The Two-Phase High-Speed Stream at the Centerline of a Hollow-Cone Spray Produced by a Pressure-Swirl Nozzle

The flow characteristics of hollow-cone sprays produced by pressure-swirl nozzles were investigated by particle image velocimetry (PIV) and computational fluid dynamics. Two high-speed characteristic droplet velocities were observed by PIV captures at the periphery and centerline of the spray cone. Such flow characteristics were also simulated by two-dimensional axisymmetric simulations. In the simulation, in addition to the two high-speed characteristic droplet velocities, a high-speed air stream at the spray centerline was also observed. This high-speed air stream converged and accelerated small droplets to form the high-speed droplet stream. After further simulation, it was found that the largest droplets carried by the high-speed air stream at the centerline were most efficient in the momentum transfer process between two phases. The influence of the two-phase high-speed stream on the heat- and mass-transfer process is meaningful for related spray operation research and should be seriously considered.