Numerical Study on Turbulent Mixing of Spray Droplets in Crossflow

A three-dimensional model for turbulent gas-droplet two-phase flow is developed to obtain a systematical understanding of the mixing process of centrifugal spray jet and turbulent crossflow in a horizontal tube. The turbulent dispersion and droplet-wall interaction are considered for modeling the dispersed phase in Lagrangian frame. The effects of influencing factors on the mixing process, including water/gas mass flow ratio, spray angle, droplet diameter, axial injection angle of spray nozzle and tangential injection angle of spray nozzle, are examined. Two indices, the degree of mixedness and the dimensionless droplet concentration, are proposed to assess the mixing performance of the spray droplets in the crossflow in a complementary way. The simulation results reveal that adding droplets into the crossflow imposes significant impact on the crossflow and in turn the affected crossflow produces considerable effect on dispersion and aggregation of the droplets. It is also found that the optimum mixing of droplets and crossflow can be achieved with the conditions that the water/gas mass flow ratio is 1:1, the spray angle is near 90 degrees, the droplet diameter is larger, the axial injection angle of spray nozzle is 90 degrees, and the tangential injection angle of spray nozzle is 0 degrees.