Rotating Detonation Engine Research Articles

Three-Dimensional Numerical Simulation of a Rotating Detonation Engine: Effects of the Throat of a Converging-Diverging Nozzle on Engine Performance

ABSTRACTThe effect of a converging-diverging nozzle on the performance of a rotating detonation engine was estimated using three-dimensional numerical simulations with a detailed chemical reaction model. The nozzle in this article is composed of a long constant cross section, a short converging section, and a diverging section. The expansion area ratios of nozzles A and B in this article are 2.0 and 1.89, respectively. The periodic exhaust oscillation due to rotating detonation is considerably reduced by nozzle A. The variation of the time-averaged pressure is approximately 0.0048 MPa and the ratio to the time-averaged value is 1.3%. For nozzle B, the variation in pressure is approximately 0.018 MPa, and the ratio to the time-averaged value is 5%. The specific impulse of nozzle A increases by approximately 11 s (3.8%) compared with the value of nozzle B.

Front Cellular Structure and Thrust Performance on Hydrogen–Oxygen Rotating Detonation Engine

Numerical simulations of three-dimensional rotating detonation engines for a hydrogen–oxygen mixture are performed using the detailed chemistry model. The grid-resolution study indicates that the cellular structure of the detonation appears near the inner wall as the circumferential grid resolution increases. However, the effects of the grid resolution are small on . The grid resolution for the high-mass-flow cases should be carefully considered because the rotating detonation velocity increases to produce higher thrust under the low grid resolution. As the annular width increases, a complicated shock structure such as a Mach stem appears, and the cycle time decreases. The effects of the annular width are small on . As the number of the rotating detonations increases, the asymmetric detonation heads rotate along the circumferential direction with the same cycle time after 30 cycles. for the two-waved rotating detonation engine decreases approximately 10% less than for the one-waved rotating detonation engine. This is because the injected mixture mass flow rate for the two-waved rotating detonation engine increases 16% larger than that for the one-waved rotating detonation engine, whereas the thrusts between them coincide.

Numerical study of rotating detonation engine with an array of injection holes

This paper aims to adopt the method of injection via an array of holes in three-dimensional numerical simulations of a rotating detonation engine (RDE). The calculation is based on the Euler equations coupled with a one-step Arrhenius chemistry model. A pre-mixed stoichiometric hydrogen–air mixture is used. The present study uses a more practical fuel injection method in RDE simulations, injection via an array of holes, which is different from the previous conventional simulations where a relatively simple full injection method is usually adopted. The computational results capture some important experimental observations and a transient period after initiation. These phenomena are usually absent in conventional RDE simulations due to the use of an idealistic injection approximation. The results are compared with those obtained from other numerical studies and experiments with RDEs.

Numerical study of hollow rotating detonation engine with different fuel injection area ratios

Three-dimensional numerical simulations are performed to study rotating detonation engines (RDEs) with a hollow combustor. The computations are based on the reactive Euler equations. The reactions of stoichiometric hydrogen–air mixtures are calculated by the one-step Arrhenius chemistry model. The hollow RDE combustors with different fuel injection area ratios on the head end wall are considered. The fuel injection area ratios range from 55.6% to 88.9%. The number of rotating detonation waves in the flow field of the hollow combustor is found to be related to the fuel injection area ratio. In the hollow combustors with fixed dimensions, the number of detonation waves increases when the fuel injection area ratio is higher. In addition, a comparative analysis of the hollow RDE model and the conventional annular RDE model is performed with respect to the flow field and fuel injection conditions. The propulsive performance of the hollow RDE with different fuel injection area ratios is also evaluated and compared with experimental data and other simulation results. It is demonstrated from several aspects that the removal of the inner wall does not sacrifice the propulsive performance of the RDE.

Steady-State Analysis of Rotating Detonation Engine Flowfields with the Method of Characteristics

A method for modeling the internal flowfield in a rotating detonation engine is developed using shock-expansion theory combined with the steady two-dimensional isentropic method of characteristics. An analytical model using the oblique shock relations, the Prandtl–Meyer function, and the detonation jump conditions is used to determine the basic shock structure. Once the structure is known, a shock-fitted method of characteristics solution is marched out to generate the rest of the flowfield. Reactant injection is handled analytically by solving the conservation equations for a flow undergoing a sudden expansion along with the method of characteristics compatibility relations to provide a new boundary condition. A new solution is then initialized using information from the previous solution to calculate the new shock structure. This process is repeated until the solutions converge. The converged solution is the ideal steady-state solution of a rotating detonation engine in the wave-fixed reference frame. The goal of this model is to provide ideal performance estimates one step up from a basic thermodynamic model that are still fast enough for large parametric studies.

