Experimental Study On In-tube Acoustic Detection Of Water Pipeline Leakage

China's water distribution system has a high average leakage rate and a large total leakage.The pipeline leakage acoustic detection technology locates the leak point by detecting the leaking sound.Although a number of researches on acoustic detection technology of pipeline leakage have been conducted,there are few studies on the near sound field of leakage source or in-tube acoustic detection.In-pipe acoustic detection of water supply pipeline leakage can receive leakage acoustic signals in a close distance,and the external interference is slight,so it is possible to excavate the acoustic characteristics of pipeline leakage and provide a basis for pipeline leakage detection.In this paper,the experimental equipment developed by the test device is used to conduct the acoustic test of the leakage of the water supply pipeline.In this study,the effects of various influencing factors such as water velocity and soil medium on the leakage sound signal are considered.The main research are as follows:(1)On the foundation of previous researches,a multi-factor simulation leakage test device was developed.The device is highly-simulated with slight outside interference and convenient disassembly.After the device was developed,a self-vibration test was conducted.(2)The leakage acoustic test was carried out using the device with no flow velocity in the pipe and the medium outside the pipe was water.The effects of leakage,water pressure,leakage aperture size and the distance of the sound sensor from the leakage point on the leakage acoustic signal were investigated.The results show that there is a significant difference in the signal with or without leakage,which proves that it is feasible to use the hydrophone to detect the pipeline leakage.Further research shows that the amplitude and energy of the leakage sound are positively correlated with the pressure inside the tube,and tend to increase as the leakage aperture rises,at the same time,it is affected by the combination of the leakage amount and the leakage flow rate.Energy decays during sound wave propagation.The attenuation is fast when sound frequency is high,and slow when it is low.(3)The leakage acoustic test was carried out using the device with no flow velocity in the pipe and the medium outside was sand to study the influence on the leakage acoustic signal caused by the difference of medium.The results show that the external medium has an influence on the sound signal,and it is more intense while the external medium was water.The amplitude and energy of the leakage sound are positively correlated with the pressure inside the tube.The leakage sound is affected by the combined effect of leakage and leakage flow rate.(4)Leakage acoustic test in a pipe with velocity is implemented with the developed device while the medium is water and sand,respectively.This paper further studied the denoising scheme of leakage noise,and the effects of leakage,water pressure,leakage pore size,in-tube flow rate,and extra-tube media on the leakage acoustic signal.The results show that the vibration caused by water flow masks the characteristics of the leakage sound signal.The leakage noise signal can be obtained by appropriate noise reduction processing.After the noise reduction process,there are obvious differences between the leakage and the leakage-free signal.The leaking sound is positively correlated with the pressure in the tube.The leakage sound is affected by the combined effect of leakage and leakage flow rate.