Rotor Shaft Cooling Venting for Trapped Air Removal
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Solution Overview
Problem
Trapped air in electric motor cooling systems leads to unbalanced centrifugal pressure and decreased heat transfer performance, increasing pressure drop and pumping power demands, especially at higher shaft speeds.
Innovation Solution
Incorporating an air vent in fluidic communication with radial coolant passages that extend through the rotor shaft, allowing trapped air to be evacuated and directing the working fluid, such as oil, to the rotor shaft bearing for additional lubrication, thereby reducing air concentration and enhancing heat removal and pumping efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If air is trapped in the coolant passages during fluid filling, then the cooling system structure remains simple, but the pressure drop increases and pumping power demands increase at higher shaft speeds
Solution Approach 1:
The patent extracts the harmful air bubbles from the cooling system by providing dedicated air vent passages that allow air to escape from the coolant passages. The air vent passages are positioned to capture air at high points in the system, separating the air removal function from the coolant flow path while maintaining system simplicity.
Solution Approach 2:
The air vent passages act as an intermediary channel that mediates between the trapped air in the coolant passages and the external environment. This intermediary structure allows air to be removed without disrupting the coolant flow or requiring complex modification of the existing cooling system architecture.
2Volume of moving object
If air is trapped in the inlet side radial coolant passage, then the cooling system remains compact, but the heat transfer performance decreases
Solution Approach 1:
The patent segments the cooling system into separate functional zones: coolant flow passages for heat transfer and air vent passages for air removal. This segmentation allows air to be extracted from specific high-point locations in the radial coolant passages without disrupting the overall compact coolant flow path or heat transfer surfaces.
Solution Approach 2:
The air vent passages utilize the vertical/dradial dimension by positioning vents at high points in the coolant passages where air naturally accumulates due to centrifugal force. This dimensional approach allows air removal without adding horizontal space or compromising the compact radial arrangement of the cooling system.
3Device complexity
If air and oil mixture flows through the rotor, then the cooling system structure remains simple, but the motor's heat transfer performance decreases
Solution Approach 1:
The patent extracts air from the oil-coolant mixture by providing air vent passages that allow air bubbles to separate and escape from the flowing coolant. This extraction occurs continuously as the coolant flows through the system, preventing air accumulation that would degrade heat transfer performance while maintaining the simple single-phase coolant flow structure.
4Reliability
If air vent is added to evacuate trapped air, then heat transfer performance improves, but device complexity increases
Solution Approach 1:
The patent merges the air vent function with the existing coolant passage structure by integrating air vent passages into the radial coolant passages. The air vent passages share the same structural framework and cooling system infrastructure, allowing air removal functionality to be added without creating entirely separate complex systems or requiring additional independent components.
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 solution effectively increases electric machine performance by reducing air concentration in the cooling system, improving heat transfer, and lowering pumping power demands, especially at higher speeds, leading to increased efficiency and lubrication of the rotor shaft bearing.
Implementation Method 1
The trapped air may lead to unbalanced centrifugal pressure and therefore increase the pressure drop over a rotor shaft, particularly at higher shaft speeds
Implementation Method 2
the working fluid (e.g., oil) which may be mixed with the air may be directed to the bearing for additional lubrication
Implementation Method 3
cooling systems that direct pressurized oil through channels in the rotor assembly
Implementation Method 4
the motor's heat transfer performance may additionally be decreased
Data Source
AI summary
Methods and systems are provided to cool an electric machine rotor. The electric machine fluid cooling system includes, in one example, an air vent in fluidic communication with a radial coolant passage of a rotor shaft. In the system, the radial coolant passage is in fluidic communication with a rotor shaft coolant passage that extends through a rotor shaft and an inlet coolant passage that extends through a rotor shaft.