Gas Turbine Thrust Strut Vibration Control
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Solution Overview
Problem
Gas turbine engine thrust struts experience vibrations that align with rotor frequencies, leading to reduced component lifespan and increased transmission of vibrations to the aircraft, as there are no frequencies at which the struts can be tuned to avoid these operating frequencies.
Innovation Solution
A mounting apparatus with a restraining structure that radially and circumferentially constrains the thrust strut while allowing axial movement, increasing its natural frequency beyond the forcing frequencies of the engine spools and preventing or attenuating vibrations, using a bracket and elongate members connected to the engine casing or nacelle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thrust strut is designed with larger diameter to increase natural frequency, then vibration resistance improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention divides the thrust strut system into two functional parts: the original thrust strut that carries axial loads, and a separate restraining structure (bracket with elongate members) that provides lateral support and increases natural frequency. This segmentation allows each component to be optimized independently, avoiding the need to redesign the entire strut with larger diameter.
Solution Approach 2:
The bracket and elongate members act as an intermediary structure that couples the thrust strut to the engine casing or nacelle. This intermediary provides the necessary lateral restraint and frequency tuning without requiring modification to the thrust strut itself, thus simplifying the overall design while achieving vibration resistance.
2Reliability
If the restraining structure is made rigid to prevent vibrations, then vibration attenuation improves, but axial movement freedom deteriorates
Solution Approach 1:
The restraining structure is designed with directionally selective stiffness: the bracket and elongate members provide high rigidity in lateral directions (radial and circumferential) to suppress vibrations, while maintaining flexibility in the axial direction to allow free movement. This local quality differentiation resolves the contradiction between vibration attenuation and axial movement freedom.
Solution Approach 2:
The elongate members are configured to be flexible or compliant along the thrust strut axis, allowing the structure to adapt dynamically to axial movements while maintaining lateral restraint. This dynamic characteristic enables the system to provide vibration attenuation without constraining axial displacement.
3Reliability
If the restraining structure is added to increase natural frequency, then vibration frequency moves beyond forcing frequencies, but manufacturing complexity increases
Solution Approach 1:
The natural frequency of the thrust strut is tuned by modifying physical parameters of the restraining structure, such as the length, cross-sectional area, and material properties of the elongate members. By changing these parameters, the lateral stiffness can be adjusted to raise the natural frequency above the forcing frequencies, achieving vibration avoidance through parameter optimization rather than complex design.
Solution Approach 2:
The restraining structure uses simple, inexpensive components (bracket and elongate members) that can be manufactured using conventional methods. The design prioritizes ease of manufacture and installation over high-performance materials or complex geometries, making it an economical solution for frequency tuning.
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 effectively prevents or reduces vibrations in the thrust strut, maintaining its statically determinate configuration and eliminating the need for excessively large diameter struts, while being easy to manufacture and retrofit, and verifiable through computational methods.
Implementation Method 1
The restraining structure may increase a natural frequency of vibration of the thrust strut outside an envelope of forcing frequencies of engine spools or rotors
Implementation Method 2
the at least one elongate member may be adapted to flex to allow the thrust strut to move along the thrust strut axis
Data Source
AI summary
A mounting apparatus for mounting a gas turbine engine to an aircraft. The mounting apparatus includes a thrust strut operably connected to the gas turbine engine and the aircraft. The thrust strut defines a thrust strut axis. The mounting apparatus further includes a restraining structure. The restraining structure includes a bracket circumferentially disposed on the thrust strut and at least one elongate member connected to the bracket and the gas turbine engine. The restraining structure radially and circumferentially constrains the thrust strut with respect to the thrust strut axis of the thrust strut while allowing the thrust strut to move in the direction of thrust strut axis.