THE APPLICATION OF NEW COMBUSTION AND TURBULENCE MODELS TO H-2 AIR NONPREMIXED SUPERSONIC COMBUSTION

Finite reaction rate effects and dilatation effects are explored using an extended laminar flamelet model and turbulence models including di latation processes. For the H-2-air nonpremixed turbulent combustion e xperiment conducted by Evans et al. in a high-speed shear flow, the fl amesheet 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 dilatat ion dissipation and pressure dilatation leads to no significant improv ement of the simulation results in this relatively low Mach number tes t case. The results predicted by the laminar flamelet model dramatical ly improve the profiles of species mass fractions. This indicates that the high turbulent strain rate usually observed in high-speed flow ha s a significant influence on the turbulent combustion. The widely used assumptions, such as fast chemical reaction rate, and unity Prandtl a nd Lewis numbers, are not suitable for this high-speed turbulent flow. It is necessary to include effects of kinetic energy changes in the c alculations. Numerical results also show that this supersonic nonpremi xed turbulent combustion flow satisfies the criteria of the laminar fl amelet model.