Decaying Modes of Propagation of Detonation and Flame Front in Narrow Channel
Decaying modes of propagation of flame front in narrow channel for acetylene-air mixtures were investigated experimentally using optical methods of diagnostics. Experiments were carried out using an open detonation channel of square cross section with transverse dimension of 3 mm and length of 1000 mm. It was connected to the detonation tube of large diameter 20 mm and length of 3000 mm. Trajectories of propagation of glowing combustion products (streak images) and frames of the reaction zone were obtained. Oscillating form of the propagation of the combustion inside the narrow channel after the decay of the stationary Chapman-Jouguet detonation into the shock wave and the flame front was registered. Parameters of velocity oscillation were obtained. The time interval of oscillations and spatial interval were measured. After the decay of the detonation wave, the average velocity of the flame front decreases first to 1000 m/s and then to 200 m/s. Minimum recorded value of the flame velocity was presented. It was shown that in spite of the substantial thermal losses to the channel walls, the propagation of detonation-like galloping combustion is possible in channels of subcritical size.
This work was supported by the Russian Foundation for Basic Research under grant no. 15-38-70017, 16-38-00682-mol-a and grant of President of the Russian Federation no. SP-1501.2016.1.