Spin Detonation Research Articles

Micro-jetting and Transverse Waves in Oblique Detonations

We present a highly-resolved 2D numerical simulation of a wedge-induced Oblique Detonation Wave (ODW) using a 9-species 21-reaction chemical kinetic mechanism for a stoichiometric H2-air mixture. Adaptive Mesh Refinement (AMR) is leveraged to obtain a resolution close to the continuum limit at the finest level (Δxfinest=0.78μm=20λ, where λ is the mean-free path of the fuel–air mixture), which spans the ODW front and its transverse waves. The simulation is performed for a sufficiently large domain, enabling us to unveil the multi-zonal structure of the ODW. We capture, for the first time, the onset of microscopic hypersonic jets (micro-jets) far downstream of the wedge tip associated with cellular structures resembling those of a multi-headed Normal Detonation Wave (NDW). In contrast, the upstream “cell-like” structure (christened as “pseudo-cellular” hence) are found to be devoid of these micro-jets with a morphology similar to that of single-headed NDWs, such as spinning/zig-zag detonations in tubes/2D channels, respectively. A detailed investigation into the transverse-shock structure downstream reveals that a colliding pair of transverse waves lead to the micro-jetting phenomenon. The absence of one of the pair of transverse waves in the upstream region results in the observed pseudo-cellular structures. The origin of these transverse waves in an ODW, unclear in previous literature, is shown to arise from coalescing and strengthening of Compression Waves (CWs) that are produced from two distinct mechanisms. During the “early” phase of the ODW stabilization, CWs are formed as a result of local blast events. In the subsequent “middle” phase, these are formed as a result of the shear-layer instabilities coupling with the local shock structure, leading to the so-called left-running transverse waves (LRTWs) upstream and the right-running transverse waves (RRTWs) downstream. The identified mechanisms offer a plausible explanation on why ODWs exhibit a multi-zonal morphology.Novelty and Significance StatementThe present study is one of the very few studies in the Oblique Detonation Wave (ODW) literature that includes multi-step chemistry while solving for the compressible reacting Navier-Stokes equations on a large simulation domain revealing the multi-zonal structure of the ODW. Furthermore, the resolution employed for the study approaches the continuum limit, making it on-par with the current state-of-the-art for ODW simulation. For the first time, this study has demonstrated the existence of microscopic hypersonic jets (micro-jets) far downstream of the wedge tip in a wedge-induced ODW and a method to isolate them in numerical simulations, leading to insights on the broader micro-jetting phenomenon in detonations. The existence of a cell-like (which we term as “pseudo-cellular”) region bearing similarity with that of single-headed spinning detonations is also noted due to the absence of a transverse wave family upstream. The exact physical mechanisms leading to the formation of transverse waves in ODW are also investigated, which were previously ambiguous in the literature.

Three-Dimensional Numerical Simulation of Heterogeneous Spin Detonation in the Al/O2 Gas Suspension in Channels with a Circular Cross Section

Three-Dimensional Numerical Simulation of Heterogeneous Spin Detonation in the Al/O2 Gas Suspension in Channels with a Circular Cross Section

Numerical study of pressure profiles in an annular combustor and a manifold during continuous spin detonation of nonstoichiometric hydrogen-air mixtures

A closed mathematical model of continuous spin detonation of nonstoichiometric hydrogen-air mixtures in a quasi-three-dimensional unsteady gas-dynamic formulation taking into account the reverse effect of the oscillation processes in the combustor on the mixture injection system is utilized in pressure profiles in the combustion chamber and in the manifold investigation. Numerical simulations are performed for the flow-type annular combustor 503 mm in diameter with an annular gap of width 18 mm and other geometric dimensions corresponding to experiments. Three-wave mode of continuous spin detonation is calculated and the flow structure is analyzed for the equivalence ratio of 0.6 and the specific hydrogen-air mixture flow rate of 390.6 kg/(s·m2). The static, the mean static and the mean total pressure distributions in the combustor are calculated. The results are validated against experimental data.

