Study On The Technique Of Simulation And Its Leakage Risk Of Gas Pipeline Network

With the rapid development of our country's economy, the consumptions of natural gas are increasingly going up in the city and its gas pipeline network become more complex, which makes human more difficult to understand and master the operation rule of the pipeline network system. The leakage accident of gas pipeline is a probability event. And it is impossible to avoid the accidents. Once gas releases through damaged pipes, accidents would happen involving substantial economic losses and even victims amongst the population. Therefore, study on the technique of simulation on gas pipeline network and its leakage risk has already become an important subject to settle in current gas transmission and distribution field.This paper first analyzed the present state, trend of development and existing problem of research on transient simulation on gas pipeline network and its leakage risk, and then the chief contents were introduced. The transient gas flow models were established and solved by fluid network theory. Compared to the conventional numerical methods (implicit difference method and character line method), the maximum deviation was about 1 percent among the methods. The fluid network theory was applied to the partial high pressure gas pipeline network at Sixth Ring Road in Peking. The results showed that the maximum deviation was about 2.1 percent between the calculations and measurements. The conventional technique of simulation on gas pipeline network claims that every node of the network should be allocated a known parameter (pressure or flow). Aim at this deficiency, the corresponding settle methods were proposed in this paper. The improved technique of simulation was applied to the partial high pressure gas pipeline network in Tianjin, and a good agreement was found between the calculations and measurements.Gaussian dispersion model has usually been used to study the process of gas dispersion. However, it doesn't reflect the true process of natural gas dispersion due to its deficiency. Ooms dispersion model was improved considering the velocity, density, concentration and temperature of the leaked gas in this paper. The improved model was applied to study the dispersion process of natural gas released from the pipeline and the hazard area of the leaked gas was obtained. According to the results, the correlations to estimate the dispersion height and distance of the leaked gas were got. Jet fire from the damaged pipeline was studied by the use of computational fluid dynamics (CFD) technique and a good agreement was found between the calculations and measurements. Based on the simulation results, a correlation for predicting the stoichiometric flame length was proposed.Through reasonably simplified the release rate model of damaged pipeline, the quantitative correlations to estimate the hazard area of gas dispersion and jet fire were obtained. Finally, a simplified method for the quantitative risk assessment for natural gas pipelines was proposed. Based on the method, pipeline managers can know about the safety condition of gas pipeline and the safety distance from the pipeline.