Numerical simulation of supersonic and turbulent combustion with transverse sonic fuel injection (original) (raw)
Related papers
Computational analysis of supersonic combustion with swept ramp injection using K- turbulence model
In this Paper numerical study with swept ramp injection in supersonic combustion of hydrogen has been presented. Coupled implicit scheme with finite rate chemistry model and K-ε Turbulence model have been used for modeling of supersonic combustion. The main issue in supersonic combustion is proper mixing within short burst of time. Because of the step on the top wall of the combustor, there exists an expansion fan generated just on the top wall at the entrance of the combustor, which is interacts with the oblique shock wave formed upstream of the combustor due to the shear layer deflecting into the core flow. The static pressures along the walls are normalized by the static pressure of the core flow. The present result is very promising and demonstrates that flamelet approach seems to be feasible to high-speed flows. The stagnation temperature in the combustion reaches up to 2830 k. Fluctuation in pressure and Mach number was due to shock train.
2011
The present study describes the numerical investigation of the effect of incidence shock wave interaction on mixing and combustion of transverse hydrogen injection. Therefore, the second – order implicit upwind TVD scheme in conjunction with local characteristic approach is used for the simulation of unsteady multidimensional chemical reacting flow in a generalized coordinate. The species equations and the convective fluid dynamic equations are solved in a coupled fully implicit form with the LU scheme. The numerical scheme employs BaldwinLomax algebraic turbulence model. Hydrogen and air combustion is simulated by means of a full chemical mechanism. Obtained results indicated that without incident shock wave auto ignition of the hydrogen jet occurs in high temperature airstream. Nevertheless the flame will subsequently quenched downstream of the injector. When the incident shock wave introduced upstream of the injector flameholding could not be achieved. On the other hand, the flam...
Computational analysis of supersonic combustion with swept ramp injection using K-ε turbulence model
2014
In this Paper numerical study with swept ramp injection in supersonic combustion of hydrogen has been presented. Coupled implicit scheme with finite rate chemistry model and K-ε Turbulence model have been used for modeling of supersonic combustion. The main issue in supersonic combustion is proper mixing within short burst of time. Because of the step on the top wall of the combustor, there exists an expansion fan generated just on the top wall at the entrance of the combustor, which is interacts with the oblique shock wave formed upstream of the combustor due to the shear layer deflecting into the core flow. The static pressures along the walls are normalized by the static pressure of the core flow. The present result is very promising and demonstrates that flamelet approach seems to be feasible to high-speed flows. The stagnation temperature in the combustion reaches up to 2830 k. Fluctuation in pressure and Mach number was due to shock train. © 2014 Elixir All rights reserved ART...
T RANSACTION ON C ONTROL AND M ECHANICAL S YSTEMS , V OL . 1, N O . 2,, 2012
This paper presents the supersonic combustion of hydrogen using strut injector along with two-dimensional turbulent non-premixed combustion model. The process of numerical analysis based on the implicit formulation method which is pressure based solver along with absolute velocity formulation and steady turbulent Navier-Stokes equations. The present model is based on the standard k-epsilon (two equations) with standard wall functions which is P1 radiation model. In this process, a probability density function (PDF) approach is created and this method needs solution to a high dimensional PDF transport equation. As the combustion of hydrogen fuel is injected from the strut, it is successfully used to model the turbulent reacting flow field. It is observed from the present work that, the maximum temperature occurred in the recirculation areas which are produced due to shock wave-expansion, wave-jet interaction and the fuel jet losses concentration and after passing successively through such areas, temperature decreased slightly along the axis.
Supersonic Combustion Regime: Numerical and Theoretical Study
combustion-institute.it
A three dimensional high order numerical simulations of the H2/air supersonic combustion were performed. Large Eddies Simulation showed to be a promising tool to investigate the fundamental physical phenomena involved in the flame/ turbulence interaction and to support the development of new subgrid scale turbulence and combustion models was investigated using LES simulations. The present LES of the HyShot II supersonic combustor showed that the interactions between the airstream entering the combustor and the H2 sonic jet produce a high turbulence intensity confirmed by an average vorticity of order 10 5 Hz. The interaction between the hydrogen transverse jets and the supersonic air flow leaded to the bow shock formation and, accordingly, the boundary layer separation. This separation allowed H2 to be convected upstream through the spanwise recirculation vortices created by the baroclinic effect. Once created, the vortices were tilted, stretched, compressed and expanded according to the vorticity transport equation. These vortices are the key structures responsible for the observed fast fuel air mixing. In this context, an analysis of the flame structure was conducted to propose a appropriate kinetic and chemical/turbulence model. The flame structure has been analyzed by means of the Burke and Schumann theory.
Supersonic mixing and combustion: advance in les modeling
Progress in Propulsion Physics, 2009
Mixing and combustion in supersonic reacting §ows are currently under investigation for new generation launchers and trans-atmospheric vehicles. Experimental results with hydrogen injected at Mach 2.5 in a Mach 2 airstreams showed combustion taking place just in ∼ 0.6 m: this indicates that supersonic combustion is feasible within short combustors. Large eddy numerical simulations including the subgrid scale (SGS) model, ISCM, developed speci¦cally for supersonic combustion have been done. This model takes into account the e¨ect of compressibility on reaction rates and on mixing. Numerical simulations have revealed that the §ame is unsteady: it anchors at about 15 cm from the injector, develops downstream, and lifts o¨. Periodical ignition and quenching have been investigated. Also, the combustion regime in supersonic §ows has been investigated and is reported.
