Control of secondary flows in a turbine nozzle guide vane by endwall contouring

Computations were performed to study the three-dimensional flow and temperature distribution in a nozzle guide vane that has one flat and one contoured endwall with and without film cooling injected from two slots, one on each endwall located just upstream of the airfoil. For the contoured endwall, two locations of the same contouring were investigated, one with all contouring upstream of the airfoil and another with the contouring starting upstream of the airfoil and continuing through the airfoil passage. Results obtained show that when the contouring is all upstream of the airfoil, secondary flows on both the flat and the contoured endwalls are similar in magnitude. When the contouring starts upstream of the airfoil and continues through the airfoil passage, secondary flows on the contoured endwall are markedly weaker than those on the flat endwall. With weaker secondary flows on the contoured endwall, film-cooling effectiveness there is greatly improved. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier- Stokes), and energy. Effects of turbulence were modeled by the low Reynolds number shear-stress transport k-ω model. Solutions were generated by a cell-centered, finite-volume method that uses thirdorder accurate flux-difference splitting of Roe with limiters and multigrid acceleration of a diagonalized ADI scheme with local time stepping on patched/embedded structured grids.