Aircraft Propulsion System Gyroscopic Force Cancellation
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Solution Overview
Problem
Aircraft propulsion systems face challenges in managing gyroscopic forces during maneuvers, which lead to increased structural loads and fatigue, requiring significant structural mass to counteract these forces, thereby increasing weight and reducing aircraft efficiency.
Innovation Solution
The propulsion system incorporates a reduction gearbox configured to reverse the rotational direction between the input and output sides, along with counter-rotating motors and propulsors, to balance angular momentum, thereby canceling or minimizing gyroscopic forces. This configuration includes an epicyclic star gearbox with a sun gear, planet gears, and a ring gear, allowing for a reduction ratio that equalizes the angular momentum of clockwise and anti-clockwise rotating components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If gyroscopic forces are not counteracted, then structural loads and fatigue increase during aircraft maneuvers, but adding structural mass to counteract these forces increases overall aircraft weight
Solution Approach 1:
The patent converts the harmful gyroscopic forces into a beneficial configuration by arranging rotating components (propellers, motors, gearbox) to rotate in opposite directions. The angular momentum vectors of counter-rotating components cancel each other, transforming the problematic gyroscopic effects into a neutral or beneficial arrangement that reduces structural loads without requiring additional counteracting mass
2Strength
If structural mass is increased to counteract gyroscopic forces, then aircraft structural strength improves, but aircraft efficiency decreases due to increased weight
Solution Approach 1:
By arranging rotating components to counter-rotate, the patent eliminates the need for additional structural mass to counteract gyroscopic forces. This converts what would have been a requirement for heavy reinforcement into a lightweight configuration where the rotating components themselves generate the counteracting effect through their angular momentum arrangement
3Object-generated harmful factors
If a reduction gearbox is used to reverse rotational direction, then gyroscopic forces are canceled, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the reduction gearbox: it provides the necessary speed reduction ratio while simultaneously reversing the rotational direction of the output shaft. This merging of functions eliminates the need for separate direction-reversal mechanisms and allows the gearbox to contribute to gyroscopic force cancellation as part of its core transmission function
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 design reduces structural loads and weight by minimizing gyroscopic forces, extending aircraft life and improving efficiency by allowing for a lighter structural framework while maintaining design flexibility in motor and gearbox configurations.
Implementation Method 1
the motor, propulsor and reduction gearbox are configured such that, at a given input and output rotational speed, the total angular momentum of clockwise rotating components is within 20% of the sum of total angular momentum of anti-clockwise rotating components
Implementation Method 2
gyroscopic forces of the propulsor, motor, prime mover and reduction gearbox generated during aircraft manoeuvres are substantially cancelled
Data Source
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AI summary
An aircraft propulsion system (5) comprises a propulsor (12), a motor (28) and a reduction gearbox (16) coupled to a prime mover (28) at an input side, and the propulsor (12) at an output side. The reduction gearbox (16) is configured to provide a reduction ratio between the input and output. The reduction gearbox is configured such that the input side rotates in an opposite direction to the output side, and the prime mover (28), motor (28), propulsor (12) and reduction gearbox (16) are configured such that gyroscopic forces of the propulsor, motor, prime mover and reduction gearbox generated during aircraft manoeuvres and / or propulsion system failures are substantially cancelled.