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This study investigates the influence of the opening pressure of the explosion‐venting surface (EVS) of a vertical branch pipeline on the deflagration characteristics of methane at different concentrations. The results indicate that the increase in the opening pressure of the EVS promotes the accumulation of deflagration pressure in the horizontal pipeline, whereas the venting effect in the vertical branch pipeline attenuates the peak value of the deflagration pressure. The vertical branch pipeline has both "promoting" and "inhibiting" effects on the flame propagation speed in the horizontal pipeline. With an increase in the methane concentration and opening pressure of the EVS, the promoting effect gradually plays a dominant role, resulting in an increase in the flame propagation speed. In actual industrial production and daily life, in order to avoid explosion hazards, it is essential to install EVSs or reduce their opening pressure in a confined space. [ABSTRACT FROM AUTHOR]

To investigate the deflagration characteristics of CH4‐air mixture in confined space, fluid dynamic software Fluidyn was used to build numerical models that each consisted of a horizontal pipe and vertical branches to study the influence of different numbers of branch pipes on the deflagration propagation characteristics of CH4. Research findings suggested that the oscillation trend of the time history curve of pressure at the test point weakened and the peak initial deflagration pressure attenuated in an approximately linear manner with the increase of the propagation distance in the horizontal pipe. With the increase of the number of branches, the peak initial deflagration pressure at the same test point declined with an increasing amplitude. The vertical branch was found to have both "boosting" and "inhibiting" effects on flame propagation. And the inhibiting effect dominated as the number of vertical branches increased, which caused the flame propagation velocity within the horizontal pipe to significantly attenuate. In addition, the functions of the peak initial deflagration pressure varying with the number of branches and propagation distance in the horizontal pipe were obtained by fitting. According to the functions, the vertical branch had marked pressure venting effect on deflagration pressure in the horizontal pipe; the more the branch pipes were, the more significant the pressure venting effect was. [ABSTRACT FROM AUTHOR]

The energy-absorbing material of metal foam have enormous potential in mitigating the consequences of natural gas explosion disaster in urban utility tunnels. When double-layer metal foam with different pore structures of first larger pores and then smaller pores (LP-SP model), the suppression efficiency of explosion overpressure can reach more than 60% and is 2–3 times that of first smaller pores and then larger pores (SP-LP model), and the error between that and that of the same thickness all with smaller pore structure is only 0.86%. Similarly, the metal foams with the LP-SP model can block the explosion flame propagation chain entirely, while reversing the combination order weakens the suppression effect on the explosion flame. Two suppression mechanisms of double-layer metal foam, including the Sudden Shrinkage Effect (SSE) of the LP-SP model and the Amplification Effect (AE) of the SP-LP model. The metal foam barrier device based on SSE is designed for utility tunnels, which can take effect within 0.1 s under electromagnetic force and gravity. This study can provide scientific theoretical support for designing gas explosion suppression measures in utility tunnels. • Double-layer metal foam have enormous potential in suppressing the gas explosion. • Metal foam with different pore structures effects explosion suppression mechanisms. • Metal foam barrier device is designed to suppress explosion in utility tunnels. [ABSTRACT FROM AUTHOR]