Visualization of high-speed gas jets and their airblast sprays of cross-injected liquid |
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Authors: | K D Kihm T K Kim S Y Son |
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Institution: | (1) Department of Mechanical Engineering, Texas A&M University College Station, Tx 77843-3123, USA, US |
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Abstract: | A planar and instantaneous visualization study of high-speed gas jets and their airblast sprays was performed to qualitatively examine the different atomization performances of different gas nozzles. For the visualization of high-speed gas jets (with no liquid injected), Nd:YAG pulsed laser sheets imaged the clustered vapor molecules in the Rayleigh range (d?λ), condensed from the natural humidity during the isentropic gas expansion through a nozzle. This method visualized both underexpanded sonic gas jets from a converging nozzle (SN-Type) and overexpanded supersonic gas jets from a converging-diverging nozzle (CD-Type). When liquid is cross-injected, the same laser sheet images the spray droplets of relatively large sizes (d?λ). The present visualization results show that the SN-Type nozzle develops a wider spray than the CD-Type nozzle, quite probably because the SN-Type nozzle has a wider gas jet (in the absence of liquid) than the CD-Type. Also, the wider spray of the SN-Type nozzle lowers the probability of droplet coalescence and generates finer sprays compared to the CD-Type nozzle. These visualization results qualitatively agree with the previous quantitative finding of the different atomization characteristics of the two types of nozzles (Park et al. 1996). |
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