Rotating detonation engines have high thermal efficiency and thus have been extensively studied. Using solid particles as fuel can reduce costs, and experiments have demonstrated the feasibility of gas-solid two-phase rotating detonation. However, numerical simulation research is required that examines the flow field characteristics of a rotating detonation engine. In order to explore the role of carbon particle fuel in a gas-solid two-phase rotating detonation wave, the weighted essentially non-oscillating scheme and third-order total variation diminishing Runge-Kutta scheme are used to solve the gas-solid unsteady Eulerian–Eulerian equations. Finite rate chemical and surface reaction models are used to simulate the combustion of gaseous substances and carbon particles. The influence of the proportion of carbon particles in the fuel and the diameter of the carbon particles on the rotating detonation flow field characteristics is analyzed. The results indicate that when the size of carbon particles is in the micrometer scale or below, the two-phase rotating detonation waves exhibit double-front or single-front detonation structures, respectively. Adding carbon particles to the fuel enables the rotating detonation engine to achieve a total pressure gain.

The propagation of multiple detonation waves in the two-dimensional modeled rotating detonation combustor fueled by premixed kerosene/air mixtures is numerically investigated with a reduced two-step global chemical mechanism. Discrete fuel injection model is adopted to simulate the discontinuous distribution of reactants in Rotating Detonation Engine (RDE) experiments. A parameter inlet-area ratio (?) is proposed to obtain the reactants with different dispersion degree. This work focuses on the effect of discontinuous reactants on detonation cells and overall flow-field structure of rotating detonation waves. The results show that with full-area injection model (? = 1.0), the reactants distribute continuously in triangular gas layers. Rotating detonation waves propagate stably with regular detonation cellular structure. When ? is less than 1.0, the injection reactants are distributed in strips. At the position far away from the head-end wall of combustor, the fresh reactants and combustion products are mixing with each other which causes the deflagration zones in triangle gas layers. The reactants remaining after deflagration process in deflagration zones cannot support the propagation of detonation leading to the partially decouple of detonation front. The large area of deflagration zones distorts the flowfield structure and reduces the propulsion performance of combustor.

Operation modes are an important topic in the research of Rotating Detonation Chamber (RDC) as it can affect the stability of RDC. However, they have not been discussed in detail due to the limitation of measurement means in experiments. The aim of this research is to investigate the mechanism of different operation modes by numerical simulation. In this paper, a numerical simulation for RDCs with separate injectors is carried out. Different operation modes and mode switching are analyzed. There is a series of reversed shock waves in the flow field. It was found that they have great effects on operation mode and mode switching in RDCs. A reversed shock wave can transit into a detonation wave after passing through isolated fresh gas region where fresh gas and burnt gas distribute alternatively. This shock-to-detonation transition (SDT) phenomenon will influence the ignition process, contra-rotating waves mode and mode switching in RDCs. SDT makes the number of detonation wave increases, resulting in multi-wave mode with one ignition. Moreover, quenching of detonation waves after collision and SDT after passing through isolated fresh gas region are the mechanism of contra-rotating waves mode in RDCs with separate injectors. In addition, when the inlet total temperature increases, a shock wave is easier to transit into a detonation wave. The distance that a shock wave travels before SDT decreases when temperature increases. This will result in mode switching. Therefore, SDT determines that there is a lower bound of detonation wave number.

The flow-field structure and pressure gain performance of a rotating detonation engine with banded distribution of reactants have been studied using two-dimensional numerical simulations. The reactants are premixed H2/Air mixture. An unsteady reacting flow solver named rhoHLLCFoam is developed based on the open source software OpenFOAM. Unsteady Reynolds Averaged Navier-Stokes (RANS) equations are solved with second order accuracy in space and time with Harten-Lax-van-Leer-Contact (HLLC) Riemann scheme. The solver resolves the combustion phenomena through finite rate chemistry reaction model with Arrhenius form of reaction rate by using Ó Conaire scheme. After checking the reliability of the solver, two sets of cases with various inlet-area ratios (ψ) and equivalence ratios (ϕ) are conducted. The result shows that with ψ<1.0, the reactants in front of detonation waves present a discretely banded distribution which causes a series of reverse compression waves in flow-field. This paper estimates the specific impulse and specific thrust of combustion chamber. It's shown that these parameters increase with the promotion of ψ. By calculating the area-averaged stagnation pressure along axial direction of combustion chamber, the pressure gain ratio (η) of the rotating detonation engine is estimated. The result suggests that η decreases dramatically with the reduction of ψ. In order to achieve pressure gain, ψ must be greater than 0.60. Moreover, the equivalence ratio should be around unity to obtain higher value of η.

In this paper, numerical simulations for Continuous Detonation Chambers (CDCs) with separate injectors are carried out and mode switching is realized by raising the inlet total temperature. It is found that there is a series of reversed compression waves. They play an important part in mode switching in CDCs. A reversed compression wave can develop into a detonation wave after passing through a distance where unburnt gas and burnt gas distribute alternatively or bumping against another compression wave. When the inlet total temperature increases, a compression wave is easier to develop into a detonation wave and result in mode switching.

The continuous detonation chamber (CDC) is a concept engine chamber using detonation as power source. Experimental researches have been done widely around the world by Wolański et al. [1], Rankin et al. [2] and Bykovskii et al. [3]. Numerical simulations of CDC with annular chamber were performed by Shao et al. [4], Schwer et al. [5] and Frolov et al. [6]. To resolve the problem of overheating of the inner cylinder in co-axial annular combustor model, a new model with hollow combustor was proposed by Tang et al. [7]. Various number of detonation fronts was observed under different fuel injection area ratios. To get closer to experimental conditions, Yao’s simulation [8] used array-hole injection model which was close to actual injection structure. Multiple detonation fronts were observed in his simulation which was consistent with the multi-head experimental results.

This paper adopts the method of injection via an array of holes in three-dimensional numerical simulations of the rotating detonation engines (RDE) with hollow combustor using the premixed stoichiometric hydrogen-air mixture. The calculation is based on the Euler equations coupled with a one-step Arrhenius chemistry model. The array hole injection method is more practical than previous conventional simulations where ideal full area injection method is used. The wave structure of the flow field is composed of obverse-rotating waves (ORWs) propagating clockwise and reverse-rotating waves (RRWs) propagating counterclockwise. ORW is detonation wave (DW) near the outer solid wall while degenerate to shock wave (SW) near the nominally inner wall. This phenomenon is never found in the previse numerical studies.