Self-excited Frequency Estimation Model of Organ-pipe Waterjet under Confining Pressure

doi:10.3901/JME.2018.18.220

Abstract

Abstract: The self-excited frequency of the organ-pipe waterjet plays a key role in the modulation of the jet to achieve strong oscillation and erosion, while it is difficult to be obtained accurately. The main reason is that the value of the Strouhal number is associated with the jet parameters, the cavitation number and the nozzle structure parameters. The self-resonating oscillation mechanismof organ-pipe waterjet is discussed, and the relationship between the self-excited frequency and the cavitation number is analyzed. The pressure signal within pipeline is detected to obtain the jet spectrum, and according to the "triad resonance" theory, the self-excited frequency is distinguished. Furthermore, the influence of the confining pressure, the jet working pressure and the cavitation number on the frequency property are analyzed, and then the relation curve between the Strouhal number and the cavitation number is acquired. The approximate fitting formula of the Strouhal number is obtained based on the least square method, then the estimation model of jet self-excited frequency is established. The test results show that, with a given nozzle structure, the value of the Strouhal number is only related to the cavitation number. The value range of the Strouhal number is replaced by the estimation model, so that the theoretical calculation accuracy of self-excited frequency is improved. The results provide a theoretical basis for the application and study of self-resonatingwaterjet technology in deep-sea area.

Key words: cavitation number, estimation model, organ-pipe waterjet, self-excited frequency, strouhal number

CLC Number:

TG156

PAN Yan, CAI Tengfei, MA Fei, QIU Linbin, CUI Lihua. Self-excited Frequency Estimation Model of Organ-pipe Waterjet under Confining Pressure[J]. Journal of Mechanical Engineering, 2018, 54(18): 220-225.

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