Patent Application
20090004012
This application relates to a cover plate for a turbine rotor disk in a gas turbine engine, wherein the cover plate has an enclosed pumping chamber for moving a cooling air from a central location to a cooling passage for delivering the air to a turbine blade.
Gas turbine engines are known, and typically include a compressor for delivering air downstream to a combustion section. The air is mixed with fuel and burned in the combustion section, and the products of combustion move downstream over turbine rotors, driving the turbine rotors to rotate. The turbine rotors typically include a rotor disk, and a plurality of circumferentially spaced removable turbine blades. Since the rotor disk and turbine blades are subject to extreme temperatures, cooling air is typically delivered to these components to cool them.
Some of the cooling air is delivered from a central location in the rotor disk radially outwardly to the interior of a disk slot in the rotor disk. The disk slot receives a root section from the turbine blade. The air then communicates into cooling air passages in the turbine blade.
To seal the cooling passages, cover plates are typically attached to the rotor disk. Cover plates that form a small gap by following the contour of the disk create a boundary layer effect that pumps cooling air from a central location to the radially outward location when the cover plate and rotor rotate. The cover plates have been formed with internal fins which increases the pumping effectiveness. However, these fins have been somewhat ineffective at locations where the rotor may bend away from the cover plate. As an example, a central web of the rotor may be thinner than radially inner and outer portions of the rotor. This may be due to a desire to reduce the weight of the rotor, or for other reasons. In the past, the cover plate has been ineffective in moving cooling air when it is spaced from this central web.
On the other hand, a cover plate that it is formed to follow the central web of the rotor, might well cause stress concentrations which would require the cover plate to be unduly large and heavy.
In the disclosed embodiment of this invention, a cover plate for a rotor disk and a gas turbine engine has a pumping chamber on an interior face, wherein the pumping chamber is enclosed between axially inner and outer walls. The enclosed chamber is associated with an axially smaller web of the rotor disk.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A gas turbine engine 10, such as a turbofan gas turbine engine, circumferentially disposed about an engine centerline 11, is shown in
A cover plate 56 is secured to the rotor disk 52. This connection may be as known in the art. As examples, a retaining ring, a bolt at the inner portion of the disk, or a clamp against the disk through various means may be used.
A cooling air supply 58 supplies cooling air to a surface between an axially downstream side of the cover plate 56 and an axially upstream face 62 of the rotor disk 52. In order to improve air pumping effectiveness, fins may be incorporated into the cover plate 56. The fins can be located on the lower portion of the cover plate 56 or inside the chamber 68 or both. Fins need not extend along the entirety of these portions or be continuous. The fin geometry shown in
A portion 59 of the cover plate may have a plurality of fins 60 which are closely spaced from the surface 62. As the rotor disk 52 and cover plate 56 are driven to rotate by the products of combustion, these fins 60 pump air radially outwardly. This portion of the illustrated embodiment is generally as known in the art.
As shown, the cover plate 56 diverges axially upstream away from the central web 64 of the rotor 52. At this portion 67 of the cover plate, an axially downstream wall 66 is spaced from the wall 67 to define an intermediate chamber 68. The chamber 68 may be provided with fins, like the radially inner portion 59 of the cover plate. Now, even though the web 64 is spaced from the cover plate, there will still be pumping through chamber 68. A downstream end 70 of the chamber 68 empties adjacent an outer face 72 of the rotor 52 and into a passage 74 leading to the disk slot which receives the turbine blade 54. As shown, the turbine blade 54 has a flow passage 100 to deliver the cooling air outwardly to its airfoil. Again, this structure is shown schematically.
By enclosing the chamber 68 along the web 64, there is still adequate pumping of the cooling air. In the prior art, since the cover plate is further spaced from the thinner web 64, adequate pumping may not have occurred.
As shown in
The cover plate can be formed by machining operations in an integral component to create the chamber 68. On the other hand, a downstream wall can be attached to a main cover plate body by methods including, but not limited to, brazing or bonding. An integral cover plate could also be cast with the chamber built into the casting. These methods do not exclude other methods of manufacturing.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
