Experimental study on the water film thickness under spray impingement based on planar LIF

Abstract

Spray impingement is widely applied in many fields, and the liquid film formed on the impact surface is closely related to the heat and mass transfer. In present paper, an experimental setup of the spray impingement with an air-atomizing nozzle was established to study the water film formed on a flat surface. And the planar laser-induced fluorescence technology was applied to measure the film thickness at different spray heights (10–40 mm) and water flow rates (60–120 ml/min). Based on the film topography, the water film was divided into the impact zone and the free flow zone. The film thickness in the impact zone was thinner than that in the free flow zone. The water film at the center of the impact surface intensely fluctuated, and the steady layer thickness was 0.33–0.73 mm. The film thickness in the free flow zone presented a camelback topography of first increasing and then decreasing with the increase of the radial distance. Besides, the film thickness in the free flow zone decreased with increasing the spray heights and increased with increasing the water flow rates. The maximum film thickness was 2.27 mm and the average film thickness in the free flow zone was 0.85–1.50 mm. The study provides much more experimental data with the study on the liquid film thickness under spray impingement.