Adjustable BOAS Assembly for Turbine Rotor Clearance Control
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Solution Overview
Problem
During rapid acceleration of gas turbine engines, the rotors expand radially outward faster than the blade outer air seals (BOAS), leading to a pinch condition and excessive rub, which increases radial clearance and reduces engine performance when returning to cruise conditions.
Innovation Solution
A BOAS assembly with adjustable BOAS segments and carriers, connected by adjustment levers and actuators, allows for controlled radial movement to maintain optimal clearance between the rotor and BOAS segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the BOAS is designed with fixed radial position, then the structure is simple and reliable, but the radial clearance increases during rapid acceleration reducing engine performance
Solution Approach 1:
The BOAS structure is transformed from fixed to dynamically adjustable. Adjustment levers with pivot axes allow the BOAS segments to move radially in response to rotor expansion during rapid acceleration, maintaining optimal clearance and preventing pinch conditions while preserving engine performance.
Solution Approach 2:
The BOAS is divided into multiple adjustable segments, each capable of independent radial movement through its own adjustment lever. This segmentation allows localized adaptation to rotor expansion without requiring complex global adjustment mechanisms, balancing simplicity with effectiveness.
2Manufacturing precision
If the BOAS segments are made movable to adjust radial clearance, then the radial gap can be optimized, but the device complexity increases with adjustment mechanisms
Solution Approach 1:
Adjustment levers with pivot axes enable dynamic radial positioning of BOAS segments. The lever mechanism provides precise control over clearance adjustment through rotational movement about the pivot axis, allowing the system to adapt to varying thermal and mechanical conditions while maintaining manufacturing precision.
Solution Approach 2:
The radial position parameter of the BOAS segments is made variable through the adjustment mechanism. By changing the radial position parameter in response to rotor expansion, the system maintains optimal clearance precision without requiring overly complex control systems.
3Reliability
If the BOAS remains stationary during rapid acceleration, then the structure is simpler, but excessive rub occurs due to rotor expansion
Solution Approach 1:
The BOAS segments are equipped with adjustment levers that enable radial movement during rapid acceleration. This dynamic capability allows the BOAS to track rotor expansion, preventing pinch conditions and excessive rub that would occur with a stationary configuration, thereby improving reliability.
Solution Approach 2:
The adjustment mechanism is designed to anticipate and compensate for rotor expansion before excessive rub occurs. The lever system can be pre-positioned or rapidly actuated to maintain appropriate clearance during the acceleration transient, preventing damage before it happens.
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 enables precise adjustment of radial gaps, reducing leakage and improving engine performance by minimizing clearance variations and preventing rubs during rapid accelerations.
Implementation Method 1
Rotation of each adjustment lever about a respective pivot axis urges movement of the plurality of BOAS segments in a radial direction thereby adjusting a radial gap between the turbine rotor and the plurality of BOAS segments
Data Source
AI summary
A blade outer airseal (BOAS) assembly of a gas turbine engine includes a plurality of BOAS segments arrayed circumferentially about the engine central longitudinal axis, and a plurality of BOAS carriers located radially outboard of the plurality of BOAS segments. Each BOAS carrier is supportive of at least one BOAS segment. The BOAS assembly includes plurality of adjustment levers. Each adjustment lever is operably connected to at least two BOAS carriers of the plurality of BOAS carriers. Rotation of each adjustment lever about a respective pivot axis urges movement of the plurality of BOAS segments in a radial direction thereby adjusting a radial gap between the turbine rotor and the plurality of BOAS segments.