Schlieren visualization of blast extinguishment with laser-induced breakdown

Abstract

After occurrence of a very large scale earthquake, multiple simultaneous fires often break out. The author proposes to use blast extinguishment as an emergency firefighting technique and damage mitigation measure for post-disaster fires. However, the blowout mechanism of blast extinguishment has not been made clear yet. In the present study, in order to clarify the blowout mechanism of blast extinguishment, extinguishing experiments of a diffusion flame have been performed with a blast wave produced by laser-induced air breakdown, and the extinguishing processes have been visualized using the schlieren technique. From the experimental results, it is found that when the breakdown point is placed at the position where the hot gas bubble driving the blast wave interacts with the flame base, its extinguishing effectiveness becomes larger than when the blast wave only affects the flame.