Numerical Simulation of Non-Premixed and Premixed Axial Stage Combustor at High Pressure

Axial-staged combustors represent an important concept that can be applied to reduce NOx emissions throughout a gas turbine engine. There are four main CFD models presented in this study that describe a highly turbulent jet-in-crossflow (JIC) simulation of partially premixed and non-premixed jets with a constant chamber pressure of 5 atm absolute. The equivalence ratio of the partially premixed jet was held constant at rich conditions with a �������� of 4 while the main stage varied from ��1 and ��2 of 0.575 and 0.73 with an average headend temperature of 1415K and 1545K, respectively. Chemistry was reduced by tabulation of eight main species using the equilibrium calculation of the software Chemkin. The centerline temperatures entering the JIC stage were measured experimentally and used as the starting point of a radial temperature profile that follows a parabolic trend. Comparison between the uniform and radial temperature profiles showed that the latter had a higher penetration depth into the vitiated crossflow due to a direct relationship between temperature and velocity. To capture the combustion process, Flamelet Generated Manifold (FGM) model was used. The progress variable source uses Turbulent Flame Speed Closure (TFC) to calculate flame propagation and position. There are two distinct flame positions of stability, the windward and leeward sides of the jet. The leeward flame positions for the two equivalence ratios showed that the richer condition sits closer to the jet due to the hotter equilibrium temperature; while the windward flame position is shifted upstream for the leaner case due to more availability of oxygen. The total temperature rise for ��1 = 0.575 and ��2 = 0.73 are T = 239 K and 186 K, respectively. The non-premixed simulations used a Steady Laminar Flamelet (SLF) approach with a headend equivalence ratio of �������� = 0.6 and a detailed prediction of CH4 usage, CO production, and temperature increase throughout the jet-in-crossflow domain. Methane was shown to be consumed at a high amount, at almost 90% conversion with a temperature rise of T = 149 K. The heat release is below the calculated equilibrium ΔT with the main reason pointed out that a significant amount of CH4 is only partially oxidized to CO due to limited oxygen availability with a fuel only configuration. Realizable K-Epsilon, SST K-Omega γ-Reθ, and Reynolds Stress Transport (RST) turbulence models were used and compared. RST turbulence model showed to over predict the penetration depths and dissipation of the jet in the downstream domain when compared to literature and experimental data