Three-Dimensional Numerical Simulation of Heterogeneous Spin Detonation in the Al/O<sub>2</sub> Gas Suspension in Channels with a Circular Cross Section

Three-Dimensional Numerical Simulation of Heterogeneous Spin Detonation in the Al/O<sub>2</sub> Gas Suspension in Channels with a Circular Cross Section

Rotating Detonation Combustion for Advanced Liquid Propellant Space Engines

Rotating (also termed continuous spin) detonation technology is gaining interest in the global research and development community due to the potential for increased performance. Potential performance benefits, thrust chamber design, and thrust chamber cooling loads are analyzed for propellant applications using liquid oxygen or high-concentration hydrogen peroxide oxidizers with kerosene, hydrogen, and methane fuels. Performance results based on a lumped parameter treatment show that theoretical specific impulse gains of 3–14% are achievable with the highest benefit coming from hydrogen-fueled systems. Assessment of thrust chamber designs for notional space missions shows that both thrust chamber length and diameter benefits are achievable given the tiny annular chamber volume associated with the rotating detonation combustion. While the passing detonation front drastically increases local heat fluxes, global energy balances can be achieved if operating pressures are limited to be comparable to existing or prior space engines.

Continuous Spin Detonation of the Kerosene–Air Mixture in a Flow-Type Radial Vortex Combustor 500 mm in Diameter

Continuous Spin Detonation of the Kerosene–Air Mixture in a Flow-Type Radial Vortex Combustor 500 mm in Diameter

Continuous Spin Detonation of the Kerosene-Air Mixture in a Flow-Type Radial Vortex Combustor 500 mm in Diameter

Continuous Spin Detonation of the Kerosene-Air Mixture in a Flow-Type Radial Vortex Combustor 500 mm in Diameter

Simulation of continuous spin detonation in an annular combustion chamber in two-dimensional statement

Simulation of continuous spin detonation in an annular combustion chamber in two-dimensional statement

Rotating Detonation: History, Results, Problems

Abstract Among of modern papers devoted to numerical modeling of rotated waves the greater part of papers are based on assumption that such wave propagates with velocity equals to the Chapman-Jouguet velocity of ideal detonation model with plane front. But the experimental velocities of rotated detonation waves, as a rule, are less (and even much less) the velocity of ideal Chapman-Jouguet detonation. Such regimes are named as low-velocity detonation or quasi-detonation and its characteristics are practically not investigated carefully. Moreover, similar to the spinning detonation, the strong connection of velocity of rotated transverse waves with the acoustic waves of reaction products was observed. So the new model with an allowance for the losses of impulse and energy must be used at numerical modeling of RDE and new experimental investigations of regimes with understated velocity must be carried out. In given paper some important aspects of rotated detonation waves and new experimental results are analyzed: the multifront system of rotated waves; correlation of rotation velocity of waves with acoustic characteristics of reaction products; streak-records trajectory of rotated waves on moving film; pressure and temperature profiles of rotating waves; velocity deficit and energy-release.

Continuous Detonation of a Mixture of Gaseous Hydrogen and Liquid Oxygen in a Plane–Radial Combustor with Exhaustion Toward the Periphery

Regimes of continuous spin detonation and continuous multifront detonation of a gas–droplet mixture of gaseous hydrogen and liquid oxygen in a plane–radial combustor (internal diameter of 100 mm and external diameter of 300 or 200 mm) with exhaustion toward the periphery are obtained for the first time. The detonation front height of the gas–droplet mixture is greater than that of the gas mixture, which is caused by the critical size of detonation existence. Centrifugal forces acting on the products behind the detonation wave front favor faster filling of the plane–radial combustor with the fresh mixture and increase the detonation front height.

Continuous Detonation of CH4/H2–Air Mixtures in an Annular Combustor with Varied Geometry

Regimes of continuous detonation of CH4/H2–air mixtures with mass fractions of H2 in the fuel equal to 0–1/5 are obtained in an annular combustor 503 mm in diameter with variation of the combustor geometry. The influence of the combustor geometry on the velocity and number of transverse detonation waves, pressure in the combustor, and specific impulse is considered. It is found that three-fold constriction of the combustor exit cross area allows obtaining two-wave regimes of continuous spin detonation in the pure methane–air mixture. Based on stagnation pressures measured at the combustor exit, the specific impulses in the case of continuous detonation are determined for different compositions of the fuel.

