Numerical Simulation On Burning Characteristic Of Two Droplets At Different Droplet Radius Ratios

The evaporation and combustion research of single droplet to spray combustion must be going through multiple droplets process.In the actual spray combustion,the droplet radius ratios among droplets are not the same,and always change.When increasing the concentration of oxygen,it can improve the efficiency of combustion and flame temperature.At present,the studies about the effects of droplet radius ratio ?(R1/R2)and oxygen concentration on spray combustion considering the droplets interaction are not plenty.So the research on the effects of droplet radius ratio and oxygen concentration on burning characteristics of two droplets enriches the basic researches of spray combustion.The results obtained provide some reference for the basic researches of spray combustion.The volume of fluid(VOF)formulation is applied to study the effects of droplet radius ratio on burning characteristics of two droplets at fixed droplet center spacing and the effects of oxygen concentration on burning characteristics of two droplets at fixed droplet radius ratio.The computational domain adopts the axisymmetric model and the droplet deformation,the variable properties of gas phase and liquid phase,heat and mass transfer between gas-liquid two-phase are considered.Irreversible one-step reaction is used Through analyzing the influences of droplet radius ratio and oxygen concentration on the burning characteristics of two droplets,the rules of the influence of the droplet radius ratio,oxygen concentration on two droplets burning characteristics under the condition of calculation are obtained.The results obtained from numerical simulation show:the overall burning rates of the front droplet and back droplet approximately linearly decrease with increasing droplet radius ratio when the droplet radius ratio ? is less than 1.The overall burning rates of the front and back droplets approximately linearly increase with increasing droplet radius ratio when the droplet radius ratio ? is greater than 1.When the overall burning rates of the front and the back droplet compare with that of the corresponding single droplet,the interaction reduces the overall burning rate of either droplet.The degree of the reduced overall burning rate for the smaller droplet is greater than that for the larger one.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.At the fixed droplet radius ratio,the larger mass fraction of oxygen is,the larger overall burning rates of droplets are and the cumulative values of diameter square of the front and the back droplet have a linear relationship with mass fraction of oxygen.The front and the back droplets burn at a lower overall rate than the corresponding single droplet under different oxygen mass fractions and the degree of the reduced overall burning rate for the smaller droplet is greater than that for the larger one.