| In every city,there are a lot of water supply pipelines,it facilitates people’s demand for tap water.But a large number of long-term service water supply pipelines have the problem of leakage due to staffs’ negligence of pipeline maintenance.Pipeline leakage not only aggravated the loss of water resources,but also buried the safe hidden trouble in people’s living environment.So if the pipeline leakage could be found and repaired in time,it would be important on the city building.Because of simple operation and high efficient detection,correlation detection based on acoustic signal processing is widely used,in which estimating time delay between the detection signals on both sides of the leakage point is the key of this method.In actual environment,there is many kinds of noise included the relevant noise which would cause serious disturbance to the delay estimation of the leak detection signal.90° elbow is a common pipe part in the water supply pipeline system.If there is a 90° elbow near the pipeline leak,a kind of water flow characteristic called "Dean Vortex" caused by the elbow would trigger the vibration of pipeline,which is a kind of non-leaking related noise mixed with leak detection signal spreading along the pipeline.The non-leaking related noise would seriously affect the accuracy of positioning,and even lead to misjudgment of the leak point.For the presence of 90° elbow,a method of suppressing the bending noise in the leak detection signal is studied deeply in this paper.The research in this paper is as follows:(1)According to the different flow state of the fluid at 90° elbow and leakage,the hydrodynamic noise model of leakage and elbow is analyzed.On the other hand,the different nature of leakage noise and bending noise is analyzed.(2)Based on the ANSYS simulation platform,the fluid-solid coupling calculation of straight leaked pipe and elbow is carried out.The movement state of the fluid in the model is observed,and the vibration data of the two models are analyzed in frequency domain.(3)The simulated vibration data are analyzed by sample entropy,and the difference in complexity of the two kinds of time domain signal is quantitatively measured by the sample entropy value,so that the leakage noise and bending noise can be distinguished simply and intuitively.(4)A method to suppress the bending noise by EMD and sample entropy is proposed.The vibration signal mixed with leakage noise and bending noise is processed by EMD,and then the decomposed IMF components are screened by sample entropy.Remove the elbow noise components to get the vibration signal of leakage noise.(5)The simulation method and the actual test are used to verify the feasibility of the method,that is removing bending noise in vibration signals of the leakage noise,in the above-mentioned. |
