Analysis of spray formation in a confined spray process for powder production

The tailoring of the particle and powder properties that are produced within spray processes is influenced by various unsteady transport processes in the dispersed multiphase spray flow in a confined spray chamber. In this context differently scaled spray structures in a confined spray environment have been analyzed experimentally and numerically. The basic setup of the study consists of a twin-fluid atomizer central top-spraying in a confined spray chamber, where the atomizer gas can be heated up to 500 degrees C. Mixing phenomena of momentum, energy and species play an even bigger role for this hot-gas atomization and drying process than in a conventional tall form spray dryer. The experimental investigations have been carried out with Particle-Image-Velocimetry to determine the kinetic data of the gas and the discrete phase. Additionally Large-Eddy-Simulations have been set up to predict the transient behaviour of the process and give more insight into the sensitivity of the droplet-gas interactions.