Prediction of confined, vented methane-hydrogen explosions using a computational fluid dynamic approach

Hydrogen is seen as an important energy carrier for the future, with a great benefit being carbon-free emissions at its point of use. A hydrogen transport system between manufacturing sites and end users is required, and one solution proposed is its addition to existing natural gas pipeline networks. A major concern with this approach is that the explosion hazard may be increased, relative to natural gas, should an accidental release occur. This paper describes a mathematical model of confined, vented explosions of mixtures of methane and hydrogen of value in performing consequence and risk assessments. The model is based on solutions of averaged forms of the Navier-Stokes equations, with the equation set closed using k-e{open} and second-moment turbulence models, and the turbulent burning velocity determined from correlations of data on CH-H mixtures reported in the literature. Predictions derived for explosions in a 70 m vessel, with and without internal pipe congestion, show reasonable agreement with available data, and demonstrate that hydrogen addition can have a significant effect on overpressure generation. Conclusions drawn from the calculations go some way to identifying safe operating limits for hydrogen addition.