Air Gap Scavenging Ring for Oil-Cooled Motor Drag Reduction
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Solution Overview
Problem
In electric motors, the radial air gap between the stator and rotor experiences flooding with coolant oil, leading to significant drag and windage losses due to shear stress and air presence, which reduces efficiency and increases heat dissipation.
Innovation Solution
A system comprising a ring and sealing plate that encapsulates the radial air gap, routing excess coolant oil and air via channels to a scavenge pump, creating a vacuum to remove excess fluids and reduce drag losses, while maintaining sufficient oil for cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant oil is pumped into the motor cavity for cooling, then cooling performance is improved, but drag losses increase due to coolant oil flooding the radial air gap
Solution Approach 1:
The air gap is segmented into two distinct zones: a first air gap region without coolant oil for minimal drag losses, and a second air gap region with coolant oil for cooling. This segmentation allows the system to simultaneously achieve effective cooling and minimize energy losses by separating the cooling function from the rotational path.
Solution Approach 2:
Different regions of the air gap are assigned different qualities: the first region maintains an oil-free environment suitable for rotation, while the second region introduces coolant oil specifically where cooling is needed. This local differentiation optimizes both cooling efficiency and rotational performance.
2Temperature
If coolant oil is routed through motor cavities, then heat dissipation is improved, but windage losses increase due to air and coolant in the radial air gap
Solution Approach 1:
The air gap is divided into a first region with reduced air content for minimizing windage losses and a second region where coolant oil is present for heat dissipation. This spatial segmentation enables the system to address both windage and cooling requirements simultaneously.
Solution Approach 2:
The coolant oil acts as an intermediary substance that is strategically positioned in the second air gap region to facilitate heat transfer from the rotor to the stator, while its presence is limited to specific zones to minimize overall windage losses.
3Temperature
If the radial air gap is enclosed to route coolant, then cooling efficiency is improved, but drag losses increase from enclosed coolant
Solution Approach 1:
The enclosed air gap is segmented into a first region where coolant is excluded to maintain low drag conditions, and a second region where coolant is present to provide cooling. This segmentation resolves the contradiction by ensuring coolant is only present where thermally necessary.
Solution Approach 2:
Different local regions within the enclosed air gap are assigned different fluid characteristics: an oil-free zone for minimal drag and an oil-present zone for effective cooling. This local quality differentiation allows the enclosed structure to achieve both cooling efficiency and acceptable drag levels.
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 system effectively reduces drag and windage losses by minimizing excess coolant and air in the radial air gap, enhancing the motor's efficiency and cooling performance without flooding the gap.
Implementation Method 1
a partial vacuum that is generated within the radial air gap
Implementation Method 2
the coolant oil contained therein may experience shear stress due to the relative motion between the rotor and stator, inducing fluid flow and dissipating the rotational energy generated by the rotor
Data Source
AI summary
Systems for removing excess coolant oil and air from a radial air gap between a stator and a rotor of an electric motor are provided. In one example, the systems may include a ring covering the radial air gap, the ring configured to route coolant out of the radial air gap via one or more channels.