Influence of local blockage on pipe transient frequency response characteristic and its application
LIU Zhiyong1, LIU Meiqing1, WANG Huachao2, WU Yuanwei1
1.Key Laboratory of Transients in Hydraulic Machinery, Ministry of Education, Wuhan University, Wuhan, Hubei 430072, China; 2.CSEPDI of China Power Engineering Consulting Group, Wuhan, Hubei 430072, China
Local blockage is a usual fault in pressurized pipe systems. In this study, the influence of a local blockage on the frequency response diagram(FRD)is analyzed and the relationship between the variation pattern of FRD and local blockage parameters, namely the location and resistance coefficient of the blockage is obtained by using transfer matrix method for a pipe system. Then, based on this relationship, a pipe local blockage detection method is proposed and its feasibility is validated through numerical experiments. The results show that the amplitudes of the even harmonics and odd harmonics of a pipe with a local blockage no longer maintain constant compared with a normal pipe, but vary periodically with the harmonic order instead. The main frequency and phase of the odd harmonics reflect the blockage location, and the amplitude of the main frequency is related to the minor resistance coefficient, consequently based on these facts the blockage location and degree can be detected. The numerical experiments confirm that the pipe local blockage detection is feasible based on FRD analysis.
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