Inhibitory effect of microparticles on hydrogen jet fires

The widespread adoption of low-emission hydrogen across petroleum refining, chemical processing, and energy sector applications confronts critical safety challenges, including leakage, fire, and explosion risks, necessitating efficient and effective mitigation strategies for hydrogen fire incidents. Unlike conventional approaches such as barrier walls, gaseous fire suppressants, and water mist, this work systematically evaluates the inhibitory effects of microparticles on vertical hydrogen jet fires through combined experimental and theoretical analyses. To facilitate this investigation, a straightforward delivery technique was developed to introduce natural yellow sand and NaHCO₃ particles into the hydrogen jet flow. Experimental results demonstrate that sand particles can completely extinguish localized flame regions where particle concentration is sufficiently high. In contrast, while NaHCO₃ decomposition creates localized dark zones via endothermic reactions, it fails to achieve complete flame suppression. Sand particles reduce jet flame length by enhancing air entrainment through particle-laden turbulent plumes. However, NaHCO₃ increases flame length due to gas-phase expansion and dilution effects of its products, as particle decomposition and vaporization eliminate particle-laden flow structures. Both agents significantly reduce flame temperature, radiant heat flux, and radiative fraction, with sand exhibiting marginally superior suppression performance. This difference stems from two factors: (1) the greater density difference enables higher mass entrainment of sand particles, enhancing physical inhibition, and (2) the limited in-flame decomposition of NaHCO₃ restricts its chemical inhibition efficacy. This study introduces a novel concept for hydrogen jet flame inhibition using particulate suppressants.