Self-excited Pressure Vibration in the Low-Pressure Pipeline Using an Automatic Pressure-reducing Valve (II)

-Prediction of Occurrence of Self-excited Pressure Vibration Based on a Period of Water Pressure Oscillation in a Closed Conduit-

抄録

  In this study, a waveform of a self-excited pressure vibration that occurs in low-pressure pipeline systems was analyzed using a pressure-reducing valve. This analysis was conducted on the basis of field measurement data that was obtained for the condition in which the pressure-reducing valve is placed in the middle of the pipeline and a direct-acting constant-flow valve is installed at the end. On obtaining the intrinsic oscillation period from the transfer matrix and the oscillation period of the field measurement waveform from the spectral analysis, it was clarified that the theoretical period of the intrinsic oscillation of the pipeline approximates the shortest oscillation period based on the measurement data and provides an indication of the periodicity of the pipeline. Moreover, on verifying the cross-correlation function and the phase-shift time between the primary and secondary pressure of the pressure-reducing valve, it was clarified that they depend on each other and the secondary pressure propagates as the primary pressure via the pressure-reducing valve. In addition, the efficacy of the installation of the surge tank and air stick for controlling the pressure oscillation was theoretically and experimentally demonstrated. Based on these results, it was proposed that the occurrence of the self-excited pressure vibration be determined based on the intrinsic oscillation period by using the dimensions of the pipeline.