Rotating Detonation Engine Research Articles

102 数値計算によるローティングデトネーションエンジンの推進性能評価 : 回転デトネーションの数及び燃焼器サイズによる影響

102 数値計算によるローティングデトネーションエンジンの推進性能評価 : 回転デトネーションの数及び燃焼器サイズによる影響

Detonation Gas Turbines

This article focuses on various technical and functional aspects of detonation gas turbines. Detonation combustion involves a supersonic flow, with the chemical reaction front accelerating, driving a shock wave system in its advancement. In the 1990s, detonation-based power concepts began with pulse detonation engines (PDEs), and have now moved into the continuous detonation mode, termed rotating detonation engines (RDEs). Modern gas turbine combustors are compact, robust, tolerant of a wide variety of fuels, and provide the highest combustion intensities. The single-spool RDE gas turbine is represented by a detonation cycle, which accounts for the supersonic features of the heat addition, starting at station 2.5′. Continued research and development by the RDE technical community is needed to see if the promise of improved performance and downsized turbomachinery for a detonation cycle is real.

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.

Numerical investigation of shock wave reflections near the head ends of rotating detonation engines

The influence of various chamber geometries on shock wave reflections near the head end of rotating detonation engines was investigated. A hydrogen/air one-step chemical reaction model was used. The results demonstrated that the variation in flow field along the radial direction was not obvious when the chamber width was small, but became progressively more obvious as the chamber width increased. The thrust increased linearly, and the detonation height and the fuel-based gross specific impulse were almost constant as the chamber width increased. Near the head end, shock waves reflected repeatedly between the inner and outer walls. Both regular and Mach reflections were found near the head end. The length of the Mach stem increased as the chamber length increased. When the chamber width, chamber length and injection parameters were the same, the larger inner radius resulted in more shock wave reflections between the inner and outer walls. The greater the ratio of the chamber width to the inner radius, the weaker the shock wave reflection near the head end. The detonation height on the outer wall and the thrust, both increased correspondingly, while the specific impulse was almost constant as the inner radius of the chamber increased. The numerical shock wave reflection phenomena coincided qualitatively with the experimental results.

NUMERICAL TOOLS FOR THREE DIMENSIONAL SIMULATIONS OF THE ROTATING DETONATION ENGINE IN COMPLEX GEOMETRIES

This paper describes the development of a computational code REFLOPS USG (REactive FLOw solver for Propulsion Systems on UnStructured Grids) based on the Favre averaged Navier-Stokes equations with chemical reactions for semi-ideal multicomponent gas to predict the structure and dynamics of three-dimensional unsteady detonation as it occurs in the Rotating Detonation Engine (RDE). This work provides an overview of second order accurate in time and space finite volume method applied to conservation equations and its implementation on unstructured self-adaptive tetrahedral or hexahedral three-dimensional cell-centred meshes. The inviscid fluxes are given by the Riemann solver and stabilization is ensured by the proper limiters inherited from the TVD theory or gradient based limiters. The stiff equations of chemical kinetics are solved by use of implicit DVODE (Double precision Variablecoefficient Ordinary Differential Equation solver, with fixed-leading-coefficient implementation) routine or by explicit Chemeq2 routine. Additional improvements are incorporated into the code such as parallelization in OpenMP and implementation of NVIDIA CUDA technology. REFLOPS USG has become a fundamental numerical tool in the research of RDE at the Institute of Aviation in Warsaw, in frame of Innovative Economy project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland. The simulations presented in this paper are based on inviscid or viscous multicomponent semi-ideal gas flow with chemical reactions. Due to high computational costs only simple chemical reaction mechanisms are used here.

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF THE COMBUSTION CHAMBER OF THE ROTATING DETONATION ENGINE

From 2010 Warsaw University of Technology (WUT) and Institute of Aviation (IoA) jointly implement the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project is to replace the combustion chamber of turboshaft engine GTD-350 with an annular detonation chamber. During the project, the numerical group that aims to develop computer code allowing researchers to simulate investigated processes has been established. Simulations provide wide range of parameters that are hardly available from experimental results and enable better understanding of investigated processes. Simulations may be also considered as a cheap alternative for experiments, especially when testing geometrical optimizations. In this paper the analysis of simulation results of the combustion chamber of the Rotating Detonation Engine (RDE) investigated at the IoA in Warsaw is presented. Primarily, REFLOPS USG which has become a fundamental numerical tool in the research of the RDE at the IoA is briefly described and governing equations and numerical methods used are shortly presented. Some aspects of numerical simulations of the RDE, related to selection of combustion mechanism, and an initiation of rotating detonation are provided. Secondly, results of simulations of inviscid gas with numerical injectors of hydrogen are compared with available experimental results. Three different wave patterns are identified in numerical solution and briefly described. Results of simulations are compared to experimental results in combustion chamber. Results presented in this paper are part of the project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland.

