A computer code has been developed to simulate the turbulent combustion flowfield of an axisymmetric swirling flow in a typical combustor. Premixed fuel (methane) and air enter the combustor through the main primary inlet. Additionally, a top wall secondary annular inlet is permitted through which cooling dilution air flows. Once the geometric sizes of the domain and inlets are specified parameters of interest include the primary fuel-air ratio and aerodynamic specification of all the inflows. This includes the secondary to primary velocity ratio, primary swirl and contraction angles, and secondary swirl and upstream angles. Combustion flowfield predictions are given to illustrate the effects of these parameters on the flowfield (velocities, species concentrations, temperature and turbulence levels), and dramatic effects are illustrated via radial profiles and streamline patterns.