Prandtl/Schmidt number effect on temperature distribution in a generic combustor

As a benchmarking of turbulence scalar transfer modeling, the effect of Prandtl/Schmidt number on the temperature field of a diffusion flame model combustor has been investigated. Some of the numerical results, obtained from the eddy dissipation combustion model with the turbulent Prandtl/Schmidt number varying from 0.25 to 0.85, are presented and compared with a comprehensive experimental database. It is found that the turbulent Prandtl/Schmidt number has significant effect on the predicted temperature field in the combustion chamber. This is also true for the temperature profile along the combustor wall. In contrast, its effect on the velocity field is insignificant in the range considered. With the optimized turbulent Prandtl/Schmidt number, both velocity and temperature fields can be reasonably and quantitatively predicted. For the present configuration and operating conditions, the optimal Prandtl/Schmidt number is 0.5, and lower than the typical used value of ∼0.7. This study suggests that the current method for scalar transfer modeling in turbulent reacting flows should be improved and new approaches should be developed.