Torque Transfer Assembly With Polymer Bushing
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Solution Overview
Problem
Hybrid gas turbine engines face challenges in accommodating alignment variations between the engine core and generator due to structural flexibility, leading to limited torque transfer and potential system instabilities, such as torsional oscillations and reduced generator efficiency.
Innovation Solution
A torque transfer assembly comprising a metal shaft with a plastic bushing and a sleeve, where the bushing has a higher thermal expansion coefficient than the sleeve, generating pressure and increasing torsional stiffness and damping to accommodate alignment variations and improve shaft stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a quill shaft is used to transfer torque between the engine core and generator, then torque transfer is achieved with some accommodation to alignment variations, but the structure lacks sufficient torsional stiffness and damping to prevent torsional oscillations and maintain generator efficiency
Solution Approach 1:
The patent employs a composite structure consisting of a metal shaft combined with a polymer bushing and polymer sleeve. The metal shaft provides structural strength and rigidity, while the polymer components provide damping and flexibility to accommodate alignment variations. This composite approach resolves the contradiction by combining materials with complementary properties to achieve both adaptability and stability.
Solution Approach 2:
The patent utilizes the temperature-dependent properties of the polymer materials, specifically their thermal expansion characteristics. The polymer bushing and sleeve have higher coefficients of thermal expansion than the metal shaft, allowing them to expand and generate interference pressure at operating temperatures. This parameter change enables the polymer components to provide sufficient damping and alignment accommodation while maintaining torsional stability through the generated contact pressure.
2Weight of moving object
If the shaft is made lighter to reduce weight, then fuel efficiency improves, but the shaft becomes more susceptible to torsional oscillations and alignment variations
Solution Approach 1:
The composite structure of metal shaft with polymer bushing and sleeve achieves an optimal balance between weight and torsional stability. The metal shaft can be designed with reduced mass while the polymer components provide the necessary damping to counteract torsional oscillations. The polymer materials' inherent damping properties compensate for the reduced structural mass, maintaining stability despite weight reduction.
Solution Approach 2:
The patent applies polymer damping materials specifically at critical locations where torsional oscillations occur - within the bushing and sleeve that surround the shaft. This localized application of damping material provides targeted suppression of torsional vibrations without requiring the entire shaft structure to be heavier, thus achieving weight reduction while maintaining local torsional stability.
3Power
If the generator is positioned in axial alignment with the engine core, then power extraction efficiency is improved, but structural flexibility causes alignment variations that limit torque transfer
Solution Approach 1:
The polymer bushing and sleeve act as intermediary elements between the metal shaft and the surrounding structure. These intermediaries provide a compliant interface that can accommodate alignment variations caused by structural flexibility while maintaining effective torque transfer. The bushing and sleeve absorb misalignment through their elastic deformation and damping characteristics, allowing the generator to remain in optimal axial alignment for power extraction while tolerating structural movements.
Solution Approach 2:
The patent exploits the temperature-dependent dimensional changes of the polymer materials. At operating temperatures, the polymer bushing and sleeve expand due to their higher coefficient of thermal expansion, generating interference pressure that enhances their ability to accommodate alignment variations. This parameter change allows the torque transfer assembly to adapt to alignment variations while maintaining efficient power extraction at the designed axial alignment.
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 assembly enhances torsional resonance frequency, reduces shaft weight, and increases damping, thereby improving shaft life and generator efficiency by maintaining alignment and reducing torsional ringing.
Implementation Method 1
the rotating bushing increasing in temperature and experiencing thermal growth greater than a thermal growth of the sleeve
Implementation Method 2
the shaft frictionally entraining rotation of a bushing coaxially surrounding the shaft, the bushing frictionally entraining rotation of a sleeve coaxially surrounding the bushing
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The torque transfer assembly (36) can include a sleeve (40) having an elongated internal opening (42), a shaft (38) having an elongated body (44) extending in the internal opening (42) of the sleeve (40), a first coupler (46) at a first end (47) of the elongated body (44) coupled to a gas turbine engine rotor (32), and a second coupler (48) at a second end (49) of the elongated body (44) coupled to a generator (34), the second coupler (48) opposite the first coupler (46) relative to a length of the elongated body (44), the shaft (38) being made of a metal, and a bushing (50) extending around the elongated body (44) of the shaft (38), trapped between the shaft (38) and the sleeve (40), the bushing (50) made of plastic, the bushing (50) having a coefficient of thermal expansion greater than a coefficient of thermal expansion of the sleeve (40).