Aircraft Turbine Engine Planetary Gearing for Split Fan-Compressor Speeds
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Solution Overview
Problem
Turbomachines for aircraft propulsion face limitations in maximizing turbine yield while keeping the blower speed below sonic limits, as existing solutions like reducers lead to size and integration issues due to the need for different speed ratios between turbine and blower.
Innovation Solution
An epicycloidal train with multiple stages, including a first and second output floor, allows the blower and compressor to operate at different speeds, enabling high turbine efficiency with a compact design by using the epicycloidal train to manage speed ratios and reduce compressor speed, thus optimizing turbomachine integration and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a reducer is placed in the transmission chain between the turbine and the fan to rotate them at different speeds, then the turbine can rotate faster to maximize efficiency, but the device complexity and radial size increase
Solution Approach 1:
The patent applies nesting by placing the epicyclic gear train inside the turbine casing, with the planet gears and carrier arranged within the radial space already occupied by the turbine structure. The sun gear is coupled to the turbine shaft, and the planet gears mesh with it while the ring gear drives the fan, effectively nesting the reduction mechanism within the existing turbine footprint without requiring additional radial space
Solution Approach 2:
The epicyclic gear train serves multiple functions simultaneously: it provides speed reduction for the fan, maintains compact radial dimensions, and integrates with the turbine structure. The same mechanism that reduces speed also allows independent rotation of the compressor and fan through the two output stages, making the transmission system multi-functional rather than requiring separate mechanisms for each function
2Speed
If the fan radius is increased to operate at lower speeds, then the fan can rotate slower while maintaining thrust, but the turbomachine radial size increases
Solution Approach 1:
The patent changes the speed ratio parameter through the epicyclic gear train, allowing the fan to rotate at a lower speed than the turbine while maintaining the required thrust. The gear ratio is designed to provide the optimal balance between fan speed and radius, enabling the fan to operate efficiently without requiring an excessive increase in radial size. The two-stage epicyclic train provides precise control over the speed reduction ratio
3Volume of stationary object
If the compressor radius is increased to integrate the epicyclic gear train close to the compressor, then the gear train can be compactly integrated, but the compressor rotational speed must be reduced to prevent blade tip speed from exceeding limits
Solution Approach 1:
The patent segments the transmission system into two independent output stages: the first output stage (ring gear 42) drives the compressor, while the second output stage (ring gear 45) drives the fan. This segmentation allows each component to rotate at its own optimal speed independently. The compressor can be driven at a reduced speed appropriate for its blade tip speed limits, while the fan operates at a different speed ratio, with both speeds optimized for their respective functions rather than being coupled at a single speed
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 solution enables high turbine efficiency with a compact design, maintaining good turbomachine integration and reducing the compressor's radial size, allowing for higher reduction ratios without increasing the turbomachine's size or limiting its performance.
Implementation Method 1
an epicyclic gear train (40) comprising an inlet (49) driven in rotation by the turbine (90), a first output stage (47) configured to drive in rotation a compressor (50) and a second output stage (48) coupled to the first output stage (47) and configured to drive in rotation a fan (20)
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Turbomachine (10) for an aircraft, comprising a casing (30), a fan (20), a compressor (50) and a turbine (90), and a planetary gearing (40) comprising an input that is driven in rotation by the turbine (90), a first output stage configured to drive in rotation the compressor (50), and a second output stage coupled to the first output stage and configured to drive in rotation the fan (20), the compressor (50) being driven in rotation by the annulus gear of the first output stage.