Role of combustion on droplet transport in pressure-atomized spray flames

The transport of droplets in a pressure-atomized kerosene spray flame was examined using a twocomponent phase Doppler system to measure the droplet size and velocity distributions at several locations within the spray. The effect of combustion on droplet transport was examined by comparing the results to a nonburning spray under similar flow conditions. Directions of motion of droplets are calculated from the measured droplet velocity components to provide information on trajectories and dispersion of droplets. Results show that combustion reduces the strength of gas recirculation as evidenced by significantly fewer droplets being transported upstream toward the nozzle along the centerline for the burning spray as compared to the nonburning spray. Combustion enhances droplet vaporization and results in reduced number density and larger droplet mean diameters and velocities when compared to the nonburning spray. At the spray centerline, there is a wide range of droplet trajectories that are associated with recirculated droplets and those originating from the nozzle. There is some correlation between droplet velocity and diameter. Some larger size droplets are also found to be entrained into the recirculation pattern. At the spray boundary, few droplets deviate from the mean direction. Also, droplet velocity is well correlated with increasing diameter but appears to approach an asymptotic value in which droplet velocity becomes insensitive to diameter.