Effects of Pipeline Pressure on Diffusion Characteristics of Leaked Natural Gas in Tunnel Space

[Image: see text] Pipeline transportation has become the main mode of natural gas transportation. Due to inevitable aging, corrosion, and third-party damage, natural gas pipeline leakage accidents occur frequently. Leakage in the tunnel will lead to the leakage and accumulation of natural gas, and the potential explosion risk will threaten the tunnel’s safety. It is significant to elaborate on the diffusion behavior of leaked natural gas in tunnel space for the traceability of leakage points and the formulation of safety technical measures. In this paper, a scale-down experimental platform for natural gas pipeline leakage in the tunnel is built, and the influence of pipeline pressure on natural gas diffusion characteristics is described. The results show that the diffusion process of leaked natural gas in the tunnel space shows obvious segmentation characteristics, and the concentration of natural gas reaches the maximum at the end of the continuous leakage stage. The increased pipeline pressure promotes natural gas diffusion, and the concentration of natural gas under 1.0 and 1.2 MPa rises sharply. First dangerous time (FDT) and maximum accumulated concentration (MAC) have a negative correlation with the leakage distance, while FDT and MAC have a good exponential and linear relationship with the pipeline pressure (0.2–1.2 MPa), respectively.