PDA measurements in a fan spray pressure atomizer arrangement used for water atomization of melts

The results of PDA investigations of nozzles used in water atomization of melts are presented. Measurements have been performed to characterize both the spray of a 4 nozzle arrangement consisting of 2 primary and 2 secondary nozzles and the spray of individual nozzles. Spraying Systems fan spray nozzles were used at atomizing pressures up to 150 bar. The comparison between the single spray and the interacting spray characteristics indicates a further break-up of the droplets to due droplet-droplet interactions especially at the maximum pressure of 150 bar, leading to a reduction of the mean diameters of the interacting sprays. This result was theoretically confirmed by an analysis of the relative droplet We-numbers, mostly being in the range between 800 and 21,000. In general, the measurements reveal some difficulties to measure inside the very dense spray regions, although the probe volume was reduced to a diameter of 42 µm. In some cases, integrated PDA mass flow rates differ by more than 70% compared to the nominal nozzle flow rate at the pressures investigated.