Turbine with a shroud ring around rotor blades and method of limiting leakage of working fluid in a turbine

1 . A turbine, comprising:

a rotor comprising a shaft and rotor blades fixed to the shaft;

a shroud ring circumscribing the shaft and surrounding the rotor blades;

a stator comprising an annular shell disposed radially outside of and circumscribing the shroud ring,

an annular washer circumscribing the shaft; and

locations circumferentially apart from one another about the shaft at which the shroud ring and the annular shell are coupled to each other,

wherein the locations comprise a region of the annular shell that forms radial-extending surfaces that are spaced axially apart from one another,

wherein the shroud ring has a surface that is adjacent one of the radially-extending surfaces,

wherein the annular washer has a surface that is adjacent one of the radially-extending surfaces, and

wherein the locations are arranged to allow the shell to thermally expand and contract thereby varying a radial distance between the annular shell and the shroud ring during operation of the turbine, and to fix a relative angular position between the shroud ring and the annular shell during operation of the turbine.

2 . The turbine of claim 1 , further comprising:

a key disposed at the locations, the key extending into the annular shell and the shroud ring.

3 . The turbine of claim 1 , wherein the rotor and the stator are made of one or more metallic materials.

4 . The turbine of claim 1 , wherein the rotor and/or the stator are made of one or more materials having a high CTE.

5 . The turbine of claim 1 , wherein said shroud ring is made of or contains a metal-alloy material or a ceramic material.

6 . The turbine of claim 1 , wherein said shroud ring is made of or contains a material having a coefficient of thermal expansion lower than 10 μm/m/° C.

7 . A turbine, comprising:

a rotor comprising a shaft and rotor blades fixed to the shaft;

a shroud ring circumscribing the shaft and surrounding the rotor blades;

a stator comprising an annular shell disposed radially outside of and circumscribing the shroud ring; and

locations circumferentially apart from one another about the shaft at which the shroud ring and the annular shell are coupled to each other,

wherein each of the locations comprises:

a pair of radially-extending surfaces that are axially spaced apart from one another and offset radially so that the top of one of the radially-extending surfaces is at or below the bottom of the other of the radially-extending surfaces; and

a key residing between the surfaces and extending into the annular shell and the shroud ring,

wherein the key allows the annular shell to thermally expand and contract thereby varying a radial distance between the annular shell and the shroud ring during operation of the turbine, and

wherein the key fixes a relative axial position between the shroud ring and the annular shell during operation of the turbine.

8 . The turbine of claim 7 , wherein the rotor and the stator are made of one or more metallic materials.

9 . The turbine of claim 7 , wherein the rotor or the stator are made of one or more materials having a high CTE.

10 . The turbine of claim 7 , wherein said shroud ring comprises a metal-alloy material or a ceramic material.

11 . The turbine of claim 7 , wherein said shroud ring comprises a material having a coefficient of thermal expansion lower than 10 μm/m/° C.

12 . A method, comprising:

on a turbine comprising a rotor wheel with rotor blades and a stator comprising an annular shell circumscribing the rotor blades,

arranging a portion of a shroud ring adjacent a first radially-extending surface on the annular shell so that the shroud ring fits concentrically about the rotor wheel and between the rotor blades and the annular shell,

locating an annular washer adjacent a second radially-extending surface on the annular shell so that the annular washer fits concentrically around part of the shroud ring; and

using a key disposed between the first radially-extending surface and the second radially-extending surface to couple the annular shell to the shroud ring,

wherein the key is removeable from the shroud ring and is disposed entirely between the shroud ring and the annular shell,

wherein the key mechanically couples the shroud ring to the annular shell to allow thermal expansion and contraction of the annular shell and to fix a relative position between the shroud ring and the annular shell during operation of the turbine, and

wherein at working temperature of turbine, tip regions of the rotor blades are in proximity to an inner region of the shroud ring.

13 . The method of claim 12 , wherein the rotor blades are in contact with the inner region of the shroud ring.

14 . The method of claim 12 , further comprising steps for:

installing a plurality of keys connecting the shroud ring and the annular shell.

15 . The method of claim 12 , further comprising steps for:

arranging a layer of abradable material at an inner region of the shroud ring.

16 . The method of claim 12 , further comprising steps for:

arranging a layer of abrading material at tip regions of the rotor blades.

17 . The method of claim 12 , further comprising steps for:

arranging a layer of abradable material at an inner region of the shroud ring,

wherein at working temperatures of the turbine, the tip regions partially penetrate into the inner region of the shroud ring.

18 . The method of claim 12 , further comprising steps for:

arranging a layer of abrading material at tip regions of the rotor blades,

wherein at working temperatures of the turbine, the tip regions partially penetrate into the inner region of the shroud ring.