CFD Investigation on Leakage Mechanism of Natural Gas Pipeline: Flow Behavior and Quantity Estimation

Abstract

Leakage in gas pipelines can lead to catastrophic consequences due to the highly flammable and explosive nature of natural gas. The main objective of this study is to investigate the leakage behavior and estimate the leakage quantity of natural gas pipelines, with the aim of timely detection of leakage sources, risk assessment, and ultimately reducing leakage disasters. To achieve this, multistage coupled numerical models considering transient gas flow and leakage diffusion are developed. The leakage behavior and the influencing factors are numerically investigated. Further, an optimal leakage rate calculation model is proposed based on simulated data sets. The results show that neglecting the boundary layer effect and the nonconstant distribution of the gas state leads to overestimation of the leakage rate. Additionally, the expansion of high-pressure gas flow in the leakage zone leads to the formation of a low-temperature zone nearby, which may further exacerbate the hazards of the leakage. The Mach disk formed impedes the diffusion of the leaking gas within the area zone. Leakage rates exhibit a basic linear relationship with pipeline operational pressure and a quadratic relationship with leakage diameter. Moreover, the deviation between real and ideal gas predictions for leakage rates increases linearly with pressure. The slight increase in leakage rate with increasing pipeline diameter is attributed to the greater density at the leak, while wall thickness and gas flow velocity within the pipeline minimally impact leakage rates. The proposed leakage model demonstrates accurate predictions across a wide range of pressures and diameters.