Turbine Shroud Assembly With Split Pins for Thermal Expansion
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Solution Overview
Problem
Turbine shroud assemblies in gas turbine engines face challenges due to differing coefficients of thermal expansion among materials, leading to misalignment and stress issues when traditional fasteners are used, which can result in leakage and reduced performance.
Innovation Solution
A turbine shroud assembly design featuring a carrier with split-pin fasteners, including forward and aft pins, and a seal segment made of ceramic matrix composite materials, allowing for independent loading and accommodating thermal expansion differences, thereby reducing stress and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fasteners are used to couple turbine shroud components, then the assembly structure is simple, but the components cannot accommodate differing thermal expansion rates leading to misalignment and stress issues
Solution Approach 1:
The fastener is divided into multiple segments along its length, with each segment capable of independent axial movement. This segmentation allows different portions of the fastener to accommodate thermal expansion of different components independently, resolving the contradiction between maintaining simple structure and accommodating differential thermal expansion.
Solution Approach 2:
The fastener transitions from a static, rigid structure to a dynamic, adaptable structure. The segments can move axially relative to each other in response to thermal expansion forces, allowing the fastener to dynamically adjust and maintain proper alignment of turbine shroud components under varying temperature conditions.
2Strength
If traditional rigid fasteners are used, then manufacturing is simple, but stress concentration occurs due to inability to accommodate thermal expansion differences
Solution Approach 1:
By segmenting the fastener into multiple movable sections, stress is distributed across multiple interfaces rather than concentrated at single rigid connection points. Each segment can move independently to absorb thermal expansion forces, preventing stress concentration while the modular design facilitates manufacturing through standardized segment production and assembly.
Solution Approach 2:
The fastener's physical parameters (length, cross-section, material properties) can be varied along its length to optimize stress distribution. Different segments may have different dimensions or material characteristics tailored to accommodate the specific thermal expansion requirements of adjacent components, improving strength while maintaining manufacturability through controlled parameter variations.
3Reliability
If components with different thermal expansion coefficients are coupled rigidly, then assembly is straightforward, but leakage occurs due to misalignment under thermal stress
Solution Approach 1:
The segmented fastener structure maintains proper alignment of sealed surfaces by allowing each segment to move independently in response to thermal expansion. This prevents misalignment that would compromise seal integrity, while the segmentation itself is integrated into the coupling mechanism rather than adding separate alignment devices.
Solution Approach 2:
The fastener segments automatically adjust their positions in response to thermal expansion forces without external intervention. This self-adjusting mechanism maintains alignment and seal integrity throughout temperature cycles, eliminating the need for complex external alignment systems or adjustment mechanisms.
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 design enhances the assembly's ability to manage thermal expansion, reduces leakage, and increases the number of loading points, leading to improved performance and durability of the turbine shroud assembly.
Implementation Method 1
Due to the differing coefficients of thermal expansion, the components of some turbine shrouds expand at different rates when exposed to high temperatures
Data Source
AI summary
A turbine shroud assembly adapted for use with a gas turbine engine includes a carrier, a seal segment, and a mount assembly. The carrier is configured to be coupled to a turbine case. The seal segment is shaped to define a gas path boundary of the shroud assembly. The mounting assembly is configured to couple the seal segment to the carrier.