Detonation effect of hydrogen-oxygen mixtures at various initial pressures and hydrogen concentrations in obstructed channels

Numerical investigations have been conducted for the effects of initial ambient pressure, hydrogen concentration, and obstacle distribution on the chemical kinetic characteristics of stable detonation propagation, as well as the changes in the shape and size of detonation cells. The configuration studied is a rectangular channel with regularly spaced obstacles containing the mixture of hydrogen and oxygen. The results indicate that under the same blockage ratio conditions, the position where detonation is generated in the channel with obstacles distributed on one side is farther than in the channel with obstacles distributed on both sides. However, there is no significant change in flame speed or detonation cell size after reaching stable detonation in both cases. The study reveals that under fuel-rich conditions, an increase in hydrogen concentration leads to an increasing duration for the flame to propagate to the end of the channel, accompanied by the distance from the ignition point to the occurrence of detonation also increases. Additionally, under fuel-lean conditions, as the hydrogen concentration decreases, the distance from the ignition point to the occurrence of detonation also increases. The study identifies the limiting concentration for hydrogen detonation is in the range of 18.3 %-60 %. As the initial pressure within the channel decreases, the location of detonation occurrence is farther away from the ignition point. And higher initial ambient pressures make detonation more likely to occur within the channel and the size of stable detonation cells decreases as the initial ambient pressure increases.