## 4 Predictions with Different Chemical Kinetic Mechanisms
Figure 8: Comparison of predicted and measured turbulent kinetic energy for the Sandia Flame D.  
Figure 7: Comparison of predicted and measured mean temperature for the Sandia Flame D.  
Figure 9: Comparison of predicted and measured mean axial velocity for the Sandia Flame D.  
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c} \hline \hline
**Scalar Peak and Its Location** & **Exp** & **RSM- EDC-53** & **Deviation** & **RSM- EDC-49** & **Deviation** & **RSM- EDC-32** & **Deviation** & **RSM- EDC-24** & **Deviation** & **RSM- EDC-21** & **Deviation** & **RSM- EDC-16** & **Deviation** & **PDF** & **Deviation** \\  
Mean axial velocity profiles along the axis and along the radius @\(x/d\) = 7.5, 30, or 45 are shown and compared with experiments in Figure 9 for the Sandia Flame D with different reaction mechanisms. Reasonable qualitative predictions were reached for the mean axial velocity profiles from the seven cases, while the predictions by the PDF model were a little under-predicted. Very small differences of mean axial velocity profiles, shown in Figure 9, were found from the predictions by the EDCs. The largest deviations were found downstream of the jet, as shown in Figure 9a,b close to the axis. This means the mixing between the jet and the pilot flows was over-predicted compared with the experiments, leading to the jet diffusing faster in this large temperature difference case. Composition profiles of major species from these seven cases are presented in Figures 10-14 for the mass fractions of CH4, O2, H2O, CO2, and N2, respectively. The mean CH4 composition profiles along the axis and along the radius @\(x/d\) = 7.5 and 30 are shown and compared with experiments in Figure 10 for the Sandia Flame D with different reaction mechanisms. The mean O2 composition profiles along the axis and along the radius @\(x/d\) = 7.5, 30, and 45 are shown and compared with experiments in Figure 11. The mean H2O composition profiles along the axis and along the radius @\(x/d\) = 7.5, 30, and 45 are shown and compared with experiments in Figure 12. The mean CO2 composition profiles along the axis and along the radius @\(x/d\) = 7.5, 30, and 45 are shown and compared with experiments in Figure 14. Deviations of predicted and measured values are shown in Table 5 for different combustion models with the RSM model the major species, where the largest deviation happened to the peak values of the O2 mass fraction shown in Figure 11a. The minimum O2 mass fraction profiles shown in Figure 11a were acceptable with the exception of a little shifting towards the burner. Again, all the predictions by the EDCs agreed very well with each other. Apparent differences of the profiles were found from the EDC-16 and PDF predictions. Most of the predictions of the mean composition profiles from the seven cases were a little over/under-predicted, especially the peaks. The best agreement with the experiments among the seven cases for the profiles of major species, with the exception of CH4, was reached by the PDF model. Figure 11: Comparison of predicted and measured mean O2 mass fraction profiles for the Sandia Flame D.  
Table 5.0 Comparison of predicted and measured mean CH4 mass fraction profiles for the Sandia Flame D.  
The predicted composition profiles of the reactant mass fractions of CH4 and O2, shown in Figures 10 and 11, were lower than the experiments and those of the product mass fractions of H2O and CO2 were larger (as shown in Figures 12 and 13), indicating that combustion progressed faster than that in the experiment. The CH4 composition profiles from the PDF model, shown in Figure 10, suggested a small amount of CH4 re-formation close to the axis. Due to the over-predicted mixing and diffusion of the jets, the data close to the axis were smaller than those of the experiments shown in Table 5.1 The formation of H2O by the EDCs was earlier than in the experiments, as shown in Figure 12 with quantitative agreement and a little over-predicted peak.