CMC Blade Outer Air Seal Rib Structure for Thermal Stability
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Solution Overview
Problem
Existing blade outer air seals in gas turbine engines, particularly those made of ceramic matrix composite materials, face challenges in maintaining structural integrity and thermal stability while minimizing thermal gradients and manufacturing complexity.
Innovation Solution
A blade outer air seal (BOAS) segment is designed with a rib structure extending between axial walls, featuring two passages with differing pressures and angles relative to the radial direction, made of ceramic matrix composite material, and incorporating cutouts and slots for enhanced support and stability, allowing for improved thermal and mechanical stress reduction and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blade assembly is disassembled to access the suction port, then the suction port can be cleaned of debris, but the blade assembly becomes difficult to reassemble and align correctly
Solution Approach 1:
The blade assembly is divided into multiple blades that can be independently removed from the hub. Each blade can be detached by pressing a release mechanism, allowing access to the suction port while maintaining a modular structure that simplifies reassembly through simple re-engagement of the blades with the hub.
Solution Approach 2:
The release mechanisms are pre-positioned on the blades and hub during manufacturing, allowing for quick and easy disassembly and reassembly operations. The preliminary setup of these mechanisms eliminates the need for complex alignment procedures during maintenance.
2Productivity
If blades are made longer to improve airflow, then airflow performance improves, but the blades become more prone to damage and harder to replace
Solution Approach 1:
The airflow path is segmented into multiple shorter blades rather than one long blade. This segmentation maintains the total airflow capability while improving reliability, as shorter blades are less prone to damage and can be independently replaced without replacing the entire assembly.
Solution Approach 2:
Different sections of the blade assembly have different characteristics - the hub portion provides structural support and connection, while the blade portions are optimized for airflow. This local differentiation allows each component to be optimized for its specific function while improving overall reliability.
3Strength
If a hub cap is used to protect the hub, then the hub is protected from damage, but the hub cap must be removed to access the suction port
Solution Approach 1:
The protective hub cap is merged with the blade release mechanisms and hub structure into an integrated assembly. This integration allows the hub cap to be removed simultaneously with the blades for accessing the suction port, eliminating the need for separate removal operations and simplifying maintenance procedures.
Data Source
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AI summary
A blade outer air seal (106) includes a base portion (124) that extends between a first circumferential side (CI) and a second circumferential side (C2) and from a first axial side (Al) to a second axial side (A2). A first wall (120) is axially spaced from a second wall (122). The first (120) and second (122) walls extend from the base portion (124) to an outer wall (126). A rib (130) extends from the base portion (124) to the outer wall (126) and spaced axially between the first (120) and second walls (122).