The combustion process in a hydrogen fueled scramjet combustor with a rearwall-expansion cavity was investigated numerically under inflow conditions of Ma ¼2.52 with stagnation pressure P 0 ¼1.6 Mpa and stagnation temperature T 0 ¼1486 K. The numerical solver was first evaluated for supersonic reactive flows in a similar combustor configuration where experimental data is available. Wall-pressure distribution was compared with the experiments, and grid independency analysis and chemical mechanism comparison were conducted. The numerical results showed fairly good agreements with the available experimental data under supersonic combustion conditions. Then the numerical solver was used to study the effects of combustor geometry, fuel injection scheme and injection equivalence ratio on the combustion process. It was found that under the same fuel injection condition, the combustor configuration with a rearwall-expansion cavity is in favor of the supersonic combustion mode and present better ability of thermal choking prevention than the other combustor configurations. For the rearwall-expansion cavity combustor, the supersonic flow field was found to be sensitive to the injector position and injection scheme, but not highly sensitive to the injection pressure. Besides, rearwall-expansion cavity with the combined fuel injection scheme (with an injection upstream the cavity and a direct injection on the rear wall) is an optimized injection scheme during the flame stabilization process.
IACSIT International Journal of Engineering and Technology, Vol.3, No.3,, 2011
In this numerical study, supersonic combustion of hydrogen has been presented for Mach 2. The combustor has a single fuel injection parallel to the main flow from the base. Finite rate chemistry model with k- ε model and Spalart-Allmaras (S-A) Model have been used for modeling of supersonic combustion. The coupled phenomena of mixing and burning cm only be numerically modeled with the inclusion of a finite-rate chemical kinetic mechanism. The main issue in supersonic combustion is proper mixing within short burst of time. Attention is paid to the local intensity of heat release, which determines, together with the duct geometry, techniques for flame initiation and stabilization, injection techniques and quality of mixing the fuel with oxidizer, the gas-dynamic flow regime. The two-dimensional mathematical model involves the k- ε and Spalarts-Allmaras turbulence model, modified for supersonic compressibility, and a detailed kinetic mechanism of mixture combustion. The five main parameters were considered like Mach number stagnation temperature, mass fraction, stagnation pressure and velocity. The result shows the better mixing of fuel and the flame speed increases almost linearly. The stagnation temperature in the combustion reaches up to 2820K. Fluctuation in pressure and Mach number was due to shock train
Mixing and Combustion in Supersonic Reactive Flows
44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008
Supersonic combustion is a key issue in any future plan to develop supersonic combustion (SC) ramjets (SCRJ) and rocket based combined cycles (RBCC) vehicles. Past experience has shown that among the major fundamental problems to be solved in SC are the need for rapid (i.e., < 1 ms) mixing and combustion efficiency. In this context numerical simulations, in particular LES, can help in improving the understanding of these issues. Current LES subgrid models developed for subsonic and adapted to supersonic combustion do not predict well or at all experimental results such as flame anchoring, whilst past experimental results with hydrogen injected at Mach 2.5 in Mach 2 airstreams showed combustion taking place in about 2 ft. In fact, theoretical analysis shows that at high Mach number mixing and combustion are driven not only by transfer of kinetic energy by vortex stretching, as in subsonic reacting flows, but also by compressibility and baroclinic effects. Compressibility favours combustion by increasing reaction rates, as supersonic combustion occurs locally at about constant volume. Thus, when modelling mixing and combustion at small scales using LES, all these effects must be accounted before attempting to reproduce experimental results and to predict performance. To this purpose, a novel sub-grid scale (SGS) model (called henceforth ISC model, or ISCM for short) including these physical effects has been developed. This model has been validated so far by means of two experimental test cases. The first is the cross-flow injection of a sonic gaseous hydrogen jet in a Mach 2 airstream in the combustor built at the University of Tokyo; the second consists in 30° oblique injection of gaseous hydrogen in a Mach 2.5 airflow, an experiment performed in the supersonic combustion facility at NASA Langley Research Centre. For brevity, only the second test case validation is reported here. LES simulations using the well known Smagorinsky-Lilly SGS closure have been also performed for comparison. Results show that the ISCM is in better agreement with experimental data. In fact, while the Smagorinsky-Lilly model predicts neither combustion nor vortex structures, ISCM predicts flame anchoring, streamwise vorticity and temperatures close to those observed in the NASA-Langley experiments.
International Journal of Soft Computing and Engineering (IJSCE) ISSN: 2231-2307, Volume-2, Issue-2, May 2012
This paper presents the supersonic combustion of hydrogen using wedge-shaped strut injector with two-dimensional turbulent non-premixed combustion model. The present model is based on the standard k-epsilon (two equations) with standard wall functions which is P1 radiation model. In this process, a PDF (Probability Density Function) approach is created and this method needs solution to a high dimensional PDF transport equation. As the combustion of hydrogen fuel is injected from the wedge-shaped strut injector, it is successfully used to model the turbulent reacting flow field. It is observed from the present work that, the maximum temperature occurred in the recirculation areas which is produced due to shock wave-expansion and the fuel jet losses concentration and after passing successively through such areas, temperature decreased slightly along the axis. From the maximum mass fraction of OH, it is observed that there is very little amount of OH around 0.0027 were found out after combustion. By providing wedge-shaped strut injector, expansion wave is created which cause the proper mixing between the fuels and air which results in complete combustion