Study On Simulation Of Leakage Process And Calculation Of Leakage Volume To The Natural Gas Pipeline

With the wide use and penetration of natural gas in China,the length of natural gas pipelines in China is gradually increasing.However,some natural gas pipelines are prone to accidents due to the long service time.Leakage is one of the most common accidents in natural gas pipelines.Predicting the leakage volume of natural gas can provide the basic parameters for the evaluation of the accident consequence and the formulation of emergency response plans.However,the leakage is a complicated process that couples the unsteady compressible flow and outflow of leakage hole,so it is difficult to calculate the volume of natural gas accurately.As a complete system,after the leakage accident,the hydrothermal parameters along the natural gas pipelines would change,which cause the flow rate,pressure and temperature at leakage point change.So the calculation of leakage volume and flow rate should be coupled with the change of hydrothermal parameters along the pipelines.This thesis combines the traditional leakage flow rate model with the natural gas pipeline simulation model to establish natural gas pipeline transient leakage model.This model considers the influence of in hydrothermal parameters along the pipeline on leakage and improves the calculation accuracy of the temperature and pressure at the leakage point.The effectiveness of the unsteady leakage model is verified by comparing with the experimental data in literature.Based on the calculation results of the model,the influences of the pressure,flow rate and temperature on the leakage volume and hydraulic parameters along the pipeline after the leakage accident occur were analyzed.The calculation accuracy of the leakage flow rate depends on the flow coefficient.So this thesis established natural gas pipe section leakage model based on the theory of computational fluid dynamics,and verified the validity of the model by comparing with the experimental results in the literature.The leakage flow rate under different leakage hole temperature,pressure and flow rate are calculated by this model and the influence of the above factors on the flow coefficient was analyzed.Finally,considering the coupling characteristics of the actual natural gas pipeline leakage process,a natural gas pipeline leakage model coupled with the characteristics of leakage outflow is established.The model can not only calculate the leakage flow rate and volume but also the hydraulic parameters along the pipelines during the leakage.The coupled model is verified by comparing the calculation result in literature.Thesis compare the results of the coupled model and the non-coupled model and found that the results of the non-couple model is smaller and the deviation of the non-couple model is large.The results of this thesis provide basis information for the risk prediction of accident.