Gas Turbine Fan Case Liner Segments for Blade-Off Retention
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Solution Overview
Problem
Fan cases in gas turbine engines face challenges in maintaining dimensional tolerance and thermo-mechanical deflections, requiring frequent repair or replacement of liners, and existing solutions do not efficiently manage blade-off events where fan blades are released.
Innovation Solution
The design incorporates an annular outer shroud with coupled liner segments that move radially to adjust their position, allowing for a smooth transition and engagement mechanism to prevent blade escape, with angled head and tail surfaces facilitating this movement, enabling efficient liner segment replacement and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liners are permanently bonded to metallic shrouds using adhesives or hanger features, then dimensional tolerance between fan blades and fan case is maintained, but liner replacement and repair become complex and time-consuming
Solution Approach 1:
The liner is divided into multiple removable liner segments that can be independently installed and removed from the fan case. Each segment has a body, head, and tail portion that can be separately positioned along the inner surface of the metallic shroud, allowing for easy replacement while maintaining dimensional tolerance through precise segment geometry
Solution Approach 2:
The liner segments are designed with movable capability along the inner surface of the metallic shroud rather than being permanently fixed. The segments can be positioned, removed, and repositioned as needed, transforming the liner system from a static permanent bond to a dynamic removable connection that facilitates maintenance while maintaining operational precision
2Ease of repair
If liners are designed to be removable for repair and replacement, then maintenance becomes easier, but dimensional tolerance and thermo-mechanical deflection control become more difficult
Solution Approach 1:
Different portions of the liner segment serve different functions: the body portion provides the abraidable surface for blade contact, the head portion engages with the metallic shroud mounting structure, and the tail portion completes the circumferential arrangement. This local differentiation allows each portion to be optimized for its specific function while maintaining overall dimensional tolerance
Solution Approach 2:
The permanent adhesive or mechanical hanger bond is replaced with a friction-based friction-fit mounting system. The liner segments are retained on the metallic shroud through friction between the segment surfaces and the shroud inner surface, eliminating the need for adhesives or complex hanger features while maintaining precise positioning and dimensional tolerance
3Device complexity
If fan case uses traditional fixed liner design, then structural simplicity is maintained, but blade-off event management and liner maintenance efficiency are reduced
Solution Approach 1:
The liner is segmented into multiple removable sections that can be independently accessed and replaced. This segmentation allows maintenance personnel to remove and replace individual liner segments without disassembling the entire fan case or metallic shroud structure, significantly improving maintenance efficiency while adding minimal structural complexity
Solution Approach 2:
The liner segments are pre-configured with head, body, and tail portions that are designed to fit together in a specific sequence. This preliminary design of the segment geometry and mounting interface allows for quick installation and removal without requiring complex alignment procedures or specialized tools during maintenance operations
Data Source
AI summary
A fan case for use in a gas turbine engine of an aircraft includes an outer shroud and a liner extending along the outer shroud. The fan case provides a protective band that blocks fan blades from being thrown out of the fan case in case of a blade-off event in which a fan blade is released during operation of the gas turbine engine.