Impeller-Shaft Friction Ring Coupling to Reduce Start-Up Vibration
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Solution Overview
Problem
Turbomachines face challenges in transferring high torque over a limited interface due to the overhang mounting of impellers, which leads to relative displacement and increased vibrations, especially during start-up, and existing solutions like Hirth couplings are laborious and costly.
Innovation Solution
A turbomachine design using a draw bolt or draw bar connection with a friction ring clamped between the shaft and impeller end faces, utilizing a draw bolt or draw bar to secure the impeller to the shaft, allowing for a simple and cost-effective solution that counteracts relative displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bolt connection is used to couple the impeller to the shaft in overhang mounting, then the impeller can be securely attached to the shaft, but relative displacement between the impeller and shaft increases during start-up, leading to increased vibrations
Solution Approach 1:
A friction ring is introduced as an intermediary element between the impeller and shaft. This friction ring creates a friction-based self-centering connection that prevents relative displacement while maintaining secure coupling. The friction ring acts as a mediator that transfers torque through friction rather than rigid mechanical connection, thereby eliminating the alignment instability problem of traditional bolt connections.
Solution Approach 2:
The traditional mechanical bolt connection system is replaced with a friction-based connection system. Instead of relying on rigid mechanical fastening that allows relative movement, the invention uses friction forces generated by the friction ring to create a self-centering effect that maintains alignment stability during operation.
2Reliability
If a Hirth coupling with tapered teeth is used to counteract relative displacement, then alignment stability is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The friction ring is a simple, inexpensive component that can be manufactured as a disposable or replaceable element. Instead of investing in complex Hirth coupling tooth profiles that are difficult and expensive to manufacture, the invention uses a simple friction ring that achieves the same alignment stability function at much lower manufacturing cost and complexity.
Solution Approach 2:
The invention changes the fundamental parameter of the coupling mechanism from mechanical interlocking (Hirth coupling teeth) to friction-based self-centering. This parameter change transforms the coupling from a complex precision-machined component to a simple friction interface, dramatically reducing manufacturing difficulty while maintaining alignment stability.
3Reliability
If intermediate pieces with tooth profiles are used between shaft and impeller, then relative displacement is reduced, but device complexity and manufacturing cost increase due to additional bolt connections
Solution Approach 1:
The invention extracts and eliminates the complex intermediate pieces with tooth profiles and their associated bolt connections. By removing these unnecessary intermediate components and replacing them with a simple friction ring, the coupling structure is simplified while maintaining the essential function of preventing relative displacement between shaft and impeller.
Solution Approach 2:
The friction ring combines multiple functions into a single component: it provides torque transmission, self-centering, and alignment stability simultaneously. This merges the functions that previously required separate intermediate pieces and bolt connections into one integrated element, reducing device complexity.
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 enhances self-centering, enabling higher speeds, power, and mass flow rates while reducing vibrations and allowing for faster speed changes, without the need for complex geometries like Hirth couplings.
Implementation Method 1
a friction ring (30) arranged around an axial protrusion (22) of the impeller (20), wherein the friction ring (30) is adapted to counteract relative displacement between the axial surface (13) at the first end of the shaft (10) and the opposite axial surface (23) of the impeller (20)
Data Source
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AI summary
Turbomachine, comprising a shaft (10) with a first end and an impeller (20) arranged at and coupled to the first end of the shaft (20), arranged together to rotate about an axis of rotation (1). The turbomachine comprises a friction ring (30) clamped between an axial surface (13) at the first end of the shaft (10) and an opposite axial surface (23) of the impeller (20). The friction ring (30) is preferably provided with a surface with hard particles, e.g. diamond or ceramic, to increase friction between the clamped parts and to interlock the clamped parts.