Numerical Investigation On Flow Field Structure And Self-sustaining Mechanism Of Rotating Detonation

Rotating Detonation Engine (RDE) is a new kind of detonation engine. In terms of propulsion, with respect to Pulsed Detoantion Engine (PDE) and Oblique Detonation Wave Engine (ODWE), RDE can start without delay time, have noiselessness and less pollution, which leads to a wide application prospect.The purpose of this thesis is to study flow field structures, propagation mechanism and propulsion performance of a rotating detonation based on numerical simulations. The computation was based on two- and three-dimensional Euler equations and elementary reaction model of hydrogen/oxygen/nitrogen (H2:O2:N2=2:1:7.3) system, which included 8 species and 48 elementary reactions, and rotating detonation in the annular combustor was simulated numerically. ASIRK-2B was used to resolve the governing equations and treat the stiffness caused by the chemical source, and the 5th order WENO scheme was utilized to discretize the convection term. According to the numerical results, the flow field structures and self-sustaining mechanisms of the rotating detonation were analyzed, meanwhile the propulsion performance of RDE was alse discussed. The results show that:(1) The detonation wavelet is connected with oblique wave, forming a detonation-shock combined wave. The rotating detonation has a character of unconfined detonation, which causes a deficit of detonation parameters. The typical flow field structure of a rotating detonation can be divided into four regions, i.e. an unburnt combustible gas region, a burnt gas region before the detonation-shock combined wave, a burnt gas region immediately behind the detonation wave and a compressed burnt gas region behind the shock wave.(2) Due to the convergence and divergence of the wall, a non-uniform distribution of the rotating detonation flow field in radial direction occurs while detonation wave propagating in the annular combustor. In the radial direction, the detonation strength increases gradually. Along the concave wall, the pressure, temperature and the chemical reaction intensity are higher than those along the convex wall. The detonation front along the inner and outer wall leads alternately, and the detonation propagation velocity oscillates periodically, which makes the rotating detonation to have a character of dynamic stability. Nevertheless the propagation velocity along the concave wall is higher than that along the convex wall, which enables the rotating detonation to propagate with a stable angular velocity and maintain the detonation steadily propagate with a planar front finally.(3) Injecting combustible gas into the combustor along the inner wall, a rotating detonation can be established steadily and propagate around the gas layer. Two sides of the detonation front touch the inner and head wall, which results in the rotating detonation being more unconfined. Behind the detonation, there is a complex wave system that consists of transmitted shock waves and reflected shock waves. Rotating detonation products move towards to the outside wall and annular combustor due to the combined effects of centrifugal force, expansion and shock waves, which generates the force and forms the background field with some density and pressure gradient which is useful for the maintaining of the rotating detonation waves.(4) RDE has a high efficiency detonation cycle. Under the conditions of this thesis, the specific impulse of RDE can be up to 4500s-9000s, and the frequency is in the range from 4 kHz to 5 kHz, which is far higher than that of PDE.