Claims
- 1. In a gas turbine engine including a rotatable rotor having a central axis and a row of blades with outer tips and a stationary casing with a shroud disposed in concentric relation with said rotor, an apparatus for controlling the clearance between said rotor blade tips and casing shroud, said apparatus comprising:
- (a) at least one shroud segment defining a circumferential portion of said casing shroud and being separate from and spaced radially inwardly of said casing and outwardly of at least one of said rotor blade tips;
- (b) at least one mounting structure on said stationary casing defining a passage between exterior and interior sides of said casing, said mounting structure being spaced radially outwardly from said shroud segment;
- (c) a positioning mechanism supported by said mounting structure, connected to said shroud segment, and being movable toward and away from said rotor blade tip; and
- (d) an actuating mechanism coupled to said positioning mechanism and being operable to move circumferentially relative to said rotor axis between first and second angularly displaced limit positions to cause nonrotatable, linear movement of said positioning mechanism and said shroud segment connected therewith radially relative to said rotor axis to a position between inner and outer positions which define maximum and minimum clearance between said shroud segment and said rotor blade tip;
- said actuating mechanism being in the form of an annular member having at least one slot defined therethrough extending in a transverse inclined relation to the respective directions of movement of said actuating and positioning mechanisms and having spaced opposite ends defining said first and second angularly displaced limit positions of said annular member at said slot therethrough.
- 2. The apparatus as recited in claim 1, wherein said positioning mechanism includes:
- an elongated support member mounted through said passage defined by said mounting structure for movement relative thereto and radially toward and away from said rotor axis, said support member having a longitudinal axis and opposite inner and outer end portions, said shroud segment being connected to said inner end portion of said support member at said interior side of said casing; and
- means for coupling said outer end portion of said support member at said exterior side of said casing to said actuating mechanism.
- 3. The apparatus as recited in claim 2, wherein:
- said mounting structure is a cylindrical boss formed on said casing, defining said passage, and projecting from said exterior side of said casing; and
- said support member is a cylindrical shaft mounted through said passage of said boss for slidable movement toward and away from said rotor axis relative to said boss.
- 4. In a gas turbine engine including a rotatable rotor having a central axis and a row of blades with outer tips and a stationary casing with a shroud disposed in concentric relation with said rotor, an apparatus for controlling the clearance between said rotor blade tips and casing shroud, said apparatus comprising:
- (a) at least one shroud segment defining a circumferential portion of said casing shroud and being separate from and spaced radially inwardly of said casing and outwardly of at least one of said rotor blade tips;
- (b) at least one mounting structure on said stationary casing defining a passage between exterior and interior sides of said casing, said mounting structure being spaced radially outwardly from said shroud segment;
- (c) a positioning mechanism supported by said mounting structure, connected to said shroud segment, and being movable toward and away from said rotor blade tip; and
- (d) an actuating mechanism coupled to said positioning mechanism and being operable to move circumferentially relative to said rotor axis between first and second angularly displaced limit positions to cause nonrotatable, linear movement of said positioning mechanism and said shroud segment connected therewith radially relative to said rotor axis to a position between inner and outer positions which define maximum and minimum clearance between said shroud segment and said rotor blade tips, said actuating mechanism being in the form of an annular member having at least one slot extending in a transverse inclined relation to the respective directions of movement of said actuating and positioning mechanisms and having spaced opposite ends defining said first and second angularly displaced limit positions of circumferential movement of said annular member, said positioning mechanism being coupled to said annular member at said slot therein;
- said positioning mechanism including
- (i) an elongated support member mounted through said passage defined by said mounting structure for movement relative thereto and radially toward and away from said rotor axis, said support member having a longitudinal axis and opposite inner and outer end portions, said shroud segment being connected to said inner end portion of said support member at said interior side of said casing, and
- (ii) means for coupling said outer end portion of said support member at said exterior side of said casing to said actuating mechanism.
- 5. In a gas turbine engine including a rotatable rotor having a central axis and a row of blades with outer tips and a stationary casing with a shroud disposed in concentric relation with said rotor, an apparatus for controlling the clearance between said rotor blade tips and casing shroud, said apparatus comprising:
- (a) at least one shroud segment defining a circumferential portion of said casing shroud and being separate from and spaced radially inwardly of said casing and outwardly of at least one of said rotor blade tips;
- (b) at least one mounting structure on said stationary casing defining a passage between exterior and interior sides of said casing, said mounting structure being spaced radially outwardly from said shroud segment;
- (c) a positioning mechanism supported by said mounting structure, connected to said shroud segment, and being movable toward and away from said rotor blade tip; and
- (d) an actuating mechanism coupled to said positioning mechanism and being operable to move circumferentially relative to said rotor axis between first and second angularly displaced limit positions to cause nonrotatable, linear movement of said positioning mechanism and said shroud segment connected therewith radially relative to said rotor axis to a position between inner and outer positions which define maximum and minimum clearance between said shroud segment and said rotor blade tip;
- said positioning mechanism including
- (i) an elongated support member mounted through said passage defined by said mounting structure for movement relative thereto and radially toward and away from said rotor axis, said support member having a longitudinal axis and opposite inner and outer end portions, said shroud segment being connected to said inner end portion of said support member at said interior side of said casing, and
- (ii) means for coupling said outer end portion of said support member at said exterior side of said casing to said actuating mechanism, said coupling means including a pin mounted to said outer end of said support member and within said slot of said annular member for translating circumferential movement of said annular member into linear radial movement of said support member.
