Gas Turbine Accessory Drive Planetary Gearbox Vibration Control

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Solution Overview

Problem

Existing engine accessory gearboxes in gas turbine engines have a fixed relative speed, leading to gear backlash, shaft vibration, and torsional resonance when accessories are sped up, slowed down, or operated intermittently, resulting in power loss and inefficiency.

Innovation Solution

Implementing a planetary gear train in the accessory drive gearbox, which is external to the engine housing, to confine backlash between the engine shaft and gearbox, allowing for variable speeds and loads of accessories, thereby reducing the impact of shaft vibration and torsional resonance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a fixed relative speed gearbox is used to drive accessories, then the structure is simple, but gear backlash and shaft vibration occur when accessories are sped up, slowed down, or stopped

Engineering Contradiction:

ImproveAccessory speed variabilityVSAvoidGearbox structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies the dynamics principle by implementing a planetary gear train that enables variable speed operation of accessories relative to the engine shaft. The planetary gear system allows different rotational speeds between the input (engine shaft) and output (accessories) by engaging/disengaging clutch mechanisms, thereby resolving the contradiction between adaptability and complexity through a structured dynamic transmission system.

Inventive Principle:

Principle #15Dynamics

2Volume of moving object

If accessories are coupled closely to the engine housing to minimize space, then space efficiency is improved, but backlash between engine and accessories causes shaft vibration and torsional resonance

Engineering Contradiction:

ImproveAccessory drive spaceVSAvoidShaft vibration and torsional resonance

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The planetary gear train acts as an intermediary mechanism between the engine shaft and accessories. It decouples the direct rigid connection that causes backlash transmission, allowing the accessories to be positioned close to the engine housing for space efficiency while preventing the transmission of vibration and resonance through the flexible and controlled gear engagement.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If power is continuously extracted to drive accessories, then accessories are always ready to operate, but power is lost when accessories are not producing output power

Engineering Contradiction:

ImproveAccessory readinessVSAvoidPower loss from idle accessories

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The clutch mechanisms in the planetary gear train enable dynamic control of power flow to each accessory. Power can be selectively engaged or disengaged based on operational requirements, allowing accessories to be ready for operation when needed while preventing energy loss when they are not actively producing output, thus resolving the contradiction between ease of operation and energy efficiency.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10273883B2Engine accessory drives systems and methods

Publication Date: 2019.04.30 THE BOEING CO

AI summary

An accessory drive for an engine includes a power takeoff (PTO) configured to couple power from a rotating shaft of the engine and to convey the power through an opening in a housing of the engine. A gearbox is coupled to and configured to be driven by the PTO. The gearbox is disposed external to the housing and includes a planetary gear train. At least one engine accessory is coupled to and configured to be driven by the planetary gear train.