Numerical analyses of two existing gas turbine combustors gave predictions of idle power emissions. The calculated exit emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO) are compared to engine test data. For the first combustor, the effects of varying fuel flow on the UHC and CO emissions were investigated while liner cooling flow changes were examined in the second combustor. A fully elliptic three-dimensional computational fluid dynamics code based on pressure correction techniques was employed to model the flow field inside the combustor. Fuel injection was handled using a Lagrangian liquid droplet spray model coupled to the gas phase equations. The combustion model consists of a two-step global reaction mechanism with reaction rates computed using a modified eddy-breakup technique. The numerical algorithm employs non-orthogonal curvilinear coordinates and the standard k-e turbulence model. The results for the first combustor agree well with the test measurements. The baseline result for the second combustor shows good agreement with test data. Predicted effects of cooling flow changes agree with trends from past experience of idle power emissions.

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