Study On Pipeline Leakage Monitoring Based On Distributed Optical Fiber Vibration Sensing

Water supply pipeline is an indispensable and important part of urban water supply system.At the same time,it is also the infrastructure of urban construction and an important guarantee of national life.Therefore,there are problems in the operation of water pipelines,which will bring double losses of economic and social benefits.At present,the detection methods for pipelines include stress wave method,negative pressure wave method,ground detection method,flow balance method and distributed optical fiber detection method.The sensing part of distributed optical fiber detection method is simple,and the optical fiber is both a sensing medium and a transmission medium.This method is convenient to use and has a high cost-effective ratio.It can realize long-distance continuous measurement.In the distributed optical fiber detection method,the vibration sensing system of ?-OTDR is more sensitive to object vibration.So this paper applies ?-OTDR detection technology to leak detection of pressure water pipeline.The main research contents of this paper are as follows:(1)Chapter 2 analyses the principle of the distributed optical fiber sensing system of ?-OTDR,introduces the principle of Rayleigh scattering and Rayleigh backscattering in the optical fiber step by step,and analyses the traditional OTDR technology and the current detection principle of ?-OTDR,introduces the most mature and convenient data processing method of ?-OTDR,mobile average difference method,and then introduces the main content of this paper.The testing instrument is introduced.(2)Chapter 3,based on the finite element analysis method of flow field,gives a brief numerical simulation of the leakage of pressure water pipeline,analyses the influence of two kinds of leakage hole sizes on the flow field,then introduces the test platform of this paper,and based on the results of numerical simulation of flow field,puts the distributed optical fiber sensor in the pressure water pipeline,using the instruments of Chapter 2 and the ?-OTDR.R data processing method,a series of experiments were carried out on pressure water pipeline.The test variables include the size of leakage hole,the size of leakage hole,the shape of leakage hole,thepressure of water pipeline and the material of pipe wall.Qualitative verification of whether the distributed optical fiber sensor based on ?-OTDR can detect the leakage of pipeline is carried out by this test method.(3)In order to avoid the influence of the flow field inside the pipeline,the fourth chapter's experiment is also based on the experimental instrument and data processing method of the second chapter.The difference is that the distributed optical fiber sensor is pasted on the outer wall of the pipeline,and a series of experiments are carried out on the pressure water pipeline.The test variables include the size of the leakage hole,the shape of the leakage hole,the pressure of the water pipeline and the material of the pipe wall.The sticking position of optical fibers is verified qualitatively by this test method whether the pipe leakage can be detected by the distributed optical fiber sensor based on ?-OTDR.Finally,experiments are carried out using the fiber grating sensor,acoustic emission technology and acceleration sensor under the same working conditions of the main test method in this paper,which is coMPared with the technology of ?-OTDR,and to study Advantages and disadvantages of ?-OTDR technology.