Electromagnetic Clutch Assembly for Gas Turbine Fault Isolation

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Solution Overview

Problem

Gas turbine engines face potential catastrophic failures due to the propagation of accessory component failures through the accessory gearbox, with existing shear-limited shafts providing protection only in extreme situations and complicating design with aerospace standards and inflexible operation.

Innovation Solution

An electromagnetic clutch assembly is introduced, featuring an input shaft, output shaft, magnetic friction plate, and magnetic flux generator, allowing for controlled engagement and disengagement to isolate faults and prevent torque transmission, thus providing earlier protective action and eliminating the need for shearing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a shear-limited shaft is used to protect the engine from accessory component failures, then catastrophic failures are prevented, but the protective function is only activated in extreme situations when torque exceeds maximum limits and the design is complicated by aerospace standards requirements

Engineering Contradiction:

Improveprotection against catastrophic failureVSAvoidflexibility of protective action

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces the purely mechanical shear-limited shaft protection system with an electromagnetic clutch system that uses magnetic fields to engage and disengage the connection between the accessory gearbox and driven components. This substitution allows for controlled, flexible protection against catastrophic failures while meeting aerospace standards, as the electromagnetic clutch can be activated at lower torque levels and provides adaptable response to various failure conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a shear-limited shaft is used to protect the engine, then protection is provided in extreme situations, but debris is generated when the shaft shears and the protection is inflexible

Engineering Contradiction:

Improveprotection against catastrophic failureVSAvoiddebris from shaft shearing

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The electromagnetic clutch system replaces the mechanical shearing mechanism with an electromagnetic disengagement mechanism. When a failure condition is detected, the electromagnetic clutch simply disengages the connection between the input and output shafts through magnetic field control, eliminating the need for physical shearing and the associated debris generation while maintaining protection against catastrophic failures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a shear-limited shaft with reduced outer diameter is used to limit maximum load, then the shaft can fail when load is exceeded to protect the engine, but the design is complicated and aerospace standards must be met for splines and seals

Engineering Contradiction:

Improveprotection through controlled failureVSAvoidshaft design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the complex mechanical shaft design with reduced outer diameter and shear limitations with an electromagnetic clutch system. This substitution simplifies the overall design by eliminating the need for specialized shear-limited shaft geometry while maintaining protection functionality through electromagnetic engagement and disengagement mechanisms that can be controlled independently of shaft dimensions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 electromagnetic clutch enables faster fault isolation and protective action at lower torque levels, reducing debris and providing flexible protection against component failures, while meeting aerospace standards and accommodating misalignment.

Implementation Method 1

Energizing the magnetic flux generator may create the magnetic flux that penetrates the engagement face, thereby creating a magnetic force between the engagement face and the magnetic friction plate

Methodology Applied

Scientific EffectMagnetic flux: Magnetic Field

Implementation Method 2

creating a magnetic force between the engagement face and the magnetic friction plate that causes the engagement face and the friction-engagement face to engage

Methodology Applied

Scientific EffectMagnetic force: Magnetism

Data Source

PatentUS11009085B2Electromagnetic clutch for gas turbine accessories

Publication Date: 2021.05.18 ROLLS ROYCE CORP

AI summary

A gearbox rigidly coupled to a static structure; a driven component rigidly coupled to another static structure; a clutch assembly floating between and coupled to the gearbox and driven component. The clutch may have aligned output and input shafts, defining an engagement surface, a bearing, and a magnetic friction plate coupled and rotating with the input shaft. The plate may have a friction-engagement face, and a magnetic flux generator. The magnetic flux generator may be rigidly coupled to a static housing and partially surrounded in the radial direction by a structure configured to reduce leakage of a magnetic flux, by defining a plurality of voids, which direct multiple passes of the magnetic flux through the engagement surface of the output shaft. The magnetic flux generator may create the magnetic flux that creates a magnetic force between the engagement face and the magnetic friction plate that causes them to engage.