Rotating Detonation Engine Research Articles

Investigation into the effective injector area of a rotating detonation engine with impact of backflow

Investigation into the effective injector area of a rotating detonation engine with impact of backflow

Combustion Characteristics in Rotating Detonation Engines

A lot of studies on rotating detonation engines have been carried out due to the higher thermal efficiency. However, the number, rotating directions, and intensities of rotating detonation waves are changeful when the flow rate, equivalence ratio, inflow conditions, and engine schemes vary. The present experimental results showed that the combustion mode of a rotating detonation engine was influenced by the combustor scheme. The annular detonation channel had an outer diameter of 100 mm and an inner diameter of 80 mm. Air and hydrogen were injected into the combustor from 60 cylindrical orifices in a diameter of 2 mm and a circular channel with a width of 2 mm, respectively. When the air mass flow rate was increased by keeping hydrogen flow rate constant, the combustion mode varied. Deflagration and diffusive combustion, multiple counterrotating detonation waves, longitudinal pulsed detonation, and a single rotating detonation wave occurred. Both longitudinal pulsed detonation and a single rotating detonation wave occurred at different times in the same operation. They could change between each other, and the evolution direction depended on the air flow rate. The operations with a single rotating detonation wave occurred at equivalence ratios lower than 0.60, which was helpful for the engine cooling and infrared stealth. The generation mechanism of longitudinal pulsed detonation is developed.

Pressure measurements in detonation engines

The influence of waveguide tubes on the signals received by remote pressure sensors measuring pressure histories in pulsed detonation engines (PDEs) and rotating detonation engines (RDEs) is studied computationally. Two types of pressure sensors are considered: low-frequency static pressure sensors and high-frequency sensors of pressure pulsations. Three approaches to solving the problem are used: based on Euler (inviscid flow), Navier–Stokes (laminar flow), and unsteady Reynolds-averaged Navier–Stokes (turbulent flow) equations. The approaches based on the inviscid and laminar flow models are shown to provide the best predictive capability. The laminar flow model is applied to analyzing the readings of pressure sensors installed remotely in the waveguide tubes attached to the hydrogen-fueled PDE, RDE, and detonation ramjet (DR). It is shown that the measurements of static pressure and pressure pulsations by remote pressure sensors do not correspond to the time-averaged mean and local instantaneous values of pressure in the combustors. The pressure time histories can be recovered based on the measurements and computational fluid dynamics calculations of the operation process. The latter is demonstrated by analyzing the results of test fires with a dual-duct DR model.

Propagation behavior of rotating detonation waves with premixed kerosene/air mixtures

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 (ψ) 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 (ψ=1.0), the reactants distribute continuously in triangular gas layers. Rotating detonation waves propagate stably with regular detonation cellular structure. When ψ 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 flow-field structure and reduces the propulsion performance of combustor.

Experimental Investigation of Detonation Propagation Modes and Thrust Performance in a Small Rotating Detonation Engine Using C2H4/O2 Propellant

A small rotating detonation engine (RDE) model and the corresponding experimental setup were constructed for the experimental investigation of the detonation propagation characteristics and thrust performance of a circular RDE. Experiments were conducted at a range of 0.3–2.5 equivalence ratio with a total mass flow rate of less than 180.0 g/s using a C2H4/O2 mixture. Irregularly unstable detonative combustion occurs immediately after the detonation initiation, which includes initiation, propagation, decaying, and the merging of detonation waves. Following this, periodically unsteady detonative combustion occurs in the circular channel, resulting in the stable operation of the RDE. During stable operation, two detonation waves are predominant, rotating along the wall at a speed lower than the Chapman–Jouguet (CJ) detonation speed. The characteristic velocity efficiency is approximately 73% on average. The low characteristic velocity efficiency is presumed to be caused by the unoptimized combustion channel and the poor mixing efficiency owing to the two-dimensional injector configuration. The effect of the RDE component design and the RDE flow field characteristics need to be further investigated for improving the performance of the RDE.

Predictive Numerical Analysis on the Mixing Characteristics in a Rotating Detonation Engine (RDE)

Predictive Numerical Analysis on the Mixing Characteristics in a Rotating Detonation Engine (RDE)

Early Assessment of Asymmetric Vortex Small Rotating Detonation Engine

Early Assessment of Asymmetric Vortex Small Rotating Detonation Engine

Effects of slot injection on detonation wavelet characteristics in a rotating detonation engine

Two-dimensional numerical simulations are performed to investigate the effects of spatially discrete slot injection of reactants on the features of detonation wavelets in a rotating detonation engine (RDE). The detonation dynamics is described by a model based on the reactive Euler equations coupled with two-step, induction-reaction kinetics. By varying injection conditions and the chemical sensitivity of the reactive mixture, a parametric study is carried out to examine the influence of the injection-slot area ratio α on the detonation wavelet patterns and different flow features inside an RDE combustion chamber. The simulation results demonstrate that the injection conditions, i.e., stagnation temperature and pressure, have a similar influence on slot-ozzle rotating detonation wavelets (RDWs) as compared with the mini-nozzle RDWs reported in a previous study. The corresponding mass flow rate and inhomogeneity generated due to the presence of slot injection, however, play a key factor in the self-sustained rotating detonation and its frontal structure.

