Turbine Shroud Split Ring Seal Thermal Expansion Management
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Solution Overview
Problem
Gas turbine engine shrouds face challenges in sealing due to components made from materials with different coefficients of thermal expansion, leading to uneven expansion and contraction, which affects the sealing efficiency and performance.
Innovation Solution
The use of a ceramic-containing blade track and a split ring seal with a W-shaped cross section, which expands and contracts to maintain engagement with both the metallic carrier and ceramic blade track, utilizing pressurized cooling air to manage thermal expansion and contraction, and incorporating biasing members like spring rings to ensure proper engagement and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If components are made from materials with different coefficients of thermal expansion, then thermal expansion management is improved, but sealing efficiency deteriorates
Solution Approach 1:
The seal is designed with a split configuration that allows it to change its dimensional parameters (circumferential expansion/contraction) in response to thermal changes. The split enables the seal to expand and contract circumferentially as temperature varies, maintaining contact with both the metallic carrier and ceramic blade track despite their different thermal expansion coefficients.
Solution Approach 2:
The seal transitions from a static rigid structure to a dynamic adaptive structure. The split ring can dynamically adjust its circumference and cross-sectional shape based on thermal conditions, allowing it to maintain effective sealing contact with components that expand at different rates during operation.
2Adaptability or versatility
If a split ring seal is used to accommodate thermal expansion, then adaptability to thermal changes is improved, but structural complexity increases
Solution Approach 1:
The seal is segmented into two portions with a circumferential gap between them. This segmentation allows each portion to move independently, enabling the seal to accommodate thermal expansion and contraction of the components it contacts. The simple split design provides thermal adaptability without requiring complex mechanisms.
Solution Approach 2:
The seal functions as a flexible element that can deform its cross-sectional shape and circumferential dimension. The split ring structure acts as a flexible shell that bends and expands/contracts to maintain contact with both the metallic carrier and ceramic blade track, providing adaptability through geometric flexibility rather than mechanical complexity.
3Area of stationary object
If the seal engages both metallic carrier and ceramic blade track, then sealing coverage is improved, but manufacturing precision requirements increase
Solution Approach 1:
The seal dynamically adjusts its position and contact pressure with the two different components. By being able to expand and contract circumferentially, the seal can maintain appropriate engagement with both the metallic carrier and ceramic blade track even when their dimensional changes differ, reducing the stringency of manufacturing precision requirements.
Solution Approach 2:
The seal can have different local properties at different circumferential positions. The split configuration allows one side of the seal to engage the metallic carrier while the other side engages the ceramic blade track, with each side adapting locally to the thermal expansion characteristics of its respective component.
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
This solution effectively blocks the ingress of hot gases and cooling air, maintaining temperature control and reducing performance loss by ensuring consistent engagement between the carrier, blade track, and seal, despite differing thermal expansion rates.
Implementation Method 1
components made from materials with different coefficients of thermal expansion, leading to uneven expansion and contraction
Implementation Method 2
pressurized cooling air provided to the cooling channel may encourage the first split ring to change size axially
Implementation Method 3
biasing members arranged to bias the first split ring toward engagement with the annular blade track
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A turbine shroud for use in a gas turbine engine that includes a metallic carrier, a blade track, and a seal is disclosed. The seal is engaged with surfaces of the metallic carrier and the blade track to block ingress of hot gasses at the interface of the blade track and the metallic carrier. A corresponding method of assembling a turbine shroud is also provided.