Damper Groove Strain Derivative Amplifying Pockets
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional friction dampers in gas turbine engines fail to maintain relative sliding between the damper ring and rotor at high speeds due to centrifugal forces, leading to 'damper lock by friction', which reduces energy dissipation and increases rotor vibratory stress, potentially causing in-flight engine failure.
Innovation Solution
The introduction of strain derivative amplifying pockets around the damper groove increases the locking force above centrifugal forces, allowing relative sliding by varying the stiffness of the rotor circumference, ensuring a Plock/Pactual ratio of at least 1.0, achieved by adding and removing material to form circumferentially spaced-apart pockets that collectively form 10% to 90% of the total volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional friction dampers are used in gas turbine engines at high speeds, then the damper ring is subjected to centrifugal forces, but the friction force becomes sufficient to stick the damper to the rotor, preventing relative sliding and causing damper lock by friction
Solution Approach 1:
The groove cross-sectional area is varied along its length to create different local stiffness characteristics. By making the groove cross-sectional area smaller at certain locations, the local stiffness increases, which prevents the damper ring from locking to the rotor at those positions. This local modification of the groove geometry creates zones of different compliance that maintain relative sliding capability even at high rotational speeds where centrifugal forces are significant.
2Loss of energy
If the damper ring sticks to the rotor due to friction, then relative sliding is prevented, but energy dissipation by the damper is significantly reduced
Solution Approach 1:
The groove cross-sectional area is varied along its length to create different local stiffness characteristics. By making the groove cross-sectional area smaller at certain locations, the local stiffness increases, which prevents the damper ring from locking to the rotor at those positions. This local modification of the groove geometry creates zones of different compliance that maintain relative sliding capability even at high rotational speeds where centrifugal forces are significant.
3Ease of operation
If the groove cross-sectional area is reduced to prevent damper lock, then relative sliding is maintained, but the structural strength of the rotor may be compromised
Solution Approach 1:
The groove cross-sectional area is varied along its length to create different local stiffness characteristics. By making the groove cross-sectional area smaller at certain locations, the local stiffness increases, which prevents the damper ring from locking to the rotor at those positions. This local modification of the groove geometry creates zones of different compliance that maintain relative sliding capability even at high rotational speeds where centrifugal forces are significant.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution prevents damper lock by friction, maintaining effective vibration damping even at high speeds, thereby extending the service life and preventing engine failure by ensuring the damper ring can slide relative to the rotor.
Implementation Method 1
the circumferentially spaced-apart pockets providing discontinuous strain around the circumferential groove such that a Plock/Pactual ratio is at least equal to 1.0
Implementation Method 2
Pactual is a centrifugal force of the damper ring when the rotor is rotating
Implementation Method 3
Conventional dampers are typically provided in the form of a wire ring installed in a corresponding groove defined in the rotating part. Such ring dampers are subjected to centrifugal loads that create reaction forces between the damper and the mating rotor part.
Implementation Method 4
When the damper effectiveness is lost, energy dissipation by the damper is significantly reduced resulting in rotor vibratory stress increase
Data Source
AI summary
The stiffness of a rotor part is varied over its circumference to allow damper rings to effectively work in high speed applications. Circumferentially spaced-apart pockets may be defined in the rotor to create discontinuous strain to increase the force required to lock the damper ring in the groove above the centrifugal force of the ring when the rotor is rotating.