Mitigation of Blast in a Water Mist

Abstract

The purpose of this work was to study blast mitigation in a water mist and more specifically the effects of the droplet size and of the water mist loading on blast mitigation. A tunnel has been equipped with a water mist fire suppression system. By using this facility, experiments of detonation were carried out in the air and in different water mists. The blast effects were evaluated by means of four pressure gauges placed on the tunnel walls and one pressure gauge placed at the end of the tunnel. The transmission factor of the initial overpressure in the water mist was around 0.8 when four nozzles were used to produce the mist, whatever the size of the droplets. The transmission factor of the initial overpressure was smaller, about 0.6, with eight nozzles generating the mist, either for small or large droplets. The shock wave was delayed by the presence of the mist. The maximum impulse was reduced by about 20% when four nozzles were used to produce the mist, whether the droplets were small or large. The maximum impulse was more reduced with eight nozzles generating the mist, i.e., by about 30% for both droplet sizes.