Rotor damper

Patent metadata

Field	Value
Publication number	US-2016298458-A1
Application number	US-201615077131-A
Country	US
Kind code	A1
Filing date	Mar 22, 2016
Priority date	Apr 13, 2015
Publication date	Oct 13, 2016
Grant date	—

Abstract

A rotor stage ( 100 ) of a gas turbine engine ( 10 ) comprises a platform ( 120 ) from which rotor blades extend. The platform is provided with a circumferentially extending damper ring ( 200 ), the damper ring having an engagement surface ( 210 ) that engages with a platform engagement surface ( 110 ) of the platform ( 120 ). The platform engagement surface ( 110 ) and the damper engagement surface ( 210 ) can move relative to each other in the radial direction. In use, the damper engagement surface ( 210 ) moves less in the radial direction than the platform engagement surface ( 110 ) in response to diametral mode excitation. This causes friction between the two surfaces, thereby dissipating energy and damping the excitation.

First claim

We claim:

1 . A rotor stage for a gas turbine engine comprising:
a plurality of blades extending from a platform, the platform extending circumferentially about an axial direction; and a circumferentially extending damper element, wherein: the platform comprises a platform engagement surface that extends in a plane that is substantially perpendicular to the axial direction; the damper element comprises a damper engagement surface that extends in a plane that is parallel to and engages with the platform engagement surface; and the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction (A), the platform being more radially deformable than the damper element under diametral mode excitation of the rotor stage.

2 . A rotor stage according to claim 1 , wherein the platform engagement surface is annular.

3 . A rotor stage according to claim 1 , wherein the damper element is a damper ring, and the damper engagement surface is annular.

4 . A rotor stage according to claim 1 , wherein the damper element has a cross-sectional shape in a plane perpendicular to the circumferential direction of the rotor stage that is stiffer about an axially extending bending axis than about a radially extending bending axis.

5 . A rotor stage according to claim 4 , wherein the dimension of the cross-section in the radial direction is greater than the dimension of the cross-section in the axial direction.

6 . A rotor stage according to claim 1 , wherein the damper element is a thin-walled annular disc.

7 . A rotor stage according to claim 1 , wherein the damper element comprises at least one axially extending stiffening rib.

8 . A rotor stage according to claim 1 , further comprising a drive assembly arranged to transfer torque to/from the platform, wherein the damper element is radially fixed to the drive assembly.

9 . A rotor stage according to claim 8 , wherein the damper element extends from a radially inner end to a radially outer end; and
the radially inner end region of the damper element is radially fixed to the drive assembly.

10 . A rotor stage according to claim 8 , wherein the drive assembly comprises a fixing hook that is engaged with a corresponding damper fixing hook to radially fix the damper element to the drive assembly.

11 . A rotor stage according to claim 8 , wherein the damper element is fixed to the drive assembly using a fixing element.

12 . A rotor stage according to claim 1 , wherein the damper engagement surface is at a radially outer end region of the damper element.

13 . A rotor stage according to claim 1 , wherein:
the platform engagement surface is part of a groove formed in a radially inner surface of the platform.

14 . A rotor stage according to claim 1 , wherein the damper element and the platform are axially biased together, thereby providing an engagement load between the damper engagement surface and the platform engagement surface.

15 . A rotor stage according to claim 1 , further comprising a biasing element that provides a force in the axial direction to the damper element to push the damper engagement surface onto the platform engagement surface.

16 . A rotor stage according to claim 1 , wherein the plurality of blades are formed integrally with the platform.

17 . A gas turbine engine comprising a rotor stage according to claim 1 .

18 . A method of damping vibrations in a rotor stage of a gas turbine engine, wherein:
the rotor stage is a rotor stage according to claim 1 ; the vibration comprises a travelling wave passing circumferentially around the circumferentially extending platform; and the damping is frictional damping generated through radial slip between the platform engagement surface and the damper engagement surface.

19 . A method of designing a rotor stage of a gas turbine engine, the rotor stage having a plurality of blades extending from a platform, the platform extending circumferentially about an axial direction and comprising a platform engagement surface that extends in a plane that is substantially perpendicular to the axial direction, the method comprising:
providing a rig having the same vibration response and platform engagement surface as the platform; providing a damper element comprising a damper engagement surface that extends in a plane that is parallel to the platform engagement surface and engages with the platform engagement surface, the rig being more radially flexible than the damper element under diametral mode excitation; providing an axial biasing force to push the damper engagement surface and platform engagement surface together; and providing diametral mode excitation to the rig and measuring the damping provided by the damper element, wherein: the method further comprises:
repeating the step of providing diametral mode excitation and measuring the damping at different axial biasing forces; and
determining, from the measured damping, the optimal axial biasing force required to provide optimal damping of the diametral mode excitation.

20 . A method of manufacturing a rotor stage of a gas turbine engine comprising:
providing a platform extending circumferentially about a axial direction, the platform having a plurality of blades extending therefrom and a platform engagement surface that extends in a plane that is substantially perpendicular to the axial direction; providing a damper element having a damper engagement surface that extends in a plane that is parallel to the platform engagement surface and engages with the platform engagement surface; and biasing the damper engagement surface and platform engagement surface together using the optimal biasing force determined using the method of claim 19 .

Assignees

• Rolls Royce Plc

Inventors

• Edwards Garry Mark

Classifications

• F05D2240/80

  Platforms for stationary or moving blades · CPC title

• F01D5/10 Primary

  Anti- vibration means {(specially adapted for radial flow machines or engines F01D5/04)} · CPC title

• F05D2260/96

  Preventing, counteracting or reducing vibration or noise · CPC title

• F01D5/30

  Fixing blades to rotors; Blade roots {; Blade spacers} · CPC title

• F01D5/16

  for counteracting blade vibration · CPC title