Aircraft Compressor Stiffener Vibration Mitigation
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Solution Overview
Problem
Aircraft low-pressure compressor engines face issues with unbalanced masses causing critical vibrations, leading to potential damage and integrity concerns, particularly at the third and fourth guide vanes, without feasible solutions to modify existing engines or change materials due to weight and strength constraints.
Innovation Solution
The implementation of aluminum stiffeners positioned between the low-pressure compressor and the casing, triangulated around the compressor to increase stiffness, using multiple stiffeners uniformly distributed to mitigate cantilever effects and reduce vibrations without altering the engine's modular breakdown or adding significant weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum stiffeners are added to reduce vibrations, then vibration levels decrease from 25 ips to 10-15 ips, but the device complexity increases due to additional components
Solution Approach 1:
The stiffener is divided into two separate parts: a first part fixed to the casing and a second part fixed to the compressor envelope. This segmentation allows the stiffener to be installed without modifying the existing modular assembly structure of the compressor, thereby reducing device complexity while still achieving the vibration reduction function.
Solution Approach 2:
The stiffener acts as an intermediary element between the casing and the compressor envelope. It provides a mechanical connection that triangulates the structure, reducing cantilever effects and vibrations without requiring direct modification of the original components, thus maintaining simplicity while improving reliability.
2Strength
If additional stiffening parts are installed, then structural stiffness increases, but weight increases due to additional material
Solution Approach 1:
The stiffener is made of aluminum, changing the material parameter from potentially heavier materials (like steel) to a lighter alternative. This parameter change maintains the required stiffness and strength while minimizing weight increase, addressing the contradiction between structural reinforcement and weight constraints.
Solution Approach 2:
The stiffener is positioned specifically at the structural arm fixed to the shell, targeting the local area where cantilever effects and vibrations are most problematic. This localized approach provides stiffness where needed without adding material throughout the entire structure, thereby minimizing overall weight increase while achieving the required structural reinforcement.
3Reliability
If the compressor assembly is modified to reduce vibrations, then vibration tolerance improves, but ease of manufacture decreases due to modification requirements
Solution Approach 1:
The stiffener is designed as two separate parts that can be independently manufactured and then assembled. The first part attaches to the casing and the second part attaches to the compressor envelope, allowing installation without disassembling or modifying the existing modular compressor assembly. This maintains ease of manufacture while improving vibration tolerance.
Solution Approach 2:
The stiffener parts are prepared in advance with appropriate mounting features (flanges, fastening means) that align with existing attachment points on the casing and compressor. This preliminary preparation enables straightforward assembly without requiring complex modifications during the assembly process, thereby maintaining ease of manufacture.
Data Source
AI summary
Unbalanced mass effects can occur at the low pressure compressor (5) of an aircraft engine.Stiffeners (20) are proposed to increase the stiffness of the assembly and therefore reduce possible cracks due to accidental unbalanced masses, one end (22) of the stiffener can be fixed to the engine casing (7) at the structural arm (10), and the other end (32) can be fixed to the compressor (5), preferably at the upstream face of the third guide vane (RD3).Advantageously, the stiffeners (20) are made of two parts fixed to each other; their manufacturing is optimized to limit the additional weight due to their presence.