ECM Electrode Insulation for Cooling Hole Asymmetry
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Solution Overview
Problem
Existing methods for forming cooling holes in turbine engine airfoils using electrochemical machining result in circular cross-sectional areas that limit heat transfer and induce high stress concentrations, particularly in airfoils with narrow trailing edges, leading to increased maintenance costs and reduced engine lifespan.
Innovation Solution
A method involving a partially insulated electrochemical machining electrode that forms cooling holes with a circular inlet and elliptical outlet cross-sectional areas, allowing for varying airflow and heat transfer while reducing stress concentrations by controlling the electrochemical dissolution process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling holes with circular cross-sectional areas are formed using conventional electrochemical machining, then the machining process is simple and reliable, but heat transfer capability is limited and stress concentrations occur in narrow trailing edges
Solution Approach 1:
The patent applies asymmetry by transitioning from circular to elliptical cross-sectional profiles for cooling holes. The elliptical outlet profile (with major axis perpendicular to the trailing edge) reduces stress concentrations in narrow trailing edges while the circular inlet maintains simple metering characteristics. This asymmetric evolution of the hole geometry along its length resolves the contradiction between heat transfer capability and stress concentration.
Solution Approach 2:
The patent applies local quality by having different cross-sectional profiles at different locations along the cooling hole. The inlet maintains a circular profile for flow metering, while the outlet transitions to an elliptical profile for reduced stress concentration and enhanced heat transfer. This localized variation in geometry allows each section to optimize for its specific function.
2Temperature
If cooling holes with varying cross-sectional areas are formed, then heat transfer and airflow are enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the electrode into distinct insulated and uninsulated portions along its length. The insulation is applied only to specific sections of the electrode, allowing different regions to perform different functions: the uninsulated tip creates the elliptical outlet, while the insulated portions control the circular inlet formation. This segmented approach enables complex geometry creation without requiring a completely complex electrode design.
Solution Approach 2:
The patent applies preliminary action by first forming a starter hole with a circular cross-sectional area, then using the electrochemical machining process to evolve it into an elliptical outlet. This two-stage approach (starter hole formation followed by ECM evolution) simplifies the overall manufacturing process compared to attempting to create the final complex geometry in a single step.
3Manufacturing precision
If circular cooling hole outlets are used, then the inlet flow metering is maintained, but the trailing edge stress concentrations increase and maintenance costs rise
Solution Approach 1:
The patent applies asymmetry by creating an elliptical outlet profile where the major axis is perpendicular to the trailing edge. This asymmetric geometry reduces stress concentrations at the trailing edge compared to a circular profile, while the circular inlet maintains the desired flow metering characteristics. The asymmetric evolution from circular inlet to elliptical outlet resolves the contradiction between manufacturing precision and reliability.
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
The method enables enhanced airflow and heat transfer while minimizing stress concentrations on the airfoil, thereby improving turbine engine performance and lifespan.
Implementation Method 1
the workpiece is dissolved by controlled electrochemical reactions to form the cooling hole
Data Source
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AI summary
An electrochemical machining (ECM) apparatus including an electrode (100) and Insulation (106) that extends only partially about the electrode. The insulation is oriented to cause the electrode to form a hole (200) having an inlet (208) defined by a first cross-sectional area (214) and an outlet (210) defined by a second cross-sectional area (226).