Gas Turbine Shaft Shear Detection Conditioning Circuit

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Solution Overview

Problem

Existing electrical control systems in gas turbine engines face challenges in reliably distinguishing between shaft shear conditions and electrical faults, often resulting in false alarms due to sensor malfunctions or damage from high-speed vibrations and hot gas environments.

Innovation Solution

An electrical control system utilizing two or more probes with associated resistors, where mechanical interference during shaft shear breakage renders the resistors non-conductive, allowing a sensor processor to determine operational status and generate appropriate fault codes to differentiate between shaft shear and electrical faults, thereby minimizing false alarms and ensuring reliable engine shutdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple sensors are installed to provide redundancy and reliability for shaft shear detection, then the reliability of detection is improved, but the complexity of the electronic control system increases and false alarms may occur due to sensor malfunction

Engineering Contradiction:

Improveshaft shear detection reliabilityVSAvoidelectronic control system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A conditioning circuit is introduced as an intermediary between the probe and sensor processor. This circuit includes a resistor connected in series with the probe, where the resistor value changes based on probe resistance. The conditioning circuit processes the raw probe signal into a standardized output signal that the sensor processor can reliably interpret, thereby simplifying the overall system while maintaining high detection reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system utilizes changes in electrical resistance parameters to detect shaft shear conditions. The probe resistance changes from a first value (normal condition) to a second value (shaft shear condition), and the conditioning circuit translates these parameter changes into distinct output signals that clearly differentiate between normal operation, shaft shear, and sensor failure conditions.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If sensors are positioned in the engine core surrounded by hot gas path and subjected to vibration, then the detection capability for shaft shear is improved, but the sensors are more susceptible to damage and malfunction

Engineering Contradiction:

Improveshaft shear detection precisionVSAvoidsensor damage from heat and vibration

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The conditioning circuit with series resistor is designed beforehand to compensate for potential probe damage. When a probe is damaged by heat or vibration, its resistance changes, and the conditioning circuit is pre-configured to interpret this resistance change as a specific output signal pattern. This allows the system to distinguish between actual shaft shear conditions and sensor damage, preventing false alarms while maintaining detection precision.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If a single probe is used for shaft shear detection, then the device complexity is reduced, but the reliability and redundancy of the detection system is compromised

Engineering Contradiction:

Improvedetection circuit complexityVSAvoiddetection system reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The detection system is segmented into multiple independent probe circuits, each with its own conditioning circuit containing a series resistor. This segmentation allows each probe to operate independently and be evaluated separately. The sensor processor can analyze the output signals from multiple probes to determine shaft shear conditions, providing redundancy while keeping each individual circuit simple and manageable.

Inventive Principle:

Principle #1Segmentation

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 system effectively distinguishes between shaft shear and electrical faults, reducing false alarms and ensuring timely engine shutdown, thus preventing catastrophic failures by using a minimal number of probes to maintain high reliability and redundancy.

Implementation Method 1

mechanical interference between one or more of the probes and the shaft component renders the associated resistor substantially non-conductive

Methodology Applied

Scientific EffectMechanical interference rendering resistor non-conductive: Electrical Resistance

Data Source

PatentUS9169742B2Electronic shaft shear detection conditioning circuit

Publication Date: 2015.10.27 PRATT & WHITNEY CANADA CORP

AI summary

An electrical control system for distinguishing between an electrical fault and a shaft shear condition in a gas turbine engine, the control system including, in one aspect, a detection circuit including: two or more probes, each probe including an associated resistor having a predetermined range of resistance, and each probe being disposed in the engine adjacent a rotary mounted shaft component, where mechanical interference between one or more of the probes and the shaft component renders the associated resistor substantially non-conductive; sensor processor(s) in communication with each probe, determining a probe operational status based on a measured resistance to current conducted through each probe, and generating a fault code when the measured resistance of at least one of the plurality of probes is not within the predetermined range of resistance.