Turbine nozzle with contoured band
A turbine nozzle includes an array of turbine vanes between inner and outer bands. Each vane includes opposed pressure and suction sides extending between opposed leading and trailing edges. The vanes define a plurality of flow passages each of which is bounded between the inner band, the outer band, and adjacent first and second vanes. A surface of the inner band in each of the passages is contoured in a non-axisymmetric shape including a peak of relatively higher radial height adjoining the pressure side of the first vane adjacent its leading edge, and a trough of relatively lower radial height is disposed parallel to and spaced-away from the suction side of the second vane aft of its leading edge. The peak and trough define cooperatively define an arcuate channel extending axially along the inner band between the first and second vanes.
1. A turbine nozzle comprising an array of stationary turbine vanes disposed between an annular inner band and an annular outer band, each of the vanes including a concave pressure side and a laterally opposite convex suction side extending in chord between opposite leading and trailing edges, the vanes arranged so as to define a plurality of flow passages each of which is bounded between the inner band, the outer band, and adjacent first and second vanes;
wherein a surface of the inner band in each of the passages is contoured in a non-axisymmetric shape including a peak of relatively higher radial height adjoining the pressure side of the first vane adjacent its leading edge, and a trough of relatively lower radial height is disposed parallel to and spaced-away from the suction side of the second vane aft of its leading edge, wherein a deepest portion of the trough is spaced-away from the suction side of the second vane;
wherein the peak and trough cooperatively define an arcuate channel extending axially along the inner band between the first and second vanes; and;
wherein the peak is centered at the pressure side of each vane midway between the leading edge and a mid-chord position, and decreases in height forward, aft, and laterally therefrom and the trough is centered at the suction side near the maximum thickness of the vanes, and decreases in depth forward, aft, and laterally therefrom.
2. A turbine nozzle according to claim 1 wherein: the peak decreases in height near the leading edge of the first vane to join the trough along the suction side of the second vane; and the trough extends along the suction side of the second vane to its trailing edge.
3. A turbine nozzle according to claim 1 wherein a line defining the deepest portion of the trough is positioned about 10% to about 30% of the tangential distance from the suction side of the second vane to the pressure side of the first vane.
4. A turbine nozzle according to claim 3 wherein a line defining the deepest portion of the trough is positioned about 20% of the tangential distance from the suction side of the second vane to the pressure side of the first vane.
5. A turbine nozzle according to claim 1 wherein the surface of the inner band aft of the trailing edge of each vane is substantially free of any ridge so as to define a sharp intersection between the trailing edge of each vane at a root thereof and the surface.