Compliant Coupling for Gas Turbine Shroud Thermal Growth
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Solution Overview
Problem
Compressor or turbine rotor blade stages in gas turbine engines face misalignment and stress issues due to differing thermal growth rates between shroud and engine casing, leading to reduced efficiency and potential manufacturing costs.
Innovation Solution
A compliant coupling system using a retaining ring, biasing clips, and bumper clips that allow radial compliance, securing the shroud to the engine casing while minimizing contact stresses and accommodating thermal growth differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the shroud is rigidly coupled to the engine casing, then structural stability is improved, but thermal stress and misalignment increase due to differing thermal growth rates
Solution Approach 1:
The coupling system transitions from a static rigid connection to a dynamic compliant connection that adapts to thermal growth differences. The compliant clips allow the shroud to move radially relative to the engine casing, accommodating differential thermal expansion while maintaining structural integrity.
Solution Approach 2:
The coupling system changes the mechanical parameter of stiffness from high (rigid) to low (compliant) in the radial direction. This allows the shroud to adjust its position according to thermal conditions while maintaining axial and circumferential stability through the retaining ring structure.
2Manufacturing precision
If the shroud is rigidly coupled to the engine casing, then alignment is improved, but misalignment occurs due to differential thermal expansion
Solution Approach 1:
The coupling system enables dynamic adjustment of the shroud's radial position in response to thermal conditions. The compliant clips allow controlled movement that maintains alignment precision across varying temperature conditions, eliminating the trade-off between initial alignment and thermal adaptability.
Solution Approach 2:
The coupling system automatically compensates for thermal growth differences through the inherent compliance of the clips. The shroud self-adjusts its position relative to the engine casing based on thermal expansion, eliminating the need for active control or complex adjustment mechanisms.
3Adaptability or versatility
If compliant coupling elements are added, then thermal compliance is improved, but device complexity increases
Solution Approach 1:
The coupling system uses thin, flexible compliant clips made from elastomeric or polymeric materials. These flexible elements provide the necessary thermal compliance while maintaining a simple, lightweight structure that does not significantly increase device complexity.
Solution Approach 2:
The coupling system combines rigid components (retaining ring, engagement features) with compliant components (elastomeric or polymeric clips). This composite approach integrates both structural stability and thermal compliance within a unified system, avoiding the need for separate complex mechanisms.
4Adaptability or versatility
If the shroud is allowed radial movement, then thermal growth accommodation is improved, but radial stability decreases
Solution Approach 1:
The coupling system segments the constraints into different directions: compliant in the radial direction to accommodate thermal growth, while maintaining rigidity in axial and circumferential directions through the retaining ring and engagement features. This directional segmentation allows radial movement without compromising overall stability.
Solution Approach 2:
The coupling system dynamically adjusts its constraint characteristics based on operational conditions. During thermal expansion, the compliant clips allow radial movement while the retaining ring maintains axial and circumferential stability, providing adaptive stability that responds to thermal conditions.
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
The system maintains concentricity and reduces manufacturing costs by enabling radial compliance, minimizing stress, and improving engine performance by allowing the shroud to adjust with thermal changes without increasing the engine casing's radial height.
Implementation Method 1
a biasing spring having a second surface, the second surface generally facing the first surface, and the biasing spring adapted to exert a force toward the positioning block when compressed
Implementation Method 2
the shroud may thermally expand or grow radially at a different rate than the engine casing
Data Source
Figure 1
Figure 1A
Figure 1B
AI summary
Compliant coupling systems and methods are provided for coupling a shroud to an engine casing. The complaint coupling system includes a retaining ring adapted to be positioned adjacent to the shroud and adapted to be coupled to the engine casing. The retaining ring defines a coupling channel about a circumference of the retaining ring and at least one notch that interrupts the coupling channel. The complaint coupling system also includes a first clip received within the coupling channel. The first clip has a biasing portion that extends into a space defined by the at least one notch, and the biasing portion is adapted to contact the shroud. The complaint coupling system includes a second clip received within the coupling channel. The second clip has a bumper portion that extends into the spaced defined by the at least one notch, and the bumper portion is adapted to contact the shroud