Fluctuations of a spray generated by an airblast atomizer
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This paper is devoted to the study of the aerodynamic instability of the spray generated by an airblast atomizer. As a result of this instability the spray shape and its velocity fluctuate with a certain frequency, which depends on the operational parameters of the atomizer. The effect of three parameters, namely; chamber pressure, liquid phase flow rate and the gas phase flow rate on the spray fluctuating frequency are investigated. The velocity vector of the drops in the spray and the arrival times to the detection volume are measured using the laser Doppler instrument. The slotting technique is applied to the data of axial velocity and arrival times of the drops in order to estimate the dominating spray frequencies. Additionally, the shape of the spray has been observed using the high-speed video system. The frequencies of the shape fluctuations are estimated using proper orthogonal decomposition of the time-resolved images of the spray. We show that the frequencies of the spray velocity and those exhibited by spray shape coincide over a wide range of spray parameters. Finally, a simple scaling for the spray frequency is proposed and validated by the experimental data.
KeywordsProper Orthogonal Decomposition Strouhal Number Power Spectrum Density Drop Diameter Proper Orthogonal Decomposition Analysis
This work is supported by the Deutsche Forschungsgesellschaft (DFG) in the framework of SFB 568 (TP A1 and TP C2). The financial support of F. Z. B. through the scholarship of Deutscher Akademischer Austausch Dienst (DAAD) is greatly acknowledged. The authors would like to thank T. Gambaryan-Roisman for providing the high-speed video camera.
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