Fire Safety Science Digital Archive

Experiments have been carried out to ascertain the effect of obstructions on gaseous explosions in duct systems containing quiescent flammable mixtures. Obstructions in the form of orifice plates, strips and pipe fittings were used. It was found that these generated turbulence in the moving mixture, which increased the combustion rate within the duct. As a result there was a considerable increase in the pressure after the flame front had reached the turbulent region downstream of the obstruction. During this stage of the explosion, high flame speeds along the duct were observed. Simple correlations between the maximum pressure and the resistance of the obstacle to gas flow were obtained. Tests with supplementary vents at various positions have shown that the most efficient venting was obtained, when an extra vent was inserted near the ignition source. This reduced the velocity of the unburnt gases thus avoiding the turbulence.