- 6. The apparatus as recited in claim 5, wherein said coupling means further includes a roller bearing disposed between said pin and one of said support member or said annular member for providing rolling contact therebetween.
- 7. In a gas turbine engine including a rotatable rotor having a central axis and a row of blades with outer tips and a stationary casing with a shroud disposed in concentric relation with said rotor, an apparatus for controlling the clearance between said rotor blade tips and casing shroud, said apparatus comprising:
- (a) a plurality of shroud segments defining circumferential portions of said casing shroud and being separate from and spaced radially inwardly of said casing and outwardly from said rotor blade tips;
- (b) a plurality of mounting structures on said stationary casing defining passages between exterior and interior sides of said casing, said mounting structures being circumferentially spaced from one another about said rotor axis and spaced radially outwardly from said shroud segments;
- (c) a plurality of positioning mechanisms supported by said mounting structures, rigidly connected to said shroud segments, and being movable toward and away from said rotor axis for moving said shroud segments toward and away from said rotor blade tips; and
- (d) an actuating mechanism coupled to said positioning mechanisms and being operable to move circumferentially relative to said rotor axis between first and second angularly displaced limit positions to cause nonrotatable, linear movement of said positioning mechanisms and said shroud segments connected therewith radially relative to said rotor axis to positions between inner and outer positions which define maximum and minimum clearances between said shroud segments and said rotor blade tips;
- said actuating mechanism being in the form of an annular member having a plurality of circumferentially spaced slots defined therethrough each extending in a transverse inclined relation to the respective directions of movement of said actuating and positioning mechanisms and having spaced opposite ends defining said first and second angularly displaced limit positions of said annular member, said positioning mechanisms being coupled to said annular member at said slots therethrough.
- 8. The apparatus as recited in claim 7, wherein each of said positioning mechanisms includes:
- an elongated suport member mounted through said passage defined by one of said mounting structures for movement relative thereto and radially toward and away from said rotor axis, said support member having a longitudinal axis and opposite inner and outer end portions, one of said shroud segments being rigidly connected to said inner end portion of said support member at said interior side of said casing; and
- means for coupling said outer end portion of said support member at said exterior side of said casing to said actuating mechanism.
- 9. The apparatus as recited in claim 8, wherein:
- each of said mounting structures is a cylindrical boss formed on said casing, defining said passage, and projecting from said exterior side of said casing; and
- each of said support members is a cylindrical shaft mounted through said passage of one of said bosses for slidable movement toward and away from said rotor axis relative to said boss.
- 10. In a gas turbine engine including a rotatable rotor having a central axis and a row of blades with outer tips and a stationary casing with a shroud disposed in concentric relation with said rotor, an apparatus for controlling the clearance between said rotor blade tips and casing shroud, said apparatus comprising:
- (a) a plurality of shroud segments defining circumferential portions of said casing shroud and being separate from and spaced radially inwardly of said casing and outwardly from said rotor blade tips;
- (b) a plurality of mounting structures on said stationary casing defining passages between exterior and interior sides of said casing, said mounting structures being circumferentially spaced from one another about said rotor axis and spaced radially outwardly from said shroud segments;
- (c) a plurality of positioning mechanisms supported by said mounting structures, rigidly connected to said shroud segments, and being movable toward and away from said rotor axis for moving said shroud segments toward and away from said rotor blade tips; and
- (d) an actuating mechanism coupled to said positioning mechanisms and being operable to move circumferentially relative to said rotor axis between first and second angularly displaced limit positions to cause nonrotatable, linear movement of said positioning mechanisms and said shroud segments connected therewith radially relative to said rotor axis to positions between inner and outer positions which define maximum and minimum clearances between said shroud segments and said rotor blade tips, said actuating mechanism being in the form of an annular member having a plurality of circumferentially spaced slots defined therethrough each extending in a transverse inclined relation to the respective directions of movement of said actuating and positioning mechanisms and having spaced opposite ends defining said first and second angularly displaced limit positions of said annular member, said positioning mechanisms being coupled to said annular member at said slots therethrough;
- each of said positioning mechanisms including
- (i) an elongated support member mounted through said passage defined by one of said mounting structures for movement relative thereto and radially toward and away from said rotor axis, said support member having a longitudinal axis and opposite inner and outer end portions, one of said shroud segments being rigidly connected to said inner end portion of said support member at said interior side of said casing; and
- (ii) means for coupling said outer end portion of said support member at said exterior side of said casing to said actuating mechanism.
