A computational study of combustor dilution flow interaction with turbine vanes

Higher efficiency and greater performance in gas turbine engines can be achieved by increasing the combustion temperature to increase power output, but is limited by durability concerns for downstream hardware. In many aircraft combustors, large-scale dilution cooling flows are injected to complete combustion and mix out hot spots. However, if not properly designed, spatial and temporal non-uniformities in flow and temperature caused by the jets can propagate downstream to the first row of turbine vanes. The non-uniform thermal loading can cause damage to vanes and increase maintenance costs. Several previous studies have examined the mean and turbulent velocity and temperature profiles at the exit of a combustor, but the temporally and spatially resolved effect of dilution jets on the turbine vane surface heat transfer has not been widely studied. This work computationally modeled the flow in a non-reacting combustor simulator, in both time-average (steady Reynolds Averaged Navier Stokes, RANS) and time-dependent (Delayed Detached Eddy Simulation, DDES) analyses. The effects of various dilution hole configurations on the temperature of downstream components was studied in the time-average approach. Configurations where the dilution jets were closer to the vane resulted in significant flow non-uniformity at the turbine inlet, and large gradients in adiabatic wall temperature of the vane. Neither the steady or unsteady computational methods captured the observed behavior of the turbulent dilution jets; however, there was a significant difference between the predicted vane temperature. Refinement of the time-dependent analysis in a region around the dilution jets did not significantly change the predicted turbine inlet flowfield.