Abstract
Finite reaction rate effects and dilatation effects are explored using an extended laminar flamelet model and turbulence models including dilatation processes. For the H 2-air nonpremixed turbulent combustion experiment conducted by Evans et al. in a high-speed shear flow, the flamesheet model can reasonably predict the combustion region but fails to predict the profiles of mass fractions, especially for H 2 near the jet axis and O 2 close to the jet edge. The inclusion of both dilatation dissipation and pressure dilatation leads to no significant improvement of the simulation results in this relatively low Mach number test case. The results predicted by the laminar flamelet model dramatically improve the profiles of species mass fractions. This indicates that the high turbulent strain rate usually observed in high-speed flow has a significant influence on the turbulent combustion. The widely used assumptions, such as fast chemical reaction rate, and unity Prandtl and Lewis numbers, are not suitable for this high-speed turbulent flow. It is necessary to include effects of kinetic energy changes in the calculations. Numerical results also show that this supersonic nonpremixed turbulent combustion flow satisfies the criteria of the laminar flamelet model.
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