Experimental Study on the Influence of Struts on Detonation Characteristics in an Annular Combustor

To investigate the influence of struts on the detonation characteristics and engine performance of an annular combustor in a rotating detonation ramjet engine, three groups of six tests were designed. These tests explored the variation laws of the flame stabilization equivalence ratio, the pressure distribution along the engine, the peak pressure and frequency characteristics of the detonation wave, and the wide-range operational characteristics of the engine under different strut configurations. Test Group 1 showed that the annular combustor with strut-supported rotating detonation ramjet engine achieved a wider flame stabilization equivalence ratio range. The struts also enhanced the pressure along the combustor, increasing it by up to 4.6% compared to the configuration without struts. Test Group 2 revealed that, compared to the no-strut configuration, the strut configuration had a lower detonation wave frequency but higher peak pressure. At an equivalence ratio of 0.8, the no-strut configuration had a detonation wave frequency of 1208.2 Hz, corresponding to a detonation wave speed of 1016.6 m/s and a velocity recovery coefficient of 60.2%. In contrast, the strut configuration had a detonation wave frequency of 1054.0 Hz, corresponding to a detonation wave speed of 886.9 m/s and a velocity recovery coefficient of 52.4%. Test Group 3 demonstrated that the strut configuration could operate across a wide range of Mach numbers from Ma3 to Ma6. At Ma3, with no risk of inlet unstart, the engine achieved a maximum average pressure along the combustor of 0.32 MPa, a detonation wave frequency of 1138.3 Hz, a detonation wave speed of 957.6 m/s, a velocity recovery coefficient of 60.6%, and an average peak detonation pressure of approximately 0.03 MPa. At Ma6, the engine achieved a maximum average pressure along the combustor of 0.28 MPa, with a unique detonation wave propagation mode. This mode was attributed to the increased presence of deflagration components ahead of the detonation wave, reduced detonable gas content, and the narrow cross-section width where the detonation wave occurred.