A fluid turbine comprises a turbine shroud, an ejector shroud, and a means for extracting energy from a fluid stream. The means for extracting energy is located in the annulus between the turbine shroud and the ejector shroud. High-energy fluid can flow through the turbine shroud to bypass the means for extracting energy. Energy is extracted from the fluid passing through the means to form a low-energy fluid stream. The high-energy fluid and the low-energy fluid can then be mixed. The turbine shroud and/or the ejector shroud has mixing lobes to increase the mixing of the two fluid streams.
1. A shrouded axial flow fluid turbine comprising:
a turbine shroud having a leading edge and a trailing edge, the turbine shroud forming an open passageway;
an ejector shroud having a leading edge and a trailing edge; and
means for extracting energy from a high-energy fluid stream;
wherein the means for extracting energy is disposed in an annulus formed between the turbine shroud and the ejector shroud; and
wherein a first plurality of mixing lobes is located along the trailing edge of either the turbine shroud or the ejector shroud such that the trailing edge has a circular crenellated shape.
2. The shrouded fluid turbine of claim 1 , wherein the leading edge of the turbine shroud is substantially coplanar with the leading edge of the ejector shroud.
3. The shrouded fluid turbine of claim 1 , wherein the turbine shroud has a radius; the annulus has a height measured from the turbine shroud to the ejector shroud; and the turbine shroud radius is equal to or greater than the annular height.
4. The shrouded fluid turbine of claim 1 , wherein the trailing edge of the turbine shroud is downstream of the trailing edge of the ejector shroud.
5. The shrouded fluid turbine of claim 1 , wherein the trailing edge of the ejector shroud is downstream of the trailing edge of the turbine shroud.
6. The shrouded fluid turbine of claim 1 , wherein the first plurality of mixing lobes is located along the trailing edge of the turbine shroud.
7. The shrouded fluid turbine of claim 6 , wherein the ejector shroud has a ring airfoil shape, with the low pressure side being on the interior of the ejector shroud.
8. The shrouded fluid turbine of claim 6 , wherein the ejector shroud further comprises a second plurality of mixing lobes such that the trailing edge of the ejector shroud has a circular crenellated shape.
9. The shrouded fluid turbine of claim 1 , wherein the first plurality of mixing lobes is located along the trailing edge of the ejector shroud.
10. The shrouded fluid turbine of claim 9 , wherein the turbine shroud has a ring airfoil shape, with the low pressure side being on the interior of the turbine shroud.
11. The shrouded fluid turbine of claim 1 , wherein the means for extracting energy comprises (i) stator vanes extending between the turbine shroud and the ejector shroud; and (ii) a rotor downstream of the stator vanes.
12. The shrouded fluid turbine of claim 11 , wherein the rotor comprises a ring having a plurality of permanent magnets arranged to form a Halbach cylinder that produces a magnetic field; and wherein the means for extracting energy further comprises at least one phase winding.
13. The shrouded fluid turbine of claim 12 , wherein the permanent magnets comprise Nd 2 Fe 14 B, SmCo 5 , or SmCo 7 .
14. The shrouded fluid turbine of claim 1 , wherein the ejector shroud is a discontinuous airfoil comprising a continuous forward ring and a plurality of shroud segments, the shroud segments being placed circumferentially around the forward ring with spaces between adjacent shroud segments, the shroud segments defining the trailing edge of the ejector shroud.
15. The shrouded fluid turbine of claim 1 , wherein the mixing lobes have full sidewalls.
16. The shrouded fluid turbine of claim 1 , wherein the mixing lobes have sidewalls with cutouts.
17. A shrouded axial flow fluid turbine comprising:
a turbine shroud having a leading edge and a trailing edge, the turbine shroud forming an open passageway;
an impeller surrounding the turbine shroud; and
an ejector shroud having a leading edge and a trailing edge, the ejector shroud surrounding the impeller;
wherein the leading edge of the turbine shroud is substantially coplanar with the leading edge of the ejector shroud; and
wherein a plurality of mixing lobes is located along the trailing edge of either the turbine shroud or the ejector shroud such that the trailing edge has a circular crenellated shape.
18. The shrouded fluid turbine of claim 17 , wherein the turbine shroud has a radius; the impeller has a height; and the turbine shroud radius is equal to or greater than the impeller height.
19. The shrouded fluid turbine of claim 17 , wherein the impeller is a permanent ring generator.
20. The shrouded fluid turbine of claim 17 , wherein the mixing lobes have full sidewalls.