Experimental Response of Capillary Tube Attenuated Pressure Measurements Under High-Amplitude, Nonlinear Forcing

The response behavior of capillary tube attenuated pressure sensor arrangements is studied using a rotating detonation engine as a nonlinear pressure wave source. The resulting measured pressures are examined as a function of the magnitude of the nonlinear pressure fluctuations, the mean pressure, and the forcing frequency applied to the pressure input port of the sensor. In addition, length and inner diameter of the sensor tubes are studied as a way to tie the current work into the established body of literature. Analytic models are used to provide understanding and predict the expected behaviors of the various tested sensor configurations, in an effort to supply reliable and accurate measurements of high-fidelity static pressures with specific application to ongoing rotating detonation engine research.

Experimental investigation on the propagation characteristics of detonations in a semi-confined straight channel

In a rotating detonation engine, detonation waves propagate in the combustor chamber with one side unconfined which will introduce lateral relief and, therefore, results in deficits of the propagation velocity and the peak pressure. To study the critical mixture height for detonation propagation, a simple combustor without considering the curvature has been used, which provides a planar semi-confined channel with different channel heights, e.g., 10 mm, 20 mm, and 30 mm. Effects of the nitrogen dilution ratio, the equivalence ratio, and the channel height on the propagation modes, the velocity deficit, and the cellular structure have been investigated when ethylene was utilized. The non-dimensional channel height (h/λa) was also adopted to evaluate the impacts of lateral relief. Experimental results indicated that three different propagation modes existed in the semi-confined channel. Velocity deficits resulted from the lateral relief mechanism were observed and the maximum velocity deficit is around 10–15%. Besides, the cell width increased and became more irregular when reducing the channel height. Successful detonation propagation can be obtained with a minimum normalized channel height of h/λa > 2, which will provide information for practical detonation operations.

Visual experimental investigation on stable operating process of the plane-radial rotating detonation engine

Using visual observation methods, assisted by synchronous measurement of dynamic pressure and ion tracks, the flow field structures of stable operating modes in plane-radial rotating detonation engine (RDE) are revealed, and the influences of injection conditions on the RDE stable operating range are analyzed. The flow field structures of single-wave mode, symmetric dual-wave mode and triple-wave mode are observed. Typical structures such as rotating detonation wave (RDW), oblique shock wave, combustion products, deflagration surface and contact discontinuity are obtained in the flow fields. Obvious reactants pre-combustion ahead of detonation wave is found in the combustor, and low-frequency oscillation phenomenon is gained under specific conditions. With the increase of wave-head number in combustor, the detonation-wave height and parameters decrease. The RDW propagating velocity and pressure peak are higher in single-wave operating mode, but the flow fields in multi-wave mode are more stable. Both the RDW velocity and pressure peak increase generally with equivalence ratio. Keeping the equivalent ratio (ER) fixed, as the mass flow rate increases, the number of detonation wave in combustor increases, and the operating mode transforms from single-wave mode to multi-wave mode. Keeping the mass flow rate fixed, when the equivalent ratio deviates from stoichiometric ratio, the operating mode varies from multi-wave mode to single-wave mode. Additionally, with the mass flow rate increasing, the ER upper and lower limits of multi-wave mode decrease linearly, and the operating range of dual-wave mode remains unchanged. Mass flow rate has little influence on the ER lower limit of the RDE stable operation, which is approximately ER=0.55 in this structure.

Experimental research on the performance of a rotating detonation combustor with a turbine guide vane

Rotating detonation engines (RDEs) have received significant attention from industry and academia alike, owing to their numerous advantages, such as pressure gain combustion, high operation frequency, and near-constant thrust output. Furthermore, there is considerable interest in combining RDEs with gas-turbine engines to further improve their overall system performance. This study examines the propagation characteristics of continuous rotating detonation waves (CRDWs) with a turbine guide vane (TGV). We develop an experimental model of a hydrogen–air rotating detonation combustor integrated with a TGV section and record the high-frequency pressure oscillations and static pressure upstream and downstream of the TGV section. The experimental results indicate that: the interactions between CRDW and the turbine blade cause the reflected shock propagating backwards to the combustor. Both pressure oscillation amplitude and static pressure decline at downstream of TGV. Notably, the pressure oscillation attenuation by the TGV is influenced by the direction of CRDW propagation. When the CRDW propagation direction and the flow path direction of the guide vane are opposite to each other, the pressure oscillation attenuation increases. The findings obtained herein provide benchmark data that help improve the fundamental understanding of CRDW and TGV interaction, and can be used to develop detonation-based propulsion technology.

