Numerical Simulation And Acoustic Location Of Water Supply Pipeline Leakage

In recent years,the infrastructure of municipal water supply pipeline has developed rapidly in China,but the pipeline damage and leakage are very serious,and the leakage rate has been at a very high level.Leakage of water supply pipeline will lead to waste of water resources,economic loss and potential pollution risk.The chronic leakage of small and low-pressure pipeline from small leakage hole has not been noticed for a long time and is difficult to find.Therefore,it is of great significance to detect and locate the chronic leakage of water supply pipeline timely and accurately.A pipeline simulation model was built according to the actual pipeline.The flow field of the fluid in the leaking pipeline and the distribution of the flow field near the pipeline with fittings were simulated at different flow rates,pressures,and different pore sizes.The results show that when the pipeline leaks,the water flows out of the pipe in the state of jet,and the velocity is the largest in the center of the leakage hole.With the increase of the inlet velocity of the pipeline,the pressure drop at the leakage hole also increases,and the low pressure area and the affected area of the fluid become wider.The influence of the pressure factor on the flow field near the leak is similar to the velocity influence.The size of the leakage aperture has little effect on the flow rate and pressure of the pipeline leakage,and it mainly affects the direction of the fluid near the leak;When there is a tee fitting in the pipeline,there will be two vortices near the tee.With the increase of the pressure and flow velocity at the inlet of the pipeline,the vortices gradually move to the direction of water flow.The vortices will gradually become larger and then disappear.The flow into the branch pipe becomes larger and larger.When there are valve fittings in the pipeline,the valve plate will have a certain blocking effect on the water flow.When the inlet pressure and flow velocity of the pipeline are small,the blocking effect of the valve plate on the water flow increases with the increase of the flow velocity and pressure in the pipeline.When the closing angle of the valve plate becomes larger,the influence of the flow field becomes more prominent.When the pressure and velocity in the pipeline reach a certain range,the blocking effect of the valve plate on the flow becomes not obvious,or even weakened.On the premise of simulating the flow field in the pipeline,the occurrence and propagation of the acoustic signal of pipeline leakage and pipe with pipe fittings under different working conditions are simulated.The results show that the average amplitude of sound pressure of pipeline vibration will change with changes in pressure and flow rate.The smaller the leakage aperture,the greater the amplitude change.The upstream amplitude of the vibration source changes more than downstream.With the increase of pressure,flow velocity and leakage aperture at the inlet of the pipeline,the power spectrum of each frequency band at each detection point increases,and the change of pressure at the inlet of the pipeline has a greater impact on the power spectrum;The frequency of pipeline vibration caused by leakage is mainly between 400-600 hz,and the frequency of tee pipe vibration is mainly under 300 Hz.The frequency of valve plate vibration is related to the angle of valve plate,when the valve plate angle is 30 degrees,it is mainly 400-500 Hz,and when the valve plate angle is 45 degrees,it is mainly 400-600 Hz.The energy of vibration caused by leakage hole,tee pipe and valve is small,and other interference signals have great interference on them.It is difficult to find out the corresponding frequency band of vibration energy through simple power spectrum analysis.According to the principle of acoustic correlation leak detection technology,a three-dimensional leakage model of pipe with fittings is established for numerical simulation,and then the acoustic signal generated after the pipe leakage is analyzed and processed.The results show that there is obvious difference between the sample entropy of pipeline leakage acoustic signal and pipe vibration acoustic signal.Combined with empirical mode decomposition(EMD),the leakage acoustic signal of water supply pipeline can be extracted to remove the interference information,and the chronic leakage of pipe with tee or valve can be located.The positioning difference is 0.29 m and 0.64 m respectively.