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A DNS study of detonation in H 2 / O 2 mixture with variable-intensity turbulences
... These studies reveal that turbulence accelerates the consumption of fuel and oxidizer by enhancing the production of intermediate radicals. [51][52][53][54] Similarly, the primary motivation of this work is to investigate the ultimate role of turbulence in hypersonic phenomena in air and, conversely, the impact of hypersonic effects on the post-shock turbulence field. This study is inspired by the efforts of the NATO-STO AVT-352 working group on hypersonic turbulence. ...
Hypersonic flight involves a variety of complex flow phenomena that directly impact the aerothermodynamic loading of high-speed vehicles. The turbulence encountered during a typical flight trajectory influences and interacts with the shock waves on and around the surface of a vehicle and its propulsion system, affecting both aerodynamic and power plant performance. These interactions can be studied by isolating a turbulent flow convected through a normal shock, commonly referred to as the canonical shock-turbulence interaction (STI) problem. Scale-resolving computational fluid dynamics (CFD) and linear interaction analysis (LIA) have been crucial in studying this problem and formulating scaling laws that explain the observed behavior. In this work, an extensive review of the theoretical (LIA) and numerical (CFD) work on the canonical STI is presented. The majority of the work conducted to date has focused on calorically perfect gases with constant heat capacities. However, in hypersonic flows, chemical and thermal non-equilibrium effects may alter the nature of the interaction. As a result, relevant LIA and CFD studies addressing high-enthalpy phenomena are also succinctly discussed.
In detonation engines and accidental explosions, a detonation may propagate in an inhomogeneous mixture with non-uniform reactant concentration. In this study, one- and two-dimensional simulations are conducted for detonation propagation in hydrogen/oxygen/nitrogen mixtures with periodic sinusoidal or square wave distribution of the reactant concentration. The objective is to assess the properties of detonation propagation in such inhomogeneous mixtures. Specifically, detonation quenching and reinitiation, cellular structure, cell size and detonation speed deficit are investigated. It is found that there exists a critical amplitude of the periodic mixture composition distribution, above which the detonation quenches. When the amplitude is below the critical value, detonation quenching and reinitiation occur alternately. A double cellular structure consisting of substructures and a large-scale structure is found for a two-dimensional detonation propagating in inhomogeneous mixtures with a periodic reactant concentration gradient. The detonation reinitiation process and the formation of the double cellular structure are interpreted. To quantify the properties of detonation propagation in different inhomogeneous mixtures, the large cell size, critical amplitude, transition distance and detonation speed deficit are compared for hydrogen/air without and with nitrogen dilution and for periodic sine wave and square wave distributions of the reactant concentration. The large-scale cell size is found to be linearly proportional to the wavelength, and both the critical amplitude and the transition distance decrease with the wavelength. The small detonation speed deficit is shown to be due to the incomplete combustion of the reactant. This work provides helpful understanding of the features of detonation propagation in inhomogeneous mixtures.
Linear interaction analysis (LIA) is employed to investigate the interaction of reactive and nonreactive shock waves with isotropic vortical turbulence. The analysis is carried out, through Laplace-transform technique, accounting for long-time effects of vortical disturbances on the burnt-gas flow in the fast-reaction limit, where the reaction-region thickness is significantly small in comparison with the most representative turbulent length scales. Results provided by the opposite slow-reaction limit are also recollected. The reactive case is here restricted to situations where the overdriven detonation front does not exhibit self-induced oscillations nor inherent instabilities. The interaction of the planar detonation with a monochromatic pattern of perturbations is addressed first, and then a Fourier superposition for three-dimensional isotropic turbulent fields is employed to provide integral formulas for the amplification of the kinetic energy, enstrophy, and anisotropy downstream. Transitory evolution is also provided for single-frequency disturbances. In addition, further effects associated to the reaction rate, which have not been included in LIA, are studied through direct numerical simulations. The numerical computations, based on WENO-BO4-type scheme, provide spatial profiles of the turbulent structures downstream for four different conditions that include nonreacting shock waves, unstable reacting shock (sufficiently high activation energy), and stable reacting shocks for different detonation thicknesses. Effects of the propagation Mach number, chemical heat release, and burn rate are analyzed.
