Flared Gas Turbine Cooling Apertures for Coating Adhesion
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Solution Overview
Problem
Conventional coatings on gas turbine components, particularly around airflow apertures, are prone to mechanical stress, fracture, ablation, and delamination due to high temperatures and pressures, necessitating a design that reduces stress and enhances adhesion.
Innovation Solution
The design features airflow apertures with a flared geometry where the aperture wall surface meets the surface, providing a radius of curvature that reduces the abruptness of the angular transition, allowing for a high-temperature, high-pressure resistant coating to be adhered to the surface and aperture wall, thereby reducing stress and increasing adhesion area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cooling apertures with walls normal to the surface are used, then cooling efficiency is achieved, but coating stress increases and coatings become vulnerable to fracture and delamination
Solution Approach 1:
The aperture walls are flared to provide a radius of curvature at the juncture with the surface, eliminating abrupt angular transitions. This curved geometry distributes mechanical stresses more evenly across the coating-aperture interface, preventing stress concentration that would otherwise cause coating fracture and delamination.
Solution Approach 2:
The aperture geometry is modified locally at the surface juncture with a flared transition zone, while maintaining the overall aperture function. This localized geometric change specifically addresses coating stress at the critical interface without compromising the cooling aperture's primary function.
2Reliability
If coatings are applied to combustion chamber walls with conventional aperture geometries, then thermal protection is provided, but coatings near apertures are prone to ablation and delamination
Solution Approach 1:
The flared aperture walls with radius of curvature create a gradual transition that eliminates sharp corners where ablation would initiate. This curved geometry allows the coating to better withstand thermal and mechanical loads, preventing ablation and delamination in the high-stress regions near apertures.
3Reliability
If the aperture width is reduced to increase coating adhesion area, then coating stress is reduced, but flow area is decreased
Solution Approach 1:
The aperture geometry is transformed by flaring the walls, which changes the distribution of coating thickness and adhesion area without significantly reducing the effective flow area. The curved transition allows for optimized coating deposition that enhances adhesion while maintaining adequate flow characteristics.
Data Source
Figure 1~2D
Figure 3~4
Figure 5A~5C
AI summary
A gas turbine component subject to extreme temperatures and pressures includes a wall (22) defined by opposite first and second surfaces (100,102). An airflow aperture through the wall is defined by an aperture wall surface (106) which extends from a first opening in the first surface to a second opening in the second surface (102). The aperture wall surface is flared at a juncture with the first surface (100), such that the first opening has a greater cross-sectional flow area than the second opening. A high-pressure, high-temperature resitant coating (108) is adhered to the first surface, and adhered to at least a portion of the aperture wall surface.