Thermocouple Probe Conduction Error Correction
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Solution Overview
Problem
Current thermocouple devices face significant uncertainties due to conduction error, particularly in high-speed flows and demanding applications like gas turbine engine development, where precise temperature measurements are crucial for efficiency, but existing methods are either impractical or yield highly uncertain results.
Innovation Solution
A temperature measurement system that includes a thermocouple probe, a computer-readable storage medium, and a processor, which forms a three-dimensional model of the probe, performs computational fluid dynamic analyses, and applies linear regression to correct for conduction errors, providing accurate gas temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wire's length is increased or diameter is decreased to minimize conduction error, then conduction error is reduced, but the wires break due to structural constraints in high-speed flows
Solution Approach 1:
The thermocouple wire is divided into multiple discrete segments or beads along its length, rather than using a continuous wire. This segmentation allows the wire to maintain structural integrity while reducing thermal conduction error, as each segment can be independently positioned and the discontinuities interrupt heat flow along the wire.
Solution Approach 2:
Different sections of the thermocouple wire have different properties - the sensing junction area maintains continuous contact for accurate temperature detection, while other sections are segmented or spaced to reduce thermal conduction. This local differentiation allows simultaneous optimization of both measurement accuracy and structural strength.
2Measurement precision
If complex solutions like heat source at support are used to reduce conduction error, then temperature difference between junction and probe is reduced, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The active heating component (heat source) is removed from the support structure entirely. Instead, the solution relies on passive thermal management through wire segmentation and strategic positioning of the thermocouple elements, eliminating the need for additional heating devices, temperature sensors, and control systems.
Solution Approach 2:
The thermocouple system self-regulates thermal conditions through its segmented wire design and natural heat dissipation characteristics. The structure itself provides the thermal management function without requiring external active control systems, making the system self-sufficient and simpler.
3Measurement precision
If numerical correction of conduction error is performed using temperature measurement at support, then conduction error can be compensated, but results have high uncertainty due to variance in estimations
Solution Approach 1:
The thermocouple wire is pre-configured with specific segmentation patterns and positioning during manufacturing, before the measurement process begins. This preliminary structural arrangement ensures that conduction errors are minimized by design rather than requiring post-measurement numerical corrections with uncertain parameters.
Solution Approach 2:
The natural thermal conduction that causes measurement error is converted into a beneficial effect through segmentation. The same thermal conduction mechanism that was harmful is now used advantageously by creating controlled thermal discontinuities that reduce overall heat flow along the wire, thereby reducing the error source itself rather than attempting to correct it numerically.
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 system efficiently and accurately corrects for conduction errors in thermocouple applications, achieving uncertainties of less than 0.1K and minimizing errors associated with wire length and thermal conductivity, thus enhancing the precision of temperature measurements in challenging environments.
Implementation Method 1
thermocouples rely on the principle that a voltage potential occurs when there is a temperature gradient along the length of a conductor
Implementation Method 2
The conduction error arises from the large temperature difference between the hot junction of the thermocouple and the varying temperature of the shield/support during the test or the day. This heat conduction causes the hot junction to reach a different temperature than the total temperature of the gas.
Data Source
AI summary
The temperature measurement system includes a thermocouple probe, a non-transitory computer-readable storage medium storing processor-executable instructions, and a processor. The processor-executable instructions are configured to enable to processor to form a model of the thermocouple probe, perform several computational fluid dynamic (CFD) analyses of the thermocouple probe using a predetermined Reynolds number, output a first temperature (T1CFD) and a second temperature (T2CFD) at the junctions for each simulation, apply a linear regression between the T1CFD and the T2CFD, output a slope from the linear regression, and output a corrected gas temperature with at least one algorithm.