Transition of combustion into detonation within a channel with the diameter less than the critical diameter of the existence of stationary detonation

An experimental investigation was carried out for transition of combustion into detonation of oxygen-hydrogen and hydrogen-air stoichiometric mixtures within a cylindrical channel with a diameter of 3 mm, which is less than the critical diameter of the existence of stationary detonation in the hydrogen-air mixture. To realize the transition of combustion into detonation in the channel, the combustible mixture was ignited within a precombustion chamber with a diameter of 14.5 mm which was arranged in line with the channel on one of its faces. The expanding products of mixture combustion within the precombustion chamber accelerate the flame front at the input of the channel, thus increasing the energy amount released during mixture combustion within the narrow channel per unit time. As a result, the ratio of the burning energy to dissipative losses in channel walls increases, which makes transition into detonation realizable. The use of the precombustion chamber allowed us to obtain the transition of combustion into the detonation wave with the Chapman–Jouguet parameters at initial mixture pressures of 1 and 2 atm. The effect of the size of the turbulizing precombustion chamber on the length of the transition of combustion into detonation is analyzed, and the average velocities of flame front propagation along the channel are determined.