Suppression of hydrogen–oxygen–nitrogen explosions by fine water mist: Part 1. Burning velocity

A work programme has been undertaken to investigate the practical viability of using fine water mists to mitigate or suppress hydrogen explosions during nuclear decommissioning operations. In the first part of this study measurements of burning velocity, required primarily for the development of explosion models, are presented. Burning velocity measurements were made with the introduction of ultrasonically generated fine water mists. With water mist, the burning velocity was reduced over a wide range of equivalence ratios for fuel-free oxygen fractions of 0.1–0.21. Flame instability increased substantially with increasing water mist density especially with lean hydrogen mixtures. The experimental results obtained for the reduction of burning velocity with entrained water mist in hydrogen–air systems are compared to computer simulated values reported earlier in the literature. An important overall objective of the work programme was to provide information to plant engineers to assess the effectiveness of using water mists for the suppression or mitigation of explosion.

► We measure LBV for H2/air/N2 mixtures with the introduction of fine water mist.
► With water mist the LBV was reduced over a wide range of equivalence ratios.
► Flame instability increased substantially with increasing water mist density.
► Results are compared to computer simulated values reported in the literature.