Tapered Tip Flag Cavity Core for Gas Turbine Airfoils
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Solution Overview
Problem
The manufacturing of gas turbine airfoils faces challenges in maintaining core integrity and producibility due to the need for small internal features that can compromise strength, especially in investment casting processes, and the requirement for reducing turbine cooling air while ensuring efficient heat transfer.
Innovation Solution
Incorporating metering pedestals within the tapering portion of the tip flag cavity core, where the core is narrower, to define the metering region of the cooling circuit and improve structural integrity, and using a tapering or narrowing tip flag cavity design that transitions from a thicker upstream portion to a thinner downstream portion, with metering pedestals positioned upstream of the exit to enhance core strength and casting yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If small internal features are used in the tip flag cavity to reduce cooling air requirements, then cooling efficiency is improved, but core strength and manufacturing integrity are compromised
Solution Approach 1:
The cavity core is designed with varying cross-sectional dimensions along its length, creating local quality variations. The upstream portion has larger dimensions providing structural strength, while the downstream portion has smaller dimensions optimizing cooling efficiency. This gradient design allows different sections to serve different functions - structural support versus cooling performance.
Solution Approach 2:
The patent changes the geometric parameters of the cavity core by implementing a tapering design where the cross-sectional area decreases from upstream to downstream. This parameter change allows the core to transition from a strength-critical region to an efficiency-critical region, resolving the contradiction between structural integrity and cooling performance.
2Ease of manufacture
If the tip flag cavity is designed with a tapering portion to maintain core strength, then manufacturing integrity is improved, but the complexity of the core design increases
Solution Approach 1:
The cavity core is segmented into distinct portions - an upstream portion with larger cross-section for strength, a tapering portion for transition, and a downstream portion with smaller cross-section for cooling efficiency. This segmentation allows each section to be optimized independently while maintaining overall manufacturability.
3Productivity
If metering pedestals are positioned within the tapering portion of the cavity, then cooling circuit metering is optimized, but the structural strength at that location is reduced
Solution Approach 1:
The metering pedestals are positioned in the axial direction within the tapering portion, utilizing the third dimension to achieve metering function without compromising the radial and circumferential strength of the core. This spatial arrangement allows metering functionality to be added without significantly impacting structural integrity.
Data Source
AI summary
Core assemblies for manufacturing airfoils and airfoils for gas turbine engines are described. The core assemblies include a tip flag cavity core having an upstream portion, a tapering portion, and a downstream portion, with the tapering portion located between the upstream portion and the downstream portion and the downstream portion defines an exit in a formed airfoil. The upstream portion has a first radial height H1, the downstream portion has a second radial height H2 that is less than the first radial height H1, the tapering portion transitions from the first radial height H1 at an upstream end to the second radial height H2 at a downstream end, and at least one metering pedestal aperture is located within the tapering portion.