Patent Application
20090004013
This application relates generally to a turbine blade damper-seal assembly.
Conventional gas turbine engines include a turbine assembly that has a plurality of turbine blades attached about a circumference of a turbine rotor. Each of the turbine blades is spaced a distance apart from adjacent turbine blades to accommodate movement and expansion during operation. Each blade includes a root that attaches to the rotor, a platform, and an airfoil that extends radially outwardly from the platform.
Hot gases flowing over the platform are prevented from leaking between adjacent turbine blades by a seal as components below the platform are generally not designed to operate for extended durations at the elevated temperatures of the hot gases. The seal is typically a metal sheet nested between adjacent turbine blades on an inner surface of the platform. The seal is flexible so as to conform to the inner surface of the platform and prevent the intrusion of hot gases below the platform of the turbine blade. Typically, the seal is disposed against a radially outboard inner surface of the platform of the turbine blade and is pressurized by relatively cooler high pressure air. Significant usage of the cooler high pressure air will be detrimental to engine performance and should be minimized.
In addition to the seal it is common practice to include a damper between adjacent turbine blades to dissipate potentially damaging vibrations. The damper is sized to provide sufficient mass and rigidity to dissipate vibration from the turbine blade.
Accordingly, it is desirable to provide a seal and damper assembly which achieves an effective seal of gaps between adjacent high pressure turbine blade platforms, and dampening of high pressure turbine blade platforms when fully assembled in a turbine disk.
This invention is a damper-seal assembly for a turbine blade that includes a seal nested within a damper such that both the seal and damper are disposed to provide sealing at an aft section of the blade platforms.
The damper provides dampening, and unlike traditional interplatform turbine blade dampers, also provides sealing. The damper also includes features that cause entrapment between blades and therefore avoids the conventionally required protrusions on the blade for retention in the assembled position. Minimization or elimination of such blade protrusions facilitates manufacture of a less complicated and stronger, yet less expensive blade.
The damper-seal assembly is centrifugally swung outward to seat against the blade under-platform surfaces when the engine begins to spin such that both the seal and damper remain positively seated throughout engine operation. The seal contacts the inner surfaces of the blade platforms and prevents hot core gas from entering the cavity between adjacent blades while minimizing the leakage of performance penalizing high pressure air into the hot flow path. The seal traverses the seal slot in the damper and seals the gap between adjacent blade platforms for the full axial length of the neck cavity between adjacent blades. The seal also includes a lengthwise seam that aligns with the intersection of the under-platform surfaces of the two adjacent blades along the circumferential gap between the blade platforms.
The damper provides a stiff bridge between adjacent blade platforms to cause damping. The damper is located in an axially aft most position of the blade platform and includes rear surfaces that form a seal between the adjacent surfaces of the blades to facilitate vibration-dampening performance. A lengthwise seal slot receives the seal when assembled, while an aft leg defines the rear surfaces that provide sealing between adjacent blade platform rear gussets that is conventionally either not sealed or requires a separate sheet-metal seal.
Accordingly, the damper-seal assembly of this invention achieves an effective seal of gaps between adjacent blade platforms, and dampening of blade platforms when fully assembled in a turbine disk
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently disclosed embodiment. The drawings that accompany the detailed description can be briefly described as follows:
Referring to
Referring to
The damper-seal assembly 28 is assembled within the cavity 32 of the turbine blade 12 such that both the damper 34 and the seal 30 are adjacent the inner surface 20. The damper 34 provides dampening, and unlike traditional interplatform turbine blade dampers, also provides sealing.
The rotor disk 15 includes a radial lug 36 on its outer diameter which further restricts the damper 34 from becoming dislodged to thereby at least partially align and position the damper-seal assembly 28. The damper 34 engages the radial lug 36 to further cause entrapment between blades and therefore avoid the conventionally required protrusions on the blade to retain it in the assembled position. Minimization or elimination of such blade protrusions facilitates manufacture of a less complicated, stronger and less expensive blade.
The damper-seal assembly 28 is centrifugally swung out to seat against the blade under-platform surfaces when the engine spins such that both the seal 30 and damper 34 remain seated throughout engine operation. The seal 30 contacts the inner surfaces of the blade platforms and prevents hot gas flow path air H from penetrating through the cavity between adjacent blade platforms and minimize the leakage of cooler high pressure air into the hot gas flow path. When the engine rpm increases, the centrifugal force on the seal increases against the inner surfaces of the platform to thus seal and bridge the gap between two adjacent blade platforms. One main function of the damper is to provide a stiff bridge between adjacent blade platforms to cause damping.
Referring to
The damper 34 is fabricated from a material that minimizes plastic deformation under the thermal and centrifugal loads produced during engine operation. Further, the material utilized for the damper 34 is selected to provide desired vibration dampening properties in addition to the thermal and high strength capacity. The damper 34 may be constructed of a cast nickel alloy material for example.
The damper 34 is located in an aft most position and includes features to facilitate vibration-dampening performance. The lengthwise seal slot 50 (
The damper aft seal surfaces 54 provide sealing in an area that is typically either not sealed or requires a separate sheet-metal seal in conventional seal-dampers. The damper 34 center of gravity (CG) is slightly aft of the damper longitudinal center (
The damper stiffener rib 52 provides increased stiffness to the damper 34. The damper stiffener rib 52 facilitates damping effectiveness of the blade platform.
Referring to
The seal 30 is manufactured of a relatively thin sheet of metal that is generally flexible to conform to the inner platform surface 20 and provide a desired seal against the intrusion of hot gases. The material utilized for the seal 30 is selected to withstand the pressures and temperatures associated with a specific application and to allow for some plastic deformation. The seal 30 plastically deforms responsive to the thermal and centrifugal loads to conform and fit the contours of the inner surface 20. The plastic deformation provides a desired seal against the intrusion of hot gases and minimizes leakage of cooler air. The seal 30 may be fabricated from 0.024 inch thick AMS5608 sheet-metal nickel alloy for example.
The seal 30 bridges the seal slot 50 in the damper 34 (
The seal 30 traverses the damper 34 to provide sealing forward and aft of the damper-to-blade under-platform contact surfaces. The seal 30 mid-section formed tangs 66—in the disclosed embodiment a 90 degree inward bend (FIG. 8B)—near the midsection captures the damper 34 in a centered position during engine assembly and operation.
The seal 30 contacts the inner surfaces of the blade platforms 16 and prevents gas path air from entering the cavity between adjacent blades while minimizing leakage of high pressure cooler air in the hot flow path. When the engine rpm increases the centrifugal force of the seal increases and pushes against the inner surfaces of the platform thus creating a seal that bridges the gap between two adjacent blades. The damper operates as a seal but primarily functions to provide a stiff bridge between adjacent blade platforms and cause damping. The damper aft seal surfaces 54 is designed such that these surfaces form a seal between the adjacent forward surfaces of the blade platform rear gussets.
The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The disclosed embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
