Biformal platform turbine blade

1. A turbine blade comprising:

an airfoil joined to a platform along laterally opposite pressure and suction sides, with said platform having corresponding laterally opposite first and second splitline edges; and

said platform is biformally contoured in elevation to include bilaterally disposed elevated ridges and depressed troughs on opposite sides of said airfoil being complementary along said splitline edges;

wherein said airfoil extends axially in chord between opposite leading and trailing edges, and a forward ridge and a forward trough are disposed forward of the airfoil midchord, and an aft ridge and an aft trough are disposed aft of said midchord;

said forward ridge extends laterally between said pressure side and said splitline first edge;

said forward trough extends laterally between said suction side and said splitline second edge;

said aft ridge extends laterally between said suction side and said splitline second edge;

said aft trough extends laterally between said pressure side and said splitline first edge; and

wherein said aft trough joins said splitline first edge in a commonly depressed saddle rising laterally in elevation to said forward ridge on one side and to said first splitline edge on an opposite side.

2. A blade according to claim 1 wherein:

said forward ridge blends axially with said aft trough adjacent said pressure side; and

said forward trough blends axially with said aft ridge adjacent said suction side.

3. A blade according to claim 2 wherein:

said platform further comprises axially opposite forward and aft ends;

said forward ridge and trough blend in common with said platform forward end before said leading edge; and

said aft ridge and trough blend in common with said platform aft end behind said trailing edge.

4. A blade according to claim 3 wherein said forward and aft ridges have maximum heights adjacent said pressure and suction sides, respectively.

5. A blade according to claim 3 wherein said forward trough has a maximum depth spaced from said suction side, and said aft trough has a maximum depth adjacent said pressure side.

6. A blade according to claim 3 wherein said troughs are deeper than said ridges are high.

7. A row of turbine blades including at least first and second turbine blades according to claim 1 adjoining circumferentially at their respective first and second platforms wherein:

said saddle on the first platform complements said forward trough on the second platform along said splitline edges; and

said saddle has a locally depressed peak and increases in depth therefrom aft to a maximum depth in said aft trough, and forward to another maximum depth in said forward trough of the second platform.

8. A blade according to claim 1 further comprising an airfoil tip having a pressure-side first rib joined to a suction-side second rib at said leading edge and spaced transversely apart at said opposite trailing edge to define an aft outlet, and a tip baffle extends chordally between said ribs to define a first pocket along said first rib laterally open at said aft outlet, and also defining a laterally closed second pocket along-said second rib.

9. A turbine blade comprising:

an airfoil integrally joined to a platform along laterally opposite pressure and suction sides extending longitudinally in span from said platform and axially in chord between opposite leading and trailing edge; and

said platform being biformally contoured in elevation to include forward and aft elevated ridges and complementary forward and aft depressed troughs along said opposite pressure and suction sides;

wherein said forward and aft ridges are bilaterally disposed along said pressure and suction sides adjacent said leading edge and before said trailing edge, respectively; and said forward and aft troughs are bilaterally disposed along said suction and pressure sides behind said leading edge and before said trailing edge, respectively;

wherein said platform has laterally opposite first and second splitline edges along said pressure and suction sides, respectively; and said forward ridge and aft trough extend along said first splitline edge to complement said forward trough and aft ridge extending along said second splitline edge;

wherein said aft trough extends from said pressure side near said trailing edge to said splitline first edge near said leading edge to complement said forward trough along said splitline second edge; and

wherein said aft trough joins said splitline first edge in a commonly depressed saddle rising laterally in elevation to said forward ridge on one side and said first splitline edge on an opposite side.

10. A blade according to claim 9 wherein:

said forward ridge blends axially with said aft trough along said pressure side: and

said forward trough blends axially with said aft ridge along said suction side.

11. A blade according to claim 10 wherein:

said platform further comprises axially opposite forward and aft ends;

said forward ridge and trough blend in common with said platform forward end before said leading edge; and

said aft ridge and trough blend in common with said platform aft end behind said trailing edge.

12. A blade according to claim 10 wherein:

said airfoil has a hump of maximum transverse width near the midchord thereof; and

said forward and aft ridges and troughs blend axially in common at said hump.

13. A blade according to claim 10 wherein said troughs are deeper than said ridges are high.

14. A blade according to claim 10 wherein said aft ridge is higher than said forward ridge.

15. A blade according to claim 10 wherein said forward trough is deeper than said aft trough.

16. A blade according to claim 10 wherein said forward and aft ridges have maximum heights disposed similarly close to said pressure and suction sides, respectively.

17. A blade according to claim 10 wherein said forward and aft troughs have maximum depths differently spaced from said suction and pressure sides, respectively.

18. A blade according to claim 9 wherein said saddle has a locally depressed peak and increases in depth therefrom aft along said aft trough and forward to said splitline first edge.

19. A blade according to claim 9 further comprising an airfoil tip having a pressure-side first rib joined to a suction-side second rib at said leading edge and spaced transversely apart at said opposite trailing edge to define an aft outlet, and a tip baffle extends chordally between said ribs to define a first pocket along said first rib laterally open at said aft outlet, and also defining a laterally closed second pocket along-said second rib.