- 11. The apparatus as recited in claim 10, wherein said means for coupling each of said support members to said actuating mechanism includes a pin mounted to said outer end of said support member and within one of said slots of said annular member for translating circumferential movement of said annular member into linear radial movement of said support members.
- 12. The apparatus as recited in claim 11, wherein said coupling means further includes a roller bearing disposed between said pin and one of said support member or said annular member for providing rolling contact therebetween.
CROSS-REFERENCE TO RELATED APPLICATIONS
Reference is hereby made to the following copending U. S. Pat. Applications dealing with related subject matter and assigned to the assignee of the present invention:
b 1. Field of the Invention
The present invention relates generally to gas turbine engines and, more particularly, to an apparatus for controlling clearance between adjacent rotating and non-rotating components of a gas turbine engine.
2. Description of the Prior Art
The efficiency of a gas turbine engine is dependent upon many factors, one of which is the radial clearance between adjacent rotating and non-rotating components, such as, the rotor blade tips and the casing shroud surrounding the outer tips of the rotor blades. If the clearance is too large, an unacceptable degree of gas leakage will occur with a resultant loss in efficiency. If the clearance is too small, there is a risk that under certain conditions contact will occur between the rotating and stator components with detrimental damage possibly occurring.
The potential for contact occurring is particularly acute when the engine rotational speed is changing, either increasing or decreasing, since temperature differentials across the engine frequently result in the rotating and non-rotating components radially expanding and contracting at different rates. For instance, upon engine accelerations, thermal growth of the rotor typically lags behind that of the casing. During steadystate operation, the growth of the casing ordinarily matches more closely that of the rotor. Upon engine decelerations, the casing contracts more rapidly than the rotor.
Control mechanisms, usually mechanically or thermally actuated, have been proposed in the prior art to maintain blade tip clearance substantially constant. However, none are believed to represent the optimum design for controlling clearance. Thus, a need still remains for an improved mechanism for clearance control that will improve engine performance and reduce fuel consumption.
The present invention provides a blade tip clearance control apparatus which satisfies the aforementioned needs and achieves the foregoing objectives. The blade tip clearance control apparatus employs a shroud segment positioning mechanism having components which achieve these objectives without a large increase in weight. The positioning mechanism is operable to maintain minimum rotor blade tip-shroud clearance during steady state operation. Also, the positioning mechanism is capable of adjusting quickly as an operating transient occurs for preventing excessive rubs during any transient operation of the engine, thereby improving engine performance. Further, the components of the positioning mechanism are located outside the casing for easy maintenance, and are few in number and easy to manufacture and assemble.
Accordingly, the clearance control apparatus of the present invention is provided in a gas turbine engine which includes a rotatable rotor having a central axis and a row of blades with tips and a stationary casing, with a shroud, disposed in concentric relation with the rotor. The clearance control apparatus, operable for controlling the clearance between the rotor blade tips and the casing shroud, comprises: (a) at least one shroud segment defining a circumferential portion of the casing shroud and being separate from and spaced radially inwardly of the casing and outwardly of at least one of the rotor blade tips; (b) at least one mounting structure on the stationary casing defining a passage between exterior and interior sides of the casing, the mounting structure being spaced radially outwardly from the shroud segment; (c) a positioning mechanism supported by the mounting structure, connected to the shroud segment, and being movable toward and away from the rotor axis for moving the shroud segment toward and away from the rotor blade tip; and (d) an actuating mechanism coupled to the positioning mechanism and being operable to move circumferentially relative to the rotor axis between first and second angularly displaced limit positions to cause nonrotatable, linear movement of the positioning mechanism and the shroud segment connected thereto radially relative to the rotor axis to a position between inner and outer positions which define maximum and minimum clearances between the shroud segment and rotor blade tip.
More particularly, the positioning mechanism includes an elongated support member mounted through the passage defined by the mounting structure for movement relative thereto and radially toward and away from the rotor axis. The support member has a longitudinal axis and opposite inner and outer end portions. The shroud segment is connected to the inner end portion of the support member at the interior side of the casing. The positioning mechanism also includes means for coupling the outer end portion of the support member at the exterior side of the casing to the actuating mechanism.
Further, the mounting structure is a cylindrical boss formed on the casing, defining the passage, and projecting from the exterior side of the casing. The support member is a cylindrical shaft mounted through the passage of the boss for slidable movement toward and away from the rotor axis relative to the boss. The actuating mechanism is an annular member having at least one slot extending in a transverse inclined relation to the respective directions of movement of the actuating mechanism and the shaft and having spaced opposite ends defining the first and second angularly displaced limit positions of circumferential movement of the annular member. The coupling means of the positioning mechanism is a pin mounted to the outer end of the shaft and within the slot for translating circumferential movement of the annular member into linear radial movement of the shaft.
These and other features and advantages and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
RIGHTS OF THE GOVERNMENT
The United States Government has rights in this invention pursuant to Contract No. F33615-87-C-2764 awarded by the Department of Air Force.
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 26211 |
Feb 1982 |
JPX |
Patent Grant
5035573
