Imaging measurement of the structure of a twin overlapping spray for ice-slurry making

Abstract

An experiment was carried out on the structure of a twin spray from two pressurized-type swirl nozzles, in order to investigate the overlapping spray characteristics of two single sprays. Using image processing methods, spray characteristics such as the droplet size distribution and number density of the spray were investigated in order to obtain design data for an lee-slurry making system. The flow rate distribution of the overlapping sprays in a horizontal plane was also measured. In the present study, a relatively simple twin spray was studied experimentally to investigate the droplet size distribution and the velocity of droplets in the overlapping spray region. By comparing experimental results of the twin spray with those from two single sprays, the flow rate was concentrated in the region of overlap between x = 0 and 50 mm, where there was vigorous interaction between the two sprays. Comparing the measured Sauter mean diameter (SMD) of the twin spray with that of the single spray, no substantial difference in the SMD distributions was found over the whole range of the spray from nozzle L (serial number 6032). The maximum SMD of both results was 60 mu m, rc which was located at the middle of the overlapping region. The twin spray showed a different distribution of the number density due to the collision between spray droplets. For the twin spray, the number density was slightly increased in the overlapping region of 15-35 mm. However, it became rather smaller at the periphery of the spray, where the influence of collision between droplets was small. For a larger-sized nozzle, the number density of the twin spray was clearly higher, by 20%. This is mainly because the spray from nozzle L had a larger flow rate and higher density. Consequently, the collision of droplets in the overlapping region suppressed the movement of large droplets to the periphery.