Formation of multiple detonation waves in rotating detonation engines with inhomogeneous methane/oxygen mixtures under different equivalence ratios

Abstract

The performance of rotating detonation engines is strongly affected by the multiple detonation waves that occur, although the reason for their formation has not yet been fully explained. In this paper, two-dimensional unfolded rotating detonation waves are simulated to investigate the effects of the equivalence ratios on the number of detonation waves. The compressible reactive Navier–Stokes equations with a detailed CH4/O2 chemistry model are solved using third-order hybrid weighted essentially non-oscillatory/centered-difference numerical methods on a structured adaptive mesh. Compared with the typical two-dimensional rotating detonation wave structures in the homogeneous environment, the flow field is more unstable in the more realistic inhomogeneous environment. As the detonation propagates, coupling, decoupling, and further coupling occur due to the discontinuity of the detonation wave. The fuel mixing is enhanced by the flow field behind the wave, and the accumulation of fuel and the generation of local hot spots lead to the formation of multiple detonation propagation modes. As the equivalence ratio increases in the inhomogeneous environment, the number of detonation waves gradually increases. The intensity of the detonation waves, height of reactants, and heat release are particularly high when the equivalence ratio is close to 1.0. Moreover, equivalence ratios in the range 0.8–1.4 have little effect on the average thrust, but multiple detonation waves can be used to stabilize the thrust in the combustion chamber.