Monolithic Direct Shell Flexures for Gas Turbine Wall Thickness Control
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Solution Overview
Problem
In investment casting of gas turbine engine components, thermal expansion and contraction cause the ceramic core and shell to shift relative to each other, leading to difficulties in precisely controlling outer wall thicknesses and creating thin walls, which are essential for efficient cooling and structural integrity.
Innovation Solution
The ceramic core and shell are formed as a monolithic, direct shell with integrated cooling hole features that include flexures following curved, serpentine, or zig-zag trajectories, allowing for increased thickness and better control over wall thicknesses, reducing stress and the need for additional support structures like platinum pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a shell and core are used in investment casting, then the component can be cast with internal cooling passages, but the shell and core shift relative to each other during thermal expansion and contraction, making it difficult to control outer wall thickness
Solution Approach 1:
The patent merges the shell and core into a monolithic direct shell structure where the core is integrated within the shell as a single piece. This eliminates the relative movement between separate shell and core components during thermal expansion and contraction, thereby solving the problem of controlling outer wall thickness precision.
Solution Approach 2:
The direct shell is segmented into multiple sections that can expand and contract independently during thermal cycling. This segmentation allows each section to accommodate thermal strain without causing relative displacement that would affect wall thickness control, while maintaining the overall monolithic structure.
2Reliability
If the void between shell and core is reduced to create thin walls, then cooling efficiency improves, but the structure becomes more prone to cracking and requires additional support structures
Solution Approach 1:
The direct shell incorporates flexible trajectories (curved, serpentine, or zig-zag paths) for cooling holes that allow the thin-walled structure to flex and accommodate thermal expansion without cracking. This flexibility enables maintaining thin wall thickness for cooling efficiency while preserving structural integrity.
Solution Approach 2:
The cooling hole trajectories are designed to be dynamic and adaptable, following curved, serpentine, or zig-zag paths that can accommodate thermal deformation. This dynamic design allows the structure to adjust during thermal cycling without requiring additional support structures, maintaining both thin walls and structural integrity.
3Manufacturing precision
If cooling hole features are added to control wall thickness, then manufacturing precision improves, but the device complexity increases
Solution Approach 1:
The cooling hole features serve multiple functions: they control wall thickness precision, provide cooling passages, and accommodate thermal expansion through their curved, serpentine, or zig-zag trajectories. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while achieving precise wall thickness control.
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
This approach enhances the precision and reliability of wall thickness control, enables the creation of thinner walled components, improves cooling efficiency, and reduces the risk of cracking by absorbing thermal strain, while eliminating the need for external support structures.
Implementation Method 1
one or more flexures (305) extending between the ceramic core (103) and the ceramic shell (101). The flexures (305) may reduce stress between the ceramic core (103) and the ceramic shell (101).
Implementation Method 2
the shell and the core may shift relative to each other during the investment casting process due to thermal expansion and contractions
Data Source
Figure 1
Figure 2~2A
Figure 3~5
AI summary
A component (200) for a gas turbine (20) engine comprises a wall (201) enclosing an interior compartment (250) of the component. The wall includes an interior surface (202) defining the interior compartment and an exterior surface (204) opposite the interior surface, and a cooling hole (230) extending from the interior surface to the exterior surface. The cooling hole includes one or more flexures, wherein the wall increases from a first thickness (Dl) to a second thickness (D2) at the cooling hole. An investment casting mold for forming a component for a gas turbine engine, comprises a ceramic core, a ceramic shell outward from the ceramic core separated from the ceramic core by a void, and a cooling hole feature extending from the ceramic core to the ceramic shell through the void. The cooling hole feature includes one or more flexures. T he void increases from a first thickness to a second thickness at the cooling hole feature. A method of manufacturing a component for a gas turbine engine comprises pouring melted metal into an investment casting mold, allowing metal to solidify within the investment casting mold and removing the investment casting mold from the metal.