Effects of Isothermal Wall Boundary Conditions on Rotating Detonation Engine

ABSTRACT Three-dimensional numerical simulations of rotating detonation engines (RDEs) are reported with stoichiometric hydrogen/air mixtures using Navier-Stokes equations with non-slip walls. The effects of isothermal wall boundary conditions at 300 K, 600 K and 900 K are investigated and further compared with the simulation under adiabatic walls. With isothermal walls of 300 K, axial detonation is formed, which further leads to the quenching of detonation. With 600 K isothermal walls, the detonation wave has a similar stably propagating process as adiabatic walls. However, due to the wall heat loss, a lower detonation velocity is obtained in the simulation with isothermal walls. With 900 K isothermal walls, it is found that detonation quenches at first due to the high temperature of the walls, then re-initiates as a result of the collisions of shock waves. In addition, the temperature and heat flux distributions in the outer wall are analyzed. Both the peak temperature and heat flux are found to appear at the detonation wavefront. The averaged heat flux in the detonation region is about three times of the averaged heat flux evaluated in the outer wall. Moreover, the averaged temperature and heat flux remain nearly unchanged in the post-detonation region. Our results are in agreement with experimental studies and provide some insights for RDE thermal management.

Modeling thermodynamic trends of rotating detonation engines

The formation of a number of co- and counter-rotating coherent combustion wave fronts is the hallmark feature of the Rotating Detonation Engine (RDE). The engineering implications of wave topology are not well understood nor quantified, especially with respect to parametric changes in combustor geometry, propellant chemistry, and injection and mixing schemes. In this article, a modeling framework that relates the time and spatial scales of the RDE to engineering performance metrics is developed and presented. The model is built under assumptions of backpressure-insensitivity and nominally choked gaseous propellant injection. The Euler equations of inviscid, compressible fluid flow in one dimension are adapted to model the combustion wave dynamics along the circumference of an annular-type RDE. These adaptations provide the necessary mass and energy input and output channels to shape the traveling wave fronts and decaying tails. The associated unit processes of injection, mixing, combustion, and exhaust are all assigned representative time scales necessary for successful wave propagation. We find that the separation, or lack, of these time scales is responsible for the behavior of the system, including wave co- and counter-propagation and bifurcations between these regimes and wave counts. Furthermore, as there is no imposition of wave topology, the model output is used to estimate the net available mechanical work output and thermodynamic efficiency from the closed trajectories through pressure–volume and temperature–entropy spaces. These metrics are investigated with respect to variation in the characteristic scales for the RDE unit physical processes.

Review on the Rotating Detonation Engine and It’s Typical Problems

Abstract Detonation is a promising combustion mode to improve engine performance, increase combustion efficiency, reduce emissions, and enhance thermal cycle efficiency. Over the last decade, significant progress has been made towards the applications of detonation mode in engines, such as standing detonation engine (SDE), Pulse detonation engine (PDE) and rotating detonation engine (RDE), and the understanding of the fundamental chemistry and physics processes in detonation engines via experimental and numerical studies. This article is to provide a comprehensive overview of the progress in the knowledge of rotating detonation engine from the different countries. New observations of injection, ignition, and geometry of combustor, pressure feedback, and combustion modes of RDE have been reported. These findings and advances have provided new opportunities in the development of rotating detonation for practical applications. Finally, we point out the current gaps in knowledge to indicate which areas future research should be directed at.

Numerical Modeling of the RDE

Abstract The idea of using the phenomenon of rotating detonation to propulsion has its roots in fifties of the last century in works of Adamson et al. and Nicholls et al. at the University of Michigan. The idea was recently reinvented and experimental research and numerical simulations on the Rotating Detonation Engine (RDE) are carried in numerous institutions worldwide, in Poland at Warsaw University of Technology (WUT) since 2004. Over the period 2010-2014 WUT and Institute of Aviation (IOA) jointly implemented the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project was to replace the combustion chamber of turboshaft engine GTD-350 with the annular detonation chamber. This paper is focused on investigation of the influence of a geometry and flow conditions on the structure and propagation stability of the rotating detonation wave. Presented results are in majority an outcome of the aforementioned programme, in particular authors’ works on the development of the in-house code REFLOPS USG and its application to simulation of the rotating detonation propagation in the RDE.

