Foil Bearing Load Transition for Bump Foil Protection
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Solution Overview
Problem
Foil bearings face performance degradation and potential damage due to excessive load causing deformation of the top foil, which can lead to reduced reliability in fluid machinery.
Innovation Solution
The foil bearing design includes a bump foil with crest and trough portions that elastically support the top foil, transitioning to a plain bearing contact when loads exceed a threshold, ensuring stable support of the rotary member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protrusions are added to the housing to prevent excessive load on the bump foil, then the bump foil is protected from damage, but the top foil deforms to conform to the protrusions which degrades bearing performance
Solution Approach 1:
The patent introduces a compliant layer between the housing and the bump foil. This compliant layer acts as an intermediary that absorbs excessive loads through elastic deformation, preventing direct transmission of impact forces to the bump foil while maintaining a smooth bearing surface that does not degrade performance. The compliant layer mediates between the rigid housing structure and the delicate bump foil, protecting the latter from damage without introducing the deformation problems caused by rigid protrusions.
Solution Approach 2:
The patent changes the mechanical properties of the bearing structure by introducing a compliant layer with specific elastic characteristics. This layer has controlled stiffness and elasticity parameters that allow it to deform under excessive load conditions while returning to its original state during normal operation. By adjusting the compliance parameters of this layer, the system can tolerate load variations without permanent deformation or performance degradation.
2Reliability
If the top foil is pressed against protrusions to limit excessive load on the bump foil, then the bump foil damage is prevented, but the top foil deformation degrades bearing performance
Solution Approach 1:
The compliant layer serves as a mediator that protects the bump foil from excessive loads without requiring the top foil to deform against rigid protrusions. During normal operation, the compliant layer remains elastic and compliant, allowing smooth relative motion between the top foil and housing. When excessive loads occur, the compliant layer absorbs the impact through controlled deformation, preventing both bump foil damage and top foil deformation that would degrade bearing performance.
3Force
If the bump foil is made more rigid to support excessive loads, then load-bearing capacity is improved, but the bump foil becomes more susceptible to breaking under sudden excessive loads
Solution Approach 1:
The compliant layer provides beforehand cushioning by being positioned between the housing and the bump foil. During normal operation, it maintains a ready state that allows it to immediately absorb sudden excessive loads through elastic deformation. This pre-positioned cushioning mechanism protects the bump foil from breakage under sudden load impacts while still providing adequate support during normal operating conditions.
Solution Approach 2:
The system uses parameter changes in the compliant layer's elastic properties to balance load-bearing capacity and breakage resistance. The compliant layer has optimized stiffness parameters that allow it to be rigid enough to support normal loads but compliant enough to absorb sudden impact forces without transmitting damaging stresses to the bump foil. This dynamic parameter management resolves the contradiction between needing rigidity for support and flexibility for shock absorption.
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
This design enhances bearing performance and reliability by maintaining effective support under varying loads, preventing damage to the bump foil and ensuring non-contact operation when feasible.
Implementation Method 1
The crest portions and the trough portions are configured to expand in the rotation direction so as to elastically support the top foil
Implementation Method 2
When the rotational speed of the rotary member reaches a no-contact rotational speed, the dynamic pressure of an air film generated between the rotary member and the bearing surface separates the rotary member from the foil bearing
Data Source
AI summary
A housing, a top foil including a bearing surface that faces the rotary member, and a bump foil placed between the top foil and the housing are provided. The bump foil is configured to elastically support the top foil by expanding in a rotation direction. When a load received by the bearing surface from the rotary member is less than or equal to a threshold value, the bump foil supports the top foil with a gap formed between the bump foil and the housing and with a gap formed between the bump foil and the top foil. When the load received by the bearing surface from the rotary member exceeds the threshold value, the top foil and the bump foil locally form a plain bearing to support the rotary member.