Experimental investigation on characteristics of deflagration to detonation transition in U-bend square tube

For the application of the curved detonation combustor in pulse detonation engine (PDE), in this paper we present the results of experimental investigation on gaseous combustion wave of C₂H₄/Air mixture propagation through a U-bend square tube. By changing the incident shock wave speed at the entrance of the bend section in U-bend square tube, the characteristics of deflagration to detonation transition (DDT) in bend section have been researched based on the pressures/velocities measure and high speed photography. When the incident shock wave speed is lower than 794 m/s(43.6%V_CJ), the detonation cannot form in the bend section; when the speed is between 870 m/s and 908 m/s(47.8%V_CJ-50.0%V_CJ), the hot spot will be formed firstly and then the detonation will form finally in the bend section; when the speed exceeds 934 m/s(51.3%V_CJ), the deflagration wave will directly transit into a detonation at the entrance of bend section.