In recent years, energy consumption has been rising steadily. The vast demand of energy requires reliable resources, which at the present is supplied by fossil fuels. However, combustion of fossil fuels also causes emissions. Most of the combustion processes in the industry are turbulent since the flow field turbulence accelerates the process and as a result, increases the energy production rate. The turbulent combustion process is very complicated due to the interaction between chemical reactions and turbulence. Therefore, it is necessary to select a suitable model in terms of precision and computational cost to simulate it. In this study, the laminar flamelet model was used regarding its high accuracy and low computational cost for combustion modeling. Furthermore, the model was applied for accounting the effect of turbulence on the flow field. Laminar flamelet model requires the flamelet library to be generated in a pre-processing simulation. The flamelet library may be produced either in the physical space or in a mixture fraction space. In the present work, both methods have been used for the generation of the flamelet library. In this study, for the formation of the flamelet library in the physical space, the opposed-flow geometry has been used and the outcome is compared with the generation of flamelet library in the mixture fraction space. In order to ensure the accuracy of the applied models, an opposed-flow flame has been numerically simulated and validated. The results of the physical space were more accurate than the mixture fraction space. The flamelet libraries resulted from three different softwares; Chemkin, Fluent, and FlameMaster, are compared. Moreover, the effect of heat loss on the flamelet is accounted for in some simulations. In most previous studies, the effect of heat loss is not considered during the formation of the flamelet library. In this study, to increase the accuracy of flamelet model, the effect of heat loss is also considered during the formation of the flamelet library. In addition to the two inputs; the mixture fraction and the stoichiometric scalar dissipation rate, the enthalpy has also been considered as the third input in the generation of the flamelet library. After generating a look up table based on the flamelet library, a bluff body flame was simulated using the generated table and the simulation results are compared with the experimental data. Heat loss effect on the scalar dissipation rate was studied. The heat loss from the flame reduces the predicted temperature, and the temperature results based on this consideration are in a better agreement with the experimental data. In this study, the effect of considering differential diffusion during flamelet library generation on the results of the bluff body flame simulation is also investigated and compared with those resulted from unity Lewis number assumption. Considering the effect of differential diffusion improves the prediction results of OH mass fraction and deteriorate those of CO 2 mass fraction. Finally, the impact of scalar dissipation rate on the results of the NO concentration at unsteady flamelet library was investigated. The results showed that although temperature and major species are not scalar dissipation rate sensitive, some minor species for instance, NO is very sensitive. At scalar dissipation rates far from the equilibrium state, mass fraction of the species NO is better predicted. Keywords: Turbulent combustion, Pollutants, Laminar flamelet model, Non-adiabatic flamelet library, Differential diffusion