Characterising blast environment and structural loading from large-scale unconfined hydrogen explosions

Understanding the risks of hydrogen explosions is essential to mitigating hazards and ensuring safe implementation in various applications. This study investigates the blast environment and structural loading associated with large-scale, unconfined hydrogen-air explosions. A 5.09 m³ tent was filled with a stoichiometric hydrogen-air mixture and ignited using various initiation methods to generate different combustion modes (deflagration, fast deflagration, and detonation). The results revealed pronounced differences in flame velocity and blast loading between these combustion modes (e.g., approximately 33 times faster flame velocity, 40 times higher peak overpressure, and 2 times higher positive phase impulse between deflagration and detonation modes). Experimental measurements of the incident and reflected blast wave parameters were processed and compared with existing empirical models and equivalent TNT. Additionally, a method to determine reflected blast parameters by converting incident blast parameters, either experimentally or empirically obtained, is proposed, which could be used by structural engineers to assess structural response to hydrogen explosions.