ROTOR DAMPER

• US 20160298546A1
• Filed: 03/24/2016
• Published: 10/13/2016
• Est. Priority Date: 04/13/2015
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: EDWARDS, Garry Mark
• Granted Patent: US 10,443,502 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01D 5/16 for counteracting blade vibration
• CPC Class Codes: F01D 5/26 Antivibration means not restricted to blade form or construction or to blade-to-blade connections or to the use of particular materials
• CPC Class Codes: F01D 5/34 Rotor-blade aggregates of unitary construction , e.g. formed of sheet laminae; discs formed of sheet laminae F01D5/028; ceramic materials F01D5/284, composite materials F01D5/282
• CPC Class Codes: F02C 7/20 Mounting or supporting of plant; Accommodating heat expansion or creep
• CPC Class Codes: F05D 2230/60 Assembly methods
• CPC Class Codes: F05D 2240/80 Platforms for stationary or moving blades
• CPC Class Codes: F05D 2260/37 by a press fit connection
• CPC Class Codes: F05D 2260/96 Preventing, counteracting or reducing vibration or noise
• CPC Class Codes: F16F 15/14 using masses freely rotating with the system, i.e. uninvolved in transmitting driveline torque, e.g. rotative dynamic dampers compensation of inertia forces F16F15/22; weights for balancing rotating bodies F16F15/32

Abstract

A rotor stage of a gas turbine engine includes a platform from which rotor blades extend. The platform is provided with a circumferentially extending damper ring, the damper ring having an engagement surface that engages with the platform. The damper ring provides damping through slip between the engagement surface and the platform. The damper ring has a hoop stress that results in a load being provided to the platform from the engagement surface. The load can be optimized in order to provide improved damping.

Claims

1. A rotor stage of a gas turbine engine comprising a plurality of blades extending from a generally circumferentially extending platform, wherein:

a circumferentially extending damper ring that has a continuous circumferential load path is provided on the platform, the damper ring having an engagement surface that engages with the platform; and

the damper ring is in compression or tension, such that the engagement surface applies a pre-load (N) to the platform.

2. A rotor stage of a gas turbine engine according to claim 1, wherein the damper ring is provided in the form of a split ring having a first end and a second end, with an adjuster connecting the first end to the second end, the adjuster being adjustable to provide a circumferential load (H₁, H₂) to the first and second ends of the split ring.

3. A rotor stage of a gas turbine engine according to claim 2, wherein the adjuster comprises a screw thread and at least one adjusting nut that is moveable along the screw thread in order to adjust the pre-load applied to the platform.

4. A rotor stage of a gas turbine engine according to claim 2, wherein the adjuster comprises a wedge adjuster having at least two wedges that can be slid past each other so as to adjust the pre-load applied to the platform.

5. A rotor stage according to claim 2, wherein the engagement surface is a part of the split ring.

6. A rotor stage for a gas turbine engine according to claim 1, wherein the damper ring is a continuous hoop of the same material, with the compression or tension being provided through an interference fit.

7. A rotor stage for a gas turbine engine according to claim 1, wherein the contact pressure applied by the pre-loaded damper ring to the platform is in the range of from 2 MPa and 100 MPa.

8. A rotor stage for a gas turbine engine according to claim 1, wherein the engagement surface of the damper ring engages a radially inner surface of the platform, and the damper ring is in compression.

9. A rotor stage for a gas turbine engine according to claim 1, wherein the engagement surface of the damper ring engages a radially outer surface of the platform, and the damper ring is in tension.

10. A rotor stage of a gas turbine engine according to claim 1, wherein the platform is provided with a slot, and the damper ring is retained by the slot.

11. A rotor stage of a gas turbine engine according to claim 10, wherein the slot has a cross-section defined by a base and two sidewalls, the angle between the base and the sidewall being greater than 90 degrees.

12. A rotor stage of a gas turbine engine according to claim 10, wherein the slot has a cross-section defined by a base and two sidewalls, and the engagement surface of the damper ring comprises side surfaces that engage with the sidewalls of the slot.

13. A rotor stage of a gas turbine engine according to claim 1, wherein:

the damper ring has a cross-sectional shape perpendicular to the circumferential direction that has a depth (a) in the radial direction, and a neutral bending axis that is spaced (b) from the engagement surface by more than half of the depth.

17. 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 slip (s) between the engagement surface of the circumferentially extending damper ring and the platform caused by the travelling wave.

14. A method of assembling a rotor stage of a gas turbine engine comprising:

providing a plurality of blades extending from a generally circumferentially extending platform;

providing a circumferentially extending damper ring that has a continuous circumferential load path on the platform, such that an engagement surface of the damper ring engages with the platform; and

applying compression or tension to the continuous damper ring, such that the engagement surface applies a predetermined pre-load (N) to the platform.

15. A method of designing a damper ring for a rotor stage of a gas turbine engine, comprising:

providing a test apparatus having a platform and the same vibration response properties to the rotor stage;

providing a circumferentially extending damper ring that has a continuous circumferential load path to the platform, the damper ring comprising;

an engagement surface that engages with the platform; and

an adjuster that is adjustable to change the load (N) applied by the engagement surface to the platform, the method further comprising;

measuring the vibration response of the test apparatus with different loads applied to the platform from the engagement surface; and

determining the load applied to the platform from the engagement surface that results in the optimum vibration response of the test apparatus.

16. A method of manufacturing a damper ring for a rotor stage of a gas turbine engine comprising:

performing the method of claim 15 in order to determine the load to be provided by the engagement surface to the platform that results in the optimum vibration response; and

forming the damper ring with the required mechanical properties and/or size and/or shape required to provide the determined load when the damper ring is provided to the rotor stage of the gas turbine engine.