Continuous Rotating Detonation Engine Research Articles

Effect of the inlet spatial fluctuation on the gas–solid continuous rotating detonation flow field characteristics

Continuous rotating detonation engines have been extensively studied due to their high thermal efficiency. The utilization of solid particles as fuel can effectively reduce costs and enhance detonation performance. We have constructed a compressible gas–solid multimedium flow combustion numerical method, employing the double flux model coupled with fifth-order weighted essentially non-oscillatory and third-order total variation diminishing Runge–Kutta schemes to solve the unsteady multi-component chemical reaction Eulerian–Eulerian equations. Finite-rate methods and surface reaction models are used to simulate the combustion of gaseous mixtures and carbon particles. The effects of the inlet total pressure spatial fluctuations and particle diameter on the flow field characteristics of the continuous rotating detonation engine are investigated. The results indicate that changing the fluctuation period significantly affects the number, propagation direction, and intensity of gas–solid two-phase continuous rotating detonation waves (CRDW). The variation of fluctuation amplitude noticeably alters the combustion characteristics of the two-phase continuous rotating detonation wave, and excessively high amplitudes cannot form continuous rotating detonation waves. Introducing solid particles into fuel significantly mitigates the impact of inlet total pressure spatial fluctuation and promotes propagation stability on the detonation waves. Moreover, when solid particle diameters reach or exceed the micrometer scale, they contribute more favorably to generating a stable detonation flow field. However, excessive particle sizes result in a low surface reaction rate and inadequate contribution of heat released from particle combustion to the propagation of detonation waves.

Experimental investigation on air-breathing continuous rotating detonation engine in the cavity-based combustor

In order to broaden the stable working range of air-breathing continuous rotating detonation engine and explore the influence of combustor configuration on the propagation characteristics of rotating detonation wave, the cavity-based annular combustor is introduced. Air-breathing rotating detonation engine experiments are conducted with non-premixed ethylene and air. A tri-propellant air-heater is used to imitate the outlet parameters of the intake of Ma4/20km. The designed mass flow is 1kg/s and the total temperature is 860K. The results show that the self-sustaining rotating detonation wave cannot be formed in the conventional annular combustor. The self-sustaining propagation of detonation wave is realized at the equivalent ratio of 0.62 to 0.72 in the cavity-based combustor, and the propagation velocity of which is about 900 m/s. It is demonstrated that the vortex zone in the cavity is conducive to the formation of rotating detonation wave, which can effectively broaden the stable working range of the engine. Feasibility of cavity-based annular combustor in rotating detonation engine is validated.

Thrust characteristics research on continuous rotating detonation engine

Detonation combustion can produce pressure enhancement effect, increasing engine thrust. In this paper, a 2D Euler control equation with chemical reaction is used to solve the periodic flow of the detonation wave in a rectangular plane. The combustion of the air-breathing continuous rotating detonation engine is simulated. The RDE thrust is obtained through the outlet parameters of the engine. The fuel used is hydrogen, with the equivalent ratio to air. The calculation reflects the working condition of the engine running at low speed. The operating conditions of the engine at low speed are calculated, with a low intake pressure and temperature of 300K and 0.2/0.35 MPa respectively. It is found that the thermal efficiency of detonation wave is higher than that of the deflagration wave under low inlet pressure and temperature, and the thrust of RDE is significantly higher than that of the deflagration engine. The pressure enhancement effect of RDE is not as strong as that of detonation wave, so the pressure ratio of detonation wave can not be used to calculate the engine efficiency.

Effects of Ozone Addition on Multi-Wave Modes of Hydrogen–Air Rotating Detonations

Ozone addition presents a promising approach for optimizing and regulating both combustion and ignition mechanisms. In Rotating Detonation Engines (RDEs), investigating the impact of ozone addition is particularly important due to the fact of their unique operating conditions and potential for improved efficiency. This study explores the influence of ozone concentration, total temperature, and equivalent ratio on the combustion characteristics of a hydrogen–air mixture infused with ozone. Utilizing the mixture as a propellant, the combustion chamber of a continuous rotating detonation engine is replicated through an array of injection ports, with numerical simulations conducted to analyze the detonation wave combustion mode. Our results show that an increase in total temperature leads to an increase in the number of detonation waves. Incorporating a minor quantity of ozone can facilitate the ignition process for the detonation wave. Increasing the ozone content can result in the conversion from a single-wave to dual-wave or multi-wave mode, providing a more stable combustion interface. A low ozone concentration acts as an auxiliary ignition agent and can significantly shorten the induction time. As the total temperature increases, the detonation propagation velocity and the peak heat release rate both decrease concurrently, which leads to a decline in the exit total pressure and an augmentation in the specific impulse. Employing ozone exerts a minimal impact on the detonation propagation and the overall propulsion performance. The requirement for ozone-assisted initiation differs noticeably between rich and lean combustion.

