Abstract:

To mitigate explosion hazards in hydrogen-blended natural gas pipelines and enhance the safety level of gas transmission infrastructure, this study independently designed and constructed a pipeline explosion experimental platform. A systematic comparison was conducted on the explosion characteristics of hydrogen-blended natural gas (i.e., CH₄/H₂/air mixtures) under three configurations: without a venting duct, with a horizontal venting duct, and with a 60° bifurcated venting duct. The study focused on analyzing the influence different directional venting duct structures on flame propagation dynamics and overpressure development inside the pipeline. The results demonstrate that, compared to the open-space condition without a venting duct, the confined directional venting configuration intensifies secondary explosions within the duct, leading to a significant increase in both explosion overpressure and flame propagation speed. In contrast to horizontal directional venting, the bifurcated structure at the entrance of the bifurcated directional venting duct reduces the flow velocity of the vented gas, prolonging the time required for the flame front to propagate into the venting duct and delaying the peak values of both flame speed and explosion overpressure. Compared to the horizontal directional venting duct, the bifurcated design reduces the maximum flame propagation speed, peak explosion overpressure, and maximum rate of pressure rise by 9%, 30%, and 24%, respectively.

Key words: directional venting, duct structure, hydrogen-blended natural gas, flame propagation, overpressure, secondary explosion, flame structure