Ceramic Seal Segment Dovetail Support for Gas Turbine Thermal Stress
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining effective tip clearance and resisting pressure gradients due to the low proportional stress limits of ceramic components, which can lead to thermal stresses and sealing performance issues.
Innovation Solution
A blade outer air seal system featuring a ceramic seal segment supported by a carrier with inward-facing dovetail hooks and an impingement cooling distributor, where the dovetail hooks are sloped to reduce stress and facilitate sealing, and the impingement cooling distributor helps manage thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic seal segments are used in blade outer air seals, then sealing performance and temperature resistance are improved, but thermal stresses and cracking risks increase due to low proportional stress limits
Solution Approach 1:
The air seal is divided into multiple discrete ceramic seal segments arranged in a circumferential array, each segment independently supported by the carrier structure. This segmentation allows individual segments to be replaced if damaged and distributes thermal stresses across multiple separate units rather than one large continuous seal.
Solution Approach 2:
A metal carrier structure with dovetail hooks serves as an intermediary between the ceramic seal segments and the blade assembly. The carrier supports the ceramic segments, distributing mechanical and thermal loads away from the brittle ceramic material to the more ductile metal support structure, thereby reducing thermal stress concentrations in the ceramic.
2Reliability
If ceramic components are used to maintain tip clearance, then sealing effectiveness is improved, but stress concentration and cracking occur due to low proportional stress limits
Solution Approach 1:
The carrier structure provides localized support at specific points beneath each ceramic seal segment through dovetail hooks and support surfaces. This localized support system distributes loads evenly across multiple contact points rather than creating stress concentrations at single critical points, reducing the risk of ceramic cracking while maintaining effective tip clearance control.
3Reliability
If ceramic seal segments are used to resist pressure gradients, then sealing performance is improved, but thermal gradients and stress accumulation increase
Solution Approach 1:
Multiple discrete ceramic segments are arranged circumferentially to create a segmented seal structure. This segmentation allows each segment to independently respond to local thermal and pressure conditions, distributing thermal gradients across multiple units and preventing stress accumulation that would occur in a single continuous seal exposed to the same thermal environment.
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 reduces thermal stresses and enhances sealing performance by distributing stresses over a larger area and managing thermal gradients, improving the durability and efficiency of the ceramic seal segment in high-temperature environments.
Implementation Method 1
the dovetail includes an impingement cooling distributor comprised of a wall between the first and second circumferential carrier sides and impingement cooling holes in the wall that open to the outer side of the ceramic seal segment
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~4
AI summary
A blade outer air seal (64; 164) includes a carrier (70; 170) that has a dovetail (76; 176) and a ceramic seal segment (68; 168) supported on the dovetail (70; 170). The ceramic seal segment (68; 168) has first and second axial ends (68a, 68b), first and second circumferential sides (68c, 68d), an inner side (68e), an outer side (68f), and first and second inward-facing dovetail hooks (72; 172) that project from the outer side (68f) and define a dovetail key (74). The ceramic seal segment (68; 168) is axially receivable onto the dovetail (70; 170) of the carrier via the dovetail key (74).