Experimental Investigation of a Cylindrical Air-Breathing Continuous Rotating Detonation Engine with Different Nozzle Throat Diameters

A continuous detonation engine with various exhaust nozzles, analogous to typical scramjet cavity combustors with variable rear-wall heights, was adopted to perform a succession of cylindrical air-breathing continuous rotating detonation experiments fueled by a non-premixed ethylene/air mixture. The results show that the detonation combustion was observed to self-sustain in the combustor through simultaneous high-speed imaging covering the combustor and isolator. A long test, lasting more than three seconds, was performed in this unique configuration, indicating that the cylindrical isolator–combustor engine exhibits potential for practical applications. Three distinct combustion modes were revealed with varied equivalent ratios (hybrid mode, sawtooth wave mode, and deflagration mode). The diameter of the nozzle throat was critical in the formation of rotating detonation waves. When the nozzle throat diameter was larger than the specific value, the detonation wave could not form and self-sustain. The upstream boundary of the shock train was supposed to be close to the isolator entrance in conditions of a high equivalence ratio and small nozzle throat diameter. In addition, it was verified that periodic high-frequency pressure oscillation could cause substantial impacts on the incoming flow as compared with the steady deflagration with the same combustor pressure.

Continuous rotating detonation engine fueled by ammonia

As a carbon-free fuel, ammonia has attracted increasing interests while the corresponding utilizations are still limited. In this paper, ammonia-oxygen continuous rotating detonation (CRD) was firstly proposed and realized in the hollow chamber with Laval nozzle. The formation process and propagation characteristics were investigated through pressure measurement and optical observation. The CRD wave formation time increased with the nozzle contraction ratio, which was mainly attributed to the slower injection recovery process under the higher chamber pressure. The operation range was large, and the CRD wave propagated in single-wave mode with the velocity of 1806 m/s in the chosen test. The propagation velocity did not increase continuously as the equivalence ratio increased, which could be attributed to the changeable reaction mechanisms and the slow heat release of ammonia. The coupling of ammonia injection and CRD wave propagation was analyzed under both supersonic and subsonic injection conditions. The synchronous fluctuations of the pressure in ammonia plenum and the intensity of detonation waves proved that the coupling was very tight under subsonic injection condition. This paper was beneficial to the improvement of the detonation theory, and it provided an efficient approach to the utilization of ammonia.

Numerical Investigation of Contact Burning in an Air-Breathing Continuous Rotating Detonation Engine

Three-dimensional (3D) numerical simulations of a continuous rotating detonation engine are carried out with an unsteady Reynolds-averaged Navier-Stokes solver. The second-order upwind advection upstream splitting method and second-order Runge-Kutta method are used to discretize space and time terms, and detailed 9-species 19-step hydrogen-oxygen reactions are applied in this study. Nonpremixed rotating detonation is successfully realized numerically, and the characteristics of the detonation wave are revealed. The expanding angle of the combustor has a great impact on the shape of the detonation wave but has little influence on the propagation velocity. The evolution of combustion on the contact region is analyzed in detail; a more accurate schematic of non-premixed air-breathing rotating detonation engines is given in this paper. A rough analysis of the heat performance of the contact region shows that the heat release of the contact region is approximately one-third of the total heat release and the configurations of the combustors do not affect the proportion.

Experimental verification of cylindrical air-breathing continuous rotating detonation engine fueled by non-premixed ethylene

An especial air-breathing continuous rotating detonation engine without a centerbody is proposed to reduce energy loss and simplify the structure, which is analogous to a typical scramjet combustor with the cavity. Non-premixed ethylene/air rotating detonation experiments are performed in a direct-connect experimental facility with an air inflow of 860 K total temperature (Ma 2.02). Two combustion modes (continuous rotating detonation and deflagration mode) are discovered with varying equivalent ratio (ER). A proper accumulation layer of the combustible mixture in the cavity re-circulation region attaching the outer wall is critical for rotating detonation realization. The average propagation velocity of the detonation wave is 1297.1 m/s (78.5% C-J velocity) at ER = 0.64 with the combustor pressure of 230 kPa. Its motion of the reaction zone is quantitatively verified to be rotating through the integral of chemiluminescence intensity. Besides, it is confirmed by the optical observation that deflagration could also self-sustain in the short combustor with the axial-moving flame. The combustor pressure of deflagration mode can reach 220 kPa with ER = 0.56. Though the combustor pressure of detonation is slightly higher than that of deflagration, the impact of combustor high-pressure on the inflow of detonation mode is much stronger through the induced oblique shock wave.

