CMC Thermal Barrier Coating for Gas Turbine Edge Stress
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Solution Overview
Problem
Gas turbine engine components made of ceramic matrix composite (CMC) experience high thermal stress due to thermal gradients from hot gas and cooling air, which existing solutions to mitigate this stress often compromise space, assembly, weight, and cost.
Innovation Solution
Applying one or more coating layers on the CMC component, with a lower thermal conductivity than the CMC material, to wrap around the edge and insulate the cooling air side, reducing thermal gradients and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If structure is added to block or divert cooling air path from outer surface, then thermal stress is reduced, but space, assembly, weight, and cost parameters are adversely affected
Solution Approach 1:
The patent applies a coating layer (thin film) on the outer surface exposed to cooling air. This coating acts as a thermal barrier that reduces heat transfer from the cooling air to the CMC component, thereby reducing thermal stress without requiring additional structural elements. The coating layer is deposited directly on the existing surface, avoiding the need for bulky blocking structures.
Solution Approach 2:
The patent uses a composite structure consisting of the CMC component combined with a coating layer having different thermal properties. The coating material is selected to have lower thermal conductivity than the CMC component, creating a composite system where the coating provides thermal insulation while the CMC provides structural integrity. This composite approach reduces thermal stress without adding structural complexity.
2Reliability
If coating layers with lower thermal conductivity are applied to the second surface, then thermal gradients are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent changes the thermal conductivity parameter of the surface layer by applying a coating with lower thermal conductivity than the base CMC material. This parameter change creates a thermal barrier effect that reduces heat transfer into the component from the cooling air, thereby reducing thermal gradients. The coating can be applied using standard deposition techniques and cured to form a integrated part.
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 coating layers effectively reduce thermal stress on CMC components by minimizing thermal gradients, thereby maintaining structural integrity and performance without adding bulk or increasing cost.
Implementation Method 1
the at least one coating layer disposed on the second surface has a lower thermal conductivity than the CMC component
Data Source
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AI summary
A ceramic matric composite (CMC) component (100) for a gas turbine engine, such as blade outer air seal (BOAS) (101), may be shielded from thermal stress. The CMC component (100) includes a first surface (110) configured for exposure to a hot gas stream (112), a second surface (120) configured for exposure to a cold gas stream (122), an edge surface (130) of the CMC component (100) disposed between and connecting the first (110) and second (120) surfaces. At least one coating layer (140) is disposed on the first surface (110) and wrapped over the edge surface (130) and the second surface (120), wherein the at least one coating layer (140) disposed on the second surface (120) has a lower thermal conductivity than the CMC component (100) so as to reduce a thermal gradient between the cooled first surface (110) and the heated second surface (120).