Evaporation of multicomponent liquid fuel droplets: Influences of component composition in droplet and vapor concentration in free stream ambience

Theoretical studies have been made to explore the coupling influences of droplet constituent compositions and free stream vapor concentrations on evaporation characteristics, namely, mass depletion rate and droplet temperature of a heptane-dodecane droplet (components with widely varying volatility) and methanol-ethanol droplet (components with close volatility) at lower and higher free stream temperatures. In case of heptane-dodecane droplet, temperature and mass depletion histories are controlled by the heavier component (dodecane). In case of methanol-ethanol droplet, the mass depletion history is controlled by the lighter component (methanol), while the droplet temperature history is controlled by the heavier component (ethanol). The presence of fuel vapors in free stream increases the droplet lifetime, and moreover, the influence is relatively more prominent with the presence of heavier component vapor alone at lower free stream temperature. The composition of component vapors for a fixed value of total vapor concentration in free stream has almost negligible influence on droplet lifetime. It is revealed that the well established empirical relation (Sh(1+Bm)0.7 = 2) for mass evaporation rate of a single component droplet can be used with reasonably fair accuracy in case of multicomponent droplet evaporation with logical modifications of mass transfer number and mass transfer coefficient for multicomponent system.