Effects of the combustor width on propagation characteristics of rotating detonation waves

To investigate effects of the combustor width on propagation characteristics and initiation processes of rotating detonation waves, this experimental study has been performed in a laboratory-scale rotating detonation combustor. Five combustor widths, including 8 mm, 11 mm, 15 mm, 19 mm, and a hollow case, have been considered, based on a fixed outer diameter and a consistent injector position. Ethylene and oxygen-enriched air have been used as fuel and oxidizer. Three propagating modes have been observed and propagation characteristics of rotating detonations have been discussed. Stable rotating detonations are easy to be obtained in the combustor with a larger width, which is beneficial for generating more homogeneous mixtures. The results indicate that the average propagation velocity will decrease when the combustor width is reduced, and a non-dimensional parameter has been proposed which associates the combustor middle diameter with the propagation velocity. In addition, when different combustor widths are utilized, the initiation times for rotating detonations are all around 2∼4ms.