EFFECT OF TRANSVERSE ACOUSTIC FORCING ON THE CHARACTERISTICS OF IMPINGING JET ATOMIZATION

This paper is focused on the systematic experimental investigation of the response of the liquid sheets to the transverse acoustic excitation. Present work is carried out in the context of the interaction of atomization process with the acoustic field in the combustors of liquid rocket engines. Liquid sheets produced by impinging jet atomizer over a range of Weber numbers (141-600) and impingement angles (60 degrees-120 degrees) are considered for this study. Freely traveling acoustic waves over a range of frequencies (100-500 Hz) and sound pressure levels (50-109 dB) are used to study the interaction. We observe that the breakup regime plays a vital role in deciding the response of the liquid sheets to the external acoustics. The effect of acoustics is quantified in terms of the sheet characteristics such as breakup length, sheet width, size distribution of primary droplets, and mean droplet size. It is observed that the sheet responds to certain discrete frequencies and consequently shows substantial reduction in breakup length. The mean drop size was also seen to decrease in the presence of acoustic field. A phenomenological analysis of the whole process shows that the average sheet thickness and the sheet area are the critical parameters in determining the quantitative response of the sheet to specific acoustic parameters and the experimental results presented here justify the analysis. It is also shown that the drop size distribution normalized by the mean drop size can be described by Gamma function irrespective of the action of the acoustic forcing.