The combustor and turbine of a gas turbine engine are directly connected, and their flow fields and performance are closely coupled. However, to reduce turn-around time and avoid numerical difficulties in the development of gas turbine engines, numerical simulations of gas turbine combustors are usually performed without turbine components attached. This decoupling approach is investigated numerically in this paper. A micro gas turbine combustor is used as a test model, and the two-phase, turbulent, reacting flow fields of the combustor with and without nozzle guide vanes (NGV) have been simulated. Complex flow phenomena such as cross-jet flows, separations, recirculation zones, conjugate heat transfers, fuel droplet heating, vaporizing and combusting etc. are observed. The flow features of axial and tangential velocities, Mach number, and static pressure at the combustor exit are substantially different between these two cases. The effect of NGV on the combustor flow field decreases as the distance away from the NGV leading edge increases. At the cross-section, one span upstream of the NGV leading edge, the distributions of flow parameters with and without NGV are almost the same. The findings suggest that for the present combustor configuration, simulations of the combustor and turbine components could be decoupled if the interfacing cross-section or combustor exit is located at one span upstream of NGV. The present study is still preliminary and the results could be configuration dependent. Further study on the combustor-turbine decoupling issue for a traditional gas turbine combustor is on the way.

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