Research on Transient Analysis Method for the Thermal-Fluid-Mechanical Coupling of Steel Pipelines under Natural Gas Jet Flame

The safe operation of parallel oil and gas pipelines has become a key research focus. Jet flame accidents resulting from natural gas pipeline leakages may lead to the adjacent pipelines’ failure. Therefore, it is imperative to investigate the thermal-mechanical failure of steel pipelines under natural gas jet flame, thereby determining the appropriate parallel pipeline spacing. In this paper, a thermal-fluid-mechanical coupling numerical model is established to analyze the jet flame combustion characteristics and pipe thermal-mechanical response condition. Then, the turbulence model, methane/air non-premixed combustion model, and radiation model are determined by comparing the simulation and experimental results of flame morphology, flame temperature, and heat flux. Combining the simulation method and thermal-mechanical failure criteria, a parallel spacing design method is developed. The results indicate that based on the 56-step reaction mechanism + realizable k-ε turbulence model + EDC combustion model + P1 radiation model, the average error of flame temperature, flame heat flux, pipeline temperature, and pipeline stress is 6.4%, 7.0%, 6.9%, and 8.5%, respectively, all of which meet the accuracy requirements of 10%. As the flow velocity of the pipeline decreases, valve chamber spacing and operating pressure increase, leading to a gradual increment in parallel spacing. The parallel spacing design method can prevent adjacent pipeline failure under natural gas jet flame.