CMC Core Inserts With Flow Modifiers for Internal Cooling Channels
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Solution Overview
Problem
Current methods for creating cooling structures in ceramic matrix composite (CMC) components are expensive, limited in flexibility, and unable to form complex or non-line of sight features, and do not optimize coolant flow.
Innovation Solution
The use of fugitive graphite-PVB core inserts with integrated flow modification elements, which are removed during the CVI process, allowing for the formation of internal cavities and complex cooling circuits within CMCs, enhancing cooling efficiency and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional drilling and machining methods are used to create cooling structures, then cooling channels can be formed, but the manufacturing cost increases and flexibility is limited
Solution Approach 1:
The patent applies preliminary action by inserting core inserts into the CMC preform before densification. These core inserts define the cooling channel geometry in advance, allowing complex internal structures to be formed without expensive post-manufacturing machining operations. The core inserts are removed after densification to create the final cooling channels.
Solution Approach 2:
The patent uses core inserts as intermediary objects to create cooling channels. These inserts serve as temporary structures during manufacturing that define the desired channel geometry, then are removed to leave the final cooling structure. This intermediary approach enables complex geometries that would be difficult or expensive to create with direct machining.
2Manufacturing precision
If mandrels are inserted during layup to create hollow cavities, then internal structures can be formed, but the method is expensive and limited to line of sight features
Solution Approach 1:
The patent changes the material parameters of the core inserts by using materials with different removal characteristics. The core inserts are made of materials that can be selectively removed after densification, such as soluble polymers or low-melting-point materials. This parameter change allows the inserts to serve their structural purpose during manufacturing and then be easily removed to create the final cooling channels.
Solution Approach 2:
The core inserts are inserted into the preform during the layup process, before densification occurs. This preliminary placement allows the inserts to define the cooling channel geometry throughout the densification process, and they are subsequently removed to create the final internal structures. This approach enables complex geometries without expensive tooling.
3Temperature
If cooling structures are added to CMC components, then cooling efficiency improves, but thermal gradients and stress may still reduce operational lifespan
Solution Approach 1:
The patent applies local quality by creating cooling channels at specific locations within the CMC component where thermal management is most critical. The core inserts are positioned to create cooling structures in the skin regions and other high-heat areas, providing localized cooling where it is most needed to reduce thermal gradients and improve reliability.
Solution Approach 2:
The cooling structures are incorporated into the CMC component during the manufacturing process itself, before the component is put into service. The core inserts are embedded in the preform, and after densification and insert removal, the cooling channels are already formed and ready to reduce thermal gradients from the outset of operation, preventing stress accumulation over time.
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 method provides cost-effective, flexible, and efficient formation of internal cooling structures in CMCs, enabling optimized coolant flow and reduced thermal gradients, thereby improving the operational lifespan of high-temperature components.
Implementation Method 1
The binder material is heated to a temperature sufficient to burn off the binder material
Implementation Method 2
subjecting the preform with the one or more integrated core inserts to a heat treatment to remove polyvinyl butyral of base structures of the one or more integrated core inserts
Data Source
AI summary
The preparation of ceramic matrix composite (CMCs) is disclosed in which a ceramic matrix composite (CMC) preform is made with one or more integrated core inserts having a base structure made of a fugitive material comprising graphite and polyvinyl butyral, and one or more flow modification elements made of a non-fugitive material. The preform with integrated core inserts is subjected to a heat treatment to remove the polyvinyl butyral (e.g., by melting or burning) while retaining the graphite and the one or more flow modification elements. Removal of the polyvinyl butyral results in formation of one or more internal cavities, with the one or more flow modification elements positioned therein, in the preform in which the retained graphite aids in maintaining the shape of the internal cavities. The preform can then be subjected to densification to form a composite and the remaining graphite can be removed from the internal cavities.