Prediction of turbulent Prandtl number in the methane-air combustion using a second-order turbulentscalar flux model

The main objective of the present study is to estimate the turbulent Prandtl number in non-premixed combustion of methane-air. In this regard, a turbulentstream of non-premixed combustion in a stoichiometric condition, is numerically analyzed using the (Reynolds averaged Navier-Stokes) (RANS). For modeling the combustion, the Eddy Dissipation Model (EDM), Eddy Dissipation Concept (EDC) and Probability Density Function (PDF) have been applied. The k-ε Realizable model and Discreet Ordinate (DO) also was used for the turbulence modeling and radiation modeling, respectively. To the turbulent heat flux in the energy equation, second order algebraic model (GGDH and HOGGDH) with simple eddy diffusivity model has been applied. Comparing the results of the numerical model SED (with the turbulent Prandtl 0.85) and second order models with available experimental data show that applyingthe SO Models significantlyled to the modification of predicting the temperaturedistribution in the combustion chamber. Moreover the NO derived from SOmodels distribution model has a good agreement with available experimental data. Calculation of Prandtl number turbulence in the combustion chamber shows that the assumption of Prandtl number of 0.85 is far from reality and based on GGDH model, Prtin different areas varies from 0.2 to 1.3. Finally, the Prandtl number of 0.45 has been proposed for the non-premixed combustion ofmethane-air.