Active Blade Outer Air Seal Assembly for Gas Turbine Clearance Control
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to increased blade tip clearance caused by thermal expansion and centrifugal force, leading to potential tip strikes and reduced performance.
Innovation Solution
An active control system is implemented to adjust the radial position of the blade outer air seal (BOAS) using a cam mechanism and actuator, allowing for real-time adjustment of blade tip clearance based on engine operating conditions to prevent strikes and maintain optimal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the blade outer air seal is positioned to minimize blade tip clearance, then turbine efficiency is maximized, but thermal expansion and centrifugal force cause the clearance to increase
Solution Approach 1:
The patent implements an active control system that dynamically adjusts the blade outer air seal position in real-time based on engine operating conditions. The system uses actuators to move the air seal radially, responding to feedback from sensors that monitor blade tip clearance, thereby maintaining optimal clearance despite thermal expansion and centrifugal force variations.
Solution Approach 2:
The control system incorporates feedback mechanisms where sensors continuously monitor the blade tip clearance and transmit this information to the control system. The control system processes this feedback and adjusts the actuator positions to maintain optimal clearance, creating a closed-loop control system that adapts to changing thermal and mechanical conditions.
2Device complexity
If the blade outer air seal position is fixed, then the structure is simpler, but the clearance cannot be adjusted for varying operating conditions
Solution Approach 1:
The system transitions from a fixed, static air seal structure to a dynamic, adjustable structure. Multiple actuators are employed to independently control the position of air seal segments, enabling the system to adapt to varying operating conditions while maintaining a relatively compact and integrated design.
Solution Approach 2:
The blade outer air seal is divided into multiple independent segments or sections, each capable of being adjusted independently by its own actuator. This segmentation allows for precise local adjustment of clearance in different radial zones while maintaining overall structural integrity and managing system complexity through modular design.
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 system effectively stabilizes engine temperatures and enhances turbine section efficiency by minimizing blade tip clearance, preventing strikes and adapting to varying operational conditions.
Implementation Method 1
A control rod, wherein the control rod is fixed to the outer case, rotates in response to the rotating of the unison ring. A gap varies in response to the rotating of the control rod, wherein the gap is located between a blade outer air seal (BOAS) and a turbine blade
Implementation Method 2
Due to thermal expansion and centrifugal force, clearance between the turbine blade array and the BOAS may be large
Implementation Method 3
Due to thermal expansion and centrifugal force, clearance between the turbine blade array and the BOAS may be large
Data Source
Figure 1
Figure 2A
Figure 2B~3B
AI summary
A blade outer air seal (BOAS) assembly (200) is provided. The BOAS assembly may comprise an outer case (240), a first support arm (242;742), a second support arm (446;746), a control rod (250), a blade outer air seal (BOAS) (220), and a unison ring (230). The unison ring may be located radially inward of the outer case and in mechanical communication with the control rod. The BOAS may be configured to expand or contract in response to a rotation of the control rod. The first support arm and the second support arm may be fixed to the outer case. The control rod may be coupled to the first support arm and the second support arm, wherein the control rod may be configured to rotate about a control rod axis. The BOAS may comprise a first segment and a second segment.