A fluid turbine comprises a turbine shroud and an optional ejector shroud. The turbine shroud and/or the ejector shroud are formed from a hard shell and a membrane. The hard shell forms a leading edge, a trailing edge, and an interior surface of the shroud. The membrane forms an exterior surface of the shroud. The resulting construction is lighter than previous turbine shrouds.
1. A fluid turbine comprising:
a shroud formed from at least one shroud segment having a leading edge, a trailing edge, an interior surface, and an exterior surface, the at least one shroud segment including a hard shell member and a membrane;
wherein the leading edge, the trailing edge, and the interior surface of the shroud segment are formed from the hard shell member, the hard shell member including:
an arcuate front edge having a first end and a second end;
a rear edge including:
a first outer edge and a second outer edge located in an outer plane;
an inner edge located in an inner plane and located between the first and second outer edges;
a first radial edge extending from a first end of the inner edge to an interior end of the first outer edge; and
a second radial edge extending from a second end of the inner edge to an interior end of the second outer edge;
an interior face extending from the front edge to the rear edge;
a front lip on the arcuate front edge transverse to the interior face; and
a rear lip on the rear edge transverse to the interior face; and
wherein the exterior surface of the shroud segment is formed from the membrane.
2. The fluid turbine of claim 1 , wherein a trailing edge of the shroud has a circular crenellated shape.
3. The fluid turbine of claim 2 , wherein a leading edge of the shroud has a circular shape.
4. The fluid turbine of claim 1 , wherein the hard shell member further comprises:
a first lateral face extending from an exterior end of the first outer edge to the first end of the front edge; and
a second lateral face extending from an exterior end of the second outer edge to the second end of the front edge.
5. The fluid turbine shroud segment of claim 1 , wherein the first outer edge and the second outer edge have a common outer radius of curvature, the inner edge has an inner radius of curvature, and the front edge has a front radius of curvature;
wherein the front radius of curvature is smaller than the outer radius of curvature; and
wherein the inner radius of curvature is smaller than the outer radius of curvature.
6. The fluid turbine of claim 1 , wherein the interior face is cambered.
7. The fluid turbine of claim 1 , wherein the hard shell member is formed from a rigid material selected from the group consisting of polymers, metals, and mixtures thereof.
8. The fluid turbine of claim 7 , wherein the rigid material is a glass reinforced polymer.
9. The fluid turbine of claim 1 , wherein the membrane comprises a film of a polyurethane-polyurea copolymer material.
10. The fluid turbine of claim 1 , wherein the membrane is reinforced with a highly crystalline polyethylene, para-aramid fibers, or a polyaramide material.
11. The fluid turbine of claim 1 , wherein the membrane comprises a plurality of layers.
12. A shrouded fluid turbine, comprising:
an impeller;
a turbine shroud surrounding the impeller, a trailing edge of the turbine shroud having a circular crenellated shape; and
an ejector shroud, an inlet end of the ejector shroud surrounding a rear end of the turbine shroud;
wherein a leading edge, the trailing edge, and an interior surface of the turbine shroud are formed from a first hard shell member, the first hard shell member including:
an arcuate front edge having a first end and a second end;
a rear edge including:
a first outer edge and a second outer edge located in an outer plane;
an inner edge located in an inner plane and located between the first and second outer edges;
a first radial edge extending from a first end of the inner edge to an interior end of the first outer edge; and
a second radial edge extending from a second end of the inner edge to an interior end of the second outer edge;
an interior face extending from the front edge to the rear edge;
a front lip on the arcuate front edge transverse to the interior face; and
a rear lip on the rear edge transverse to the interior face; and
wherein an exterior surface of the turbine shroud is formed from a first membrane.
13. The fluid turbine of claim 12 , wherein a leading edge, a trailing edge, and an interior surface of the ejector shroud are formed from a second hard shell member; and wherein an exterior surface of the ejector shroud is formed from a second membrane.
14. The fluid turbine of claim 13 , wherein the second hard shell member comprises a circular front lip, a circular rear lip, and a cambered interior face extending from the front lip to the rear lip; and
wherein the front lip and the rear lip are transverse to the interior face.
15. The fluid turbine of claim 12 , wherein the leading edge of the turbine shroud has a circular shape.