CMC Component Cooling Cavity Formation via Green State Machining
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Solution Overview
Problem
Ceramic matrix composite (CMC) components in gas turbine engines face challenges in forming complex cooling geometries due to their lower thermal conductivity and brittleness, which complicates the integration of cooling features and increases the risk of material failures from high combustion gas temperatures.
Innovation Solution
A method involving the machining of cooling cavities on the exterior surface of a green state CMC core, followed by the insertion of filler materials and wrapping with composite plies to form an outer enclosure, allowing for more complex cooling geometries and robust film cooling, reducing the need for internal conduits and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for turbine components to withstand extreme temperatures, then temperature resistance is improved, but thermal conductivity decreases necessitating cooling features closer to the airfoil surface
Solution Approach 1:
The patent applies preliminary action by forming cooling cavities and positioning cooling features during the green state (before final sintering) when the CMC material is more compliant and easier to machine. This allows precise positioning of cooling features closer to the airfoil surface without the difficulty of machining brittle, fully-sintered CMC materials, thereby resolving the contradiction between temperature resistance and manufacturing precision.
2Reliability
If cooling features with complex geometry are added to CMC components, then cooling effectiveness is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent forms complex cooling cavities and geometric features while the CMC material is in its green state, before final sintering. At this stage, the material is more compliant and can be easily shaped using conventional machining techniques. This preliminary formation of complex geometry avoids the manufacturing difficulties that would arise from attempting to machine complex features in the brittle, fully-sintered state, thereby resolving the contradiction between cooling effectiveness and manufacturing ease.
Solution Approach 2:
The patent exploits the parameter change in material properties between the green state and the final sintered state. In the green state, the CMC material has lower strength and higher compliance, making it easy to machine complex geometries. After sintering, the material gains its full strength and temperature resistance. This parameter change allows complex cooling features to be formed without compromising the final component's mechanical properties, resolving the contradiction between cooling effectiveness and manufacturing ease.
3Reliability
If internal conduits are used to supply cooling air, then cooling coverage is improved, but device complexity increases
Solution Approach 1:
The patent extracts the cooling air supply function from complex internal conduits and relocates it to external cooling cavities formed on the surface of the CMC component. By machining cavities into the green state material and filling them with filler material that is later removed, the patent creates cooling chambers that can be directly filled with cooling air. This eliminates the need for complex internal conduit networks while maintaining effective cooling coverage, resolving the contradiction between cooling coverage and device complexity.
Data Source
AI summary
A method of forming a composite component. The method includes laying up a plurality of composite plies to form a composite ply core. Another step of the method includes partially processing the composite ply core to form a green state core. The method further includes machining a cooling cavity on an exterior surface of the green state core. Additionally, the method includes inserting a filler material within the cooling cavity. A further step includes wrapping composite plies around the green state core and filler material to secure the filler material and form an outer enclosure. In one step, the method includes processing the green state core and outer enclosure to form the composite component.