Gas Turbine Vibration Reducing Device with Eccentric Mass
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Solution Overview
Problem
Conventional squeeze film dampers in gas turbine engines face limitations in effectively attenuating centrifugal whirling vibrations due to restricted oil film thickness, which becomes rigid under large vibrational loads, and fail to provide sufficient damping when a fan blade breaks, leading to increased susceptibility to centrifugal whirling.
Innovation Solution
A vibration reducing device for gas turbine engines featuring an annular second mass member with an internal diameter larger than the rotating shaft, positioned to counterbalance centrifugal forces through inertial forces, which automatically engages and disengages based on vibration levels, utilizing a breakable support and low friction state to enhance damping effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a small oil film thickness is set for the squeeze film damper, then the damping effect is improved under normal conditions, but the oil film becomes rigid when large vibrational loads occur, reducing effectiveness
Solution Approach 1:
The patent applies the dynamics principle by making the oil film thickness variable rather than fixed. The flexible support member allows the bearing to dynamically adjust its position, thereby changing the oil film thickness in response to vibration amplitude. Under normal conditions, the oil film remains thin for effective damping, while under large vibrational loads, the bearing moves to maintain adequate film thickness and prevent rigidification.
Solution Approach 2:
The patent implements parameter changes by varying the oil film thickness parameter based on operating conditions. The flexible support member enables the system to change the physical parameter of oil film thickness dynamically, transitioning from a thin film state during normal operation to a thicker film state when subjected to large centrifugal whirling vibrations, thus adapting to different load conditions.
2Adaptability or versatility
If a large oil film thickness is set for the squeeze film damper, then the oil film remains flexible under large loads, but the damping effect is reduced and the rotating shaft becomes susceptible to centrifugal whirling
Solution Approach 1:
The flexible support member creates a dynamic system where the oil film thickness is not statically determined but evolves with vibration conditions. This dynamic adjustment allows the system to achieve thin film damping under normal conditions while maintaining film flexibility under large loads, resolving the contradiction between damping effectiveness and load adaptability.
Solution Approach 2:
The system employs self-service through the flexible support member that automatically adjusts the bearing position based on vibration amplitude. The bearing self-regulates the oil film thickness without external control, achieving thin films when damping is needed and thicker films when flexibility is required, based on the actual vibrational state of the rotating shaft.
3Device complexity
If a conventional squeeze film damper is used, then the structure is simple, but sufficient damping effect cannot be obtained when a fan blade breaks and large centrifugal whirling vibration is generated
Solution Approach 1:
By introducing the flexible support member, the patent transforms a static bearing arrangement into a dynamic one. This relatively simple modification enables the bearing to move and adjust oil film thickness in response to large vibrations caused by fan blade failure, significantly improving damping effectiveness without substantially increasing structural complexity.
Solution Approach 2:
The flexible support member enables parameter changes in the oil film thickness under extreme conditions. When fan blade failure causes large centrifugal whirling vibrations, the bearing moves to maintain appropriate film thickness, ensuring the squeeze film damper remains effective even in failure scenarios, while keeping the overall structure relatively simple.
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 counterbalances centrifugal forces, reducing shaft amplitude and vibration across a wide frequency range, thereby enhancing damping and mitigating centrifugal whirling vibrations caused by imbalance, especially during increased vibrational loads.
Implementation Method 1
counterbalance the centrifugal force acting on the first mass member with the inertial force acting on the second mass member
Implementation Method 2
counterbalance the centrifugal force acting on the first mass member with the inertial force acting on the second mass member
Implementation Method 3
the second mass member is supported on the stationary body via a break portion that breaks when the centrifugal whirling vibration of the rotating shaft attains the predetermined value or greater
Data Source
AI summary
A vibration reducing device for a gas turbine engine includes a rotating shaft containing a first mass member, a plurality of bearings rotatably supporting the rotating shaft, and a stationary body supporting the bearings. An annular second mass member having an internal diameter thereof larger than an external diameter of the rotating shaft is rotatably supported in a contact state at a position on the rotating shaft, at which position centrifugal whirling vibration is generated due to imbalance of the first mass member. Therefore, due to the second mass member being eccentric in an opposite phase with respect to the rotating shaft eccentrically undergoing centrifugal whirling, it is possible to counterbalance a centrifugal force acting on the first mass member with an inertial force acting on the second mass member, thus enabling a damping effect to be exhibited and reducing effectively the centrifugal whirling vibration of the rotating shaft.