Flow control structures for turbomachines and methods of designing the same
Flow control devices and structures designed and configured to improve the performance of a turbomachine. Exemplary flow control devices may include various flow guiding channels, ribs, diffuser passage-width reductions, and other treatments and may be located on one or both of a shroud and hub side of a machine to redirect, guide, or otherwise influence portions of a turbomachine flow field to thereby improve the performance of the machine.
1. A radial turbomachine, comprising:
an impeller including a hub and a plurality of blades and having an exit, each of the plurality of blades having a trailing edge proximate the exit and extending in a spanwise direction between the hub and a shroud side of the blade;
a shroud adjacent said shroud sides of said blades, said shroud and said hub defining an impeller passageway having a width extending from the hub to the shroud; and
a diffuser having an inlet, a shroud side aligned with the shroud side of the blades, and a hub side aligned with the hub, the shroud side and the hub side of the diffuser defining a diffuser passageway having a width extending from the hub side to the shroud side;
wherein the diffuser includes at least one pinch region, wherein the diffuser passageway width in the at least one pinch region is less than the impeller passageway width at the impeller exit, the pinch region including a convex surface on the hub side of the diffuser passageway, the convex surface providing a reduction in the diffuser passageway width that is greater than any diffuser passageway width reduction on the shroud side of the diffuser in the pinch region.
2. A radial turbomachine according to claim 1 , wherein the hub includes a hub surface and an exit portion, the hub surface including an inward curvature in the spanwise direction in the exit portion.
3. A radial turbomachine according to claim 1 , wherein the convex surface begins adjacent the impeller exit.
4. A radial turbomachine according to claim 1 , wherein the convex surface begins upstream of the impeller blade trailing edges.
5. A radial turbomachine according to claim 4 , wherein the hub includes a cutback portion, at least one of the impeller blades extending in a meridional direction downstream of the cutback portion, wherein a beginning location of the convex surface is upstream of the trailing edges and adjacent the cutback portion.
6. A radial turbomachine according to claim 1 , wherein the pinch region is located in an inlet portion of the diffuser.
7. A radial turbomachine according to claim 1 , wherein the impeller has a meridional length and a beginning location of the pinch region is located a distance D along a centerline of the diffuser passageway downstream of the diffuser inlet, wherein D is substantially equal to or less than 200% of the meridional length.
8. A radial turbomachine according to claim 7 , wherein D is substantially equal to or less than 100% of the meridional length.
9. A radial turbomachine according to claim 7 , wherein D is substantially equal to or less than 50% of the meridional length.
10. A radial turbomachine according to claim 7 , wherein D is substantially equal to or less than 30% of the meridional length.
11. A radial turbomachine according to claim 1 , wherein the shroud side of the diffuser is substantially flat in the pinch region.
12. A radial turbomachine according to claim 1 , wherein the shroud side of the diffuser includes a concave surface in the pinch region.
13. A radial turbomachine according to claim 12 , wherein the concave surface is selected from the group consisting of a full smoke shelf, a partial smoke shelf, and a curved surface.
14. A radial turbomachine according to claim 1 , wherein the shroud side of the diffuser includes a trapped corner stall cell.
15. A radial turbomachine according to claim 1 , wherein the pinch region further includes a concave surface upstream of the convex surface on the hub side of the diffuser.
16. A radial turbomachine according to claim 1 , wherein at least one of the hub side and the shroud side of the diffuser is moveable to thereby adjust an extent of the passage width reduction in the pinch region.
17. A radial turbomachine according to claim 1 , wherein the shroud side of the diffuser includes at least one channel extending in a flow-wise direction that is designed and configured to increase a meridional velocity of the shroud side of a flow field in the radial turbomachine.
18. A radial turbomachine according to claim 1 , wherein the impeller is designed and configured to generate a flow field at the diffuser inlet having a greater meridional velocity along the hub side than along the shroud side of the diffuser, the hub side of the diffuser being a strong side and the shroud side being a weak side, further wherein the pinch region is a strong-side pinch region.
19. A radial turbomachine according to claim 1 , wherein the convex surface has a shape that is defined by at least one of a curved section or a linear section.
20. A diffuser for use with an impeller, the impeller having an exit, a hub side and a shroud side, the hub side and shroud side defining an impeller passageway having a width extending from the hub side to the shroud side, the impeller configured to generate a flow field having a greater meridional velocity along one of the hub side and the shroud side than the other one of the hub and shroud sides, the diffuser comprising:
an inlet, a shroud side configured to be aligned with the shroud side of the impeller, and a hub side configured to be aligned with the hub side of the impeller, the shroud and the hub sides of the diffuser defining a diffuser passageway having a width extending between the diffuser shroud and hub sides, wherein the one of the shroud and hub sides of the diffuser configured to have a greater meridional velocity along its corresponding side is a strong side and the other one is a weak side;
wherein the diffuser includes at least one strong-side pinch region, wherein the diffuser passageway width in the at least one strong-side pinch region is less than the impeller passageway width at the impeller exit, the strong-side pinch region including a convex surface on the strong side of the diffuser passageway, the convex surface providing a reduction in the diffuser passageway width that is greater than any diffuser passageway width reduction on the weak side of the diffuser in the strong side pinch region and wherein the strong side of the diffuser is the diffuser hub side.
