Experimental Investigation on the Propagation Process of Combustion Wave in the Annular Channel Filled with Acetylene-Air/Oxygen Mixture

To understanding the initiating process in the pulse detonation curved-chamber and rotating detonation chamber, this article conducted an experimental study on the flame acceleration and the transition to detonation in the annular channel. With different equivalence ratios of acetylene-air and acetylene-oxygen as explosive mixtures, based on high-speed photography and shadow technology, the propagation characteristics of combustion waves in the annular channel were analyzed by the use of high-speed photography and shadow image technology. The results showed that only low-speed flame was formed in the 360° annular channel filled with the acetylene-air mixture. The flame propagation characteristics were affected by the reflection of compression waves in the pipeline. When the annular channel exit was closed, the interaction between the stronger compression waves and the flame front destroyed the flame structure and formed a “flame kernel” at the boundary layer. When the annular channel exit was open, the interaction between the weak compression waves and the flame front only made the flame front more wrinkled. A deflagration to detonation transition process was observed in the annular channel for the acetylene-oxygen mixture. In contrast, detonation can only be triggered in the longer straight tube under the same condition. The self-ignition of the unreacted band-shaped zone between the outer wall of the channel and the flame front was the key to initiate the detonation in the annular channel.