Detonative propulsion

A survey of propulsion based on detonation of chemical systems is provided in this paper. After a short historical review, basic schematics of engines utilizing detonation as the combustion mechanism are described. Possible improvement of propulsive efficiency due to detonative combustion which results in a significant pressure increase is presented, and a comparison of deflagrative and detonative combustion is discussed. Basic research on Pulsed Detonation Engines (PDE) and rotating detonations in cylindrical and disk-like chambers for different mixtures is presented. Basic principles of engines utilizing Standing Detonation Waves as well as Ram Accelerators are also provided. Detailed descriptions of PDE as well as Rotating Detonation Engines (RDE) are given. Different implementations of the PDE concept are presented and experimental and theoretical results to date are reviewed. Special attention is given to RDE, since rotating detonation can be applied to all kinds of propulsive engines including rocket, ramjet, turbine, and combined-cycle engines. A survey of detonative propulsion research carried out at different laboratories is presented, and possible future applications of such propulsion systems are discussed. A short note on detonative propulsion using non-chemical energy sources is also given.

US Navy developing rotating detonation engine

US Navy developing rotating detonation engine

Fluid dynamics of rotating detonation engines with hydrogen and hydrocarbon fuels

Rotating detonation engines (RDE’s) represent a logical step from pulsed detonation engine concepts to a continuous detonation engine concept for obtaining propulsion from the high efficiency detonation cycle. The hydrogen/air and hydrogen/oxygen RDE concepts have been most extensively studied, however, being able to use hydrocarbon fuels is essential for practical RDE’s. The current paper extends our hydrogen/air model to hydrocarbon fuels with both air and pure oxygen as the oxidizer. Before beginning the RDE calculations, several detonation tube results are summarized showing the ability of the code to reproduce the correct detonation velocity and CJ properties. In addition, a calculation capturing the expected irregular detonation cell patterns of ethylene/air is also shown. To do the full range of fuels and oxidizers, we found the use of temperature-dependent thermodynamic properties to be essential, especially for hydrocarbon/oxygen mixtures. The overall results for air-breathing RDE’s with hydrocarbons ranged from 1990 to 2540s, while in pure oxygen mode the specific impulse varied from 700 to 1070s. These results were between 85% and 89% of the expected ideal detonation cycle results, and are in line with previous hydrogen/air estimates from our previous work. We conclude from this that hydrocarbon RDE’s are viable and that the basic flow-field patterns and behaviors are very similar to the hydrogen/air cases detailed previously.

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.

Numerical investigation of flow particle paths and thermodynamic performance of continuously rotating detonation engines

Based on the two-dimensional numerical simulation of continuously rotating detonations in an annular chamber, the paths of flow particles burned by three different processes are tracked and analyzed in detail. The detonation wave, the deflagration wave, the oblique shock wave, and the contact surface have a small influence on the paths of flow particles. The fluctuation of paths in the azimuthal direction is less than 12% of the circumference of the combustion chamber. The path will deflect when the flow particle encounters the detonation wave or the oblique shock wave, and it will not deflect when encounters the deflagration wave or the contact surface. About 23.6% fuel is burned by deflagration, and the left is burned by rotating detonation wave. The thermodynamic performance of continuously rotating detonations is then discussed. The p–v and T–s diagrams obtained by numerical simulation are qualitatively consistent with the ideal ZND model. The average thermal efficiency of the detonation combustion in 2D RDE is 31%, and its average net mechanical work is 1.3MJ/kg. The thermal efficiency of the entire RDE is 26.4%, and its net mechanical work is 30% of the ideal ZND model. The superior performance of continuously rotating detonations is determined.

