Annular Cooling Channels in Grease-Packed Bearings
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Solution Overview
Problem
Existing cooling systems for electric generators in aerospace applications are heavy, complex, and inefficient, failing to effectively manage heat generated by the generators and their components, particularly in high-power density systems where additional cooling capacity is lacking.
Innovation Solution
The design incorporates a cooling-fluid flowpath with annular passages around enclosed bearings, utilizing a fluid-tight coupling between the housing and a sleeve to direct cooling fluid in close proximity to the bearings, enhancing thermal communication and heat removal while minimizing the introduction of external cooling fluid, which could strip grease from grease-packed bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an oil system is used to cool the generator and its components, then cooling effectiveness is improved, but weight increases
Solution Approach 1:
The patent extracts the cooling function from a separate oil system and integrates it into the generator's structural components. The housing and end caps themselves serve as cooling channels, eliminating the need for dedicated external oil cooling systems and their associated pumps, lines, and heat exchangers, thereby reducing weight while maintaining cooling effectiveness.
Solution Approach 2:
The patent merges the structural housing components with the cooling system. The housing and end caps are designed to simultaneously provide mechanical support and serve as cooling fluid passages, combining structural and thermal management functions into single components, thus reducing overall system weight and complexity.
2Temperature
If an oil system is used to cool the generator and its components, then cooling effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent removes the complexity of external oil system components (pumps, lines, seals, heat exchangers) by extracting these functions and integrating them directly into the generator housing and end cap structures, which serve as built-in cooling channels.
Solution Approach 2:
The housing and end cap components perform multiple functions simultaneously: they provide mechanical support, contain the generator components, and serve as cooling fluid passages. This multi-functionality eliminates the need for separate dedicated cooling system components, reducing overall system complexity.
3Temperature
If cooling fluid is introduced close to grease-packed bearings, then heat removal from bearings is improved, but grease lubrication may be stripped
Solution Approach 1:
The patent applies different qualities to different regions: the cooling fluid flowpath is positioned to maximize heat removal from the bearing outer races and housing, while the bearing inner races and rolling elements maintain grease lubrication. The cooling channels are strategically located to provide thermal management without compromising the lubrication environment.
Solution Approach 2:
The patent uses the bearing outer race and housing as intermediary thermal pathways. Heat is transferred from the bearing inner race through the rolling elements to the outer race, and then to the housing and cooling fluid, rather than introducing cooling fluid directly onto the grease-lubricated bearing surfaces. This indirect thermal pathway protects the grease lubrication while achieving effective heat removal.
4Power
If permanent magnet generators are used to achieve increased power density, then power output is improved, but heat generation increases requiring more cooling
Solution Approach 1:
The patent merges the thermal management system with the generator structure itself. The housing and end caps serve dual purposes as both mechanical components and cooling channels, providing the enhanced cooling capacity needed for high-power density permanent magnet generators without adding external cooling system weight and complexity.
Solution Approach 2:
The patent employs a liquid cooling system with dedicated flowpaths through the housing and end caps to efficiently remove the increased heat generation from high-power density permanent magnet generators. The hydraulic cooling system provides controlled thermal management capability matched to the higher power output.
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 configuration improves heat transfer efficiency, reduces weight and complexity, and maintains lubrication in grease-packed bearings, thereby enhancing the power generation efficiency and reliability of electric generators without the drawbacks of traditional oil-based cooling systems.
Implementation Method 1
direct cooling fluid in close proximity to the bearings, enhancing thermal communication and heat removal
Implementation Method 2
cooling-fluid flowpath with annular passages around enclosed bearings... flowing said cooling fluid in said cooling-fluid channel
Data Source
AI summary
An electric starter-generator is described. The generator may comprise a rotor, a housing, two bearings, a stator, and a cooling-fluid flowpath. The cooling-fluid flowpath may comprise a cooling-fluid entrance and exit, and a cooling-fluid channel in fluid communication with the entrance and exit. At least a portion of the channel may be defined by a fluid-tight coupling of the housing and a sleeve radially surrounding the outer race of either the bearings. The portion may form an annulus about the axis. The portion may comprise a radially inner surface defined by the sleeve, a radially outer surface define by said housing, and two axial surfaces. The two axial surfaces may extend a distance from the radially inner to outer surfaces that is less than a distance from one of the two axial surfaces to the other of the two axial surfaces.