Patent Application
20130004313
The present disclosure relates to an integrally bladed rotor (IBR), and more particularly to a damper system therefor.
Turbomachinery may include a rotor such as an integrally bladed rotor (IBR). The IBR eliminates individual blade attachments and shrouds but has reduced inherent rotor damping. Reduced damping may result in elevated vibratory responses and potentially High Cycle Fatigue. Systems which involve friction dampers may be utilized to dissipate energy and augment rotor damping.
Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:
The engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis C relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a geared architecture 48 to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 and high pressure turbine 54. A combustor 56 is arranged between the high pressure compressor 52 and the high pressure turbine 54. The inner shaft 40 and the outer shaft 50 are concentric and rotate about the engine central longitudinal axis C which is collinear with their longitudinal axes.
The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The turbines 54, 46 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.
With reference to
With reference to
The hub inner surface 72 defines a circumferential groove 78 which receives a split ring damper 80. The split ring damper 80 is generally U-shaped in cross-section with a first leg 82 and a second leg 84 interconnected by an interface 86. The split ring damper 80 may be manufactured of a steel or titanium alloy with a coefficient of friction in the range of 0.20 to 0.60. The split ring damper 80 may also be coated with a silver or other coating material to provide a desired coefficient of friction.
The first leg 82 is engaged with the groove 78 and the second leg 84 is adjacent to the face 68, 70 of the rotor hub 62. It should be understood that a split ring damper 80 may be mounted adjacent to either or both faces 68, 70. The second leg 84 may include a bulbed end 85 which rides upon the face 68, 70. Dependant on, for example, the sensitivity of the vibration modes, the groove 78 may be of various widths to provide a desired rim stiffness.
The interface 86 between the first leg 82 and the second leg 84 surrounds a radial lip 88 of the hub inner surface 72. A tab 90 on the split ring damper 80 engages a slot 92 on the radial lip 88 generally opposite a split 94 in the split ring damper 80 (
The second leg 84 includes a multiple of radially extending slits 96 (
An idealization of the force balance at the split ring damper 80 contact interface is schematically illustrated in
It should be noted that an optimum configuration is stiff in the circumferential direction yet light weight to ensure slip will take place. This is expressed in the well known relationship:
KΔμN
where
K=damper stiffness in the tangential direction,
Δ=deflection of damper,
μ=coefficient of friction between damper and IBR.
N=the contact force normal to the direction of damper motion.
For a single point of contact, for example, point 1, the condition for slip is K1Δ1μF1 as shown in
The amount of energy dissipated during one cycle of oscillation is the shaded area A1. For multiple points of contact undergoing large enough vibration amplitudes, slip will occur at each location contributing to the overall system damping A*, where
With reference to
With reference to
The split ring damper 80 is effective for both axial and radial modes, does not result in a significant change of rim stiffness such that the airfoil fundamental mode frequencies are not changed by more than 1 to 2%; provides multiple points of contact which capture both axial and radial deflections resulting in higher system damping; and does not clock circumferentially relative to the disk to assure the maintenance of rotor balance.
It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.
It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.
The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.
