Effect of Gas Pipeline Pressure on Leaked Gas Diffusion Behavior in Urban Utility Tunnels

It is necessary to investigate the gas diffusion behavior following gas pipeline leakage and uncover the extent of the explosion hazard area and migration patterns, to prevent accidents caused by a gas leak in the underground utility tunnels effectively. By utilizing numerical simulation software FLUENT, the diffusion behavior of gas leaked from pipelines with various pressures for a ventilated partition length (200m) were analyzed within an urban common utility tunnel. The focus lied on understanding the impact of pipeline pressure on the concentration field of gas leak diffusion over time and space within the chamber. The hazardous and sub-hazardous areas of the chamber were defined and their evolution under different pipeline pressures were investigated. The results demonstrated that, the gas diffusion rate from small holes on the downwind side was proportional to pipeline pressure directly under constant mechanical ventilation conditions. Moreover, the diffusion rate at the top of the gallery exceeded that at the bottom. Notably, lower pipeline pressures during the diffusion process tended to result in larger explosion hazard areas. In the case of continuous leakage, the gas concentration within the gallery would reach a dynamic stable state ultimately, with higher pipeline pressures leading to larger final stable concentration values. The research outcomes provided a theoretical foundation for ensuring the safe operation of gas transmission pipelines with varying pressures within the utility tunnel and preventing gas leakage disasters effectively.