Superposition Gearbox Hybrid Propulsion for Cruise-Efficient Thrust
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Solution Overview
Problem
Gas turbine engines operate inefficiently at cruise altitudes due to excessive size and power capacity designed for takeoff, and electric propulsion systems lack sufficient energy density for commercial aircraft applications.
Innovation Solution
A hybrid propulsion system combining a core gas turbine engine with an electric motor, utilizing a superposition gearbox and one-way clutch to supplement power during high thrust demands, allowing the core engine to be downsized and optimized for cruise conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the gas turbine engine is sized to provide sufficient thrust for takeoff, then the power availability for high thrust demands is improved, but the engine operates inefficiently at cruise altitudes due to excessive size and power capacity
Solution Approach 1:
The propulsion system is segmented into two independent power sources: a core gas turbine engine and an electric motor. The core engine is downsized to optimize for cruise efficiency, while the electric motor provides supplemental power during high thrust demands. This segmentation allows each component to be optimized for its specific operating regime, resolving the contradiction between power availability and energy efficiency.
Solution Approach 2:
The system dynamically transitions between different power configurations: the core engine operates alone during cruise, while the electric motor engages during takeoff and high thrust conditions. The superposition gearbox enables dynamic power combination, allowing the system to adapt its power delivery to match varying operational requirements, thus maintaining efficiency across different flight phases.
2Loss of energy
If the core engine is downsized to optimize for cruise conditions, then the energy efficiency is improved, but the power availability for high thrust demands deteriorates
Solution Approach 1:
The system merges the core gas turbine engine with an electric motor through a superposition gearbox. The electric motor is selectively engaged during high thrust demand conditions (takeoff, climb) to supplement the downsized core engine, ensuring sufficient power availability while maintaining the core engine's optimized size for cruise efficiency. This combination resolves the power deficiency of the downsized engine.
Solution Approach 2:
The superposition gearbox acts as an intermediary mechanism that enables selective power combination. It allows the electric motor to engage with and supplement the core engine's output during high thrust conditions, while permitting the core engine to operate independently during cruise. This intermediary device facilitates the dynamic power sharing necessary to resolve the contradiction between engine size and power availability.
3Power
If a hybrid propulsion system with electric motor is used, then the power availability during high thrust demands is improved, but the device complexity increases due to superposition gearbox and one-way clutch
Solution Approach 1:
The one-way clutch enables the electric motor to automatically engage with the core engine when high thrust is required, without requiring complex control systems. The clutch self-activates based on torque conditions, allowing the system to autonomously transition between power configurations. This self-service mechanism reduces control complexity while maintaining the power benefits of the hybrid system.
4Loss of energy
If the electric motor supplements power during high thrust demands, then the core engine can be downsized, but the manufacturing complexity increases due to integration requirements
Solution Approach 1:
The superposition gearbox serves as an intermediary transmission system that simplifies the integration of the electric motor with the core engine. By providing a standardized mechanical interface and power combining mechanism, it facilitates the integration process and reduces manufacturing complexity compared to direct coupling arrangements. The gearbox mediates the power flow between the two power sources, making the integration more manageable.
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 hybrid propulsion system reduces core engine size while maintaining power availability for high thrust demands, improving thermal, transfer, and propulsive efficiencies by optimizing engine performance across varying operational conditions.
Implementation Method 1
a one-way clutch to allow the electric motor to engage and disengage from the core engine
Implementation Method 2
a superposition gearbox to combine the power from the core engine with the power from the electric motor
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
A gas turbine engine (20) includes a core engine (22), a fan section, and a superposition gearbox (42) that includes a sun gear (74). A plurality of intermediate gears (76) are engaged to the sun gear (74) and supported in a carrier (78) and a ring gear (80) circumscribing the intermediate gears (76). The core engine (72) drives the sun gear (74) and an output from the superposition gearbox (42) driving the fan section. An electric motor (66) is coupled to a portion of the superposition gearbox (42) to provide a portion of power to drive the fan section through the superposition gearbox (42).