Epicyclic Turbomachine Gear Train for Fan and Compressor Speed Split

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Solution Overview

Problem

Turbomachines used for aircraft propulsion face limitations in maximizing efficiency due to the need for the fan's rotation speed to be lower than the speed of sound, while the turbine's speed is constrained by the blade tip speed, leading to suboptimal performance and space requirements.

Innovation Solution

An aircraft turbomachine incorporating an epicyclic gear train with multiple stages allows for independent speed control of the turbine, compressor, and fan, using a sun gear, planet gears, and ring gears to achieve high turbine speed and low fan speed while maintaining compactness, reducing the compressor's rotation speed to prevent blade tip speed exceeding sound limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the turbine rotates as quickly as possible to maximize efficiency, then the turbine efficiency is improved, but the fan speed must be limited below the speed of sound which reduces overall system performance

Engineering Contradiction:

Improveturbine efficiencyVSAvoidfan speed

Core Design Contradiction:

Loss of energyVSSpeed

Solution Approach 1:

The transmission system is segmented into multiple independent speed control stages: the turbine operates at high speed independently, the compressor operates at an intermediate speed, and the fan operates at a lower speed. This segmentation allows each component to operate at its optimal speed without being constrained by the speed limits of other components, resolving the contradiction between turbine efficiency and fan speed limits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The epicyclic gear train acts as an intermediary mechanism between the turbine and the fan, enabling speed transformation and independent control. This intermediary allows the turbine to rotate at high speed while the fan rotates at a lower speed below the speed of sound, maintaining both high turbine efficiency and safe fan operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the compressor radius is increased to integrate the epicyclic gear train, then the integration is improved, but the compressor rotation speed must be reduced to prevent blade tip speed from exceeding sound limits

Engineering Contradiction:

Improveintegration of epicyclic gear trainVSAvoidcompressor rotation speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The epicyclic gear train is integrated in a radial dimension around the compressor, allowing the transmission mechanism to occupy space in the radial direction rather than increasing the axial length. This dimensional change enables the gear train integration without requiring a significant increase in compressor radius, thereby maintaining the compressor's rotation speed within acceptable limits.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Speed

If a reduction gear is placed between the turbine and the fan to allow different rotation speeds, then the speed differentiation is improved, but the device complexity and space requirements increase

Engineering Contradiction:

Improveindependent rotation speeds of turbine and fanVSAvoidtransmission system complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The epicyclic gear train merges multiple functions into a single compact mechanism: it provides speed reduction, enables independent speed control of the turbine and fan, and integrates the transmission function within the existing turbomachine structure. This merging reduces the overall device complexity compared to using separate reduction gears for each function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The epicyclic gear train serves multiple functions simultaneously: it acts as a reduction gear for the fan, provides intermediate speed control for the compressor, and enables independent operation of the turbine. This multi-functionality reduces the need for additional separate transmission components, thereby reducing overall device complexity and space requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances the integration and efficiency of the turbomachine by allowing high turbine and low fan speeds, maintaining compactness, and reducing the compressor's speed to prevent blade tip speed from exceeding sound limits, thereby improving overall performance and reducing space requirements.

Implementation Method 1

an epicyclic gear train comprising an input driven in rotation by the turbine, a first output stage configured to drive in rotation the compressor and a second output stage coupled to the first output stage and configured to drive in rotation the fan

Methodology Applied

Scientific EffectEpicyclic gearing: Epicyclic Gearing

Data Source

PatentUS11994073B2Aircraft turbomachine

Publication Date: 2024.05.28 SAFRAN AIRCRAFT ENGINES SAS

AI summary

Aircraft turbomachine comprising a casing, a fan, a compressor and a turbine and an epicyclic gear train comprising an input driven in rotation by the turbine, a first output stage configured to drive in rotation the compressor and a second output stage coupled to the first output stage and configured to drive in rotation the fan, the compressor being driven in rotation by the ring gear of the first output stage.