Electric Motor Cooling with Segmented Stator and Rotor Flows
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Solution Overview
Problem
The existing cooling systems for electric motors, particularly in aircraft applications, face inefficiencies due to the need for high-pressure air to force cooling flow through a minimized gap between the stator and rotor, which reduces motor performance and burdens the cooling source, while also not effectively utilizing cooling air for the stator.
Innovation Solution
A separate cooling flow system for the stator and rotor, where the quantity, pressure, and temperature of each flow can be independently controlled, using a low-pressure cooling source for the stator and a higher-pressure source for the rotor, allowing for improved airflow through the gap without compromising motor efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gap between stator and rotor is minimized to improve motor performance, then motor efficiency is improved, but cooling air flow through the gap is restricted making rotor cooling more difficult
Solution Approach 1:
The cooling system is segmented into two independent sources: a first cooling source for the stator and a second cooling source for the rotor. This allows independent control of cooling parameters for each component, enabling the gap to be minimized for motor efficiency while the rotor receives dedicated high-pressure cooling air through the journal bearing.
2Temperature
If high pressure air is used to force cooling flow through the minimized gap, then rotor cooling is achieved, but motor performance and efficiency are reduced
Solution Approach 1:
The cooling system separates the high-pressure cooling requirement from the motor operation by using a dedicated second cooling source that flows through the journal bearing to cool the rotor. This eliminates the need to use high-pressure air through the gap for cooling purposes, allowing the gap to be minimized for optimal motor performance.
3Temperature
If high pressure cooled bleed air is used as the motor cooling source, then cooling capability is provided, but engine performance is reduced
Solution Approach 1:
Different cooling pressures are applied locally to different components: the first cooling source provides lower pressure air to the stator, while the second cooling source provides higher pressure air to the rotor through the journal bearing. This localized quality approach optimizes cooling efficiency while minimizing the overall burden on the cooling source and engine performance.
4Device complexity
If a single cooling source is used for both stator and rotor, then system complexity is reduced, but cooling efficiency for both components is compromised
Solution Approach 1:
The cooling system is divided into two independent sources with separate flow paths: the first cooling source flows through stator slots, and the second cooling source flows through the journal bearing to the rotor. This segmentation enables optimized cooling efficiency for both components while maintaining manageable system complexity through modular design.
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 solution enhances motor efficiency by optimizing cooling airflow, reducing the need for high-pressure air and minimizing the impact on the cooling source, thereby improving overall cooling performance and reducing bleed air usage.
Implementation Method 1
the first cooling flow flows through an inlet into the slots and exits an outlet
Implementation Method 2
the second cooling flow is provided to the journal bearing, flows through the journal bearing
Implementation Method 3
the second cooling source is at a higher pressure than the first cooling source, resulting in a differential pressure
Data Source
Figure 1
Figure 2~4
AI summary
An electric motor cooling system is provided that includes a housing (16) and first (40) and second cooling sources that are different from one another respectively to provide first and second cooling flows. A stator (14) is mounted in the housing and receives the first cooling flow. A rotor (12) is rotatable relative to the stator and receives the second cooling flow. In the examples, the housing supports a journal bearing (22) upon which the rotor is supported, and the second cooling flow flows through the journal bearing. The first cooling flow is provided by a low pressure source such as ram air, and the second cooling flow is provided by high pressure source such as bleed air, for example. A circumferential gap is provided between the rotor and stator. In one example, a seal is arranged between the housing and a stator for providing a cavity in fluid communication with the journal bearing and the gap. The cooling flow from the journal bearing passes through the cavity and into the gap for cooling the rotor. In another example, the rotor includes circumferentially spaced magnets providing spaces. The spaces are arranged interiorly of an exterior surface of the rotor. A passage is in communication with the spaces and journal bearing. The second cooling flow from the journal bearing passes through the passage and into the spaces for cooling the rotor.