Fastback turbulator structure and turbine nozzle incorporating same
A heat transfer apparatus, includes a member defining a wall exposed to fluid flow in a predetermined direction of flow; and a plurality of turbulators disposed on the wall. Each turbulator includes an upright front face which generally faces the direction of flow, and a back face which defines a ramp-like shape tapering from the front face to the wall.
1. A turbine nozzle comprising:
(a) a hollow, airfoil-shaped turbine vane;
(b) an arcuate first band disposed at a first end of the turbine vane, the first band having a flowpath face adjacent the turbine vane, and an opposed back face;
(c) wherein the back face includes at least one open pocket, the at least one pocket defined in part by a bottom wall recessed from the back face, opposed ends of the bottom wall merging with the back face, where the pocket is exposed to fluid flow in a predetermined direction of flow; and
(d) a plurality of turbulators disposed on the bottom wall, each turbulator having:
(i) an upright front face which generally faces the direction of flow, and
(ii) a back face which defines a ramp-like shape tapering from the front face to the bottom wall of the pocket.
2. The turbine nozzle of claim 1 wherein the turbulators are spaced apart from each other in the direction of flow by a distance of about 8 to 10 times a peak height of the turbulator above the bottom wall.
3. The turbine nozzle of claim 1 wherein each of the back faces forms an angle of about 20 degrees or less with the bottom wall.
4. The turbine nozzle of claim 1 wherein each of the back faces forms an angle of about 7 degrees with the bottom wall.
5. The turbine nozzle of claim 1 wherein each turbulator has a peak height above the bottom wall of about 0.18 mm (0.007 in.) to about 0.64 mm (0.025 in.).
6. The turbine nozzle of claim 1 wherein each turbulator has a peak height above the bottom wall of about 0.25 mm (0.010 in.).
7. The turbine nozzle of claim 1 wherein the back face of each turbulator extends all the way to a root of the front face of a downstream turbulator.
8. The turbine nozzle of claim 1 wherein, excepting the turbulators, the bottom wall is substantially free of interior corners.
9. The turbine nozzle of claim 1 wherein an angled transition region is disposed at each of the opposed ends of the bottom wall where it intersects the back face.
10. The turbine nozzle of claim 1 wherein a radiused transition region is disposed at each of the opposed ends of the bottom wall where it intersects the back face.
11. The turbine nozzle of claim 1 wherein the bottom wall is bounded by opposed forward and aft walls extending between the bottom wall and the back face.
12. The turbine nozzle of claim 11 wherein the forward and aft walls are generally planar and parallel to each other.
13. The turbine nozzle of claim 1 further comprising an arcuate second band disposed at an opposite end of the turbine vane from the first band.
14. The turbine nozzle of claim 1 wherein a plurality of hollow, airfoil-shaped turbine vanes are disposed between the first and second bands.
15. The turbine nozzle of claim 1 wherein the bottom wall comprises a central portion disposed between end portions, each of the end portions forming a ramp between the back face and the central portion of the bottom wall.
16. The turbine nozzle of claim 15 wherein each of the end portions forms an angle of about 20 degrees or less with the back face.