Multiple ignitions and the stability of rotating detonation waves

We perform a numerical study on rotating detonation engines (RDE). The simulations demonstrate the feasibility of creating multiple detonation waves and examine their stabilization process. The computations are based on the three-dimensional Euler equations with reactive sources. The Arrhenius chemistry model is used to calculate the reaction rate of the pre-mixed stoichiometric hydrogen-air mixture. The simulations show the oscillation phenomenon characterized by the pressure-time traces and the stabilization process. Also, the results indicate the existence of one-, two-, and eight-wave propagation modes in the fully-developed detonation flow. The initial detonation waves dominate the flow throughout the stabilization process in the one- and two-wave modes. On the other hand, the eight-wave mode is the result of the generation of new detonation waves during the intermediate stage. The simulations are compared with the experimental studies to confirm the existence of the multi-wave modes discussed herein. In addition, it is found that the velocity of detonation waves decreases with the increase of the number of detonation waves, which is also reported in some experiments.

Numerical investigation on detonation velocity in rotating detonation engine chamber

A two-dimensional investigation is conducted to clarify the velocity decrease mechanism of a detonation wave propagating within a rotating detonation engine (RDE) chamber, focusing on the effect of injection conditions of the fuel and oxidizer. Two numerical studies are conducted; the first imitates the RDE chamber with injection ports in a rectangular computational domain, and the second simplifies the flow field in the RDE chamber based on observations of the first simulation. The injection is parameterized by the geometrical jet and the gas conditions (i.e., premixed or non-premixed). In the first simulation of the RDE chamber, the total length of the injection nozzles constitutes 20% of the length of the chamber's lower end. The number of nozzles, N, ranges from 10 to 500 under premixed and 25 and 125 under the non-premixed condition. As the nozzle interval increases, more burned gas exists in front of the detonation wave. Under thenon-premixedcondition for N=25, the propagation velocity decreases to 84% of the CJ velocity, and 82.4% of the injected C2H4 is burned by the detonation. The CJ velocity is theoretically calculated, based on the amount of burned C2H4, to be 2283m/s, which is not close to the propagation velocity of the simulation, 1999m/s. In the simplified model in the second study, C2H4, O2, and burned gas are quiescently placed rather than injected, and the role of the upper wall is also examined. Significant velocity decrease, down to 86% of the CJ velocity, is observed when C2H4 and O2 are placed separately with a large width of burned gas between them. The amount ofincompletely combusted C2H4 is inversely proportional to the propagation velocity except in the case with an upper wall. Therefore, burned gas has a larger effect on propagation velocity in the non-premixed condition.

Rocket rotating detonation engine flight demonstrator

Purpose Today’s modern liquid propellant rocket engines have a very complicated structure. They cannot be arbitrarily downsized, ensuring efficient propellants’ mixing and combustion. Moreover, the thermodynamic cycle’s efficiency is relatively low. Utilizing detonation instead of deflagration could lead to a significant reduction of engine chamber dimensions and mass. Nowadays, laboratory research is conducted in the field of rotating detonation engine (RDE) testing worldwide. The aim of this paper is to cover the design of a flight demonstrator utilizing rocket RDE technology. Design/methodology/approach It presents the key project iterations made during the design of the gaseous oxygen and methane-propelled rocket. One of the main goals was to develop a rocket that could be fully recoverable. The recovery module uses a parachute assembly. The paper describes the rocket’s main subsystems. Moreover, vehicle visualizations are presented. Simple performance estimations are also shown. Findings This paper shows that the development of a small, open-structure, rocket RDE-powered vehicle is feasible. Research limitations/implications Flight propulsion system experimentation is on-going. However, first tests were conducted with lower propellant feeding pressures than required for the first launch. Practical implications Importantly, the vehicle can be a test platform for a variety of technologies. The rocket’s possible further development, including educational use, is proposed. Originality/value Up-to-date, no information about any flying vehicles using RDE propulsion systems can be found. If successful in-flight experimentation was conducted, it would be a major milestone in the development of next-generation propulsion systems.

