Composite Ceramic Core Inserts for Gas Turbine Airfoils
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Solution Overview
Problem
The complexity of advanced cooling schemes in gas turbine engines' ceramic cores, requiring intricate air cooling channels, is limited by tooling design and fabrication capabilities, leading to assembly issues, dimensional variability, and the formation of flash in internal cavities, which affects airflow and increases handling scrap.
Innovation Solution
A method involving the formation of a composite core insert by preforming and in-situ connecting fugitive core inserts, which are then molded together with ceramic material, eliminating the need for assembly and adhesives, and allowing for the creation of complex geometries that cannot be formed in a single tool plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple fugitive core inserts are assembled manually in a core die, then complex cooling schemes can be formed, but dimensional variability and flash formation occur due to poor locating and intimate contact
Solution Approach 1:
Multiple fugitive core inserts are merged into a single integral composite insert formed by injection molding. The composite insert includes multiple discrete insert portions (skin core segments, trailing edge features, leading edge features) that are monolithically formed as one piece, eliminating assembly operations and ensuring perfect dimensional accuracy without flash formation.
Solution Approach 2:
The composite insert is pre-formed with all required cooling scheme features integrated into a single molded component before insertion into the core die. This preliminary formation of the complete multi-feature insert eliminates the need for subsequent assembly operations and ensures precise dimensional control from the outset.
2Adaptability or versatility
If multiple fugitive core inserts are assembled with adhesives, then complex geometries can be formed, but assembly complexity and labor requirements increase
Solution Approach 1:
Multiple discrete core insert portions are combined into a single integral composite insert formed by injection molding. This merging eliminates the need for adhesives, mechanical fasteners, or assembly operations, reducing device complexity while maintaining the capability to form complex geometries with multiple cooling features.
Solution Approach 2:
The manufacturing process transitions from discrete component assembly requiring adhesives to a single-step injection molding process. This parameter change in the formation method eliminates assembly complexity while preserving the ability to create complex multi-feature geometries through mold design.
3Manufacturing precision
If flash is removed from internal cavities, then airflow accuracy improves, but inspection and removal become impossible in hidden features
Solution Approach 1:
The injection molded composite insert prevents flash formation at the source by ensuring intimate contact between insert portions through integral formation. This preliminary prevention eliminates the need for subsequent flash removal operations, maintaining manufacturing precision while avoiding the inaccessibility problem of internal cavity flash.
Solution Approach 2:
The potential harm of flash formation in hidden internal cavities is converted into a benefit by using injection molding to prevent flash formation altogether. The molding process inherently ensures perfect contact between composite insert portions, transforming what would be an intractable inspection problem into a non-issue through process selection.
4Reliability
If tooling capabilities are expanded to form complex cores in single plane, then assembly issues are eliminated, but tooling design and fabrication complexity increases
Solution Approach 1:
The tooling design transitions from single-plane operations to multi-dimensional injection molding capabilities. The core insert includes features in multiple planes (skin segments, trailing edge, leading edge) that are formed simultaneously through sophisticated mold design, eliminating assembly issues while managing tooling complexity through advanced molding technology.
Solution Approach 2:
Multiple tooling operations that would be required to form different core features separately are merged into a single injection molding operation. The composite insert is formed in one step with all features (cooling channels, skin segments, edge features) integrated, improving reliability while consolidating tooling requirements.
Data Source
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AI summary
A multi-wall ceramic core for casting an airfoil with one or more internal cooling passages is made by preforming at least one fugitive core insert, then forming at least one core insert in-situ adjacent and fused to the at least one preformed core insert by introducing fluid fugitive pattern material into a composite core insert mold whereby the fugitive core inserts are integrally connected as a single composite core insert that includes features to form internal passage surfaces in the core when the composite core insert is removed. The composite core insert is placed in a core molding die cavity, and a fluid ceramic material is introduced into the die cavity to form the ceramic core body incorporating the fugitive composite core insert therein.