Experimental investigation on n-decane plasma cracking in an atmospheric-pressure argon environment

In order to solve the problem of the difficulty of igniting and steadily propagating a continuous rotating detonation engine when using liquid hydrocarbon fuel, an experiment was carried out using a dielectric barrier discharge excited by a nanosecond power supply to crack n-decane, the single alternative fuel to aviation kerosene, in a pre-heated argon environment. By changing the voltages and the discharge frequencies, the concentrations of different components as well as a number of different species were acquired. The generating mechanism of olefins and alkanes together with their competition mechanism were acquired. The influence of the voltage on isomer products was also analyzed. The results demonstrate that the bond energy distribution and the species generating condition are the main factors affecting the formation of the products. With the increasing of voltage and discharge frequency, small molecule olefins, large molecular olefins, large molecular alkanes, small molecular alkanes, and hydrogen were detected, and in turn, their concentrations were also increased except for ethylene; what is more, when the voltage was increased over 8.5 kV, the n-butene converted to trans-butene, and the n-pentene converted to isoamylene.

Experimental Research on the Propagation Characteristics of Continuous Rotating Detonation Wave Near the Operating Boundary

Propagation characteristics of continuous rotating detonation wave near the operating boundary are presented. A series of tests have been carried out, and an operating domain is obtained, beyond which the continuous rotating detonation wave cannot be maintained. Based on the high frequency pressure measurements, flow-field structure in a continuous rotating detonation engine (CRDE) is constructed. The features include an upstream detonation wave and a downstream oblique shock wave. Propagation velocity deficits of the detonation wave have been calculated, and a critical value of 15–16.5% is obtained. When the velocity deficit is less than the critical value, the reactants are mainly consumed by the upstream detonation wave. Otherwise, further heat release may occur when the unburned mixture encounters the downstream shock wave.

Experimental Research on the Propagation Process of Continuous Rotating Detonation Wave

Abstract In order to study the propagation mechanism of continuous rotating detonation wave, the H 2 /air continuous rotating detonation engine ignited by tangentially installed H 2 /O 2 pre-detonation tube is studied experimentally using a tilt slot injector structure. The experimental results show that the stable rotating detonation wave can be gained successfully with the equivalent ratio of 0.93. The propagation frequency and velocity of rotating detonation wave range from 5200 to 5500 Hz and from 1518.5 to 1606.1 m/s, respectively. Three propagation modes, such as rotation, reversal and bifurcation, of detonation wave are verified through the analysis of propagation mechanism of rotating detonation wave.

Experimental Realization of H2/Air Continuous Rotating Detonation in a Cylindrical Combustor

Results of experimental studies on a H2/air continuous rotating detonation engine (CRDE) in an annular combustor are presented. A tangentially injected H2/O2 hotshot jet is used to ignite the engine. H2/air continuous rotating detonations are realized at a wide range of total mass flow and equivalence ratio conditions. The detonation propagation modes of all the tests can be divided into four kinds: two-wave, hybrid two/one wave, one-wave, and transient one wave. The mean propagation velocities of the two-wave and one-wave modes are in the range 1365–1476 m/s and 1606–1791 m/s, respectively. The propagation mode and velocity are influenced by both the total mass flow rate and equivalence ratio. Detonation wave propagation processes of the two-wave and one-wave modes are also observed, which further demonstrates the realization of CRDE.

Thrust Vectoring of a Continuous Rotating Detonation Engine by Changing the Local Injection Pressure

The thrust vectoring ability of a continuous rotating detonation engine is numerically investigated, which is realized via increasing local injection stagnation pressure of half of the simulation domain compared to the other half. Under the homogeneous injection condition, both the flow-field structure and the detonation wave propagation process are analyzed. Due to the same injection condition along the inlet boundary, the outlines of fresh gas zones at different moments are similar to each other. The main flow-field features under thrust vectoring cases are similar to that under the baseline condition. However, due to the heterogeneous injection system, both the height of the fresh gas zone and the pressure value of the fresh gas in the high injection pressure zone are larger than that in the low injection pressure zone. Thus the average pressure in half of the engine is larger than that in the other half and the thrust vectoring adjustment is realized.