Erratum to: Role of inlet reactant mixedness on the thermodynamic performance of a rotating detonation engine

Erratum to: Role of inlet reactant mixedness on the thermodynamic performance of a rotating detonation engine

Coexistence of detonation with deflagration in rotating detonation engines

Rotating detonation engines of high thermal efficiency and specific impulse have been studied a lot. However, rotating detonation waves lead to uneven flow field, local high temperature and high pressure, tending to damage the combustor. An experimental way to keep both rotating detonation waves and deflagration in the combustor and to combine the advantages of rotating detonation engines and deflagration engines, is introduced here. Pressure sensors measure the pressure of rotating detonation waves and gas mass flow controllers control the mass flow rates of reactants. A standard speed camera captures the events of rotating detonation and deflagration. It is discovered that the rotating detonation is much more intense than deflagration. Both upstream rotating detonation waves and downstream deflagration respectively dependent on the trunk stream and the tributary can coexist in the combustor. The predetonator is the boundary between the detonation region and deflagration region in the combustor. The coexistence of detonation and deflagration weakens the combustion instability caused by rotating detonation, which may be helpful for rotating detonation to be applied.

Rotating detonation in a combustor of trapezoidal cross section for the hydrogen–air mixture

Rotating detonation engines are being studied widely because of high thermodynamic efficiency and high specific impulse. The combustors studied before were annular or hollow cylinders. Here, a combustor of annular trapezoidal cross section is numerically studied for the first time. The transient density-based solver with explicit formulation, the laminar finite-rate model with one step reaction and the standard k-epsilon model with standard wall functions are used. Numerical results show that reflected shock waves, explosions and new detonation waves occur near the corners of the combustor, but they do not stop the continuous propagation of the rotating detonation wave. Reactant gap of low temperature tends to intrude into weak detonation waves. Transverse waves move back and forth between the inner and outer walls due to the unsteady heat release along the detonation wave front. The unsteady heat release is mainly caused by the collisions between the detonation and corners. Since the detonation can pass the corners of right, acute and obtuse angles, it may be concluded that a detonation combustor of any convex polygon section is feasible. Thus, the study helps to design many new structures for rotating detonation engines, such as rectangle, rhombus, or trapezoid cross section.

Three-dimensional, numerical investigation of reactant injection variation in a H2/air rotating detonation engine

This study characterizes the mixing performance and non-reacting injection flow field within a rotating detonation engine. Initial reactant mixing is accomplished through a counter-rotating vortex pair developing from a jet-in-a-crossflow situation. Radially injected air wraps around the fuel jet, shearing the hydrogen into the vortex structure. The three-dimensional baseline geometry produces poor hydrogen/air mixing in the injection zone due to low fuel penetration into the wide, cross-flowing air stream and low air entrainment into the vortex structure. Injection parameters, including reactant flow rate, injection area, and fuel injection distribution, are varied to assess the impact on mixing. Decreasing air injection area and fuel injection area improve fuel penetration into the air stream and the vortex mixing mechanism, enhancing the level of mixedness within the annulus. For a given air injection area, an optimized number of fuel injection holes exists that provides the greatest level of mixedness. Variations from the optimized geometry reduce the effectiveness of the vortex mixing mechanism. Staggering fuel injection holes produces a decrease in mixedness when compared to collinear fuel injection.

Experimental Study of Propulsion Performance by Single-Pulse Rotating Detonation with Gaseous Fuels-Oxygen Mixtures

AbstractA rotating detonation engine (RDE) is one of candidates of aerospace engines for supersonic cruse, which is better for propulsion system than a pulse detonation engine (PDE) from the view of continuous thrust and simple structure. The propulsion performance of a proto-type RDE and a PDE by single pulse explosion with methane-oxygen is investigated. Furthermore, the performance of the RDE with acetylene-oxygen gas mixtures is investigated. Its impulse is estimated through ballistic pendulum method with maximum displacement and damping ratio. The comparison of specific impulses of the mixture gases at atmospheric pressure is shown. The specific impulses of the RDE and the PDE are almost same with methane-oxygen gas. Furthermore, the fuel-base specific impulse of the RDE with acetylene-oxygen gas is about over twice as large as one of methane-oxygen, and its maximum specific impulse is 1100 seconds.

Quasi-steady State Simulation of Rotating Detonation Engine

We performed a numerical simulation based on the two-dimensional (2-D) unsteady Euler's equation with a single-step Arrhenius reaction model in order to investigate the detonation wave front propagation of an Argon (Ar) diluted oxy-hydrogen mixture (<TEX>$2H_2+O_2+12Ar$</TEX>). This simulation operates in the detonation frame of reference. We examine the effect of grid size and the performance impact of integrated quantities such as mass flow. For a given set of baseline conditions, the minimal and maximum grid resolutions required to simulate the respective detonation waves and the detonation cell structures are determined. Tertiary shock wave behavior for various grids and pre-exponential factors are analyzed. We found that particle fluctuation can be weakened by controlling the mass flow going through the oblique shock waves.

