CMC Airfoil Porous Ceramic Cooling Film
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Solution Overview
Problem
Gas turbine engine components, particularly airfoils, face challenges with ceramic matrix composite (CMC) materials due to their high temperature resistance, as they are prone to recession when thermal barrier coatings spall off, exposing the underlying silicon-containing ceramics to high-velocity combustion gases, leading to material loss and reduced durability.
Innovation Solution
A gas turbine engine component featuring a ceramic matrix composite (CMC) body with a radially-extending blind cavity and a porous ceramic body within, which has a porosity of 15% to 70% and is lined with a ceramic body forming an open, interconnected network of pores, providing film cooling and reducing recession rates by allowing pressurized air to flow through and cool the exposed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used in airfoils due to their high temperature resistance, then temperature resistance is improved, but recession occurs when thermal barrier coatings spall off exposing the CMC to high-velocity combustion gases
Solution Approach 1:
The patent applies porous ceramic materials to line the blind cavity within the CMC airfoil. The porous structure allows cooling air to flow through and form a protective film on the CMC surface, reducing recession caused by high-velocity combustion gases while maintaining the high temperature resistance of the CMC material.
Solution Approach 2:
The patent uses pneumatic cooling by introducing pressurized cooling air into the blind cavity and allowing it to flow through the porous ceramic lining. This creates a protective gas film that shields the CMC airfoil from direct exposure to combustion gases, thereby preventing recession while preserving temperature resistance.
2Temperature
If thermal barrier coatings are applied to CMC airfoils, then temperature resistance is improved, but the coatings spall off under high-velocity combustion gases exposing the underlying CMC
Solution Approach 1:
The patent incorporates a blind cavity lined with porous ceramic material within the CMC airfoil structure before exposure to combustion gases. This pre-installed cooling system cushiones the CMC from thermal and mechanical stresses that would otherwise cause thermal barrier coating spallation, maintaining both temperature resistance and coating stability.
Solution Approach 2:
The cooling air flow path is pre-configured through the blind cavity and porous ceramic lining during airfoil manufacturing. This preliminary arrangement ensures that cooling protection is immediately available when the airfoil enters service, preventing thermal barrier coating spall before it can occur.
3Reliability
If a blind cavity is created in the CMC airfoil for cooling, then recession is reduced through film cooling, but the structural complexity increases
Solution Approach 1:
The patent nests the porous ceramic lining within the blind cavity of the CMC airfoil, creating a compact integrated structure. The porous ceramic itself contains the pore network that guides cooling air flow, eliminating the need for separate complex internal cooling channels while achieving effective film cooling and recession protection.
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 porous ceramic body effectively lowers the recession rate of the CMC airfoil by facilitating film cooling, thereby enhancing the durability and longevity of the component by mitigating the effects of high-temperature combustion gases.
Implementation Method 1
The porous ceramic body defines an open, interconnected network of pores... providing film cooling and reducing recession rates by allowing pressurized air to flow through and cool the exposed regions
Implementation Method 2
The ceramic body defines an open, interconnected network of pores. The ceramic body has a porosity, by volume, of 15% to 70%.
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A gas turbine engine (20) component includes a ceramic matrix composite (CMC) body (68) that includes an interior surface (74) that defines a blind cavity (76). A barrier coating (72) is disposed on an exterior of the CMC body (68). A ceramic body (80; 180) in the blind cavity (76) lines at least a portion of the interior surface (74) of the CMC body (68). The ceramic body (80; 180) defines an open, interconnected network of pores (80a).