Detonation and its limit in small tubes with ozone sensitization

Ozone as an ignition promoter was used to study the detonation limit behavior in small, round tubes. Experimentally, detonation cellular structures and velocity deficits of fuel-oxygen mixtures with and without 3000 PPM of ozone were measured in tubes of 32 and 6 mm in inner diameter. Both hydrogen-oxygen and methane-oxygen mixtures were tested. The addition of ozone reduces the detonation cell size and extends the transition to spinning detonation to lower initial pressures. Ozone addition, however, produces a negligible effect on velocity deficit far from the detonation limit while providing a measurable extension of the limit. The change in deficit caused by ozone does not correlate with the reduction in cell size, suggesting that the velocity deficit behavior is not solely a function of the detonation structure. By analyzing the velocity deficit data in the d/λ (the ratio of tube diameter to cell width) domain, two regimes of detonation limits are identified: a loss-governed regime where velocity deficiency results from various losses (mass, momentum, and heat) and is insensitive to detonation structure, and a geometry-limited regime determined by the geometric accommodation of the detonation structures. Two velocity deficit models were evaluated against the experimental results: a modified ZND model with heat and momentum losses (HML) and the flow divergence (FD) model. Velocity deficits in the loss-governed regime are well predicted by the HML model but not by the FD model. Velocity deficits in the geometry-limited regime can be correlated with the critical condition of d/λ=1/π and the transition point between the two regimes. Ozone addition extends the detonation limit by moving the reactive mixtures away from its geometric detonation limit, and promotes detonation propagation in miniaturized geometries.

Modeling of Continuous Spin Detonation of a Hydrogen–Air Mixture in an Annular Cylindrical Combustor

A closed mathematical model of continuous spin detonation with the chemical kinetics equation correlated with the second law of thermodynamics is developed for a hydrogen–air mixture within the framework of the quasi-three-dimensional unsteady gas-dynamic formulation. The model takes into account the reverse influence of the oscillation processes in the combustor on the injection system of the mixture components. For comparisons with experimental data, the numerical simulations are performed for the geometric parameters of the flow-type annular combustor with an outer diameter of 306 mm used in the experiments. For the flow rates of the mixture varied in the interval 73.1–171.3 kg/(s $$\, \cdot\,$$ m $$^{2}$$ ), the one-wave, two-wave, and three-wave regimes of continuous spin detonation are calculated, the flow structure is analyzed, the specific impulses are determined, and comparisons with experimental data are performed. It is shown that the use of a simplified single-stage kinetic scheme of hydrogen oxidation, which was used in some investigations, for simulating continuous spin detonation leads to results that differ from the experimental data by several times.

Parameters of Continuous Detonation of Methane/Hydrogen–Air Mixtures with Addition of Air to Combustion Products

Results of experimental investigations in a flow-type annular cylindrical combustor with an outer diameter of 503 mm are reported. The influence of air addition to products of continuous spin detonation of CH4/ $$m$$ H2–air mixtures on the parameters of detonation waves, the pressure in the combustor, and the specific impulse is considered. It is demonstrated that air injection into detonation products increases the velocity of continuous spin detonation, the pressure in the combustor, and the thrust, whereas the specific flow rate of the fuel decreases.

A Detonation Afterburner

For the first time, a detonation afterburner (DA) for continuous detonation combustion of TS-1 aviation kerosene was developed, manufactured, and tested. Test fires of the DA in combination with a TJ100S-125 small-sized single-circuit turbojet engine were carried out on a ground test bench. In the test fires, stable modes of continuous detonation combustion of aviation kerosene were registered: a near-limit mode of longitudinally pulsating detonation (LPD) and a spin detonation (SD) mode with one detonation wave. Compared to a conventional afterburner, at the same in-chamber pressure, the specific fuel consumption in the DA was 30% lower and the specific thrust and thrust boosting coefficient were 30% higher. It is shown that, when operating in the LPD mode, the average heat flux to the DA walls is about 0.5 MW/m2 and, in the SD mode, 0.86 MW/m2. These values indicate the high potentiality of the DA when used in advanced jet engines.

