Blade Damper Seal

1. Technical Field

The invention relates to blade dampeners and seals for use in gas turbines particularly in high performance engines for aircraft.

2. Background Art

Blade dampers for the rotors of turbine engines have been positioned between the groups of adjacent blades and serve to damp the vibration of the individual blades. The dampers have been routinely made relatively thick resulting in a very stiff design. This stiffness frequently prevents the damper from full contact with the blade platforms thereby reducing the effectiveness of the damping action. It is also desirable to use these dampers as seals to minimize leakage between adjacent platforms from within the rotor. A full contact between the damper and blade platforms is necessary to obtain the most effective sealing against air leakage.

A feature of the invention is a damper with much greater flexibility permitting it to deform under load for a better contact with the blade platforms.

Another feature is a multipiece bumper on the damper in order not to diminish the flexibility of the damper to improve its sealing action.

Another feature is the use of wear strips on the damper on the surfaces adjacent the blade platforms to assure more complete contact between the damper and the platform for effectively minimizing leakage.

According to the invention the damper extends axially of the rotor between adjacent blades and has laterally extending flanges to engage with the underside of the blade platforms. The damper has one or more short bumper elements on its outer surface to extend into a recess formed on the underside of the platforms of adjacent blades. If there is no more than one of these bumpers, they are axially spaced apart and relatively short in axial dimension in order not to diminish the damper flexibility. To minimize air leakage past the damper, the flanges on the damper which in effect form the main plate of the damper carry narrow integral wear strips for direct engagement with the blade platforms. These strips will in use wear down until there is full lengthwise contact between these strips and the associated platforms. In addition the damper has a projecting tab that closely engages the disk periphery to hold the damper radially in position and the damper length is closely matched to the axial spacing between a lug on the blade and a cover plate on the disk to retain the damper in precise axial position within the rotor.

The foregoing and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of the preferred embodiments thereof as shown in the accompanying drawing.

FIG. 1 is a transverse sectional view through the damper and associated blade.

FIG. 2 is an axial sectional view along the line 2--2 of FIG. 1.

FIG. 3 is a side elevation of the damper removed from the rotor.

FIG. 4 is a perspective view of the damper.

A rotor to which the damper is applied includes a disk 2 having slots 4 in the periphery to retain the roots 6 of blades 8 therein. Each of the blades has a stem 10 extending from the root outwardly to a platform 12 and the airfoil portion 14 of the blade extends radially outward from the platform. The under surfaces of the platform are smooth.

Adjacent blade platforms have cooperating recesses 15 on the underside of the platforms large enough to receive the projecting bumpers 16 on the damper 18. Above the recess the platforms are close to or in contact with one another, as shown. The damper is essentially a plate 20 with sufficient width circumferentially to overlie the platforms of adjacent blades and this plate carries the spaced apart bumpers in alignment with one another midway of the width of the plate. Although a plurality of bumpers are described it will be obvious that in many instances a single bumper may be adequate for retaining the damper in position.

Extending around the periphery of the plate is a wear strip 22 in a position to engage the undersides of the platforms and to prevent leakage between the platforms and the plate. This rib or wear strip is relatively thin and also relatively narrow in a circumferential direction and after several hours of operation of the rotor, the surface of this strip will wear against the blade platforms until the strip is in complete contact substantially over its entire surface with the platforms.

As will be apparent from FIG. 4 the damper is longer axially of the rotor than the circumferential dimension so that the width of the plate is hereafter intended to mean the circumferential dimension of the plate whereas the length of the plate is intended to define the axial dimension. The plate has longitudinal edges extending axially of the damper.

The spaced apart bumpers do not diminish the flexibility of the damper and the relatively thin plate makes the damper flexible enough so that it may be deformed by centrifugal force as the device operates to assure contact with the wear strip over the entire area. The bumpers are relatively small in an axial direction thereby not diminishing the ability of the damper to deform for more complete contact with the blade platforms. A relatively small number of bumpers are used in order to reduce the total effective length of the bumpers thereby assuring the desired flexibility.

The damper has an inwardly extending tab 24 that reaches nearly into contact with the periphery of the rotor and this serves to hold the damper in radial position. The damper also has a precision surface 26 adjacent one end in a position to engage a cooperating surface 28 on an inwardly projecting lug 30 on the blade to limit axial movement of the damper in one direction. Another precision surface 32 properly spaced from the surface 26 is in a position to be engaged by an end plate 34 on the rotor. This plate in cooperation with the lug on the blade defines the precise axial location of the damper within the rotor. The blades are held in axial position by the above-mentioned end plate and a cooperating end plate 36 on the other side of the rotor.

Although the invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that other various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.