Ceiling-vented deflagrations of a hydrogen-air mixture in a 75 m3 container

A series of hydrogen explosions were conducted in a real scale container with and without vents. The effects of hydrogen concentration, ignition location, obstacles on the vented hydrogen-air explosions were investigated. Hydrogen explosions with concentration of 12% and 16% were conducted in constant volume container, and the maximum peak overpressure can reach 45 kPa and 175 kPa, respectively. During the vented hydrogen ex-plosions, three overpressure peaks generated by the vent rupture, Helmholtz oscillation, and the thermo-acoustic-vibration coupling, respectively, were recorded. The maximum peak overpressure is about several kilopascal, the pressure reduction can reach 97.1% by comparison with peak overpressure developed in closed container. The obstacles change the way that the flame travel inside the container, and resultantly the flame propagates vertically and increases the flame area, which promotes the reaction and increases the peak overpressure, which also increases with the hydrogen concentration. Three engi-neering models used to depict the relationship between the vent area and the maximum reduced explosion pressure were assessed. Results show that the these models over-predict the maximum reduced explosion pressure for high-reactivity mixtures. However, for low reactivity, the Molkov' models show a scatter while the NFPA68 gives a better prediction. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the effects of hydrogen concentration, ignition location, and obstacles on vented hydrogen-air explosions. Results showed that obstacles changed the flame propagation inside the container and increased the flame area, promoting the reaction. Existing engineering models over-predicted the maximum reduced explosion pressure for high-reactivity mixtures.