Segregation of drop size and velocity in jet impinging splash-plate atomizers

Abstract

Atomization of a liquid jet as it impinges on the flat end of a circular rod (splash plate) is studied experimentally. The effects of the splash-plate diameter (surface diameter) and the jet velocity on the disintegration of the jet are investigated. Six surface-to-jet diameter ratios of 2.3, 3.0, 5.1, 5.3, 8.7, and 13.9 are used, while the jet velocity is varied from 7.4 to 31 m/s. A hollow cone sheet and consequently a spray are formed as a result of this type of impingement. A phase Doppler particle analyzer (PDPA) is used to measure the diameter and velocity variations in the resulting sprays simultaneously. The diameter and velocity of the drops at the region of the spray with the highest volume flux are measured for various surface diameters and the jet velocities. It is found that the mean diameter of the drops at this region decreases as the jet velocity increases. In addition, at low jet velocities (uj < 18 m/s), the mean drop diameter increases with an increase in the surface to jet diameter ratio; however, at high jet velocities (uj > 18 m/s), it is insensitive to the changes in the surface to jet diameter ratio. Empirical correlations are derived and reported for these variations. It is also found that the mean drop diameter and velocity are the largest at the outer edges of the spray, and they continuously decrease across the spray toward the spray axis. This result indicates that the impinging jet atomizers segregate drop sizes and velocities. The suspected cause of this segregation is the flow currents inside the hollow cone spray.