The flowfield downstream of a strut-based injection system in a supersonic combustion ramjet is investigated using large-eddy simulation with a new localized dynamic subgrid closure for compressible turbulent mixing. Recirculations are formed at the base of the strut in the nonreacting flow and trap some of the injected fluid. The high levels of turbulence along the underexpanded hydrogen jets and in the shear layer lead to a high level of mixing of fuel and freestream fluids. Furthermore, the shear layer unsteadiness permits efficient large-scale mixing of freestream and injected fluids. In the reacting flowfield, the flame anchoring mechanism is, however, found to depend more on a recirculation region located downstream of the injectors than on their sides. A region of reverse flow is formed that traps hot products and radicals. Intermittent convection of hot fluid toward the injector occurs and preheats the reactants.

Simulation of Turbulent Mixing Behind a Strut Injector in Supersonic Flow

In this study, Large Eddy Simulation (LES) has been used to examine supersonic flow and combustion in a model scramjet combustor. The LES model is based on an unstructured finite volume discretization, using total variational diminishing flux reconstruction, of the filtered continuity, momentum, enthalpy, and passive/reactive scalar equations, used to describe the combustion process. The configuration used is similar to the laboratory scrarmjet at the Institute for Chemical Propulsion of the German Aerospace Center (DLR) and consists of a one-sided divergent channel with a wedge-shaped flameholder at the base of which hydrogen is injected. Here, we investigate supersonic flow with hydrogen injection and supersonic flow with hydrogen injection and combustion. For the purpose of validation, the LES results are compared with experimental data for velocity and temperature at different cross-sections. In addition, qualitative comparisons are also made between predicted and measured shadowgraph images. The LES computations are capable of predicting both the non-reacting and reacting flowfields reasonably well-in particular we notice that the LES model identifies and differentiates between peculiarities of the flowfields found in the experiments. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Michael Oevermann

Papers

Numerical investigation of turbulent hydrogen combustion in a SCRAMJET using flamelet modeling