Monolithic Ceramic Core for Gas Turbine Vane Segment Casting
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Solution Overview
Problem
Existing investment casting methods for gas turbine engine vane segments struggle to precisely form fine features on the backside surface of the shroud, as these features are often distorted or lost during the dipping process when using a wax pattern, and the use of discrete ceramic inserts for shroud features is difficult to control and results in lower casting quality.
Innovation Solution
The method employs a flexible core die liner to form both the airfoil portion and the shroud portion of the vane segment simultaneously, allowing for the direct formation of fine features on the shroud backside surface, eliminating the need for separate ceramic inserts and reducing the risk of feature distortion or misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wax pattern is used to define the backside surface of the shroud, then the shroud surface can be formed, but the small features on the wax pattern are distorted and lost during the dipping process
Solution Approach 1:
The patent changes the material parameter from soft wax to rigid ceramic for the core material that defines the shroud backside surface features. This parameter change allows the features to maintain their integrity during the dipping process, as rigid ceramic does not deform under the same conditions that cause wax distortion.
Solution Approach 2:
The patent uses a composite approach by forming the core from ceramic material that can be integrated with the shell structure. The core includes both an airfoil portion and a shroud portion, creating a composite ceramic structure that maintains feature integrity while defining both the internal cooling channel and the shroud backside surface.
2Manufacturing precision
If discrete ceramic inserts are used to form small features on the shroud backside surface, then the features can be formed, but the position control is difficult and casting quality decreases
Solution Approach 1:
The patent merges the airfoil core and shroud core into a single integrated ceramic core structure. This unified core is formed as one piece with both the airfoil portion defining the internal cooling channel and the shroud portion defining the backside surface features, eliminating the need for separate ceramic inserts and simplifying position control.
Solution Approach 2:
The ceramic core serves multiple functions simultaneously: it defines the internal cooling channel geometry, defines the shroud backside surface features, and acts as a support structure during the casting process. This multi-functionality eliminates the need for separate components and reduces overall device complexity.
3Ease of manufacture
If the airfoil and shrouds are cast separately and then welded together, then the vane segment can be assembled, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent merges the airfoil and shroud casting operations into a single simultaneous casting process. The ceramic core is formed first, then the shell is formed around it in one continuous operation, allowing both airfoil and shroud to be cast together as a monolithic structure, eliminating separate welding operations.
Solution Approach 2:
The ceramic core is formed in advance with the complete geometry including both the airfoil portion and shroud portion. This preliminary formation of the complete core structure enables the subsequent shell casting to produce the entire vane segment in one operation, improving productivity by eliminating sequential casting and assembly steps.
Data Source
Figure 1~2
Figure 3~4A
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AI summary
An investment casting method for a cast ceramic core (110), including an airfoil portion (116) shaped to define an inner surface (56) of an airfoil (52) of a vane segment (50) and an integral shell portion (122) having a backside-shaping surface (120) shaped to define a backside surface (68) of a shroud (62) of the vane segment. The backsideshaping surface has a higher elevation (132) and a lower elevation (134). The higher elevation is set apart from a nearest point (138) on the airfoil portion by the lower elevation. The airfoil portion and the shell portion are cast as a monolithic body during a single casting pour.