Simulation Study On Leakage And Diffusion Characteristics Of Natural Gas In Double-layered Pipeline

The single pipe is mostly used in present pipeline transport, which is easy to fracture， broken and fracture caused by the influence of factors such as oxidation corrosion of water vapor, construction and earthquake, that eventually led to the pipeline leakage accidents. New double-layered pipeline system can be better used for transport of dangerous goods and be better used to prevent leakage of pipeline. The outer tube of double-layered pipeline system can protect internal tube, prevent the oxidation corrosion. If the pipe leaks, dangerous gas will leak in the pipe sandwich, that can prevent dangerous gas from diffusing into the environment, improve the safety of the pipeline transport and reduce the risk of leakage accident.In this paper, the leakage diffusion process of natural gas in new double-layered pipeline is studied, whose physical model and mathematical model is established. The temperature measurement experiment of leakage diffusion in double-layered pipeline is studied. The leakage and diffusion characteristics of double-layered pipeline is simulated and studied from the theory and experiment. Main work includes the following three aspects:1. In building and solving model, according to the theory of heat transfer and fluid mechanics, considering the joule-Thomson effect, the physical and mathematical model of leakage diffusion of natural gas in double-layered pipeline are based on the finite volume method, the business software Fluent is used for numerically solving the simulation parameters of leakage diffusion of natural gas in double-layered pipeline.2. In numerical analysis of leakage diffusion of natural gas in double-layered pipeline, the numerical simulation is done by using the business software Fluent to analyze the effect of different leakage medium temperature, leak pressure difference, leakage diameters and interlayer heights on the pressure field, velocity field and temperature field of interlayer space in double-layered pipeline. The temperature drop values of theory is8.61℃and the temperature drop values of simulation is9.10℃, both are roughly similar.3.In the temperature measurement experiment of leakage diffusion of natural gas in double-layered pipeline, the temperature test bench is built to study the effect of different pressure difference and hole location of leakage on the temperature field of interlayer space in double-layered pipeline, the result of the experiment, theoretical analysis and simulation results were analyzed, the temperature drop value of experiment is4.70℃, which is relatively anastomosed with the temperature drop values of theoretical calculation and simulation. The uncertainty analysis of experimental results is done; the biggest uncertainty of temperature measuring system in leakage experiment is0.145.The conclusions of this paper have some reference for leakage and diffusion gas in limited space.