Experimental study of the structure of forward-tilting rotating detonation waves and highly maintained combustion chamber pressure in a disk-shaped combustor

The structure of detonation waves in rotating detonation combustors (RDCs) and their combustion chamber pressure characteristics have not yet been fully clarified due to the complexity and shape of the RDC combustion chamber. Therefore, a disk-shaped RDC was used in this study to visualize the inside of the combustion chamber while simultaneously measuring its pressure. Forward-tilting rotating detonation waves were observed, and a schematic was proposed for them. The initial velocity of the forward-tilting rotating detonation wave was 1200 ± 160 m/s, and it subsequently increased to 1600 ± 160 m/s; meanwhile, the Chapman-Jouguet (CJ) velocity was 2376 m/s. There are several reasons why the velocity may have differed so widely from the CJ value, including the presence of burned gas in front of the detonation wave, the complicated wave structure due to non-uniformity of the mixture in the RDC, insufficient propellant mixing, and the difference between the true and actual wave propagation direction. The velocity and amplitude of the combustion chamber static pressure appeared to be correlated. Averaged combustion chamber static pressure reached 0.432 MPa, which was 89.0% and 92.8% of the fuel and oxidizer plenum pressure, respectively. Dynamic pressure was also estimated using an equilibrium calculation. The resulting dynamic pressure was 0.008 MPa, and estimated total pressure was 0.440 MPa; these values were 90.1% and 94.6% of the fuel and oxidizer plenum total pressure, respectively, even though pressure was lost through the small diameter injector holes.