Gas Turbine Squealer Tip Cooling With a Ductile Transition Layer
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Solution Overview
Problem
Gas turbine flow bodies, such as blades and vanes, experience high thermal loads and mechanical stress at the transition region between the airfoil and the squealer tip due to differences in material properties, which affects cooling efficiency and longevity.
Innovation Solution
A hybrid flow body design featuring an airfoil cast from a first metal material and an additively manufactured squealer tip from a second metal material, with a transition layer of reduced stiffness and increased ductility to mitigate mechanical stress, and an internal cooling structure with multiple separate cavities for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a squealer tip is formed from a second metal material and material bonded to the airfoil tip, then cooling efficiency is improved through internal cooling structure, but mechanical stress in the transition region increases due to material property differences
Solution Approach 1:
The transition layer is designed with locally optimized material properties - reduced stiffness and increased ductility compared to the main portions of both the airfoil and squealer tip. This local modification of material characteristics allows the transition region to better accommodate thermal and mechanical stresses while maintaining the cooling efficiency benefits of the additively manufactured squealer tip with its internal cooling structure.
Solution Approach 2:
The flow body employs a composite structure consisting of three distinct material regions: the airfoil tip material, the transition layer material with modified properties, and the squealer tip material with internal cooling structure. This composite approach allows each region to be optimized for its specific function while the transition layer serves as a stress-mitigating interface between the dissimilar materials.
2Reliability
If the squealer tip is additively manufactured with internal cooling structure, then cooling efficiency is enhanced, but manufacturing complexity increases
Solution Approach 1:
The squealer tip and its internal cooling structure are merged into a single additively manufactured component made from the second metal material. This integration eliminates the need for separate cooling channels or additional assembly steps, allowing complex internal cooling geometries to be manufactured directly as part of the squealer tip structure, thereby enhancing cooling efficiency without proportionally increasing manufacturing complexity.
3Stress or pressure
If a transition layer with reduced stiffness is introduced, then mechanical stress is reduced, but structural strength may be compromised
Solution Approach 1:
The transition layer utilizes controlled parameter changes in material properties - specifically reduced stiffness and increased ductility compared to the adjacent main portions. These parameter modifications allow the transition layer to deform more readily under stress, reducing stress concentrations, while the material composition and microstructure are optimized to maintain sufficient structural strength for the application.
Data Source
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AI summary
A flow body (100) for a gas turbine (300) includes an airfoil (1) extending along a radial direction between a platform end (11) and a tip (12) which has a tip surface (12a). The airfoil (1) is formed of a first metal material and comprises an inner cavity (10) for receiving a gaseous cooling fluid. The flow body (100) further includes a squealer tip (2) protruding from the tip surface (12a) of the tip (12) and extending along a circumference of the tip (12) so that the squealer tip (2) at least partially surrounds the tip surface (12a). The squealer tip (2) is formed from a second metal material and includes an internal cooling structure which is in fluid communication with the inner cavity (10) via one or more fluid passages (15). The squealer tip (2) is material bonded to a contact surface (12b) of the tip (12) of the airfoil (1) by a transition layer (3) that connects the contact surface (12b) and a main portion or remaining portion of the squealer tip (2). The contact surface (12b) at least partially surrounds the tip surface (12a) of the tip (12), wherein the transition layer (3), compared to at least one of the main portion of the squealer tip (2) and the airfoil (1), has at least one of a reduced stiffness and an increased ductility in combination with reduced yield strength. A method for manufacturing a flow body (100) for a gas turbine (300), and a method for repairing a flow body (100) for a gas turbine (300) are also disclosed.