eVTOL Gearbox Oil Circulation for Fire-Safe Lubrication and Cooling
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Solution Overview
Problem
Conventional aircraft driven by electric propulsion systems face challenges in frequent use, noise reduction, vibration management, and safety, particularly in densely populated areas, with a need for components that withstand frequent operation, generate low noise, and have redundancy to avoid single points of failure.
Innovation Solution
The development of a distributed electric propulsion system with tiltable electric engines and a tilt propeller subsystem that allows for vertical and horizontal flight, incorporating a fire protective barrier design to minimize risk and optimize energy efficiency, weight, and noise levels, while ensuring safety through redundancy and efficient lubrication and cooling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lubrication systems are used in gearboxes, then components are adequately lubricated, but oil leakage and fire hazards occur due to flammable lubricating oil
Solution Approach 1:
The patent changes the chemical composition parameter of the lubricating fluid by using synthetic lubricating oil with specific fire-resistant properties (flash point above 200°C) instead of conventional flammable oil, thereby maintaining lubrication effectiveness while eliminating fire hazards
Solution Approach 2:
The patent converts the harmful effect of lubricating oil into a beneficial fire-resistant coolant by using the same oil circulation system to both lubricate gears and actively cool the gearbox, with the fire-resistant property preventing fire hazards while the circulation provides thermal management
2Reliability
If fire protective barriers are installed around engines, then fire safety is improved, but aircraft weight increases
Solution Approach 1:
The patent extracts and eliminates the need for separate fire protective barriers by integrating fire resistance directly into the lubricating oil itself, removing the additional weight of barrier structures while maintaining fire safety
Solution Approach 2:
The lubricating oil serves multiple functions simultaneously: lubrication of gears, active cooling of the gearbox, and fire protection. This multi-functionality eliminates the need for separate fire protective barrier systems, reducing aircraft weight
3Reliability
If distributed electric propulsion system is used, then safety through redundancy is improved, but device complexity increases
Solution Approach 1:
The patent divides the propulsion system into multiple independent distributed electric engines, each capable of independent operation. This segmentation provides redundancy where failure of one engine does not compromise the entire propulsion system, while each module remains relatively simple in 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
The solution enables efficient, safe, and quiet operation of electric propulsion systems in densely populated areas, with enhanced safety features and reduced noise and vibration, allowing for frequent use without compromising performance or increasing weight.
Implementation Method 1
A motor-gearbox assembly may include an oil pump configured to circulate a lubricating oil through the motor-gearbox assembly to cool and lubricate the gearbox and electric motor components
Implementation Method 2
A heat exchanger may be present that cools the lubricating oil using an air flow that passes through fins of the heat exchanger
Data Source
AI summary
An electric propulsion system comprising an electric motor assembly. The electric motor assembly may include a housing having an internal volume, a stator ring disposed about a perimeter of the internal volume, and a rotor positioned within the stator. The electric motor assembly may include a main shaft connected to the rotor via a gear reduction, wherein the main shaft extends through the rotor. The electric motor assembly may include a collar connected to the main shaft, wherein the collar encircles the main shaft, and at least a portion of the collar is configured to direct a fluid away from the main shaft and toward the stator ring.