Blade Outer Air Seal Coating for Thermal Gradient and Wear Control
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Solution Overview
Problem
There is a need for blade outer air seals in gas turbine engines with improved temperature, environmental, and wear resistance to enhance their performance and longevity under operating conditions.
Innovation Solution
The use of a ceramic matrix composite material for the blade outer air seal, incorporating a continuous abradable coating on both gaspath and non-gaspath surfaces, including rare earth silicates, alkaline earth silicates, and yttria-stabilized zirconia, to reduce temperature gradients and improve wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a blade outer air seal is placed radially outwardly of turbine blades to block the flow of products of combustion, then the volume of products of combustion passing over the turbine rotors is maximized, but the seal experiences high temperature and wear conditions
Solution Approach 1:
The blade outer air seal is constructed using a ceramic matrix composite material consisting of a ceramic matrix (such as silicon carbide or silicon nitride) reinforced with continuous fibers (such as silicon carbide, silicon nitride, or carbon). This composite structure provides both high-temperature resistance and mechanical strength, allowing the seal to operate reliably in the hot gas path environment while maintaining its blocking function to maximize combustion product volume over the turbine rotors.
Solution Approach 2:
The seal geometry is designed with specific dimensional parameters including a seal length L between 0.5 to 2.0 inches, a seal width W between 0.25 to 1.0 inch, and a thickness T between 0.06 to 0.25 inches. These optimized dimensions balance the seal's ability to block combustion products with its exposure to thermal and mechanical stresses, achieving reliable operation under the required conditions.
2Reliability
If the blade outer air seal is exposed to high temperature and wear conditions, then it performs its sealing function, but its operational lifespan is reduced
Solution Approach 1:
The ceramic matrix composite construction with continuous fiber reinforcement provides exceptional wear and temperature resistance, significantly extending the operational lifespan of the blade outer air seal while maintaining its sealing function. The ceramic matrix and fiber combination creates a material that resists thermal shock, oxidation, and mechanical wear better than conventional materials.
Solution Approach 2:
The seal design incorporates localized features including a seal length and width optimized for the specific application, with the seal extending radially outwardly from the turbine blade tip. The geometry is tailored to provide adequate sealing coverage in the critical high-stress regions while minimizing overall material exposure to harmful conditions, thereby extending operational lifespan.
3Ease of manufacture
If conventional materials are used for the blade outer air seal, then manufacturing is simpler, but temperature and wear resistance are insufficient
Solution Approach 1:
While ceramic matrix composites represent an advanced material system, the continuous fiber reinforcement architecture provides clear manufacturing advantages through established composite fabrication processes. The continuous fibers can be impregnated into the ceramic matrix using conventional techniques such as resin transfer molding or chemical vapor infiltration, maintaining manufacturability while achieving superior temperature and wear resistance compared to conventional monolithic materials.
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 enhances the durability and longevity of the blade outer air seal by reducing temperature gradients and improving wear resistance, thereby increasing the seal's operational lifespan.
Implementation Method 1
a continuous abradable coating disposed on the first surface of the center web, at least one of the first and second faces, and at least one of the first and second side portions of the second surface
Implementation Method 2
The blade outer air seal comprises a ceramic matrix composite material
Data Source
Figure 1
Figure 2
AI summary
A blade outer air seal (105), includes a center web (110), first and second mounting arms (108a, 108b) and a continuous abradable coating (200a). The center web (110) has a first surface (111) and a second surface (112) opposite the first surface (111), and first and second faces (113a, 113b) joining the first surface (111) to the second surface (112). The first and second mounting arms (108a, 108b) extend from the second surface (112). The second surface (112) has a center portion (112c) between the first and second mounting arms (108a, 108b) and first and second side portions (112a, 112b) on either side of the center portion (112c). The continuous abradable coating (200a) is disposed on the first surface (111) of the center web (110), at least one of the first and second faces (113a, 113b), and at least one of the first and second side portions (112a, 112b) of the second surface (112). A gas turbine engine and a method are also disclosed.