CMC Heat Shield Mechanical Fastening for Gas Turbine Combustors
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Solution Overview
Problem
Existing gas turbine engine heat shields, typically made of metal or metal alloys, have limited durability and require frequent replacement due to thermal stress, and machining threads into ceramic matrix composite (CMC) heat shields is challenging and can cause fractures.
Innovation Solution
The use of CMC heat shields mechanically fastened to a dome plate using threaded members and retainers, eliminating the need for integral threading on the heat shields, and employing a method that includes fabricating CMC heat shields with annular flanges and rings for secure coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal heat shields with integral threading are used, then the heat shields can be easily manufactured and assembled, but they have limited durability and require frequent replacement due to thermal stress
Solution Approach 1:
The patent applies composite materials by transitioning from metal heat shields to ceramic matrix composite (CMC) heat shields. CMC materials provide superior thermal resistance and durability under thermal stress while maintaining manufacturability through specialized joining techniques like mechanical fastening with retainers and threaded members designed for ceramic materials.
2Ease of operation
If threading is machined into CMC heat shields, then the heat shields can be fastened to the dome plate, but the machining process can cause fractures in the brittle material
Solution Approach 1:
The patent applies segmentation by separating the threading function from the CMC heat shield body. Instead of machining threads directly into the brittle CMC material, the design uses a distinct threaded retainer component that fastens to the dome plate and secures the heat shield, thereby avoiding direct machining of the CMC and preserving its structural integrity.
Solution Approach 2:
The patent uses an intermediary component (the threaded retainer) that mediates between the CMC heat shield and the dome plate. This retainer absorbs the mechanical fastening function, allowing the CMC heat shield to be secured without direct threading, thus preventing fractures while achieving secure attachment.
3Temperature
If traditional metal heat shields are used, then cooling air must be impinged on the heat shields to maintain operating temperature, but this increases cooling requirements and NOx emissions
Solution Approach 1:
The patent applies parameter changes by transitioning the heat shield material from metal to ceramic matrix composite, which fundamentally changes the thermal properties. CMC materials can withstand higher operating temperatures without active cooling, thereby reducing cooling air requirements and associated NOx emissions while maintaining structural integrity.
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
This approach enhances the durability of heat shields, reduces cooling requirements, and lowers NOx emissions by up to 90%, enabling more efficient and longer-lasting gas turbine engine combustors with improved thermal resistance.
Implementation Method 1
at least one heat shield comprised of a ceramic matrix composite coupled at the aft end of the dome plate
Data Source
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AI summary
A combustor (20) for a gas turbine engine (10) is disclosed. The combustor (20) is described as comprising a dome plate (25) coupled to a liner thereof, with at least one heat shield (26) comprised of a ceramic matrix composite coupled at the aft end of the dome plate (25). Also described is a method for assembling a combustor (20) for a gas turbine engine (10), including releasing a metal alloy heat shield from a dome plate (25) and providing a ceramic matrix composite heat shield (26) as replacement.