Comparative studies of different inflow turbulent forcing effects on detonation front dynamics and the flow statistics are conducted through direct numerical simulations of turbulence-detonation/shock interactions. Highresolution bandwidth-optimized weighted essentially nonoscillatory scheme of spatial discretization and total variation diminishing temporal integration are used to solve the three-dimensional chemically reactive Navier-Stokes equations. The turbulent inflow vertical and entropic forcing effects on the three-dimensional detonation front and cellular structures are first analyzed. The influence of the inflow forcing on the generated regular cell patterns with diamond shape is compared. The vortex behind the detonation is quite different from that behind shock waves with the same inflow fluctuations. This also results in the larger increase of velocity variances downstream of detonation than the turbulence-shock case. The similar trend can also be found for the Taylor microscales. Effects of different inflow turbulence intensities are investigated. The irregular cellular detonations under vertical inflow forcing are also analyzed.
To complement our previous analysis of interactions of large-scale turbulence with strong detonations, the corresponding theory of interactions of small-scale turbulence is presented here. Focusing most directly on the results of greatest interest, the ultimate long-time effects of high-frequency vortical and entropic disturbances on the burnt-gas flow, a normal-mode analysis is selected here, rather than the Laplace-transform approach. The interaction of the planar detonation with a monochromatic pattern of perturbations is addressed first, and then a Fourier superposition for two-dimensional and three-dimensional isotropic turbulent fields is employed to provide integral formulas for the amplification of the kinetic energy, enstrophy, and density fluctuations. Effects of the propagation Mach number and of the chemical heat release and the chemical reaction rate are identified, as well as the similarities and differences from the previous result for the thin-detonation (fast-reaction) limit.
In this paper we further explore a class of high order Total Variation Diminishing (TVD) Runge-Kutta time discretization initialized in Shu & Osher (1988), suitable for solving hyperbolic conservation laws with stable spatial discretizations. We illustrate with numerical examples that non-TVD but linearly stable Runge-Kutta time discretization can generate oscillations even for TVD spatial discretization, verifying the claim that TVD Runge-Kutta methods are important for such applications. We then explore the issue of optimal TVD Runge-Kutta methods for second, third and fourth order, and for low storage Runge-Kutta methods.
Direct numerical simulation is conducted to address the detonation–turbulence interaction in a stoichiometric hydrogen/oxygen/argon mixture. The argon dilution rate is varied so that the mixture composition is 2H 2 + O 2 + 7Ar and 2H 2 + O 2 + Ar to discuss the effects of cell regularity on the sensitivity to turbulence. Turbulent Reynolds number and turbulent Mach number are taken to be common for both mixtures. The results show that the shock and flame of detonation in both mixtures are significantly deformed into corrugated ones in the turbulent flow, producing many small unburned gas pockets. However, one-dimensional time-averaged profiles reveal the different sensitivity of the mixtures: in the highly diluted mixture (2H 2 + O 2 + 7Ar), the reaction progress is not much influenced by turbulence, whereas in the less-diluted mixture (2H 2 + O 2 + Ar), the reaction takes place more rapidly with turbulence. Analysis of the properties of turbulence and turbulent fluctuations in the detonations clarifies that the direct contribution of turbulence to the flame front is weaker; there is no clear correlation between the heat release and the curvature of the flame. On the other hand, a broader Mach number distribution just upstream of the shock front creates more hot spots in the less-diluted mixture, which results in a shorter induction length. These results indicate that the main contribution of turbulence is creation of different shock strength, which could lead to different reaction rates depending on the cell regularity.
