Analysis of the reflected light brightness to determine structural changes in the fluid flow from a spray device

Abstract

Visual and instrumental observations of a liquid sprayed by the nozzle showed an uneven distribution of the reflected light brightness in the spray cone. The structure of the spray cone produced by centrifugal nozzles was experimentally investigated. A simple approach to the analysis of spray cone images is proposed, which allows tracking the change in the spray structure. The approach is based on measuring the integral brightness of the reflected light, which is uniquely related to the area of ​​the interface between the media. Measurements showed that the integral brightness changes with increasing distance from the nozzle. Three characteristic areas can be seen on the brightness change graph with increasing distance from the atomizing device. In the first area, a sharp increase in the reflected light brightness is observed, which reaches the maximum upon transition to the second area. In the second area, the reflected light brightness drops sharply. In the third area, the brightness practically stops changing. In this case, structural changes in the spray pattern are visually observed with increasing distance from the nozzle. A detailed analysis of these structural changes was performed using macrophotography and the Glare Point Technique (GPT). It was found that the liquid flies out of the nozzle in the form of an expanding cone of a solid film. Then, in the second area, the film breaks into separate fragments of a complex shape, which, under the action of surface tension forces, begin to turn into spherical objects. In the third area, all fragments turn into spherical objects, while their number and shape practically stop changing.