Numerical Investigation Of Wave Structure Evolution In Rotating Detonation Engine

Rotating Detonation Engine(RDE)is a new concept engine which uses detonation for combustion propulsion.Detonation is similar to constant volume combustion which has theoretically higher thermal efficiency than conventional deflagration.In addition,RDE has the advantages of self pressure-gain,simple structure,large thrust-weight ratio,single ignition,wide working range and adjustable thrust,which is expected to break the limit of traditional engine performance and realize the leap forward improvement of thermal efficiency.In this paperx,through numerical simulations,the wave structure evolution of various configurations of RDE combustor are comprehensively summarized and studied,so as to deeply understand the intrinsic mechanism and guide the stability control of RDE in engineering application.The main research contents are summarized as follows:(1)The wave structure evolution in RDE with hollow combustor is systematically studied,and the key factors affecting the mode change and stability are summarized.Wave structure evolution can be divided into three categories: two-wave collision(consisting of symmetric detonation collision,asymmetric detonation collision and detonation/shock wave collision),abscission of detonation tail,and shock wave to detonation transition.Considering the number of detonation waves,asymmetric detonation collision,abscission of detonation tail and shock wave to detonation transition will affect the working mode and stability of RDE with hollow combustor.(2)The wave structure evolution in RDE with array-hole injection is studied.Threedimensional numerical simulations of coaxial annular combustor with whole face injection,single row array-hole injection and double row array-hole injection are carried out and compared.The results show that in RDE with array-hole injection,the reverse-rotating wave phenomenon is unique.The shape and distribution of irregular injection triangle are different from those in RDE with whole face injection.V-shaped wave and plane wave are the two propagation modes of detonation wave when using array-hole injection,the mechanism of which is directly related to the lack of fresh gas on the inner and outer walls caused by irregular injection triangle.(3)The mechanism of mode transition in RDE is studied.The numerical simulation realizes the transition from single wave(SW)mode to single wave with counter-rotating component(SWCC)mode and then to two counter-rotating wave(2CR)mode.The wave structure of each mode is analyzed,and the mechanism of mode transition process is explained.The mechanism of the transition from SW mode to SWCC mode is that the transverse wave is gradually strengthened to produce counter-rotating waves.The mechanism of the transition from SWCC mode to 2CR mode is that the energy gain of the counter-rotating wave is more than loss in one cycle,causing the intensity to become stronger and finally strong enough to ignite the fresh gas and initiate the detonation wave.(4)The coupling between pre-detonator and combustor is studied.Three-dimensional numerical simulations of coaxial annular combustor with pre-detonator and array-hole injection method are carried out.The coupling happens when shock waves injected into the predetonation re-inject into the combustion chamber after reflection,and initiate detonation waves in some cases.The tangentially installed pre-detonator is not able to control the propagating direction of the initiated detonation wave,but it can provide asymmetry for the flow field.When the distance between the pre-detonator and the headwall is small,strog coupling is established as the detonation wave periodically injects shock waves into the pre-detonator.When the distance is big,oblique shock wave takes the place of detonation wave and weak coupling is established.One possible way to avoid the ablation of pre-detonator joint in long-run experiments is to increase the distance between pre-detonator and headwall.