CMC Turbine Tip Clearance via Thermal Growth Matching
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Solution Overview
Problem
Conventional gas turbine engine tip clearance control systems are impractical for frequent throttle movements due to weight and complexity penalties, and existing CMC components do not effectively manage thermal growth to maintain optimal tip clearances.
Innovation Solution
The use of Ceramic Matrix Composites (CMCs) with low thermal expansion characteristics in the turbine section, where CMC disks and airfoils are designed to match the thermal growth of both rotational and static structures, providing controlled tip clearances through a splined interface and abradable outer air seals, eliminating the need for active clearance control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If active clearance control systems are used to impinge cooler air on the outer static structure, then tip clearance control is improved, but weight and device complexity increase
Solution Approach 1:
The patent changes the thermal expansion parameter of the outer static structure by using CMC materials with low thermal expansion characteristics. This allows the structure to maintain dimensional stability at high temperatures, achieving tip clearance control through material property modification rather than active mechanical control systems.
Solution Approach 2:
The CMC outer static structure self-regulates its dimensional changes through its inherent low thermal expansion properties. The material naturally resists thermal growth without requiring external active control systems, making the structure self-sufficient for clearance control.
2Manufacturing precision
If active clearance control systems are used to impinge cooler air on the outer static structure, then tip clearance control is improved, but weight increases
Solution Approach 1:
The CMC outer static structure self-regulates its dimensional changes through its inherent low thermal expansion properties. The material naturally resists thermal growth without requiring external active control systems, making the structure self-sufficient for clearance control.
Solution Approach 2:
The patent extracts and eliminates the heavy active clearance control system components (cooling air supply systems, control mechanisms) by replacing them with a passive CMC structure that inherently provides thermal stability. This removes unnecessary weight while maintaining clearance control functionality.
3Ease of manufacture
If conventional materials are used in the turbine section, then manufacturing is easier, but thermal growth causes poor tip clearance control
Solution Approach 1:
The patent uses Ceramic Matrix Composite (CMC) materials for the outer static structure and rotor module components. These composite materials provide both thermal stability (low thermal expansion) and structural integrity at high temperatures, achieving precise tip clearance control while remaining manufacturable through established CMC fabrication processes.
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 approach maintains efficient and robust gas turbine engine operation by maintaining optimal tip clearances without the weight and complexity of conventional control systems, ensuring consistent performance across varying flight conditions.
Implementation Method 1
The use of Ceramic Matrix Composites (CMCs) with low thermal expansion characteristics in the turbine section, where CMC disks and airfoils are designed to match the thermal growth of both rotational and static structures
Data Source
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AI summary
A gas turbine engine (20) includes a ceramic matrix composite (CMC) static structure (60) and a rotor module (62) with a multiple of CMC airfoils (66), a radial growth of said rotor module (62) matched with said CMC static structure (60). A corresponding method of tip clearance control is also provided.