This paper aims to study the isothermal flow field in a gas turbine combustor under different swirl conditions. The main objective is to determine the effects of primary and secondary air swirl on isothermal flow field patterns, time- mean velocities, turbulence quantities, and pressure distribution in the gas turbine combustor.
A well established computer model, STARPIC, has been applied and modified to predict the individual and combined effects of primary and secondary air swirl on the flow field in the gas turbine combustor. The primary air swirl number is varied from 0.0 to 1.224 while two strengths of secondary air swirl are considered. Predictions of streamlines, velocity profiles, turbulence energy, and pressure distribution under these primary and secondary air swirl conditions have been obtained. Results show that primary and secondary air swirl greatly affects the flow field in the gas turbine combustor. For runs with primary air swirl only, central toroidal recirculation zone appears near the inlet of the combustor, this zone becomes wider as the swirl number is increased. For runs with secondary air swirl only, the streamlines are distributed across the radial direction in the combustor starting from the point where the secondary air is introduced. in the combined primary and secondary air swirl case the recirculation zone becomes wider, suggesting that good mixing of fuel with air and increased residence time can be obtained, As a result. good combustion is realized and minimum pollutant's emission is expected, during operation. The currently predicted results of velocity profiles at different primary air swirl numbers have been compared with previous work results at the same conditions and good agreement is obtained.