Experimental study on wave propagations in a rotating detonation chamber with different outlet configurations

To improve the propulsive performance, exhaust nozzles are desired for rotating detonation engines in practical applications. Therefore, their effects on the upstream behaviors inside the combustion chamber are required to be clarified. This study focuses on the characteristics of rotating detonation waves influenced by different outlet configurations. Three types of aerospike nozzle configurations are developed with different throat areas. Ethylene and oxygen-enriched air with an oxygen volume fraction of 50% are utilized in this study. When nozzles are employed, five wave propagation modes (i.e., the single-wave mode, the counter-rotating wave mode, the self-adjustive mode, the periodic oscillation mode, and the deflagration mode) are observed with the equivalence ratio ranging from 0.33 to 1.39, while only single-wave mode appears in the nozzle-less case under the same operating conditions. When increasing the equivalence ratio or reducing the nozzle throat area, those unstable propagation modes are more likely to happen and three boundaries of the equivalence ratio for the wave propagation transformation are clarified. On the contrary, the standard deviations of propagation velocities in the stable propagation process are smaller when employing nozzle configurations compared to the nozzle-less cases, which indicates a more stable state of the wave propagation although the stable propagation range is narrowed. Besides, the pressure rise and specific thrust are analyzed under different outlet configurations.