Rotating detonation engines (RDEs), which are hoped to achieve significant performance improvements in propulsion systems, have received much attention in recent years. The annular RDE and hollow RDE are two of the major configurations of which the structure is very similar to each other. However, there has been a lack of experimental research discussing the differences in their performance. In the present study, experiments on hollow and annular RDEs are conducted. Four configurations in total are tested at ambient conditions: hollow and annular combustion chambers with two exit throat areas. The gaseous methane and gaseous oxygen are used as propellants. The results reveal that the c*-efficiency of the two hollow combustion chamber configurations is on average 0.7 and 0.79, which is lower than the 0.75 and 0.84 of annular chambers. However, it is exhibited that the hollow RDE can ensure high detonation efficiency at a lower injection pressure ratio. From this perspective, the hollow RDE can be considered a more promising configuration for practical application because it provides a new approach to reducing injection pressure loss. In addition, the analysis of nozzle indicates that the Laval nozzles overperform the aerospike nozzles, which goes against previous studies. The mechanism that accounts for this phenomenon needs further investigation.
View Video Presentation: https://doi.org/10.2514/6.2022-0231.vid A joint project team of Nagoya University, Keio University, Muroran Institute of Technology, and Institute of Space and Astronautical Science at Japan Aerospace Exploration Agency developed Detonation Engine System (DES) toward an in-space flight demonstration on a sounding rocket S-520-31. The flight experiment was conducted and a detonation engine system (DES), which was equipped with an rotating detonation engine (RDE) and a pulse detonation engine (PDE), was launched at 5:30 a.m. (Japan standard time) on July 27, 2021, from the Uchinoura Space Center (USC) in Kagoshima, Japan. All of the operations of RDE and PDE were conducted above 100 km in altitude as it was planned. The RDE generated average thrust of 518 N in the direction of movement. In addition, the angular velocity around the axis of the movement of DES during the RDE operation was changed and the torque by the rotating detonation was confirmed. The PDE operation despined the rocket and the change in the angular velocity in the direction of the movement of DES for three runs were 23.2, 23.5 and 23.5 deg/s, respectively.
View Video Presentation: https://doi.org/10.2514/6.2022-0229.vid A research group at Nagoya University, in collaboration with Keio University, the Muroran Institute of Technology, and Institute of Space and Astronautical Science at the Japan Aerospace Exploration Agency (ISAS/JAXA), has successfully demonstrated world’s first operation of Detonation Engine System (DES) in space using the sounding rocket S-520-31, which lifted off from the JAXA Uchinoura Space Center, Japan, at 5:30 a.m. (Japan Standard Time) on July 27, 2021. The DES was equipped with two different types of detonation rocket engines, namely a rotating detonation engine (RDE) and a pulse detonation engine (PDE), which generated 500-N-class axial thrust and 1-Nm-class rolling torque, respectively. The RDE and PDE were tested in space during the ballistic flight of the rocket. In this manuscript, the system-level design of the DES was disclosed. Key point are as follows: the DES consists of an RDE and a PDE, and propellant storage/feed, avionics, instrumentation, and structure subsystems; the overall dimensions are 480 mm in the diameter x 1810 mm in the length. The dry mass was 175 kg, while gross (wet) mass was 181 kg including propellant and pneumatic gases. Commercial off-the-shelf (COTS) components are widely utilized after careful evaluation and testing, and with redundant architecture.
View Video Presentation: https://doi.org/10.2514/6.2022-0232.vid To create a new flyable propulsion system, Detonation Engine System (DES) has developed which can be stowed in the sounding rocket S-520-31. This paper focused on the first flight demonstration of RDE in space environment, which is integrated into DES, using S-520-31. The flight result was compared with the ground test data to validate its performance. In the flight experiment, the stable combustion of the RDE with aerospike nozzle was observed by onboard digital and analog cameras. With time-averaged mass flow of 182 ± 11 g/s and equivalence ratio of 1.2 ± 0.2, the RDE generated the time-averaged-thrust of 518 N, and the specific impulse achieved 290 ± 18 s, which is almost identical to the ideal value of constant pressure combustion. Due to the RDE combustion, the angular velocity increased by 5.7 deg/s for total, and the time-averaged torque during 6 s of operation was 0.26 N∙m. The high frequency sampling data identified the detonation frequency during record time as 20 kHz in the flight, which was confirmed in the DES ground test through the high frequency sampling data analysis and high-speed video imaging.
