Squirrel Cage Bearing Support Damping via Viscoelastic Ligaments
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engines face excessive vibration due to rotor instabilities and critical speeds, where traditional squeeze-film damping can sometimes enhance vibrations instead of damping them, especially when the oil acts as a stiffener at specific shear angles.
Innovation Solution
A bearing centering spring with a damping assembly that includes a squirrel cage supported by a stationary housing, featuring ligaments with a damping layer and an oil supply system that can be switched off to prevent oil from acting as a stiffener, and a viscoelastic damping layer to absorb vibrations directly through the squirrel cage when oil supply is ceased.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If oil is supplied to the annulus for squeeze-film damping, then vibration damping is improved, but the oil may act as a stiffener and increase vibration transmission at certain shear angles
Solution Approach 1:
The patent applies dynamics by making the damping system adaptive rather than static. The oil supply to the annulus is controlled dynamically based on operating conditions, allowing the system to switch between damping and stiffening modes. The bearing centering spring with its flexible ligaments also provides dynamic response to varying vibration frequencies and amplitudes, adjusting the damping characteristics in real-time to prevent the oil from acting as a stiffener during certain operational phases.
Solution Approach 2:
The patent utilizes parameter changes by modifying the physical state and flow characteristics of the oil in the annulus. By controlling oil supply pressure, flow rate, and viscosity parameters, the system optimizes the shear angle of the oil to maintain damping effectiveness while preventing stiffening behavior. The bearing centering spring parameters (ligament flexibility, spring constant) are also adjusted to complement the oil damping characteristics across different operating conditions.
2Object-affected harmful factors
If the squirrel cage is made flexible to bend in response to bearing loads, then vibration absorption is improved, but the structural strength may be compromised
Solution Approach 1:
The patent applies composite materials by constructing the squirrel cage from multiple materials with complementary properties. The ligaments are made from materials that combine flexibility for vibration absorption with sufficient structural strength to support bearing loads. This composite approach allows the squirrel cage to bend and absorb vibrations while maintaining the structural integrity needed to withstand operational forces without permanent deformation or failure.
3Stability of the object's composition
If the bearing centering spring is designed to support the bearing, then bearing stability is improved, but vibration transmission to the engine structure increases
Solution Approach 1:
The patent uses an intermediary approach by introducing the annulus with oil supply as a mediating element between the bearing and the stationary housing. The oil in the annulus acts as a damping intermediary that absorbs and dissipates vibrations generated by the bearing, preventing direct transmission to the engine structure. The bearing centering spring also serves as an intermediary with its flexible ligaments that isolate bearing vibrations from the housing while maintaining bearing stability through controlled flexibility.
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
Effectively reduces engine vibrations by ensuring the oil in the squeeze-film damper maintains a 90-degree shear angle for damping, and when it acts as a stiffener, the system switches off oil supply to prevent vibration transmission, relying on the viscoelastic damping layer to absorb vibrations, thus maintaining efficient vibration reduction across operational speeds.
Implementation Method 1
a damping layer comprising a viscoelastic material covering at least one of the plurality of ligaments
Implementation Method 2
the damping layer comprising a viscoelastic material covering at least one of the plurality of ligaments
Implementation Method 3
Squeeze film damping can be used in a bearing support assembly that supports a rotatable shaft of a gas turbine engine
Implementation Method 4
Squeezing the oil in the annulus creates a pressure wave that may comprise a damping force
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A damping treatment (32) is applied to the ligaments (22) of a squirrel cage (12) type bearing support. The damping treatment (32) reduces the vibrations transmitted to the engine casing as the engine passes through various resonance frequencies of the various parts of the gas turbine engine. A squeeze-film damper damps engine vibrations, but the oil in the squeeze-film damper can act as a stiffener during certain operational ranges, which increases the transmission of vibrations to the engine structure. Applying a damping treatment (32) to the ligaments (22) of the squirrel cage (12) provides effective vibration damping.