Patent Application
20080008574
Aspects of the present invention relate to a system and method for extending seal life and for reducing leakage flow in a turbine engine. Embodiments of the invention will be explained in connection with the potential leakage flow path between a turbine vane and the neighboring rotating structures, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in
A system according to aspects of the invention can be used in connection with an interface between rotating and stationary turbine components.
The seal can be a substantially 360 degree ring, or it can comprise a plurality of segments that collectively form a ring. In one embodiment, the seal can be a brush seal 52. While well-suited for an interface that includes a brush seal, aspects of the invention are not limited to brush seals and can be applied to an interface having any of a number of seals. For instance, the seal can be a felt metal seal, a honeycomb seal, a seal made of a flexible or compliant material, a knife edge seal, or a seal made of a non-flexible material.
According to aspects of the invention, the rotating components can be configured to minimize fluid leakage and to prolong brush seal life.
An outer peripheral surface 54 of the axial extension 46 includes a first region 56 at a first radius R1 relative to a longitudinal axis 58 of the rotor 18 and a second region 60 at a second radius R2 relative to the axis 58 of the rotor 18. The second radius R2 is larger than the first radius R1. The first and second radii R1, R2 can be sized as appropriate, depending on the engine system. In one embodiment, the difference between the first and second radii R1, R2 can be up to about 15 millimeters. In another embodiment, the difference between the first and second radii R1, R2 can be from about 3 millimeters to about 5 millimeters.
The outer peripheral surface 54 of the axial extension 46 can include a transition region 62 between the first and second regions 56, 60. The transition region 62 can have any of a number of forms. For instance, the outer peripheral surface 54 of the axial extension 46 can be flared or stepped in the transition region 62. In one embodiment, the outer peripheral surface 54 of the axial extension 46 can flare radially outward at about 25 degrees to about 40 degrees relative to the axis 58 of the rotor 18 in the transition region 62. More particularly, the outer peripheral surface 54 of the axial extension 46 can flare radially outward at about 30 degrees relative to the axis 58 of the rotor 18 in the transition region 62. In other embodiments, the transition between the first region 56 and the second region 60 can be more abrupt, such as by a single, substantially 90 degree step. Preferably, the transition region 62 is configured so that sharp edges are avoided.
As shown in
During engine operation, it may be desirable to reduce the clearance C1 so as to minimize fluid losses through the clearance C1. According to aspects of the invention, the rotating components and/or the stationary components can be selectively moved so that the interface 50 is moved into a second position in which the brush seal 52 is disposed over at least a portion of the second region 60 of the axial extension 46, as shown in
Relative movement between the stationary and rotating components can be achieved in various ways. In one embodiment, at least some of the rotating components defining the clearance can be axially moved. For example, U.S. Patent Application Publication No. 2002/0009361 A1, which is incorporated herein by reference, discloses a system for selectively axially moving a turbine engine rotor. As a result, any of the components operatively attached to the rotor (discs, axially extensions, disc cover plates, etc.) are axially moved as well.
Alternatively, at least some of the stationary components defining the clearance can be axially moved. For instance, U.S. Pat. No. 6,676,372, which is incorporated herein by reference, teaches a system in which a vane carrier can be selectively axially moved. Naturally, such axial movement causes the vanes attached to the vane carrier to also be moved in the axial direction. Yet another possibility according to aspects of the invention is for both the stationary and rotating components to be axially moved so as to bring the interface 50 to the second position. The teachings of U.S. Pat. No. 6,676,372 and U.S. Patent Application Publication No. 2002/0009361 A1 can be combined to achieve such movement.
The interface 50 can be moved into the second position upon the occurrence of one or more operational parameters. For instance, the operational parameter can be steady state engine operation, such as at base load, where all of the components that form the interface have thermally grown to their final shapes. The operational parameter can also be at any engine condition where improved performance is desired.
The interface 50 can remain in the second position for as long as desirable or until the occurrence of a second operational parameter. For example, the interface 50 can be returned to the first position when the engine is shut down or under non-standard engine operating conditions. Alternatively, the interface 50 can be returned to the first position to minimize wear of the brush seal 52.
It should be noted that aspects of the invention are not limited to embodiments in which the clearance is defined in part by the outer peripheral surface 54 of the axial extension 46. Rather, clearance can be defined between the stationary seal and any rotating component. The rotating component can be a disc, mini-disc, the rotor itself, other rotating components or any combination thereof.
It will be appreciated that the aspects of the invention can minimize the amount of contact between a seal and the neighboring rotating turbine components during engine operation. While the aspects of the invention may not completely eliminate all instances of seal rubbing, the duration and overall amount of such rubbing can be reduced. Naturally, the brush seals will wear at a much more gradual rate such that the life expectancy of the brush seals can be prolonged. The brush seals will require less maintenance and replacement over the life of the engine, thereby minimizing outages. Thus, the system and method according to aspects of the invention can yield appreciable life cycle cost reductions.
Further, aspects of the invention can maintain or improve engine performance and efficiency by actively controlling fluid leakage through the clearance. According to one analytical model, a system according to aspects of the invention can reduce the leakage flow at the interface by about 0.5 percent to about one percent of the compressor inlet flow. One engine study shows a 0.6 percent reduction in leakage flow compared to an interface that does not use brush seals.
The foregoing description is provided in the context of various possible systems for extending brush seal life and/or improving engine efficiency and performance. While especially suited for minimizing the clearance between a vane and the neighboring rotating turbine components, aspects of the invention can be applied to any and all potential leakage areas between stationary and rotating components in the turbine section. Moreover, aspects of the invention can be applied to leak paths in other portions of a turbine engine, such as in the compressor section. However, the most significant benefits of aspects of the invention can be gained in the turbine section of the engine. Thus, it will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.
