Studies on wave propagation stabilities and the propulsive performance of rotating detonations under different chamber characteristic dimensions

To clarify the effects of the chamber characteristic dimensions on the detonation wave propagation and the propulsive performance, five combustors with increasing characteristic length (L∗ = 439–563 mm), named Chambers A to E, have been employed in this experimental study. The fuel is ethylene, and the oxidizer is a mixture of oxygen and nitrogen with an oxygen volume fraction of 50 %. Four detonation modes and a deflagration mode have been observed as L∗ increased from 439 mm to 563 mm within the global equivalence ratio of 0.3–1.4. The equivalence ratio range for the unstable detonation modes expanded, whereas the range for the stable single-wave mode was narrowed when L∗ increased. As L∗ exceeded 528 mm, the wave propagating velocity fluctuations of the single-wave propagating process increased distinctly, indicating that L∗ is a critical parameter for the wave propagation stability. Propulsive performance analysis shows that the increase in L∗ will reduce the available pressure ratio and the specific impulse, which is attributed to the intensified parasitic deflagration. The distinct propulsive performance difference between chambers with the maximum and the minimum L∗ has reached 9.8 % at the equivalence ratio of 1.1 in the available pressure ratio, and the maximum difference in specific impulse is 18.4 % at the equivalence ratio of 1.3.