Work

Influence of In-Duct Blockage Ratio on Hydrogen–Air Explosion Behaviour Inside a Vented Duct and in the External Space

Year: 2026

Type: article

Abstract: Vented hydrogen explosions in ducts can transfer flame and pressure loads to external spaces, yet how internal obstructions regulate this external hazard remains insufficiently understood. Here, a three-dimensional FLACS model was used to examine hydrogen–air explosions with in-duct blockage ratios of 0–66.8%. Results show that the internal peak overpressure and flame propagation speed increased with increasing blockage ratio. At a blockage ratio of 66.8%, the internal peak overpressure exceeded 1.75 bar, more than twice that of the unobstructed case. In contrast, the external peak overpressure decreased markedly, with a reduction of approximately 79% at 66.8% blockage. The simulated results are consistent with stronger velocity shear and a less compact released hydrogen-cloud front at high blockage, which coincided with a weaker external second explosion. The findings support comparative hazard assessment of vented narrow hydrogen-handling spaces under the tested fuel-rich condition.

Source: Fire

DOI: 10.3390/fire9090364