to the capillary oscillations. Subsequently, the trapped bubbles of the less volatile fluid are ejected out as the daughter droplets. These ejections are more predominant in higher surfactant concentrations. The ejections frequency reduces with an increase in water %. This enabled the rapid burning of the droplet when compared to base fuel combustion.