| Leak detection technology is an important means to prevent pipeline failure and reduce pipeline risk.In order to reduce the economic losses,casualties and environmental damage caused by the leakage of urban gas pipelines and ensure the safe and stable operation of natural gas pipelines,it is necessary to detect the leakage timely and locate the leakage point accurately.Due to the limitations of single detection technology widely used in urban gas pipelines,improving the reliability and positioning accuracy of leakage detection technology for urban gas pipelines is an important direction in the field of safety engineering.Aiming at solving the limitation of identifying urban gas pipeline with single signal,a method based on sound pressure interaction is studied to improve the accuracy of pipeline leakage identification.The main work and conclusions of this paper are as follows:(1)CFD numerical simulation of gas pipeline leakage.The CFD calculation model of gas pipeline leakage is established to simulate the dynamic development process of pipeline flow field from closing to opening of pipeline leakage.The change of pipeline local flow field under leakage state is recognized.The pressure fluctuation and noise level of pipeline leakage jet area are analyzed,and the generation and propagation process of sound pressure signal are analyzed.The feasibility of pipeline leakage identification method based on sound pressure interaction is demonstrated.(2)The theoretical study of sound pressure characteristics under the condition of small hole leakage.According to the phenomenon that the sound intensity of the pipe wall rises and the pressure of the pipe decreases simultaneously in the process of leakage,a pipeline leakage identification method based on the sound pressure interaction is proposed.According to the velocity difference of noise propagating in pipe wall and pressure wave in gas flow field and the time difference between the two signals detected by the same position,the distance between leakage point and sensor measurement point is measured and the location of leakage point is determined.(3)Parametric experimental study on the correlation between leakage signal characteristics and working parameters.The variation trend of leakage noise and pressure drop under different working pressure,leakage diameter and pipeline diameter was studied experimentally.The experimental results show that the leakage noise intensity increases with the increase of working pressure,and the pressure reduction rate increases with the increase of working pressure.The leakage noise intensity increases with the increase of the leakage diameter,but the higher the working pressure in the pipe,the smaller the influence of the leakage diameter.The larger the diameter of the pipe,the greater the average sound intensity of the leakage noise,and the smaller the rate of pressure reduction in the pipe.(4)Study on correlation function value and influence of sound pressure interactive recognition method.The time interval ?t=0.1s is selected when considering about catching sudden changes and fluctuations.Comparing the correlation function values under different pipeline pressure,leakage diameter and diameter,it is found that the correlation function values decrease with the decrease of working pressure,leakage diameter and leakage diameter in the pipeline.(5)Experimental study on anti-interference ability of sound pressure interactive identification method.A set of experimental schemes with leakage and three typical external disturbances were set up to study the filtering ability of the acoustic pressure interactive identification method for typical disturbances in gas pipelines.The results show that,compared with the simple acoustic method or pressure wave method,the two signals in the acoustic pressure interaction method play a gate function to each other and filter the non-leakage interference signals.Thus,the anti-interference ability of the sound pressure interactive recognition method is improved. |
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