Abstract-It has some significance to study the influences of the droplet radius ratios on spray combustion due to the varying droplet radius ratios among droplets in the actual spray combustion. The volume of fluid (VOF) formulation is applied to model the combustion process of two decane droplets with different radiuses in a hot convective flow and the effects of the droplet ratios on burning rates of two droplets at fixed droplet center spacing are analyzed. The results show: when the burning rates of the front and the back droplets compare with that of the corresponding single droplet, the interaction reduces the burning rate of either droplet under different droplet radius ratios. For the same initial droplet radius, the burning rate of droplet located at the front is larger than that at the back under different droplet radius ratios. The results obtained provide some reference for the basic researches of spray combustion.

Numerical computation with Transition k-kl-ω model is conducted to investigate the heat transfer characteristics for the single jet impingement cooling. The effects of the jet Reynolds number and the impingement spacing (jet-to-surface spacing, Zn/D) on heat transfer characteristic are researched. Results show that the numerical predictions are in good agreement with the analytical solution and experiment data. The maximum value of the Nusselt number is located in X/D=0.75. The bigger Reynolds number is, the better cooling effect is. There exists an optimal impingement spacing for heat transfer effect, the Nusselt number could reach the highest value in Zn/D=4.