Thermocouple Array Failure Detection via Shunt Voltage Measurement

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Solution Overview

Problem

Existing temperature instrumentation in aircraft engines, particularly thermocouples, face challenges in detecting failures due to harsh operating environments, making it difficult to monitor critical temperature locations effectively.

Innovation Solution

A method and system that measures voltage across an array of thermocouples during operation and shunts the array during failure detection, comparing the shunt voltage to an expected value to generate a failure signal when deviations exceed a threshold, allowing for early detection of thermocouple failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an array of thermocouples is used to provide redundancy and extend lifetime, then reliability is improved, but the ability to detect individual failures is lost

Engineering Contradiction:

Improveinstrumentation lifetimeVSAvoidfailure detection capability

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The system performs preliminary failure detection by periodically shunting the thermocouple array and measuring resistance during operation, before actual failure occurs. This allows early identification of degraded thermocouples while the system is still functioning normally.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A shunting device is introduced as an intermediary component that temporarily connects across the thermocouple array during detection cycles. This shunt provides a known reference resistance that enables measurement of the array's total resistance without permanently altering the parallel configuration.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If thermocouples operate in harsh environments, then temperature monitoring capability is maintained, but failure rate increases

Engineering Contradiction:

Improvetemperature monitoring capabilityVSAvoidinstrumentation failure rate

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system implements continuous feedback by monitoring the resistance of the thermocouple array during operation. When resistance deviates from expected values, the controller generates alerts, allowing real-time assessment of instrumentation health in harsh environments.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If thermocouples are connected in parallel for redundancy, then temperature reading stability is improved, but individual fault identification becomes difficult

Engineering Contradiction:

Improvetemperature reading stabilityVSAvoidindividual thermocouple status information

Core Design Contradiction:

Stability of the object's compositionVSLoss of information

Solution Approach 1:

The system segments the fault detection process into distinct phases: normal operation mode where thermocouples function in parallel, and detection mode where the shunting device isolates the array for resistance measurement. This segmentation allows both stable temperature monitoring and individual fault identification.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The shunting device operates periodically, switching between open and closed states at predetermined intervals. During closed states, resistance measurement occurs; during open states, normal temperature monitoring resumes. This periodic action enables fault detection without continuous disruption of temperature monitoring.

Inventive Principle:

Principle #19Periodic action

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

Enables reliable detection of thermocouple failures, ensuring continued accurate temperature monitoring and extending the lifespan of temperature instrumentation by identifying issues before they cause significant disruptions.

Implementation Method 1

measuring a voltage V across the array of thermocouples, the voltage V associated with a temperature T

Methodology Applied

Scientific EffectSeebeck effect: Seebeck Effect

Implementation Method 2

measuring a shunt voltage Vs occurring across a resistive element connected in series with the array of thermocouples

Methodology Applied

Scientific EffectOhm's law: Ohm's Law

Data Source

PatentEP4151969B1Method and system for detecting failure in an array of thermocouples connected in parallel

Publication Date: 2024.10.30 PRATT & WHITNEY CANADA CORP

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AI summary

A method of detecting failure in an array (300; 402) of thermocouples (304; TCN) connected in parallel. The method comprising: during an operation mode of the array (300; 402) of thermocouples (304; TCN), measuring a voltage (V) across the array (300; 402) of thermocouples (304; TCN), the voltage (V) associated with a temperature (T); during a failure detection mode of the array (300; 402) of thermocouples (304; TCN), shunting the array (300; 402) of thermocouples, (304; TCN) and measuring a shunt voltage (Vs) occurring across a resistive element connected in series with the array (300; 402) of thermocouples (304; TCN); comparing the shunt voltage (Vs) to an expected shunt voltage (Vs_exp) for the array of thermocouples (304; TCN) at the temperature (T); and generating a failure signal indicative of a detected failure in the array (300; 402) of thermocouples (304; TCN) when the shunt voltage (Vs) deviates from the expected shunt voltage (Vs_exp) by more than a deviation threshold.