Ceramic Blade Track Axial Keying for Thermal Expansion
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Solution Overview
Problem
Gas turbine engine shrouds face issues due to differing coefficients of thermal expansion in materials, leading to misalignment and performance loss as components expand and contract during operation.
Innovation Solution
A turbine shroud design featuring a one-piece annular ceramic runner with integral keys and insulator tabs, connected via a cross-key mechanism to an annular metallic carrier, allowing for uniform expansion and insulation from hot gases, using ceramic matrix materials with silicon-carbide reinforcements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fasteners (rivets or bolts) are used to couple shroud components, then the components can be assembled together, but the components cannot accommodate differing levels of thermal expansion and contraction during operation
Solution Approach 1:
The connection structure is divided into multiple keys that fit into corresponding keyways, allowing each key to independently accommodate thermal expansion movements between the metallic carrier and ceramic blade track, while maintaining overall structural integrity
Solution Approach 2:
The connection design allows for dimensional changes in the key-keyway interface during thermal cycling, enabling the components to expand and contract at different rates without causing misalignment or damage to the rigid fastener connection
2Stability of the object's composition
If components with different coefficients of thermal expansion are coupled together, then a complete shroud structure can be formed, but misalignment occurs during operation due to differential expansion and contraction
Solution Approach 1:
The key-keyway connection design explicitly accommodates thermal expansion by allowing controlled movement and dimensional changes at the interface between the metallic carrier and ceramic blade track, preventing misalignment caused by differential expansion coefficients
Solution Approach 2:
The keys act as intermediary elements between the metallic carrier and ceramic blade track, absorbing and distributing the thermal stress caused by differential expansion, thereby maintaining stable alignment of the complete shroud structure
3Stability of the object's composition
If a one-piece ceramic runner is used, then uniform thermal expansion can be achieved, but the component needs effective connection to the metallic carrier
Solution Approach 1:
The connection between the one-piece ceramic runner and metallic carrier is segmented into multiple keys distributed around the circumference, providing multiple load paths and maintaining strong connection while allowing uniform thermal expansion of the ceramic 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
The design maintains a consistent gap between blades and the shroud, enhancing engine performance by accommodating thermal expansion and insulating the metallic carrier from hot gases, thus improving operational efficiency.
Implementation Method 1
The one-piece ceramic runner may include ceramic matrix material and ceramic-containing reinforcements suspended in the ceramic matrix material. The ceramic matrix material may include silicon-carbide and the ceramic-containing reinforcements may include silicon-carbide.
Implementation Method 2
The shroud may include a plurality of insulator tabs. The insulator tabs may extend in an axial direction from the one-piece annular ceramic runner parallel to the central axis circumferentially between the plurality of keys and radially inward of a portion of the annular metallic carrier. The plurality of insulator tabs may insulate at least some of the annular metallic carrier from hot gasses during use of the turbine shroud within a gas turbine engine.
Data Source
AI summary
A turbine shroud for a gas turbine engine includes an annular metallic carrier, a blade track, and a cross-key connection formed between the annular metallic carrier and the ceramic blade track. The cross-key connection locates the ceramic blade track relative to the metallic carrier.