Gas Turbine Airfoil Trailing Edge Radius and Coating Step
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Solution Overview
Problem
The existing manufacturing process for gas turbine engine airfoils results in a thin trailing edge due to the removal of thermal barrier coatings, making it difficult to machine a full radius and creating a step between coated and uncoated surfaces, which reduces turbine efficiency.
Innovation Solution
The airfoil's trailing edge is formed by machining a substrate with additional casting stock to achieve a full constant radius, allowing for the removal of coating at the trailing edge and utilizing a core center discharge for cooling airflow, thereby improving the aerodynamic shape and reducing surface mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal barrier coating is applied to the airfoil surface, then heat protection is improved, but trailing edge thickness is reduced
Solution Approach 1:
The patent applies preliminary action by adding extra coating thickness at the trailing edge region before final machining. The coating is applied to the entire airfoil surface including the trailing edge, then the trailing edge is machined to the precise final dimensions. This ensures the trailing edge achieves both the required thickness and the full constant radius aerodynamic shape, while the coating provides heat protection to the airfoil body.
2Ease of manufacture
If trailing edge is left uncoated during manufacture, then coating application complexity is reduced, but trailing edge thickness is insufficient for full radius machining
Solution Approach 1:
The coating is applied in advance to the entire airfoil surface including the trailing edge region with increased thickness. This preliminary coating application allows the trailing edge to be subsequently machined to achieve both the precise full constant radius shape and adequate thickness, resolving the conflict between ease of coating application and manufacturing precision.
Solution Approach 2:
The patent changes the coating thickness parameter locally at the trailing edge region by applying extra coating material there. This localized parameter change ensures sufficient material remains after machining to achieve the desired full constant radius trailing edge geometry while maintaining heat protection on the airfoil body.
3Productivity
If full constant radius trailing edge is machined, then turbine efficiency is improved, but trailing edge thickness becomes insufficient after coating removal
Solution Approach 1:
The coating is applied preliminarily to the airfoil body with the understanding that the trailing edge will be machined afterward. The coating application includes the trailing edge region with sufficient thickness to allow for subsequent machining operations that will create the full constant radius shape while maintaining adequate final thickness.
Solution Approach 2:
The patent segments the coating application and trailing edge formation into distinct operations: first applying coating to the airfoil body including the trailing edge region, then separately machining the trailing edge to achieve the full constant radius shape. This segmentation allows each operation to be optimized independently.
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 enables the formation of an airfoil with a full constant radius trailing edge, enhancing operational efficiency by maintaining the desired thickness and reducing the step between coated and uncoated surfaces, thus improving turbine performance.
Implementation Method 1
a coating, such as a thermal barrier coating (TBC) applied to the airfoil
Implementation Method 2
a core center discharge is located at the trailing edge to exhaust a cooling airflow from an interior of the airfoil
Data Source
Figure 1
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AI summary
An airfoil (60) for a gas turbine engine (20) includes a substrate portion (76) extending from an airfoil leading edge (64) to an airfoil trailing edge portion (66). The airfoil trailing edge portion includes a flared portion (82) wherein a substrate portion thickness increases along a camber line (80) of the airfoil, and a trailing edge defined as a full constant radius (84) extending from a pressure side (68) of the airfoil to a suction side (70) of the airfoil. A coating portion (78) includes a coating applied over at least a portion of the substrate portion.