Research On Motion And Leak Sound Source Identification Of Spherical Detector For Small Diameter Oil Pipeline

During the operation of oil pipelines,small leakage often causes serious accidents and causes great losses because it is not easy to find and easily develop into large leakage.Since the completion of oil pipeline,many scholars have proposed various theories and methods for pipeline leakage detection.Among these methods,the internal detection technology is widely used because of its high precision.For small diameter oil pipeline,due to the limitation of diameter,the traditional internal detector is very easy to jam in the pipeline.Therefore,this research proposes an internal detector with a spherical appearance,which can pass through the pipeline smoothly without jamming.At the same time,the internal detector also collects the near-field acoustic signal at the leak hole,which can greatly improve the detection accuracy.The internal detector used in this research does not carry the driving device.Its power is from the thrust by the pipeline.There will be many factors in the pipeline that affect the force.After searching for relevant literature,four variables,such as flow rate,pressure in the pipeline,pipe diameter ratio and upstream and downstream length,are selected for simulation to explore the relationship between these factors and the stress of the detector in the pipeline.The results show that: in the range of parameters selected in this study,the thrust of detector increases with the increase of flow velocity and the pipe diameter ratio,which is independent of the pressure in the pipeline and the length of upstream and downstream of detector.Then,the computational fluid dynamics model of the spherical detector is established,and the dynamic grid technology is used to simulate the passing performance of the detector.The results show that the optimal diameter ratio range is 0.4 ? 0.8.Under the conditions of flow rate of 1 m/s and pressure of 1.5 MPa,as long as the detector mass is no more than 4 kg,it can pass smoothly in the pipeline without blocking.In view of the acquisition and analysis of near-field acoustic signal,the location of the leaking sound source is determined by the simulation calculation of the established hydrodynamic model.According to the simulation results,the acoustic model of leakage calculation is established,and the propagation and distribution of leakage noise in the pipeline are studied.The relationship between the leakage aperture,pressure of different pipeline and the distance of different sound source and the distribution of leakage sound signal is obtained.According to the collected acoustic signal spectrum,the analysis range of sound frequency is 3220 Hz ? 22020 Hz,which provides reference and basis for the selection of internal sensors of the detector.In order to make it more convenient for the spherical detector to be put into use,the dropping and recycling device of the detector is designed.The gravity of the detector is used for dropping and recycling.At the same time,the traditional dropping and recycling device is optimized,which greatly reduces the operation cost and limitations,and improves the use efficiency.According to the previous simulation results,a prototype of spherical detector is processed,and a multi-functional pipeline leakage detection test bench is built to test the passing performance of detectors with different quality in horizontal,inclined and vertical pipelines under different flow rates,and collect the noise information near the leakage hole.The experimental results show that the detector with a diameter of 80 mm and a mass of 1.5 kg can pass through the vertical pipe section smoothly at a flow rate of 0.5m/s without blockage,which is consistent with the simulation results.Through analysis and comparison,the collected leakage acoustic signal is in good agreement with the simulation results.According to the previous simulation results,a prototype of spherical detector is manufactured,and a multi-functional pipeline leakage detection test bench is built to test the passing performance of detectors with different quality in horizontal,inclined and vertical pipelines under different flow velocities.Then,the acoustic signal information near the leakage hole is collected.The experimental results show that the detector with a diameter of 80 mm and a mass of 1.5 kg can pass through the vertical pipe section smoothly at a flow rate of 0.5 m/s without blockage,which is consistent with the simulation results.Through analysis and comparison,the collected leakage acoustic signal is in good agreement with the simulation results.