Recent accomplishments related to the performance, application, and analysis of rotating detonation engine technologies are discussed. The pioneering development of optically accessible rotating detonation engines coupled with the application of established diagnostic techniques is enabling a new research direction. In particular, OH∗ chemiluminescence images of detonations propagating through the annular channel of a rotating detonation engine are reported and appear remarkably similar to computational fluid dynamic results of rotating detonation engines published in the literature. Specific impulse measurements of rotating detonation engines and pulsed detonation engines are shown to be quantitatively similar for engines operating on hydrogen/air and ethylene/air mixtures. The encouraging results indicate that rotating detonation engines are capable of producing thrust with fuel efficiencies that are similar to those associated with pulsed detonation engines while operating on gaseous hydrocarbon fuels. A rotating detonation engine is coupled with a turboshaft engine for the first time. The performance of the rotating detonation engine gas turbine engine is similar to or better than that of the conventional gas turbine engine across a broad range of operating conditions. Realizing the advantages of pressure gain combustion in rotating detonation engines is enabling new combustion system design opportunities and supporting the development of efficient and sustainable power and propulsion technologies.
The present paper reports the results of an experimental study of detonation limits for H2/O2/Ar mixtures. Two stoichiometric mixtures (2H2 + O2 + 3Ar and 2H2 + O2) in three different diameter round tubes (D = 1.8, 4.6 and 10.9 mm) were tested. The choice of the mixture represents those considered as "stable" with a regular cellular pattern and "unstable" with an irregular cellular pattern. Detonation velocity was measured by ionization probes spaced at regular intervals along the small tubes. Consistent with previous findings, the present results show that well within the limits the detonation wave in hydrogen mixtures propagates at a steady velocity close to the theoretical Chapman-Jouguet (CJ) value. With decreasing initial pressure, the velocity deficit increases. It is found that the detonation velocity decreases with decreasing tube diameter, which is a result of the wall boundary layer effect being more prominent for smaller tubes. At the limiting pressure, the steady velocity deficit for both tested mixtures in three different diameter tubes is about 15-18%. Velocity deficits were also estimated theoretically using the Fay model. For the mixture of 2H2 + O2 + 3Ar, good agreement is found between the theoretical prediction and the experimental result of detonation velocity. For the mixture of 2H2 + O2, however, the theoretical prediction deviates from the experimental measurement. The latter thus suggests that, apart from losses due to the flow divergence caused by the boundary layer effect, instabilities are also significant for the detonation propagation and failure in 2H2 + O2 mixture. Lastly, at the limits, the value of D/λ is found to agree well with that for the onset of single-headed spin detonation. Thus, it can be concluded that the single-headed spin criterion can also be used for defining the detonation limits for hydrogen mixtures.
Behavior of detonation waves in mixtures with concentration gradients
normal to the propagation direction was studied experimentally. Mixtures
with various concentration gradients were formed by sliding the
separation plate which divides a detonation chamber from a diffusion
chamber in which a diffusion gas was initially introduced. A
stoichiometric hydrogen oxygen mixture was charged in the detonation
chamber, while oxygen or nitrogen was filled in the diffusion gas
chamber. Temporal concentration measurement was conducted by the
infrared absorption method using ethane as alternate of oxygen. Smoked
foil records show a deformation of regular diamond cells to
parallelogram ones, which well corresponds to local mixture
concentration. Schlieren photographs reveal the tilted wave front whose
angle is consistent with the deflection angle of the detonation front
obtained from trajectories of the triple point. The local deflection
angle increases with increase in local concentration gradient.
Calculation of wave trajectory based on the ray tracing theory predicts
formation of the tilted wave front from an initial planar front.
