Droplet behaviors of a spray impinging on an oil film by planar laser induced fluorescence

Abstract

Microscopic characteristics of a spray impinging on an oil film have a great influence on the atomization and pollutant emissions. Therefore, the droplet behaviors from the impinging spray and oil film are significantly important to evaluate the spray/film process and need to be deeply understood. In this study, under different viscosity and thickness of the oil film, the droplet behaviors from a spray after impinging on an oil film at different locations were analysed by planar laser induced fluorescence. Results showed that an obvious crown structure is generated after the spray impinged on the oil film in the selected conditions. With the rise of viscosity of the oil film, the crown size becomes larger and larger size droplets are generated. The droplet diameter with maximum frequency and the maximum droplet diameter both display an increase trend as the viscosity rises. However, the maximum droplet velocity declines. The crown structure gets smaller and fewer droplets with large size and low velocity are generated when the oil film thickness declines from 0.5 to 0.2 mm. Besides, a decreasing total number of droplets and a higher probability of relatively smaller droplets are observed at smaller oil film thickness condition. On the contrary, the diameters with maximum frequency are comparable for two film thicknesses. The maximum droplet velocity enlarges as the oil film thickness decreases.