Foil Bearing Retention Structure for Oil-Free Compressor Support
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Centrifugal compressors face challenges in using CFC-free refrigerants due to incompatibility with existing lubricants and the need for high manufacturing accuracy and tight tolerances, limiting their application in lower-capacity systems.
Innovation Solution
A foil bearing assembly with an outer foil, inner foil, and bump foil is used within a bearing housing with a locking feature to maintain the foil bearing assembly at a fixed rotational position, compatible with CFC-free refrigerants and suitable for high-speed environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If oil-based lubricants are used in compressor bearings, then friction is reduced, but compatibility with CFC-free refrigerants is lost
Solution Approach 1:
The patent removes the oil-based lubricant from the bearing system and replaces it with a foil bearing structure that operates without lubrication, eliminating the compatibility issue with CFC-free refrigerants while maintaining low friction through the foil bearing mechanism
Solution Approach 2:
The patent replaces the traditional oil-lubricated mechanical bearing system with a foil bearing system that uses a different mechanical principle (flexible foil deflection and gas film formation) to achieve low friction without requiring oil-based lubricants that are incompatible with modern refrigerants
2Productivity
If centrifugal compressors are designed for high-speed operation, then efficiency is improved, but manufacturing accuracy requirements increase
Solution Approach 1:
The patent divides the bearing support system into modular foil bearing assemblies that can be manufactured and assembled with relaxed tolerances, reducing the overall manufacturing precision requirements while maintaining high-speed operational efficiency
Solution Approach 2:
The patent changes the bearing design parameters from tight-tolerance rigid bearings to flexible foil bearings that can accommodate larger dimensional variations, allowing high-speed operation without requiring extremely precise manufacturing of the impeller and bearing interfaces
3Adaptability or versatility
If magnetic bearings are used to support driveshaft, then lubrication compatibility is improved, but device complexity and weight increase
Solution Approach 1:
The patent uses simple, inexpensive foil bearing components that can be easily manufactured and replaced if needed, avoiding the complex and expensive magnetic bearing systems while achieving the same lubrication compatibility benefits
Solution Approach 2:
The patent employs flexible foil elements that deflect to form bearing surfaces, providing a simple yet effective bearing solution that is compatible with all refrigerants without the complexity of magnetic fields and heavy magnet assemblies
4Ease of manufacture
If foil bearing assembly is not fixed in rotational position, then assembly is simpler, but operational stability decreases
Solution Approach 1:
The patent incorporates retention features during the manufacturing process that automatically maintain the correct rotational position of the foil bearing assembly, so no additional assembly steps are needed and the bearing remains stable during operation
Solution Approach 2:
The patent uses asymmetric retention features such as keys or splines that engage with corresponding features on the foil bearing assembly, preventing rotational movement while maintaining simple assembly through the inherent asymmetry of the engagement features
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 foil bearing assembly provides low friction support without oil-based lubricants, enhancing compatibility with various refrigerants and reducing manufacturing complexity, enabling the use of lighter materials and improving the durability and reliability of centrifugal compressors.
Implementation Method 1
a bump foil positioned between the outer foil and the inner foil
Implementation Method 2
support the driveshaft on a fluid layer formed between the driveshaft and the foil elements when the rotation speed of the driveshaft exceeds a threshold speed termed liftoff speed
Data Source
AI summary
A bearing system includes a bearing housing that includes a sleeve and a mounting structure for connecting the bearing system to a compressor housing. The sleeve has a radial inner surface that defines a cylindrical bore, and includes a locking feature located along the radial inner surface. The mounting structure is located radially outward from the sleeve. The bearing system also includes a foil bearing assembly positioned within the cylindrical bore. The foil bearing assembly includes an outer foil, an inner foil, and a bump foil positioned between the outer foil and the inner foil. At least one of the outer foil and the inner foil includes a bearing retention feature cooperatively engaged with the locking feature to maintain the foil bearing assembly within the bearing housing at a fixed rotational position.