Turbine Shroud Sealed Pin Mounting for Thermal Expansion
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Solution Overview
Problem
Gas turbine engine shrouds face challenges due to differing coefficients of thermal expansion in materials, leading to issues with expansion and contraction, which traditional mounting arrangements fail to accommodate effectively.
Innovation Solution
A shroud assembly comprising a ceramic matrix composite seal segment and a metallic carrier with a mount system that includes pins and a cover plate, which interlock to securely couple the seal segment with the carrier, reducing stress and leakage while allowing for thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional mounting arrangements are used to couple seal segment with carrier, then the structure is simple, but the arrangement cannot accommodate differing thermal expansion rates of ceramic matrix composite and metallic materials
Solution Approach 1:
The mounting arrangement is segmented into multiple functional components: pins for mechanical coupling, support arms for positioning, and cover plates for sealing. This segmentation allows each component to address specific requirements (mechanical strength, thermal expansion accommodation, gas sealing) independently, resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The seal segment is nested within a cavity formed by support arms on the carrier, creating a hierarchical structure. The pin passes through multiple components (carrier, seal segment, support arm) to interlock them, while the cover plate nests over the pin to provide sealing. This nesting approach accommodates thermal expansion through the layered structure while maintaining mechanical integrity.
2Temperature
If ceramic matrix composite materials are used for seal segment, then the material can withstand high temperatures, but the material has different coefficient of thermal expansion from metallic carrier causing expansion and contraction issues
Solution Approach 1:
The pin acts as an intermediary mechanical connector between the ceramic seal segment and metallic carrier. It transmits mechanical loads while allowing independent thermal expansion of each material. The support arms serve as intermediaries that position and support the seal segment, accommodating dimensional changes during thermal cycling without compromising the high-temperature performance of the ceramic material.
Solution Approach 2:
The mounting arrangement is designed to accommodate parameter changes (dimensional changes) during thermal cycling. The pin and support arm configuration allows the seal segment to expand and contract independently from the carrier, maintaining dimensional stability of the overall assembly while preserving the high-temperature resistance of the ceramic matrix composite material.
3Strength
If the pin extends through openings in carrier and seal segment, then the seal segment is securely coupled with the carrier, but gas leakage paths are created through the openings
Solution Approach 1:
The cover plate serves as an intermediary sealing element that bridges the pin openings. It maintains the mechanical coupling provided by the pin while eliminating gas leakage paths through the openings in the carrier and seal segment. The cover plate is positioned to contact both the pin and the seal segment, creating a sealed environment that preserves coupling strength while preventing gas leakage.
4Object-generated harmful factors
If the cover plate is added to close the opening and block gas leakage, then gas sealing is improved, but the device complexity increases
Solution Approach 1:
The cover plate is designed to perform multiple functions simultaneously: it seals the pin opening to prevent gas leakage, provides a mounting surface for additional sealing elements, and structurally reinforces the mounting arrangement. This multi-functionality justifies the addition of the component by delivering multiple benefits (gas sealing, structural support, leak prevention) that outweigh the increase in device complexity.
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 seals and supports the shroud assembly, reducing stress on the ceramic matrix composite materials and preventing leakage, while accommodating thermal expansion differences, thus enhancing the durability and performance of gas turbine engines.
Implementation Method 1
The pin may extend through the first opening, the second opening, and into the third opening to interlock the seal segment with the carrier
Implementation Method 2
The cover plate may close the first opening to block gases from passing into the cavity through the first opening and to block the pin from escaping through the first opening
Implementation Method 3
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 shroud assembly adapted for use with a gas turbine engine includes a seal segment, a carrier, and a mount system. The seal segment extends circumferentially at least partway around an axis to define a gas path boundary of the shroud assembly. The carrier is configured to support the seal segment in position radially relative to the axis. The mount system couples the seal segment with the carrier.