Experimental Study of the Performance of a Rotating Detonation Engine with Nozzle

A rotating detonation engine is experimentally tested with various nozzle configurations for the purpose of measuring the propulsive performance of these devices in terms of thrust and specific impulse. Particular attention is given to comparing different internal nozzle configurations, which include bluff body, aerospike, and choked aerospike arrangements. The nozzle throat exit choke present in the rotating detonation engine exhaust is analyzed to provide insight into the stagnation pressure gain nature of the device.

Numerical investigation of injection within an axisymmetric rotating detonation engine

This investigation characterizes the mixing processes and injection flow field within a rotating detonation engine. The axisymmetric baseline geometry produces poor fuel/air mixing in the immediate injection region due to reduced fuel penetration into the wide, perpendicularly flowing air stream. Injection parameters including reactant flow rate, injection area, and placement of the fuel injection are varied from the baseline geometry to assess the impact on mixing. Decreasing reactant injection areas improves fuel penetration into the cross-flowing air stream, and turbulent diffusion of the fuel is enhanced within the annulus increasing local equivalence ratio. When fuel is injected into the air slot, local equivalence ratio is enhanced due to the increasing mixing length between the recirculation region and fuel injection. Emulating nozzle integration by increasing annulus back-pressure increases local equivalence ratio in the injection region due to increased convection residence time.

Numerical Study of the Propulsive Performance of the Hollow Rotating Detonation Engine with a Laval Nozzle

AbstractThe aim of the present paper is to investigate the propulsive performance of the hollow rotating detonation engine (RDE) with a Laval nozzle. Three-dimensional simulations are carried out with a one-step Arrhenius chemistry model. The Laval nozzle is found to improve the propulsive performance of hollow RDE in all respects. The thrust and fuel-based specific impulse are increased up to 12.60 kN and 7484.40 s, respectively, from 6.46 kN and 6720.48 s. Meanwhile, the total mass flow rate increases from 3.63 kg/s to 6.68 kg/s. Overall, the Laval nozzle significantly improves the propulsive performance of the hollow RDE and makes it a promising model among detonation engines.

Experimental research on initiation characteristics of a rotating detonation engine

An experimental study on a rotating detonation engine model using hydrogen/air mixture as propellant was conducted to analyze the initiation characteristics of detonation wave. Three ignition methods, including the ordinary spark plug, high-energy spark plug and thermal-jet tube, were used in the tests. The initiation process of rotating detonation wave was recorded and analyzed by a high frequency pressure measurement system and high-speed photographs. Operating range of the model engine was determined by series of experiments. Results indicate that the model engine could be successfully run by all the three ignition methods. Although the detonation formation time using spark plugs is quite stochastic, increasing the ignition energy can reduce the formation time of the detonation wave. Among the three ignition methods, thermal-jet provides the shortest detonation formation time. It is also found that the operating characteristic of the model engine is independent of the ignition device in the same operating condition. Three operation modes of the engine model have been observed, which are failed initiation of the detonation, unstable detonation and continuous rotating detonation. The experimental results show that the stable operating range can be extended by increasing the fuel mass flow rate.

Multidimensional wave fronts propagation along the beams associated with thermodynamic model of a rotating detonation engine

The main purpose here is to develop an analytic approach for investigating the wave front propagation on a surface of a cylinder that can be used as a descriptor of a detonation engine. The analysis is based on a weakly nonlinear approximated gas dynamic equations with incorporated approximation of the Korobeinikov’s chemical reaction model that are used to describe the two-dimensional detonation field on a surface of a two-dimensional cylindrical chamber without thickness. We found that the wave fronts can be expressed analytically in explicit form for special classes of flow (e.g. isentropic gas flow). In more general cases, the dynamics of wave fronts can still be determined explicitly provided that the wave front is known at initial time and the exact solution is either known a priori, e.g. from experimental or numerical analysis.

Conservation laws and invariant solutions of the non-linear governing equations associated with a thermodynamic model of a rotating detonation engines with Korobeinikov׳s chemical source term

The non-linear governing gas dynamics equations that are used as a descriptor of a rotating detonation engine are investigated from the group theoretical standpoint. The equations incorporate approximation of Korobeinikov׳s chemical reaction model that are used to describe the two-dimensional detonation field on a surface of a two-dimensional cylindrical chamber without thickness. The transformations that leave the equations invariant are found. On the basis of these transformations, the conservation equations were constructed and the invariant solutions were obtained for specific form of the equation of state, for which the equations are non-linearly self-adjoint. The invariant solutions are given in terms of the functions that satisfy non-linear ordinary differential equations. The above reduction simplifies the analysis of the original non-linear system of partial differential equations on a surface of rotating cylinder.