Epicyclic Fan Speed Reducer for Compact Turbine Power Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing propulsion assembly systems face challenges in efficiently transmitting power from a free power turbine to a fan while minimizing the radial crowding and space constraints within the exhaust casing of a gas generator, particularly due to the need for large-diameter gears which can cause crowding and dynamic parasitic phenomena.
Innovation Solution
The implementation of an epicyclical speed reducer with a sun gear, rocker gears, and a crown, where the rotation axis of the rocker gears is inclined relative to the sun gear axis, allowing for a high global reduction ratio and reduced radial crowding, and incorporating homo-kinetic joints and sliding links to facilitate efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If single conical gears are used to transmit power from the turbine to the fan, then the power transmission is achieved, but the radial crowding increases due to the large diameter of the driving wheel required for high reduction ratios
Solution Approach 1:
The patent employs a compound gear system where a first conical gear set and a second conical gear set are nested together. The first gear set includes a driving wheel on the turbine shaft and a driven wheel on an intermediate shaft, while the second gear set includes a driving wheel on the intermediate shaft and a driven wheel on the fan shaft. This nested arrangement allows the power transmission to be achieved in stages, with each gear set providing partial reduction, thereby reducing the diameter of individual gears and minimizing radial crowding within the exhaust casing.
2Speed
If the reduction ratio of the bevel gear is increased to achieve higher fan speed reduction, then the fan speed control is improved, but the diameter of the driving wheel increases causing integration difficulties within the exhaust casing
Solution Approach 1:
The patent divides the total speed reduction requirement into two separate gear sets. The first conical gear set provides a first reduction ratio, and the second conical gear set provides a second reduction ratio. By segmenting the reduction function across two stages, each individual gear can have a smaller diameter compared to a single-stage gear system that would provide the same total reduction ratio. This segmentation enables better integration within the exhaust casing while achieving the desired fan speed control.
3Area of stationary object
If the driving wheel diameter is reduced to minimize radial crowding, then the space utilization is improved, but the torque transmission capability is compromised
Solution Approach 1:
The patent ensures continuous and efficient torque transmission through the two-stage conical gear system. The first gear set transmits torque from the turbine shaft to the intermediate shaft, and the second gear set continues this transmission from the intermediate shaft to the fan shaft. This continuous action across two stages allows each gear to operate within optimal torque ranges, maintaining transmission capability while using smaller diameter gears that reduce radial crowding.
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 configuration enables a compact and efficient power transmission system that reduces radial crowding, optimizes available space, and minimizes torsional stress, enhancing the integration and performance of the propulsion assembly by using smaller diameter wheels and reducing efficiency losses.
Implementation Method 1
the speed reducer being an epicyclical reducer having a sun gear, rocker gears and a crown, the sun gear forming the inlet and the crown forming the outlet of the reducer
Data Source
AI summary
The present invention relates to an aircraft propulsion assembly comprising a turbine (15), at least one fan (10) and a mechanism for transmitting power between the turbine and the fan, characterized in that the power transmission mechanism comprises a speed reducer (20) with a motion input and a motion output, the input being in the continuation of the axis (16) of the turbine and the output connected to the fan.