Epicyclic Geartrain Braking for Selective Aircraft Power Split
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Solution Overview
Problem
Current aircraft propulsion systems face inefficiencies in power distribution between different rotors, particularly in modes that require horizontal and vertical propulsion, where generating horizontal thrust can hinder vertical lift operations and waste engine core power.
Innovation Solution
An aircraft propulsion system incorporating an epicyclic geartrain with a sun gear, ring gear, intermediate gears, and a carrier, along with brake systems that allow selective power distribution between propulsor rotors, enabling operation in star, planetary, and open modes to optimize power transfer for different flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If power is transferred to both propulsor rotors simultaneously, then total thrust is maximized, but power distribution efficiency deteriorates and horizontal thrust generation hinders vertical lift operations
Solution Approach 1:
The power transmission system is segmented into multiple independent pathways through the epicyclic geartrain, allowing power to be selectively directed to different propulsor rotors. The sun gear, ring gear, and carrier can independently transmit power to first and second propulsor rotors, enabling separate control of power distribution to maximize efficiency for specific flight modes.
Solution Approach 2:
The system dynamically reconfigures power distribution by engaging or disengaging specific geartrain pathways based on flight mode requirements. During vertical lift operations, the system can disengage the pathway to the first propulsor rotor (via braking the ring gear), while during horizontal thrust operations, it can disengage the pathway to the second propulsor rotor (via braking the carrier), optimizing power efficiency for each mode.
2Use of energy by moving object
If the epicyclic geartrain is configured for selective power distribution, then power efficiency improves, but device complexity increases due to multiple brakes and gear components
Solution Approach 1:
The epicyclic geartrain components serve multiple functions: the sun gear, ring gear, and carrier not only transmit power but also serve as braking surfaces for selective power distribution control. The intermediate gears meshing between the sun and ring gears provide both power transmission pathways and mechanical leverage for the braking system, reducing the need for separate control mechanisms.
Solution Approach 2:
The power transmission and power distribution control functions are merged into a single integrated epicyclic geartrain system. The same mechanical components that transmit power (gears, carrier, sun gear) are also used for selective engagement and disengagement through braking, eliminating the need for separate clutch mechanisms and simplifying the overall system architecture.
3Ease of operation
If brakes are engaged to stop rotor rotation, then selective power distribution is achieved, but energy loss increases due to friction
Solution Approach 1:
The braking function is extracted as a selective control mechanism rather than a continuous energy dissipation system. Brakes are engaged only transiently to switch between power distribution modes, rather than being continuously applied, minimizing frictional energy loss while maintaining operational control capability.
Solution Approach 2:
The brake engagement operates periodically and intermittently to switch between different power distribution modes (star system mode, planetary system mode, open system mode), rather than being continuously engaged. This periodic action allows the system to minimize energy loss by engaging brakes only when mode transitions are required.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An assembly for an aircraft propulsion system (20) includes a sun gear (80), a ring gear (81), a plurality of intermediate gears (82), a carrier (84), a first brake (98) and a second brake (100). The sun gear (80) is rotatable about a centerline axis (86). The ring gear (81) circumscribes the sun gear (801) and is rotatable about the centerline axis (86). The intermediate gears (82) are arranged circumferentially about the centerline axis (86). Each of the intermediate gears (82) is meshed between the sun gear (80) and the ring gear (81). The carrier (84) is rotatable about the centerline axis (86). Each of the intermediate gears (82) is rotatably mounted to the carrier (84). The first brake (98) is configured to slow and/or stop rotation of the ring gear (81) about the centerline axis (86). The second brake (100) is configured to slow and/or stop rotation of the carrier (84) about the centerline axis (86).