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

An experiment was carried out on the structure of a twin spray from two pre ssurized-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 o f the spray were investigated in order to obtain design data for an lee-slu rry making system. The flow rate distribution of the overlapping sprays in a horizontal plane was also measured. In the present study, a relatively si mple 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 sin gle 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 spra ys. Comparing the measured Sauter mean diameter (SMD) of the twin spray wit h that of the single spray, no substantial difference in the SMD distributi ons was found over the whole range of the spray from nozzle L (serial numbe r 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 dropl ets. For the twin spray, the number density was slightly increased in the o verlapping region of 15-35 mm. However, it became rather smaller at the per iphery 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 dropl ets in the overlapping region suppressed the movement of large droplets to the periphery.