Axial Friction Ring Coupling for Impeller Alignment Under High Torque
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Solution Overview
Problem
Turbomachines face challenges in transferring torque over a limited interface due to high rotational speeds and mass imbalances, particularly during start-up, leading to vibrations and alignment issues, which existing solutions like Hirth couplings are laborious and costly to manufacture and maintain.
Innovation Solution
A turbomachine design featuring a friction ring clamped between the axial surfaces of the shaft and impeller, utilizing a draw bolt connection to counteract relative displacements and provide self-centering without the need for additional parts or complex tooth profiles, allowing for efficient torque transfer and improved alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a bolt connection is used to couple the impeller to the shaft, then the impeller can be mounted in overhang, but the torque transfer over the limited interface becomes insufficient and relative displacement occurs
Solution Approach 1:
A friction ring is introduced as an intermediary element between the impeller and shaft. This friction ring increases the frictional force at the interface, thereby enhancing torque transfer capability while maintaining the overhang mounting configuration. The friction ring acts as a mediator that strengthens the connection without requiring additional bolts or complex coupling mechanisms.
2Strength
If the impeller is made heavier to increase torque capacity, then more torque can be transmitted, but the rotational mass imbalance increases and vibrations become unacceptable
Solution Approach 1:
The friction coefficient at the interface is changed by introducing the friction ring with specific material properties. This parameter change allows for increased torque transmission capability without increasing the mass of the impeller, thereby avoiding the vibration problems associated with heavier rotors. The friction ring enables torque enhancement through friction rather than mass.
3Manufacturing precision
If a Hirth coupling is used to achieve self-centering and counteract relative displacement, then alignment is improved, but the manufacture becomes laborious and expensive
Solution Approach 1:
The friction ring serves as a simpler, more economical alternative to Hirth couplings. While the friction ring may wear over time and require replacement, its initial manufacture is much simpler and less expensive than precision Hirth coupling teeth. The friction ring achieves adequate self-centering through friction forces without requiring complex gear-like tooth profiles.
4Manufacturing precision
If intermediate pieces with tooth profiles are used to achieve Hirth coupling, then self-centering is achieved, but additional bolt connections are required and the problem of relative displacement shifts to the spacer interfaces
Solution Approach 1:
The friction ring combines multiple functions into a single element: it provides torque transfer enhancement, self-centering capability, and acts as a spacer. By merging these functions into one component, the need for separate intermediate pieces with tooth profiles and additional bolt connections is eliminated, reducing overall device complexity while maintaining self-centering performance.
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 friction ring design enhances self-centering, reduces vibrations, and enables higher speeds, power, and mass ratios while maintaining alignment quality, allowing for quicker speed changes and increased torque transmission without the need for costly self-centering couplings.
Implementation Method 1
a friction ring clamped between an axial surface (face) at the first end of the shaft and an opposite axial surface (end face) of the impeller
Data Source
AI summary
A turbomachine includes a shaft with a first end and an impeller arranged at and coupled to the first end of the shaft, arranged together to rotate about an axis of rotation. The turbomachine further includes a friction ring clamped between an axial surface at the first end of the shaft and an opposite axial surface of the impeller.