Effects of flame jet configurations on detonation initiation

Deflagration-to-detonation transition (DDT) using flame jets was experimentally studied to improve performance of pulse detonation engines. The detonation tube has a total length of 7350 mm and an inner diameter of 50 mm. Three types of flame jets were arranged by changing configuration of sub-chamber: two flame jets colliding at the tube center (counter type), two flame jets forming a swirl inside the detonation tube (offset type), and one flame jet supplied in the axis direction of the detonation tube (conventional type): Test gas was a stoichiometric acetylene-air mixture. The experimental results show that the shortest DDT time is provided by a swirling flame jet emanating in the oblique direction to the tube axis. The DDT time decreases with increase in the orifice diameter and length of the sub-chamber. It was also found that DDT distance is not significantly affected by types of the flame jets and slightly decreases with decrease in length of the sub-chamber.