Study on Coupled Acoustic Wave Propagation in a Metal Pipe for Monitoring of Gas Leakage Based on a Correlation Method

摘要

The circular cylinder pipe is extensively used for supplementing gas. Without any monitoring, leakage of this gas induces a catastrophic problem when it leaks into open areas of a city. To develop a leakage monitoring system, we theoretically investigated the propagation of the acoustic wave in a circular cylinder pipe containing gas in a pipe. The acoustic wave propagates through the waveguide of the circular pipe with the characteristics acoustically coupled by the gas contained in a cylinder and the shell. However, as a special case, the acoustic waves in a metal pipe containing gas correspond closely to the uncoupled in-vacuo shell waves and to the rigid-wall duct fluid waves. In this case, the dominant acoustic energy can be estimated at the frequencies in which coincidence between the shell modes and the acoustic modes occurs. This study theoretically investigated the characteristics of the dominant waves and experimentally analyzed them with a long steel pipe. The measured data was clearly analyzed by the continuous wavelet transform and by spectral density analysis. The bandwidth of the frequency necessary for a good estimation of the correlation is suggested by considering the coherence function between two sensors.