Ceramic Matrix Composite Shroud Radial Movement Control
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Solution Overview
Problem
Turbine shroud assemblies in gas turbine engines face challenges due to differing coefficients of thermal expansion in materials used, leading to misalignment and movement issues under high-temperature conditions, which traditional fasteners cannot adequately address.
Innovation Solution
A turbine shroud assembly comprising a ceramic matrix composite shroud segment, a metallic carrier, and a retainer system with setscrews and pins that apply radial bias forces to minimize movement between the shroud segment and the carrier, ensuring stability and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fasteners (rivets or bolts) are used to couple shroud components, then the structure is simple and easy to manufacture, but the fasteners cannot accommodate differing thermal expansion rates of materials with different coefficients of thermal expansion, leading to misalignment and movement under high-temperature conditions
Solution Approach 1:
The retainer system incorporates a spring element that provides a biasing force, allowing the shroud segment to dynamically adjust its position relative to the carrier. This dynamic mechanism accommodates thermal expansion and contraction while maintaining alignment, replacing static traditional fasteners with a flexible, adaptive system.
Solution Approach 2:
The retainer system acts as an intermediary between the shroud segment and the carrier, mediating the thermal expansion differences between materials. The spring-loaded retainer absorbs expansion forces while maintaining coupling, preventing direct stress transmission that would cause misalignment with rigid fasteners.
2Temperature
If ceramic matrix composite materials are used for the shroud segment to withstand high temperatures, then temperature resistance is improved, but the differing coefficient of thermal expansion relative to metallic carrier materials causes expansion and contraction mismatches during operation
Solution Approach 1:
The retainer system changes the mechanical parameters of the coupling by introducing a spring element with specific stiffness and preload characteristics. This allows the system to accommodate the thermal expansion parameter differences between ceramic matrix composite and metallic materials while maintaining reliable operation across the temperature range.
3Manufacturing precision
If rigid coupling is used to minimize movement between shroud components, then alignment is maintained, but thermal expansion forces cannot be accommodated, leading to stress concentration and potential failure
Solution Approach 1:
The spring element in the retainer system provides beforehand cushioning by pre-loading the coupling with a controlled biasing force. This cushioning effect absorbs thermal expansion forces before they can cause stress concentration or failure, while the spring maintains sufficient constraint to prevent excessive movement and maintain alignment.
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 solution effectively minimizes radial movement and chatter of the shroud segment, maintaining alignment and reducing the risk of damage from thermal expansion differences, thereby enhancing the operational reliability and longevity of gas turbine engines.
Implementation Method 1
a spring, located radially between the shroud segment and the carrier, so as to apply a biasing force to the shroud segment to minimize radial movement of the shroud segment relative to the carrier
Implementation Method 2
components made from materials that have different coefficients of thermal expansion. Due to the differing coefficients of thermal expansion, the components of some turbine shrouds expand at different rates when exposed to combustion products
Data Source
AI summary
A turbine shroud assembly adapted for use with a gas turbine engine includes a shroud segment and a carrier. The shroud segment extends circumferentially partway around an axis to define a gas path boundary of the turbine shroud assembly. The carrier is configured to support the shroud segment in position radially relative to the axis.