Numerical Simulation Study of Gas Leakage and Diffusion in Underground Comprehensive Pipe Gallery

To reveal the dispersion characteristics of gas leaks in a comprehensive pipe gallery under different leakage parameters, a refined model for gas leak dispersion was established based on CFD simulation. By studying parameters such as alarm time, methane diffusion distance, and backflow length, the impact of leakage aperture and pipeline operating pressure on the distribution characteristics of gas leaks in the comprehensive pipe gallery was investigated. Furthermore, prediction models for alarm time, methane diffusion distance, and backflow length were developed. The results show the following: (a) When the pipeline operating pressure is constant, the leakage rate increases according to a power-law relationship with the size of the leakage aperture. However, when the leakage aperture size is constant, the leakage rate exhibits a linear relationship with the pipeline operating pressure; (b) The alarm time decreases with an increase in both the leakage aperture and pipeline operating pressure. Similarly, the methane diffusion distance increases with an increase in these two factors. Moreover, the methane backflow length increases according to a power-law relationship with the dimensionless leakage aperture and pipeline operating pressure, with exponents of 0.83 and 0.63, respectively. (c) The fitted predictive models for alarm time and methane diffusion distance yielded correlation coefficients of 0.97 and 0.98, with average residuals of 2.53 and 1.97, respectively, at each point. These findings can further provide a basis for the safe operation of the underground comprehensive pipe gallery.