Experimental study on the risk of explosion from hydrogen-air mixtures in confined and semi-confined concrete structures

When constructing hydrogen infrastructure in confined or semi-confined spaces, the significance of ventilation systems increases, necessitating measures to mitigate explosion damage. This study experimentally investigated the risk of hydrogen explosions in such spaces and analyzed the effectiveness of explosion venting in reducing internal explosion pressure. The experiments were conducted in concrete structures filled with a hydrogen-air mixture. The results showed that explosion venting substantially reduced internal explosion pressure; the maximum pressure difference between confined and semi-confined conditions was approximately 14.3 times, with significant pressure reduction observed under confined conditions due to the presence of a minimal vent area. In confined spaces, the probability of fatalities from concrete fragments generated by the blast wave, which could scatter up to approximately 80 m from the structure, ranged from 0.065 % to over 99 %, indicating a lethal threat to humans. Conversely, in semi-confined spaces equipped with explosion venting, the maximum external peak overpressure measured was 3.44 kPa, posing no significant harm to humans. These findings confirm that incorporating a minimal explosion vent area in confined or semi-confined spaces can significantly reduce both property and human damage by lowering internal explosion pressures.