Angled Tip Rods for Swept Airfoil Casting Stability
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Solution Overview
Problem
In gas turbine engines, the curvature of airfoil tips with a sweep configuration poses challenges in meeting producible tip rod sizing criteria, leading to potential breakage during casting and increased scrap rates, especially for radially oriented rods that fail to meet embedded length and core thickness requirements.
Innovation Solution
The use of alumina or quartz tip rods extending at an angle of 5-12 degrees relative to the normal angle of the wall, combined with additional core support features like bumpers, to form through-holes that meet the necessary sizing criteria and ensure stability during the casting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If radially oriented tip rods are used in airfoils with sweep configuration, then the casting process can be simplified, but the tip rods fail to meet producible sizing criteria leading to breakage and increased scrap
Solution Approach 1:
The tip rod is angled relative to the radial direction, creating an asymmetric configuration that accommodates the airfoil sweep geometry. This asymmetric orientation allows the rod to maintain proper embedded length and clearance distances while forming through-holes that align with the swept airfoil tip, preventing breakage during casting.
Solution Approach 2:
Instead of orienting the tip rod purely radially, the solution introduces an angular dimension by tilting the rod at a specific angle relative to the radial direction. This dimensional change enables the rod to simultaneously satisfy multiple geometric constraints including embedded length, clearance distances, and through-hole alignment in swept airfoils.
2Manufacturing precision
If tip rod embedded length is increased to meet sizing criteria, then casting stability improves, but the rod may protrude too far and interfere with other blade features
Solution Approach 1:
The tip rod is positioned at a specific angle and location to achieve optimal local embedded length within the airfoil tip region. This localized optimization ensures sufficient embedment for casting stability while controlling the protrusion distance to prevent interference with other blade features, rather than uniformly increasing or decreasing rod length throughout.
3Strength
If tip rod diameter is increased to meet minimum sizing requirements, then rod strength improves, but the rod creates larger holes that may negatively impact blade performance
Solution Approach 1:
The solution optimizes the tip rod diameter parameter to meet the minimum sizing requirement for casting stability while minimizing the hole size impact on blade performance. By carefully selecting and controlling this parameter, the design achieves sufficient rod strength without excessive material removal from the airfoil tip.
Data Source
AI summary
A core is provided for fabricating a blade to include an airfoil. The airfoil includes pressure and suction surfaces, leading and trailing edges extending along the pressure and suction surfaces and a tip shelf with a first sweep configuration and a wall. The core includes channel sections configured to form internal channels within the airfoil by casting processes and tip rods extending from respective portions of the channel sections proximate to a tip shelf location. The respective portions of the channel sections have a second sweep configuration corresponding to the first sweep configuration. The tip rods are configured to extend through the wall at an angle of about 5-12 degrees inclusive relative to a normal angle of the wall during the casting processes to form through-holes angled at about 5-12 degrees inclusive in the wall.