Study on Horizontal Leakage Diffusion Characteristics of Small and Medium Aperture in High-Pressure Natural Gas Pipelines with Large Open Spaces.

In all leakage incidents, the failure frequency of pinholes and cracks is significantly higher than that of other aperture types, making them the most critical points of failure in natural gas pipeline accidents. This paper presents a full-scale field test of aperture leakage in a high-pressure natural gas pipeline conducted in an open space for a horizontal jet leakage scenario. A proportional leakage diffusion numerical model was developed and validated by using the test results. The study investigates the effects of ambient wind speed, pipeline pressure, and leakage aperture size on the gas diffusion characteristics. The findings reveal that in the downwind direction, wind speed initially disturbs and then dilutes gas diffusion, with a critical wind speed of around 6 m/s. In headwind conditions, the forward diffusion of the gas cloud is significantly reduced, leading to greater lateral diffusion. Pipeline pressure is a key factor influencing gas leakage rates. The higher the pipeline pressure, the faster the expansion of the gas cloud at the lower explosion limit and the shorter the time needed to reach a stable state. There is a positive correlation between aperture size and the gas cloud's area, concentration, and diffusion distance. Specifically, the gas cloud area for a 25 mm aperture is approximately four times larger than that of a 5 mm aperture. The results of this research provide crucial support for mitigating the consequences of long-distance natural gas pipeline accidents and planning emergency response efforts.