Variable Speed Aircraft Transmission for Noise Reduction
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Solution Overview
Problem
Conventional aircraft gearboxes struggle to efficiently reduce main rotor speed while maintaining engine performance, leading to increased noise and fuel consumption, as they typically operate at a single engine speed.
Innovation Solution
A variable state planetary shifting mechanism that allows for output speed reduction ratios from 20% to 80% without altering engine RPM, utilizing a dual planetary pinion configuration to maintain proper rotational direction and achieve efficient speed reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the engine speed is reduced to achieve lower main rotor speed, then noise is reduced, but engine efficiency deteriorates
Solution Approach 1:
The transmission system is segmented into multiple independent planetary gear sets (first and second planetary gear sets) that can operate independently or in combination. This allows the engine to maintain optimal speed while the rotor speed is reduced through gear reduction, separating the engine operation from the rotor speed control.
Solution Approach 2:
A variable speed transmission mechanism acts as an intermediary between the engine and the main rotor. This transmission includes planetary gear sets with controllable carriers that can selectively engage different gear ratios, allowing the engine to operate at efficient speeds while the rotor operates at lower speeds for reduced noise.
2Speed
If a conventional gearbox is used to reduce main rotor speed, then rotor speed is reduced, but engine performance deteriorates due to operating at non-optimal speeds
Solution Approach 1:
The transmission system employs dynamic control of the planetary gear carriers, allowing the gear ratio to be variable rather than fixed. The carriers can be selectively engaged or disengaged to change the effective gear ratio, enabling the system to adapt to different flight conditions and maintain both engine performance and desired rotor speed.
Solution Approach 2:
The planetary gear sets are designed to perform multiple functions: they can operate in direct drive mode (1:1 ratio) for high-speed operations, or in reduced gear mode for low-speed operations. The same mechanical components serve both high-performance and noise-reduction requirements without sacrificing engine efficiency.
3Object-affected harmful factors
If engine speed is reduced to achieve lower rotor speed, then noise is reduced, but fuel consumption increases
Solution Approach 1:
The transmission is segmented into multiple planetary gear sets that can be independently controlled, allowing the engine to maintain optimal operating speed while the rotor speed is reduced through mechanical gear reduction. This segmentation enables decoupling of engine speed from rotor speed.
Solution Approach 2:
The variable speed transmission acts as an intermediary mechanism between the engine and rotor, using planetary gear sets with controllable carriers to achieve speed reduction without affecting engine operating efficiency, thereby preventing increased fuel consumption.
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
Enables reduced rotor RPM for cruise flight conditions while maintaining engine efficiency, enhancing operational performance, range, and reducing noise.
Implementation Method 1
A variable speed transmission for a vehicle, such as an aircraft, includes a planetary gear set having a sun gear, a ring gear, and a carrier having a plurality of planetary gears mounted thereon for rotation about the sun gear and in mesh with the ring gear
Data Source
AI summary
A variable state planetary shifting transmission can include an input shaft, an output shaft; and a planetary system having a sun gear associated with the input shaft, a planetary carrier, and a ring gear associated with a ring housing. The transmission can include an overrunning clutch operably coupled to the planetary carrier. The transmission can include a clutch assembly coupled to the planetary carrier. The transmission is capable of changing the speed ratio between the input shaft and the output shaft by selective engagement of the clutch assembly against the ring gear which can cause either the freeing or locking of the planetary carrier by the overrunning clutch.