Thrust Validation of Rotating Detonation Engine System by Moving Rocket Sled Test

This Paper presents the results of a rotating detonation engine rocket sled test demonstration on a 127 mm gauge rail at 100 m long high-speed running track test equipment to evaluate the thrust performance of a stand-alone rotating detonation engine propulsion system. The developed sled test demonstrator contained all onboard subsystems, including engine, gas cylinders, valves, controller, and a data logger. The sled test demonstrator successfully generated thrust, and three or four detonation waves of 1460 to were observed during the 2.0 s burn time. The measured specific impulse in the sled test was 144 s as estimated from the acceleration of the demonstrator and the mass decrease in the onboard cylinders. The test results were compared with the data from a laboratory-stand firing test using a load cell, and the specific impulses of the sled test were found to be comparable to the results of the stand firing test.

Study on the performance of a rotating detonation chamber with different aerospike nozzles

To generate thrust efficiently is the ultimate objective of developing a practical propulsion device utilizing detonation. The rotating detonation engine shows its great potentials because of pressure gain combustion is produced while detonations rotate inside the chamber. In order to improve the propulsive performance of a rotating detonation engine, investigations have been carried out theoretically and experimentally focusing on aerospike nozzles. A method of designing aerospike nozzles for the rotating detonation chamber was proposed. Three aerospike nozzles, with different geometry structures including conical and flat configurations and design pressure ratios, were developed in different design points. Compared to the nozzle-less condition, three operation modes have been obtained in the combustion chamber with nozzles. The results indicate that the reflected wave caused by the convergent section will induce the generation of multiple waves. The pressure gains in the combustion chamber were varied with different nozzle geometries. The propulsive performance of the conical configuration nozzle was better than the flat one. In addition, with the increase of the mass flow rate, the thrust was increased for all the cases while the maximum specific impulse was achieved at a flow rate of 0.190 kg/s.

Recent Progress, Development Trends, and Consideration of Continuous Detonation Engines

The continuous detonation engine (CDE) is based on detonation waves and is a new jet engine concept that is expected to bring a technical revolution to current aviation and aerospace propulsion systems. Some scholars have also called this concept the continuously rotating detonation engine or rotating detonation engine. The advantages and application potential of the CDE have been widely recognized and verified with research focused in three directions: continuous detonation rocket engines, continuous detonation ramjet engines, and continuous detonation turbojet engines. This paper reviews recent progress (primarily in the last five years) of CDE from the perspective of engineering applications. Research on continuous detonation rocket engines has gone from concept exploration to mechanism research, and it is moving toward engineering applications. Large-scale prototype testing may be the next step, especially with experiments based on liquid methane and liquid oxygen that need further development. The continuous detonation ramjet engine is still in the conceptual design and principle exploration stages. To adapt to broader inflow conditions and working Mach numbers, the combination of different working modes of a CDE may be of further interest. The continuous detonation turbojet engine is still in the scheme demonstration stage. Significant research work is needed in terms of experimental, numerical, and theoretical analyses, especially toward finding individual phenomena, mechanism exploration, and multicomponent coupling test. The performance of continuous detonation with solid fuels will also benefit from additional investigations and verifications.

The effects of mixture preburning on detonation wave propagation

Pressure gain combustion in the form of continuous detonations can provide a significant increase in the efficiency of a variety of propulsion and energy conversion devices. In this regard, rotating detonation engines (RDEs) that utilize an azimuthally-moving detonation wave in annular systems are increasingly seen as a viable approach to realizing pressure gain combustion. However, practical RDEs that employ non-premixed fuel and oxidizer injection need to minimize losses through a number of mechanisms, including turbulence-induced shock-front variations, incomplete fuel-air mixing, and premature deflagration. In this study, a canonical stratified detonation configuration is used to understand the impact of preburning on detonation efficiency. It was found that heat release ahead of the detonation wave leads to weaker shock fronts, delayed combustion of partially-oxidized fuel-air mixture, and non-compact heat release. Furthermore, large variations in wave speeds were observed, which is consistent with wave behavior in full-scale RDEs. Peak pressures in the compression region or near triple points were considerably lower than the theoretically-predicted values for ideal detonations. Analysis of the detonation structure indicates that this deflagration process is parasitic in nature, reducing the detonation efficiency but also leading to heat release far behind the wave that cannot directly strengthen the shock wave. This parasitic combustion leads to commensal combustion (heat release far downstream of the wave), indicating that it is the root cause of combustion efficiency losses.