Numerical Simulation of the Impact of Pressure on Leakage and Diffusion in Underground Hydrogen-blended Natural Gas Pipeline Corridors

A key problem in the use of hydrogen-blended natural gas is its potential for leakage. Therefore, a simplified model of gas cabin of urban underground comprehensive pipe gallery is established to study the effect of pipeline pressure on gas diffusion characteristics. It is found that the gas in the pipe gallery space flows upward to the top of the cabin, and then it moves along the wall to both sides in a symmetrical pattern when there is no wind. Hydrogen-blended natural gas reaches its highest diffusion rate and concentration at the leakage site, and the hydrogen gas first reaches the lower explosive limit, resulting in a higher risk of explosion. Pipeline pressure is positively correlated with leakage rate and velocity. The pressure positively correlates with both the concentration of gases and the extent of their distribution range. At 60 seconds of leakage of gas, the concentration of gas at a pressure of 1.6 MPa is nearly twice that at 0.2 MPa, and the period needed to achieve the lower explosive limit is earlier than that at medium and low pressures. The farther the leakage point is from the ventilation opening, the less conducive it is to gas diffusion.