Review of combustion stabilization for hypersonic airbreathing propulsion

High-pressure jet injection into quiescent air is a challenging fluid dynamics problem in the field of aerospace engineering. Although plenty of experimental, theoretical, and numerical studies have been conducted to explore this flow, there is a dearth of literature detailing the flow evolution and instability characteristics, which is vital to the mixing enhancement design and jet noise reduction. In this paper, a density-based solver for compressible supersonic flow, astroFoam, is developed based on the OpenFOAM library. Large-eddy simulations of highly underexpanded jets with nozzle pressure ratios from 5.60 to 11.21 at a Reynolds number around 105 are carried out with a high-resolution grid. A grid-convergence study has been conducted to confirm the fidelity of the large-eddy simulation results. The large-eddy simulation results have also been validated against available literature data in terms of the time-averaged near-field properties of underexpanded jets. The turbulent transition processes are r...

Large-Eddy Simulation of Time Evolution and Instability of Highly Underexpanded Sonic Jets

Large eddy simulation of turbulent supersonic hydrogen flames with OpenFOAM

Numerical Computation of Internal and External Flows. By C. H IRSCH . Wiley. Vol. 1, Fundamentals of Numerical Discretization. 1988. 515 pp. £60. Vol. 2, Computational Methods for Inviscid and Viscous Flows. 1990, 691 pp. £65.

Local and global flame characteristics in a liquid kerosene fueled supersonic combustor equipped with a thin strut

To explore the combustion performance of nonrectangular supersonic combustors, the flow and combustion characteristics in the round and round-to-elliptic shape-transition scramjet combustors were c...

https://arc.aiaa.org/doi/pdf/10.2514/1.B36721

Comparative Study of Elliptic and Round Scramjet Combustors Fueled by RP-3

To alleviate the huge computational cost in supersonic combustor modeling and to improve the accuracy of traditional unsteady flamelet model, a zone flamelet is proposed. The main idea of zone flamelet is to divide the whole turbulent combustion field into a finite number of control zones and the chemical status in each zone is represented by a single flamelet. With proper zone division, the scattering of variables over the mixture fraction space is in controllable small, thus the representative flamelet approaches the real scalar distribution. The flamelets exchange information through flux-conserved convection when across the zone boundary, thus the flamelet variables can be transport from upstream to downstream in a flow manner. Although one additional mixture fraction space is resolved, great computational cost is still saved because the zone division in physical space is much coarser than the flow simulation mesh. A simple historical statistics approach is proposed to estimate the representative temperature, in order to further alleviate the computational cost in solving the flamelet temperature equation usually with numerous sub-models for non-adiabatic terms, e.g. radiation and wall heat loss. The zone flamelet model is then applied to model a scramjet combustor operated at a flight Mach number of 6.5 and a fuel equivalence ratio of 0.8. The performance of zone flamelet model in highly non-equilibrium supersonic combustion is compared with the traditional PaSR model.

Development of zone flamelet model for scramjet combustor modeling

Supersonic combustion in the hydrogen fueled DLR model scramjet combustor was computationally investigated by using Large Eddy Simulation (LES) combined with the latest detailed reaction mechanism for hydrogen combustion. Two computational models were employed including a two-dimensional reduced model and a three-dimensional model with periodicity in the spanwise direction. The two-dimensional model was fully validated against the three-dimensional model and the experimental data for the wall pressure measurements and the axial velocity under non-reacting flow condition. For reacting flow, the present model shows good agreement with the experimental axial velocity and static temperature measurements. Furthermore, radical evolution and heat release analysis were conducted both qualitatively and quantitatively to reveal the flame stabilization mechanism in the DLR combustor. The results show that the combustion is characterized by a three-stage combustion mode, namely induction, radical transportation and intense turbulent combustion stages. 漏 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

LES Study of Flame Stabilization in DLR Hydrogen Supersonic Combustor with Strut Injection

To explore the combustion performance of non-rectangular type supersonic combustors, the flow and combustion characteristics in round and round-to-elliptic shape-transition (RdEST) supersonic combustors under the same configurations of flight Mach number and fuel equivalence ratio were compared based on modeling results. The fuel equivalence ratio is maintained the same as 0.8, while two inlet Mach numbers of 2.5 and 3.0 both corresponding to a real flight Mach number of 6.5 are tested. To alleviate the strict requirements on wall-normal and -parallel grid spacing, Improved Delayed Detached Eddy Simulation (IDDES) is employed in this study to enable an automatic choice of RANS or LES mode depending on the local boundary layer thickness and turbulent viscosity. To reduce the computational cost of stiff kerosene oxidation chemistry, a total of four versions of skeletal mechanisms (respectively 48s/197r, 39s/153r, 28s/92r and current 19s/54r) have been developed based on the detailed 2815s/8217r Dagaut mechanism by using a highly efficient and reliable directed relation graph with error propagation and sensitivity analysis (DRGEPSA) method together with manual path analysis. Although the mechanism size has been significantly reduced, key kinetic properties such as adiabatic flame temperature, heat release rate, ignition delay and laminar flame speed all agree well with the original detailed mechanism. The static pressure along streamwise direction is compared with the measurement to validate the modeling results. Two key aspects are well predicted, i.e. the pressure ratio and the initial pressure rise location, indicating that the flame anchoring location and the distribution of wave structures inside the combustor are close to the actual situation. Then the aerodynamic fields are analyzed for the round and elliptic combustors to compare their flow, mixing and combustion related flow structures. The three-dimensional wave structures inside the elliptic combustor are firstly shown to reveal the influence of non-axisymmetric cross-section on the shock train and Mach field. Especially the time evolution of the flame region is analyzed, and dominant flame modes are extracted by the aid of proper orthogonal decomposition (POD) method. 漏 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

A comparative study of elliptical and round scramjet combustors by Improved Delayed Detached Eddy Simulation

The current work is an experimental investigation of the dependence of film-cooling effectiveness on the injection angle, mass flux and injection temperature in supersonic combustors. The mainstream Mach number is 2.5, and the coolant was injected with sonic speed. The total temperature of the mainstream is 1500K, and for the injection it ranges from 300K to 1060K. Three injection angle is respectively 0, 43, 137 . The coolant mass flux ranges from 1% to 6% of the mainstream mass flux, and the mainstream mass flux is 2.5kg/s. The results show that a smaller injection angle has a better performance in film cooling effectiveness and indicate that an increase in film-cooling effectiveness with the increase of the coolant mass flux. The influence of coolant temperature is more complex. The rising of coolant temperature reduces the film-cooling effectiveness without kerosene combustion, while has not significant difference with kerosene combustion.

Xuejun Fan

Papers

Comparative Study of Elliptic and Round Scramjet Combustors Fueled by RP-3

Development of zone flamelet model for scramjet combustor modeling

LES Study of Flame Stabilization in DLR Hydrogen Supersonic Combustor with Strut Injection

A comparative study of elliptical and round scramjet combustors by Improved Delayed Detached Eddy Simulation

Experimental Studies of Film Cooling in Supersonic Combustors