Transverse wave generation mechanism in rotating detonation

Detonation engines are expected to be included in a number of aerospace thrusters in the future. Several types of detonation engines are currently under examination, including the rotating detonation engine (RDE). Although the RDE has been explored experimentally, its rotating detonation propagation mechanism is not well understood. This paper clarifies the detonation mechanism and dynamics of the RDE by 2D and 3D simulation using compressible Euler equations with a full chemical reaction mechanism of H2/O2 and H2/Air, especially from the triple-point and transverse detonation points of view. A total variation diminishing (TVD) scheme is used for the mixture of H2/Air, and an advection upwind splitting method difference vector (AUSMDV) scheme is used for the mixture of H2/O2. The use of an AUSMDV scheme provides a much clearer detonation structure than does the TVD scheme. We focus on the complex interaction mechanism of the detonation front and burned mixture gases. We found out that at this interaction point, an unreacted gas pocket appears and ignites periodically to generate transverse waves at the detonation front and maintain detonation propagation.

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.

Propulsive Performance of a Continuously Rotating Detonation Engine

Propulsive Performance of a Continuously Rotating Detonation Engine

Detonation Limit Thresholds in H2/O2 Rotating Detonation Engine

The rotating detonation engine (RDE) is a new engine system using detonation, which may provide a higher performance and smaller and simpler design in comparison with the pulse detonation engine (PDE) and other traditional engines. However the research on RDE stands just at the first step now. The authors perform a numerical analysis to understand about RDE in terms of features of rotating detonation and its propagation limit. The lower threshold pressure of detonation limit was 2.6 MPa and the upper threshold pressure of detonation limit was 7.1 MPa. The engine performance analysis shows that the maximum mixture based specific impulse (I spm ) was about 440 s, which is comparable with that of the present typical rocket engine.

Numerical Investigation of Rotating Detonation Engine Propulsive Performance

A series of 3- and 2-dimensional numerical simulations of a rotating detonation engine (RDE) are carried out with a 1-step chemical reaction model to investigate the RDE's propulsive performance. First, the performance is computed by a 3-dimensional simulation. After the initial instability dies down, the specific impulse and mass flux of RDE converge to constant values. Then, some simplified 2-dimensional cases are simulated. The following propulsive performance collusions are obtained: with the injection stagnation pressure increases, the mass flux increases linearly and the specific impulse decreases a little. With combustor length larger than a special value, specific impulse and mass flux change a little. The propulsive parameters obtained from the 3-dimensional simulation case agree with simplified 2-dimensional simulation cases.

Oblique detonation waves stabilized in rectangular-cross-section bent tubes

Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through rectangular-cross-section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The oblique detonation waves were stabilized under the conditions of high initial pressure and a large curvature radius of the inside wall of the rectangular-cross-section bent tube. The geometrical shapes of the stabilized oblique detonation waves were calculated, and the results of the calculation were in good agreement with those of our experiment. Moreover, it was experimentally shown that the critical condition under which steady-state oblique detonation waves can stably propagate through the rectangular-cross-section bent tubes was the curvature radius of the inside wall of the rectangular-cross-section bent tube equivalent to 14–40 times the cell width.

The symmetry of time in physics

Rotating detonation engines are widely studied because of their compact configurations and high thermal cycle efficiency. For briefty, most of the numerical simulations of rotating detonation engines used premixed reactant mixtures. The rotating detonation waves under non-premixed condition are not studied enough. Here, a series of three-dimensional numerical simulations of a rotating detonation engine under both premixed and non-premixed conditions using H2/air mixture are performed. The explicit formulation of density-based solver in ANSYS Fluent is used to perform the simulations. Two total mass flow rates of 272.3 g/s and 500 g/s are selected. When the total mass flow rate is 272.3 g/s, the engine operates at single-wave mode under both premixed and non-premixed conditions. When the total mass flow rate is 500 g/s, the engine operates at single-wave mode under premixed condition. While under non-premixed condition, a spontaneous formation of dual-wave mode is observed. This case agrees well with the phenomenon observed in experiments that as the total mass flow rate increases, the number of rotating detonation waves tends to increase. Pressure waves caused by the high pressure behind the detonation waves can propagate upstream to the H2 and air plenums. The pressure feedback in the H2 plenum is much more obvious than that in the air plenum. Due to the imperfect mixing of H2/air and the more deflagration combustion caused by the hot detonation products, the thrust of the RDE under non-premixed condition is smaller than that under premixed condition.