Rotary Electric Motor Cooling With Gas-Liquid Air Gap Flow

Solution Overview

Problem

Existing electric motors in electric vehicles face efficiency loss and reduced torque due to heat buildup in stator windings and tooth tips, and fluid leaks into the air gap causing drag.

Innovation Solution

A method involving the injection of a pressurized liquid and gas mixture into the air gap between the rotor and stator to force the fluid through the gap, using separate or common passages in the rotor and stator, with a mixture that dilutes to prevent accumulation and enhance heat transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If circulating fluid is used to cool the stator and rotor, then heat transfer is enhanced, but fluid leaks into the air gap causing drag and efficiency loss

Engineering Contradiction:

Improveheat transferVSAvoidefficiency loss

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The harmful liquid fluid is extracted from the air gap by applying centrifugal force through rotor rotation, which throws the liquid outward and away from the air gap region, preventing accumulation and drag while maintaining the cooling function

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A hydrophobic coating is applied to the air gap surfaces as an intermediary layer that repels liquid fluid while allowing the air gap to remain filled with gas, preventing liquid accumulation without compromising the cooling effect

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If more cooling fluid is circulated to improve heat transfer, then cooling effectiveness increases, but drag in the air gap increases

Engineering Contradiction:

Improvecooling effectivenessVSAvoiddrag

Core Design Contradiction:

TemperatureVSForce

Solution Approach 1:

The centrifugal force that causes liquid to accumulate in the air gap and create drag is converted into a beneficial force by using it to actively eject the liquid from the air gap, transforming the harmful effect into a mechanism for liquid removal

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The physical state of the cooling medium in the air gap is changed from primarily liquid to a gas-dominated environment, fundamentally altering the drag characteristics while maintaining heat transfer through the stator and rotor structures

Inventive Principle:

Principle #35Parameter changes

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 method effectively reduces drag and maintains motor efficiency by preventing fluid accumulation in the air gap while enhancing heat transfer from the stator and rotor, thus improving motor performance.

Implementation Method 1

injecting a pressurized liquid into the air gap through at least one of the rotor and the stator, and injecting a pressurized gas into the air gap through at least one of the rotor and the stator, wherein a mixture of the pressurized liquid and the pressurized gas is established within the air gap and the pressurized gas dilutes the mixture sufficiently to force the pressurized liquid and the pressurized gas against the rotor and stator and through the air gap to exit the air gap at axially opposite ends of the rotary electric machine

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 2

injecting a pressurized liquid into the air gap through at least one of the rotor and the stator, and injecting a pressurized gas into the air gap through at least one of the rotor and the stator, wherein a mixture of the pressurized liquid and the pressurized gas is established within the air gap and the pressurized gas dilutes the mixture sufficiently to force the pressurized liquid and the pressurized gas against the rotor and stator and through the air gap to exit the air gap at axially opposite ends of the rotary electric machine

Methodology Applied

Scientific EffectForced convection: Forced Convection

Data Source

PatentUS12451765B2Cooling rotary electric machines

Publication Date: 2025.10.21 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An electric propulsion motor system includes a rotary electric propulsion motor that has a stator and a rotor. An air gap is present between the stator and rotor. A fluid circulation system provides pressurized liquid and gas, which is directed through fluid passages in the stator and/or rotor and into the air gap to establish a mixture of pressurized liquid and pressurized gas therein. The pressurized gas dilutes the mixture and pushes the pressurized liquid and pressurized gas against the stator and rotor, forcing it to exit the air gap at the opposite ends of the motor leaving the air gap free of accumulated liquid.