Experiment And CFD Modeling Of Methane Gas Leakage And Dispersion From Urban Gas Pipelines In A Restricted Space

Based on the data of a natural gas company, this paper carried out a series of experiments to detect the CH4 concentration diffusion of NO.58 and NO.45 rooms, which had been detected a gas leakage from pipeline. Meanwhile, CFD software was apllied to simulate methane gas dispersion of NO.58 room, and the applicability of CFD models for the analysis of traces gas pipeline leakage and the dispersions were discussed. The diffusion and tansport of CH4 under steady and unsteady conditions were simulated. Major conclusions and research results are as follows:(1) The leakage source and concentration sampling points in NO.58 and NO.45 room were identified and marked and measured using a laser methane detector. Experiments show that methane concentration is inversely proportional to the distance from the source to the sampling point when there is single leakage source in limited space, the corner and the narrow area are easy to form methane concentration retention area; methane concentration distribution of indoor space is determined by the leakage rate of multiple sources, the dangerous area grows fast as the leak rate increases.(2) The CFD steady simulation shows that methane concentrations of sample points are lower than experiment data in all directions, but the trends are consistent with experiments, indicating that the steady state simulation is more sutable for a qualitative description of the methane gas leakage and diffusion. The simulation results indicate that there is a backflow in confined space produced by the influence of wind speed, which will make areas including near walls, corners, backflow centers, become methane retention areas. Methane concentration accumulation rates in these areas are so high that could pose a high risk of safety and should be focused on the early stage once the leakage was identified.(3) The transitional simulation was performed for 7 hours, and the results suggested a low accumulation rate of methane concentration caused by trace leakage could hardly reach the explosion point in normal indoor space. However, the same leakage in 58 room only for 0.5h, will cause methane concentration of adangeous range for professional contact, threatening the safety of human.The simulation results show that the area of the dangerous contact area varies exponentially with time, and can be calculated by.