Blade Outer Air Seal Partial Ceramic Coating Cooling
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Solution Overview
Problem
Conventional blade outer air seal members in gas turbine engines face challenges with thermal expansion and contraction due to high temperatures, leading to coating wear and potential degradation of the underlying metal, especially at the blade rub area where ceramic coatings are exposed to hot combustion gases.
Innovation Solution
A blade outer air seal member with a distinct metal body featuring a ceramic coating on the gas path side, including a bare area separating the coating portions, and a cooling passage that extends axially under the coating to maintain the blade rub area at a desired temperature, reducing thermal mechanical fatigue and the need for additional cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic coating is applied to the gas path side of the blade outer air seal, then thermal and corrosion resistance is improved, but thermal expansion and contraction cause coating wear and degradation of the underlying metal
Solution Approach 1:
The patent applies a ceramic coating to specific regions of the gas path side while leaving other areas bare. The coating is positioned to protect high-temperature zones, while uncoated areas allow direct cooling airflow to reach the blade rub region, creating different functional zones on the same component surface
Solution Approach 2:
The gas path side surface is divided into distinct zones: coated portions for thermal protection and a bare area for cooling access. This segmentation allows each zone to perform its specific function optimally without interfering with the other
2Reliability
If cooling passages are added to maintain blade rub area temperature, then thermal mechanical fatigue is reduced, but device complexity increases
Solution Approach 1:
The cooling passage is integrated directly into the body of the blade outer air seal, merging the cooling function with the structural component. This eliminates the need for separate cooling systems while maintaining effective temperature control of the blade rub area
Solution Approach 2:
The cooling passage serves multiple functions: it cools the blade rub area to reduce thermal mechanical fatigue, provides a pathway for cooling airflow, and is structurally integrated into the seal body. This multi-functionality reduces the need for additional separate components
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 solution effectively manages thermal expansion and contraction, reduces coating wear, and minimizes thermal mechanical fatigue by providing targeted cooling to the blade rub area, thereby extending the lifespan of the seal member.
Implementation Method 1
relatively cool air is taken from an air flow through the engine (e.g., compressor) and routed through an intricate system of cooling passages in the seal to maintain a desirable seal temperature
Implementation Method 2
The gas path surface of the blade outer air seal may include a thermal, environmental or corrosion resistance coating system to help protect the underlying metal alloy
Data Source
AI summary
A blade outer air seal member includes a distinct body that has two circumferential sides, a leading edge and a trailing edge, and a gas path side and a radially outer side opposite the gas path side. A ceramic coating is initially disposed on a portion of the gas path side. The ceramic coating includes a forward coating portion and an aft coating portion. The gas path side has a bare area axially separating the forward coating portion and the aft coating portion. The bare area excludes any of the ceramic coating. One or more cooling passages have an outlet that opens at the bare area. The cooling passage extends in the body in an axial direction under the ceramic coating.