CMC Blade Outer Air Seal Feather Seal for Thermal Expansion
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Solution Overview
Problem
Existing blade outer air seal assemblies in gas turbine engines face challenges in ensuring effective sealing across turbine blades due to thermal expansion and mismatched growth rates between ceramic matrix composite and metallic components, leading to potential leakage and reduced efficiency.
Innovation Solution
A blade outer air seal assembly featuring a support structure with radially extending slots and a feather seal that accommodates thermal expansion by rotating within these slots, maintaining sealing effectiveness across a range of temperatures and thermal expansions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If blade outer air seals are made of ceramic matrix composite fiber layers, then high temperature resistance is improved, but thermal expansion mismatch with metallic components causes sealing effectiveness to deteriorate
Solution Approach 1:
The air seal assembly is divided into multiple seal segments arranged circumferentially, with feather seals positioned at the interfaces between segments. This segmentation allows each component to accommodate thermal expansion independently while maintaining overall sealing integrity at high temperatures.
Solution Approach 2:
The feather seal acts as an intermediary element between the ceramic matrix composite seal segments and the turbine blade. It accommodates thermal expansion differences by rotating within its slot, ensuring continuous sealing effectiveness despite differential thermal growth between dissimilar materials.
2Stability of the object's composition
If seal segments are rigidly fixed in the support structure, then structural stability is improved, but thermal expansion causes leakage and sealing integrity deteriorates
Solution Approach 1:
The feather seal is designed to rotate dynamically within its radially extending slot in response to thermal expansion. This dynamic adjustment allows the seal to maintain contact and sealing integrity with the turbine blade surface as temperature and expansion conditions change during operation.
Solution Approach 2:
The system accommodates parameter changes in thermal expansion by allowing the feather seal to change its angular position within the slot. As temperature increases and segments expand, the feather seal rotates to maintain proper sealing geometry, adapting to the changing dimensional parameters of the assembly.
3Volume of moving object
If the feather seal thickness is reduced to minimize space requirements, then compactness is improved, but the slot width to thickness ratio must be precisely controlled to maintain sealing effectiveness
Solution Approach 1:
The design specifies a controlled parameter range for the slot width to feather seal thickness ratio (between 1.5 and 2.5). This parameter control ensures that even with reduced feather seal thickness for compactness, the sealing effectiveness is maintained through precise geometric relationships between the slot dimensions and seal thickness.
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 maintains sealing integrity across varying temperatures and thermal expansions, reducing leakage and enhancing the durability and efficiency of gas turbine engines by using a ceramic matrix composite material for the seal segments and a metallic or ceramic feather seal.
Implementation Method 1
accommodates thermal expansion by rotating within these slots, maintaining sealing effectiveness across a range of temperatures and thermal expansions
Data Source
AI summary
A blade outer air seal assembly includes a support structure. A blade outer air seal has a plurality of segments that extends circumferentially about an axis and is mounted in the support structure. At least two of the segments have a base portion that extends from a first circumferential side to a second circumferential side. A first protrusion extends from the first circumferential side and has a first radially extending slot. A second protrusion extends from a second circumferential side and has a second radially extending slot. A feather seal is arranged in the first radially extending slot and the second radially extending slot between at least two segments.