Modeling of Continuous Spin Detonation of a Hydrogen-Air Mixture in an Annular Cylindrical Combustor

Modeling of Continuous Spin Detonation of a Hydrogen-Air Mixture in an Annular Cylindrical Combustor

Flame Propagation and Acoustics

An intense effect of acoustic waves on the structure and shape of the burner flame was discovered by Rayleigh. The present paper deals with acoustic waves in the case of flame propagation in a tube. The flame emits acoustic waves generating the flow in the tube. Being actually a wave beam, the flow bounded by the walls experiences friction and also diffraction divergence, resulting in the emergence of secondary waves, i.e., waves of flow disturbances. They induce the formation of a cellular structure of the flame; at high velocities, the flame becomes turbulent. All these processes play important roles in the deflagration-to-detonation transition in tubes. Emission of acoustic waves by the flame is also responsible for the formation of spherical detonation. Spin and pulsed detonation can be interpreted on the same basis.

Three-dimensional numerical simulation of continuous spin detonation in hydrogen-oxygen and hydrogen-air mixtures using OpenFOAM package

A mathematical model of continuous spin detonation for hydrogen-oxygen and hydrogen-air mixtures is developed within the framework of a nonstationary gas-dynamic formulation. An OpenFOAM package is used to carry out numerical calculations in an annular cylindrical combustor in order to compare the main solution parameters with experimental data for geometric dimensions of combustors 40 mm and 306 mm in diameter corresponding to the experiments for hydrogen-oxygen and hydrogen-air mixtures. Regimes with a single continuously rotating transversal detonation wave are obtained for given fuel mixtures. It is shown that the solution significantly depends on the coordinate along the radius. The results for the hydrogen-oxygen mixture are in good agreement with an experiment in terms of a wave velocity and satisfactory agreement relative to a front height and the number of waves (a 1.5- to 2-fold difference). The results for the hydrogen-air mixture are in satisfactory agreement with an experiment for the wave velocity and front height and significantly differ from it on a minimal flow rate of the mixture, in which the existence of continuous spin detonation is possible in the combustor.

Calculation of continuous spin detonation of a hydrogen-oxygen mixture in an annular combustor with oxygen ejection

A closed mathematical model of continuous spin detonation in a H2-O2 mixture with oxygen ejection from the environment has been developed. The model takes into account the inverse effect of pulsation processes in the combustor on oxygen ejection. A numerical study was performed for a 10 cm diameter ramjet annular combustor with geometric dimensions corresponding to experiments. One-wave modes of continuous spin detonation were calculated and the flow structure was analyzed with variation in the specific hydrogen flow rate from 3 to 3.75 kg/(s·m2). Decreasing the flow rate of ejected hydrogen during continuous detonation in the combustor is found to lead to a monotonic decrease in the detonation velocity, wave front height, average static pressure, and equivalence ratio, but to an increase in the oxygen ejection coefficient. The results are validated against experimental data.

Continuous detonation of a hydrogen–oxygen gas mixture in a 100-mm plane-radial combustor with exhaustion toward the periphery

Regimes of continuous spin detonation and continuous multifront detonation in a hydrogen–oxygen mixture are obtained in a plane-radial combustor with an inner diameter of 100 mm and exhaustion toward the periphery. The fuel-lean limits of detonation in terms of the specific flow rate of the mixture are determined. For continuous spin detonation, transverse detonation waves and the flow in their vicinity in the combustor plane are reconstructed. The detonation wave is found to be significantly curved because of the increase in the tangential component of the velocity along the combustor radius. It is demonstrated that the scale effect is manifested only in the number of rotating waves. However, their velocity increases with increasing the combustor size. The velocity deficit of continuous detonation is 20–40% as compared to the velocity of the ideal Chapman–Jouguet detonation. (The smaller value corresponds to the fuel-lean mixture.)