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.
This review is intended to be exhaustive and at the same time modern in its approach. While it was intended to cover all recent work on gas phase detonations the review also emphasizes the newer quantitative approach to the study of detonation structure, in which concepts from the field of reactive gas dynamics are extensively applied to all phases of detonation research. In the reviewer's opinion two major conclusions may be drawn from the recent results. These are: (1) the Chapman Jouguet criterion is at present unjustifiable (even though it is still useful for estimating global effects), and (2) virtually all extant detonation problems may be handled with the assumption that the flow is locally non-steady and contains infinitely thin unreactive shock discontinuities followed by inviscid reactive flow regimes.
A detailed kinetic mechanism has been developed to simulate the combustion of H2/O2 mixtures, over a wide range of temperatures, pressures, and equivalence ratios. Over the series of experiments numerically investigated, the temperature ranged from 298 to 2700 K, the pressure from 0.05 to 87 atm, and the equivalence ratios from 0.2 to 6.
Ignition delay times, flame speeds, and species composition data provide for a stringent test of the chemical kinetic mechanism, all of which are simulated in the current study with varying success. A sensitivity analysis was carried out to determine which reactions were dominating the H2/O2 system at particular conditions of pressure, temperature, and fuel/oxygen/diluent ratios. Overall, good agreement was observed between the model and the wide range of experiments simulated. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 603–622, 2004
Procedures to define boundary conditions for Navier-Stokes equations are discussed. A new formulation using characteristic wave relations through boundaries is derived for the Euler equations and generalized to the Navier-Stokes equations. The emphasis is on deriving boundary conditions compatible with modern non-dissipative algorithms used for direct simulations of turbulent flows. These methods have very low dispersion errors and require precise boundary conditions to avoid numerical instabilities and to control spurious wave reflections at the computational boundaries. The present formulation is an attempt to provide such conditions. Reflecting and non-reflecting boundary condition treatments are presented. Examples of practical implementations for inlet and outlet boundaries as well as slip and no-slip walls are presented. The method applies to subsonic and supersonic flows. It is compared with a reference method based on extrapolation and partial use of Riemann invariants. Test cases described include a ducted shear layer, vortices propagating through boundaries, and Poiseuille flow. Although no mathematical proof of well-posedness is given, the method uses the correct number of boundary conditions required for well-posedness of the Navier-Stokes equations and the examples reveal that it provides a significant improvement over the reference method.
In this paper, we further analyze, test, modify and improve the high order WENO (weighted essentially non-oscillatory) finite difference schemes of Liu, Osher and Chan. It was shown by Liu et al. that WENO schemes constructed from the r-th order (in L1 norm) ENO schemes are (r+1)-th order accurate. We propose a new way of measuring the smoothness of a numerical solution, emulating the idea of minimizing the total variation of the approximation, which results in a 5-th order WENO scheme for the case r = 3, instead of the 4-th order with the original smoothness measurement by Liu et al. This 5-th order WENO scheme is as fast as the 4-th order WENO scheme of Liu et al., and both schemes are about twice as fast as the 4-th order ENO schemes on vector supercomputers and as fast on serial and parallel computers. For Euler systems of gas dynamics, we suggest computing the weights from pressure and entropy instead of the characteristic values to simplify the costly characteristic procedure. The resulting WENO schemes are about twice as fast as the WENO schemes using the characteristic decompositions to compute weights, and work well for problems which do not contain strong shocks or strong reflected waves. We also prove that, for conservation laws with smooth solutions, all WENO schemes are convergent. Many numerical tests, including the 1D steady state nozzle flow problem and 2D shock entropy wave interaction problem, are presented to demonstrate the remarkable capability of the WENO schemes, especially the WENO scheme using the new smoothness measurement, in resolving complicated shock and flow structures. We have also applied Yang's artificial compression method to the WENO schemes to sharpen contact discontinuities.
Dual time stepping method for chemical kinetic codes
- E Shima
- Y Morii