Investigation on the flame and pressure behaviors of vented hydrogen-air deflagration from a duct-connected vessel: Effects of venting diameter and static activation pressure

To investigate the effect of venting diameter and static activation pressure on the explosion venting behavior of hydrogen-air mixtures, tests were performed utilizing the explosion venting test platform. The pressure and flame propagation characteristics under different venting diameters (30–70 mm) and pressures (0.1–0.4 MPa) were experimentally examined, and numerical calculation was employed to analyze the explosion venting characteristics of hydrogen at a stoichiometric ratio. Compared to fuel-lean and fuel-rich hydrogen conditions, the first peak pressure within the container is maximal under the hydrogen-air mixtures at a stoichiometric ratio. Under stoichiometric and fuel-rich hydrogen-air mixtures, pressure peak structures inside the container are both bimodal. When D = 30 mm, as P_stat is increased from 0.1 to 0.2 MPa, P_max11 increases. However, when P_stat exceeds 0.2 MPa, with the increase of P_stat, P_max11 remains at the level of 0.69 MPa, reaching the “venting bottleneck”. The discovery of this phenomenon is crucial for the research and development of the venting device for hydrogen storage equipment. Numerical simulations indicate the formation of the second peak pressure inside the container is primarily attributed to the intense obstruction of venting by secondary explosions within the duct.