Visualization of the flashing spray generating by the expansion-chamber nozzle using R134a

Flashing spray could generate the desired fine atomization due to the bubble explosion at the nozzle exit at the low injection pressure. This paper presents an experimental study on both the internal flow and the spray pattern outside the nozzle tip so as to further understand the mechanism of the flashing spray. One straight tube nozzle made of the transparent quart glass and five expansion-chamber nozzles with different aspect ratio are employed. The result finds that the internal flow within the straight tube nozzle presents the symmetric cavitation flow, asymmetric cavitation flow and finally the slug cavitation flow with increasing the injection pressure. The spray angle almost remains constant for the slug cavitation flow. For the expansion-chamber nozzles, the spray angle maintains at the relatively smaller values as the aspect ratio of the length to the diameter of the expansion chamber ranges from 1:2 to 2:1, andthe optimal spray angle keeps fluctuating around 70°.