21. A radial turbomachine, comprising:
an impeller including a hub and a plurality of blades and having an exit, each of the plurality of blades having a trailing edge proximate the exit and extending in a spanwise direction between the hub and a shroud side of the blade;
a shroud adjacent said shroud sides of said blades, said shroud and said hub defining a first portion of a working fluid passageway having a width; and
a diffuser including a back plate having a back surface and a front plate having a front surface, the front and back surfaces defining a second portion of the working fluid passageway, the front surface aligned with the shroud side of the blades, and the back surface aligned with the hub;
wherein the back surface includes a convex surface that defines a pinch region, the working fluid passageway width in the pinch region being less than the working fluid passageway width at a location immediately upstream of the pinch region, the convex surface providing a reduction in the working fluid passageway width that is greater than any working fluid passageway width reduction on the front surface or shroud of the working fluid passageway in the pinch region.
22. A radial turbomachine according to claim 21 , wherein the convex surface begins adjacent the impeller exit.
23. A radial turbomachine according to claim 21 , wherein the convex surface begins upstream of the impeller blade trailing edges.
24. A diffuser for use with an impeller, the impeller having a plurality of blades with trailing edges an exit, a hub side and a shroud side, the hub side and shroud side defining an impeller passageway having a width extending from the hub side to the shroud side, the impeller configured to generate a flow field having a greater meridional velocity along one of the hub side and the shroud side than the other one of the hub and shroud sides, the diffuser comprising:
an inlet, a shroud side configured to be aligned with the shroud side of the impeller, and a hub side configured to be aligned with the hub side of the impeller, the shroud and the hub sides of the diffuser defining a diffuser passageway having a width extending between the diffuser shroud and hub sides, wherein the one of the shroud and hub sides of the diffuser configured to have a greater meridional velocity along its corresponding side is a strong side and the other one is a weak side;
wherein the diffuser includes at least one strong-side pinch region, wherein the diffuser passageway width in the at least one strong-side pinch region is less than the impeller passageway width at the impeller exit, the strong-side pinch region including a convex surface on the strong side of the diffuser passageway, the convex surface providing a reduction in the diffuser passageway width that is greater than any diffuser passageway width reduction on the weak side of the diffuser in the strong side pinch region, wherein the convex surface begins upstream of the impeller blade trailing edges.
25. A diffuser according to claim 24 , wherein the strong side of the diffuser is the diffuser hub side.
26. A radial turbomachine, comprising:
an impeller including a hub and a plurality of blades and having an exit, each of the plurality of blades having a trailing edge proximate the exit and extending in a spanwise direction between the hub and a shroud side of the blade;
a shroud adjacent said shroud sides of said blades, said shroud and said hub defining a first portion of a working fluid passageway having a width; and
a diffuser including a back plate having a back surface and a front plate having a front surface, the front and back surfaces defining a second portion of the working fluid passageway, the front surface aligned with the shroud side of the blades, and the back surface aligned with the hub;
wherein the impeller is designed and configured to generate a flow field at an inlet of the diffuser having a greater meridional velocity along one of the back and front surfaces than along the other one of the back and front surfaces, the one of the front and back surfaces having the greater meridional velocity being a strong side and the other one being a weak side; and
wherein at least one of the front surface and the back surface includes a convex surface, the convex surface located on the strong side and defining a strong-side pinch region, the working fluid passageway width in the strong-side pinch region being less than the working fluid passageway width at a location immediately upstream of the strong-side pinch region, the convex surface providing a reduction in the working fluid passageway width that is greater than any working fluid passageway width reduction on the weak side of the working fluid passageway in the strong-side pinch region, wherein the convex surface begins upstream of the impeller blade trailing edges.
27. A radial turbomachine according to claim 26 , wherein the strong side of the diffuser is the back surface of the diffuser back plate.
28. A radial turbomachine according to claim 26 , wherein the back surface includes a cutback portion, at least one of the impeller blades extending in a meridional direction downstream of the cutback portion, wherein a beginning location of the convex surface is adjacent the cutback portion.
29. A radial turbomachine according to claim 26 , wherein the weak side of the diffuser is substantially flat in the strong-side pinch region.
30. A radial turbomachine according to claim 26 , wherein the weak side of the diffuser includes a concave surface in the strong-side pinch region.
31. A radial turbomachine according to claim 30 , wherein the concave surface is selected from the group consisting of a full smoke shelf, a partial smoke shelf, and a curved surface.
32. A radial turbomachine according to claim 26 , wherein the weak side of the diffuser includes a trapped corner stall cell.
33. A radial turbomachine according to claim 26 , wherein at least one of the back surface and the front surface of the diffuser is moveable to thereby adjust an extent of the passage width reduction in the strong-side pinch region.
34. A radial turbomachine according to claim 26 , wherein the weak side of the diffuser includes at least one channel extending in a flow-wise direction that is designed and configured to increase the meridional velocity of the weak side of the flow field.