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Department of Mechanical Engineering and
Center for Turbulence Research
Stanford University
Abstract-
Large eddy simulations (LES) of turbulent mixing
and combustion in a co-axial jet combustor have been performed. A
simplified model is used to generate swirl in the air stream, and the
effect of swirl on mixing and flame stabilization is demonstrated via
flow visualization. The dynamic procedure, in which the sub-grid scale
model coefficients are computed during the calculation rather than
prescribed, is extended to the problem of modeling the sub-grid scale
variance and dissipation rate of a conserved scalar. It is shown that
LES does a much better job of predicting scalar mixing than the
Reynolds averaged approach.
To account for the effects of heat release, the Favre-filtered Navier Stokes equations in the low Mach number limit are solved. Heat release leads to a reduction in turbulent mixing. The fast chemistry and flamelet approaches with full chemistry do not predict a lifted flame as observed in the experiment. Apparently, the model fails to predict the ignition phenomenon. Inclusion of a single-step chemical model with a progress variable shows promise.
The presentation is concluded with a brief report on the plans and progress made in the simulation of the complete combustor of a gas turbine engine being carried out as part of the ASCI program at Stanford.
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