Airfoil Cooling Holes With Flared EDM Diffuser Walls
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Solution Overview
Problem
The existing methods for manufacturing diffuser sections of airfoil cooling holes using rapid EDM processes are limited by the inability to achieve smooth, linear walls, resulting in a maximum diversion angle of 10°, which restricts airflow and cooling efficiency due to boundary layer separation.
Innovation Solution
The EDM electrode is advanced in fewer incremental steps, creating longer and deeper notches in the side walls, allowing for increased included angles up to 30° by reducing the number of steps from 100 to 4-12, and adjusting notch dimensions to 0.002-0.010 inches in length and 0.000-0.006 inches in depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the electrode is advanced in many incremental steps (100 steps) to form the diffuser section, then the wall smoothness is improved, but the included angle is limited to 10° due to boundary layer separation
Solution Approach 1:
The patent changes the parameters of the EDM process by reducing the number of incremental steps from 100 to fewer steps, and by modifying the notch dimensions (length 0.002-0.010 inches and depth 0.000-0.006 inches). This parameter change allows the included angle to be increased beyond the conventional 10° limit while maintaining acceptable wall quality through the altered step structure.
2Productivity
If the electrode is advanced in fewer incremental steps to increase the included angle beyond 10°, then the cooling efficiency is improved, but the wall smoothness deteriorates due to larger notches
Solution Approach 1:
The patent optimizes the parameters by specifying precise notch dimensions (length 0.002-0.010 inches and depth 0.000-0.006 inches) that balance wall smoothness with the ability to achieve larger included angles. This controlled parameter change enables increased cooling efficiency while maintaining acceptable wall quality.
3Manufacturing precision
If a large shaped EDM electrode is used to form the diffuser section in a single stroke, then the wall smoothness is improved, but the manufacturing time increases significantly
Solution Approach 1:
The patent segments the diffuser section formation into a series of incremental steps with notches, replacing the single-stroke large electrode method. This segmentation allows the use of a smaller electrode that can reciprocate rapidly, significantly reducing manufacturing time while the controlled notch dimensions maintain acceptable wall smoothness.
Solution Approach 2:
The patent employs a dynamic reciprocating motion of a small electrode, advancing it in steps along the length of the diffuser section. This dynamic approach replaces the static single-stroke method, enabling rapid formation of the diffuser section with reduced manufacturing time.
4Productivity
If the included angle is increased beyond 10° to improve cooling efficiency, then the airflow separation is reduced, but the boundary layer separation occurs with conventional methods
Solution Approach 1:
The patent changes the geometric parameters by increasing the included angle beyond the conventional 10° limit and adjusting the notch dimensions. This parameter change allows the airflow to adhere to the walls at higher angles, improving cooling efficiency while preventing boundary layer separation through the optimized geometry.
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 airflow adherence to the hole walls, increasing the diffuser angle and improving cooling efficiency beyond the conventional 10° limit, enabling more effective heat dissipation for airfoils in gas turbine engines.
Implementation Method 1
an appropriately shaped electrode contacts a structure that is typically immersed in a dielectric fluid. Near contact between the electrode and the structure, combined with a pulsed voltage, creates a spark between the electrode and the structure, thereby causing the structure to erode in the shape of the electrode
Data Source
AI summary
The diffusion opening in the cooling hole of an airfoil is formed by an EDM process in which the outwardly flaring sidewalls of the opening, rather then having surfaces that are approximated to be smooth by having many small ribs formed therein, are formed with relatively few ribs with both longitudinally extending and radially extending surfaces that are substantially greater in dimension than those as normally formed. In this manner, the machining process is simplified and expedited, while at the same time, the cooling efficiency is increased.