Vented combustion of hydrogen-air mixtures in large volumes

Abstract

Vented combustion experiments with hydrogen-air mixtures were conducted in a 2.3-m-diameter sphere connected to a cylinder (volume, 10.3 m 3). The experiments were carried out over a concentration range of 6 to 42% hydrogen by volume and at near atmospheric temperatures and pressures. Vent sizes of 15 and 25 cm have been used. It was found that venting was effective in reducing the peak pressures at low hydrogen concentrations; at high hydrogen concentrations, because of short combustion times, venting was less effective. In many cases instantaneous peak pressures exceeding the adiabatic pressures were observed. Experiments carried out with the igniter located at the near end, centre, and far end relative to the vent position showed that the igniter location had only a slight effect on combustion pressures. Increase in the vent area by a factor of 1.8 caused only marginal reductions in peak pressures for high hydrogen concentrations. Vent size did not have much effect on the peak pressures at low hydrogen concentrations.