Deformable Coupling Protects Motor Shaft from Impeller Failure
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Solution Overview
Problem
Directly driven centrifugal compressors in industrial applications face significant challenges due to impeller failures, which generate unbalanced loading that can lead to damage of the electric motor shaft and its bearings, especially in high-power transmission scenarios, where prior breakaway solutions are not effective.
Innovation Solution
A coupling design with a deformable section is implemented, featuring a coupling body with a wider and narrower axial bore portion, allowing the coupling to permanently deform under unbalanced loading without exceeding the material's ultimate strength, thereby preventing damage to the motor shaft and bearings, while still transmitting torque effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a rigid coupling is used to transmit torque from the motor shaft to the impeller, then torque transmission efficiency is improved, but the motor shaft and bearings are vulnerable to damage from unbalanced loading during impeller failure
Solution Approach 1:
The coupling body incorporates a deformable section with reduced wall thickness at a specific location, creating a localized weak point. This allows the coupling to maintain rigid structure for torque transmission while having a specific region that can deform to absorb unbalanced loads, resolving the contradiction between overall rigidity and localized flexibility.
Solution Approach 2:
The wall thickness parameter of the coupling body is varied along its length, with the deformable section having reduced wall thickness compared to other portions. This parameter change creates the desired mechanical property gradient, allowing the coupling to be sufficiently rigid for power transmission while having a controlled deformation zone for protecting against unbalanced loading.
2Object-affected harmful factors
If a breakaway coupling design is used to protect against impeller failure, then motor shaft protection is improved, but the coupling cannot effectively handle high-power transmission scenarios
Solution Approach 1:
The coupling transitions from a static rigid structure to a dynamic system where the deformable section can change its mechanical properties during operation. Under normal conditions, the coupling remains rigid for effective power transmission. Upon impeller failure, the deformable section yields plastically, dynamically adapting to protect the motor shaft while maintaining high-power transmission capability during normal operation.
Solution Approach 2:
The deformable section is designed in advance to undergo plastic deformation at a controlled stress level, creating a cushioning effect before the unbalanced loads can reach the motor shaft. This pre-planned deformation mechanism provides protection before actual damage occurs, allowing the coupling to handle both high-power transmission and failure protection requirements.
3Ease of manufacture
If the coupling body is made with uniform wall thickness, then manufacturing simplicity is improved, but the coupling cannot selectively deform to protect the motor shaft during impeller failure
Solution Approach 1:
Instead of uniform wall thickness throughout the coupling body, the design implements local variation in wall thickness at the deformable section. This allows the majority of the coupling to maintain simple geometry for ease of manufacture, while a specific localized region provides the necessary deformation capability for motor shaft protection during impeller failure.
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 coupling design effectively limits unbalanced loads, preventing motor shaft deformation and potential bearing failure, allowing the impeller to fail before causing damage to the electric motor, thus safeguarding the motor and potentially extending the life of the bearings.
Implementation Method 1
the deformable section will permanently deform under an unbalanced loading exerted against the coupling body upon a failure of the impeller, without exceeding the ultimate strength of a material forming the coupling body and prior to permanent deformation of the shaft
Data Source
Figure 1
Figure 2
AI summary
A coupling to attach an impeller of a compressor to a shaft of an electric motor. The coupling has a coupling body that is attached at a first of the ends thereof to the impeller and at the opposite second end, to the motor shaft. The coupling body has a deformable section between the first and second ends of the coupling body. The deformable section is configured such that under an unbalanced loading exerted against the coupling body upon a failure of the impeller, the deformable section will permanently deform without the ultimate strength of a material forming the coupling body being exceeded and prior to a permanent deformation of the shaft. In such manner, the electric motor is protected from damage upon a failure of the impeller.