Fire Safety Science Digital Archive

The explosion behavior has been studied experimentally using small scale test vessels. The effects of gas flow turbulence, gas concentration distribution, and flame front instability, which are the most probable causes to disturb the propagating flame front during gas explosions, on the flame behavior and pressure variation have been examined. It is shown that the gas flow turbulence increases the flame propagating velocity and the pressure rising rate. When the flow is turbulent the pressure rise p -po is proportional to about the 3.6th power of the time from ignition t, while when the flow is quiescent it is proportional to the 3rd power of t. When the concentration distribution of a combustible gas was non-uniform, the gas explosion behavior strongly depends on the local concentration. The rate of the pressure rise increases with the nonuniformity of the combustible gas concentration. The flame front becomes unstable by an interaction with a pressure wave and generated flame front disturbance grows rapidly by acceleration of the gas induced by a following pressure wave in the direction toward the unburned gas side, so that the flame propagating velocity and the pressure rising rate are extremely increased. In this case, the pressure rise is proportional to the 6.4-6.8th power of t.