Compliant Retention System for Gas Turbine Shroud Alignment
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Solution Overview
Problem
In gas turbine engines, differences in thermal growth rates between shroud and engine components can lead to misalignment and point loading issues, affecting efficiency and lifespan, as existing coupling systems fail to adequately manage these differences.
Innovation Solution
A compliant retention system is introduced, featuring anti-rotation pins and load spreaders that distribute point loads and maintain alignment by using materials with different thermal growth rates, ensuring radial and axial compliance and reducing point loading on the shroud.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the shroud is rigidly coupled to the engine case, then alignment and tip clearance are maintained, but point loads are applied to the shroud reducing its lifespan
Solution Approach 1:
The retention system is divided into multiple discrete components: anti-rotation pins, load spreaders, and compliant members. Each component performs a specific function - the pins prevent rotation, the load spreaders distribute forces, and the compliant members accommodate thermal growth. This segmentation allows the system to maintain alignment while avoiding concentrated point loads on the shroud.
Solution Approach 2:
Load spreaders serve as intermediary elements between the anti-rotation pins and the shroud. Instead of pins directly contacting the shroud and creating point loads, the load spreaders intercept and distribute these forces across larger areas of the shroud, thereby maintaining alignment while preserving shroud lifespan.
2Duration of action of stationary object
If the shroud is coupled to accommodate thermal growth, then point loading is reduced, but misalignment between shroud and rotor blade tips occurs
Solution Approach 1:
The compliant members are designed with specific geometric parameters (curved shapes, varying thicknesses) that allow them to change their physical state in response to thermal growth. As temperature increases, these members flex and change shape to accommodate the differential thermal expansion between the shroud and engine case, maintaining alignment throughout the thermal cycle.
Solution Approach 2:
The retention system transitions from a static rigid connection to a dynamic compliant connection. The compliant members can flex and deform to accommodate thermal growth, while the anti-rotation pins and load spreaders dynamically adjust to maintain alignment. This dynamic behavior allows the system to adapt to changing thermal conditions without creating point loads or misalignment.
3Stability of the object's composition
If anti-rotation pins directly contact the shroud, then rotation is prevented, but point loads are applied reducing shroud life
Solution Approach 1:
Load spreaders are positioned between the anti-rotation pins and the shroud to intercept and distribute the contact forces. The pins still perform their anti-rotation function by preventing rotational movement, but the load spreaders ensure that the resulting forces are distributed across larger areas of the shroud rather than concentrated at single points, thereby preventing stress concentrations that would reduce shroud lifespan.
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 effectively maintains alignment and reduces point loading, enhancing the lifespan and efficiency of the shroud by distributing loads and accommodating thermal growth differences between the shroud and engine components.
Implementation Method 1
a. The compliant retention system includes a compliant member disposed between the anti-rotation pin and the shroud
Implementation Method 2
the shroud may thermally expand or grow radially at a different rate than surrounding components
Data Source
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AI summary
A system for coupling a shroud to a case associated with a gas turbine engine and a gas turbine engine including such a system includes the case defining a bore and the shroud retained within the case. The shroud defines a pocket. The system includes a pin received through the bore and at least partially positioned within the pocket. The pin has a perimeter. The system includes a load spreader including a first side and a second side opposite the first side. The first side is interconnected to the second side by a flexible portion. The first side, the second side and the flexible portion are received about a portion of the perimeter of the pin, and the load spreader is configured to transmit at least one of an axial point load and a circumferential point load from the pin over a surface of the shroud.