Blade Outer Air Seal with Leaf Seal for Gas Turbine
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Solution Overview
Problem
Current blade outer air seals in gas turbine engines face challenges in effectively sealing between rotating blades and the engine casing, leading to airflow leakage and heat loss, particularly during varying operating conditions.
Innovation Solution
A blade outer air seal design featuring a seal body with a radially inner and outer face, a retention flange, and a leaf seal with a flexible arcuate portion that applies a constant load, brazed to both the retention flange and the seal body, providing secondary air sealing and heat shielding by engaging with a groove in the casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid seal structure is used to seal between blades and casing, then sealing effectiveness is improved under stable conditions, but the seal cannot adapt to varying operating conditions and thermal expansion
Solution Approach 1:
The patent employs a dynamic seal mechanism where the seal member is biased by a spring to maintain contact with the blade tip. The spring force automatically adjusts to accommodate thermal expansion and contraction of the blade during varying operating conditions, ensuring continuous sealing effectiveness without requiring a rigid fixed-position seal.
Solution Approach 2:
The seal system changes its physical parameters dynamically through the spring mechanism, which compresses and expands based on thermal conditions. This allows the seal to adapt its position and contact pressure in response to temperature variations, maintaining sealing effectiveness across different operating states.
2Reliability
If the seal is positioned in close proximity to the blade tip to reduce leakage, then sealing effectiveness is improved, but the seal is exposed to higher temperatures and mechanical stresses
Solution Approach 1:
The patent uses a flexible seal member that can deform and adapt to the blade tip geometry. This flexible structure allows the seal to maintain close proximity to the blade tip for effective sealing while accommodating thermal distortion and mechanical stress through its inherent flexibility rather than rigid contact.
Solution Approach 2:
The spring mechanism provides a cushioning force that maintains optimal seal-blade contact pressure while absorbing thermal and mechanical shocks. This beforehand cushioning protects the seal from excessive stresses during transient operating conditions while maintaining sealing effectiveness.
3Device complexity
If a simple seal structure is used to reduce complexity, then manufacturing and installation are easier, but the seal cannot provide both sealing and constant load application
Solution Approach 1:
The spring-loaded seal mechanism is self-regulating, automatically maintaining constant load on the blade tip through the spring force without requiring external control systems. The spring continuously applies and adjusts the necessary load to compensate for wear, thermal expansion, and operational variations, providing reliable constant loading with relatively simple structure.
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 airflow leakage and heat loss by maintaining a consistent seal across varying conditions, including engine shutdown, through the use of a flexible leaf seal that applies a constant load, ensuring efficient energy extraction and operational reliability.
Implementation Method 1
a flexible arcuate portion coupling the base portion to the radially outer sealing end
Implementation Method 2
The leaf seal is brazed to the retention flange and to the radially outer face of the seal body
Data Source
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AI summary
A blade outer air seal (BOAS) for a gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a seal body having a radially inner face and a radially outer face that axially extend between a leading edge portion and a trailing edge portion. A retention flange extends from the leading edge portion and a leaf seal contacts the retention flange.