Superposition Gearbox Load Sharing in Multi-Spool Turbofans
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Solution Overview
Problem
Current gas turbine engines face limitations in incorporating electric power beyond accessory components, and there is a need for improved engine performance, particularly in propulsive efficiency and responsiveness to environmental changes.
Innovation Solution
The integration of a superposition gearbox and integrated motor generator system within the turbofan engine, which allows for load sharing and proportional control between spools using electric motors and generators, enhancing the engine's ability to adjust to power changes quickly and efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electric motors and generators are integrated into the turbofan engine for load sharing between spools, then engine responsiveness and efficiency are improved, but device complexity increases
Solution Approach 1:
The patent combines multiple electric motors and generators into a single integrated motor generator system that interfaces with both the high-pressure and low-pressure spools. This merging approach enables load sharing between spools while improving responsiveness, though it does increase device complexity as acknowledged in the contradiction
Solution Approach 2:
The integrated motor generator system performs multiple functions: it can drive the high-pressure spool, drive the low-pressure spool, and enable load sharing between them. This multi-functionality improves engine responsiveness and efficiency while requiring a sophisticated control system to manage the different operational modes
2Loss of energy
If a superposition gearbox is added to enable load sharing between spools, then propulsive efficiency is improved, but device complexity increases
Solution Approach 1:
The superposition gearbox acts as an intermediary mechanism between the integrated motor generator and the two spools. It enables efficient power transfer and load sharing by providing appropriate gear ratios and torque multiplication, thereby improving propulsive efficiency while managing the complexity through a dedicated transmission component
Solution Approach 2:
The gearbox enables dynamic load sharing between the high-pressure and low-pressure spools by allowing the system to adjust power distribution based on operating conditions. This dynamic capability improves propulsive efficiency across different flight regimes
3Use of energy by moving object
If electric power is incorporated beyond accessory components, then engine efficiency is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical load sharing mechanisms with an electrically-driven system using motors and generators. This substitution enables more precise and efficient power management between spools, improving engine efficiency while requiring sophisticated electrical and control systems
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 system reduces lag in power adjustments, improves engine efficiency, and enhances safety by enabling rapid response to changes in power demands, facilitating smoother operation and simultaneous engine starts.
Implementation Method 1
A drive motor is engaged to drive the sun gear, an inner electric motor, a stator disposed radially outside of the inner electric motor; and an outer electric motor disposed radially outside the stator
Data Source
AI summary
A turbofan engine includes a first spool including a first turbine, and a first tower shaft engaged to the first spool. A second spool includes a second turbine, and a second tower shaft is engaged to the second spool. A superposition gearbox includes a sun gear, a plurality of intermediate gears engaged to the sun gear, and is supported in a carrier and a ring gear circumscribing the intermediate gears. The first tower shaft or the second tower shaft drives one of the intermediate gears. A drive motor is engaged to drive the sun gear, an inner electric motor, a stator disposed radially outside of the inner electric motor, and an outer electric motor disposed radially outside the stator. A first load on the first spool and a second load on the second spool is adjusted by operation of at least one of the inner electric motor and the outer electric motor.