Thermocouple Probe Channel Design for Thermal Gradient Reduction
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Solution Overview
Problem
High temperature measurement in gas turbine engines is challenging due to the high working gas temperatures, which can lead to errors in thermocouple readings caused by coolant-induced thermal gradients.
Innovation Solution
A high temperature measurement probe with an elongate probe body and a thermocouple extending along a channel within the probe body, where the thermocouple junction is positioned near the upstream end of the channel section, allowing a longer portion of the thermocouple to be exposed to the fluid flow and reducing thermal gradients near the junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant is circulated within the probe to protect from high working gas temperatures, then the probe is protected from thermal damage, but the thermocouple temperature measurement becomes inaccurate due to coolant-induced thermal gradients
Solution Approach 1:
The invention extracts the thermocouple from the cooled region near the probe inlet and positions it in a region where coolant influence is minimized. The thermocouple is placed in a channel that extends along the probe body, with the sensing junction positioned downstream where the thermal gradient from coolant is reduced, thereby separating the measurement function from the thermal protection function.
Solution Approach 2:
The invention introduces a channel as an intermediary structure that carries the thermocouple through the probe body. This channel provides a thermal pathway that isolates the thermocouple junction from direct coolant cooling while still allowing the probe to be cooled. The channel acts as a thermal mediator between the hot gas environment and the thermocouple.
2Device complexity
If the thermocouple junction is positioned close to the inlet for compact design, then device complexity is reduced, but thermal gradients from coolant cause large measurement errors of 50-80 K
Solution Approach 1:
The invention extends the thermocouple channel along the length of the probe body in the axial direction, creating a long narrow channel geometry. This dimensional arrangement allows the thermocouple to run parallel to the coolant flow path, positioning the junction downstream where thermal gradients are reduced, thereby achieving accurate measurement without excessive compactness requirements.
3Measurement precision
If a long portion of the thermocouple is exposed to fluid flow to reduce thermal gradients, then measurement accuracy improves, but the probe structure becomes more complex
Solution Approach 1:
The channel structure serves multiple functions simultaneously: it provides a pathway for the thermocouple, guides the hot gas flow over the thermocouple junction, and creates a controlled thermal environment that minimizes coolant influence. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving improved measurement accuracy.
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 design improves the accuracy of temperature measurements by minimizing the impact of coolant-induced thermal gradients and reduces measurement errors from 50-80 K to about 10 K.
Implementation Method 1
a thermocouple extending along the interior of the probe body to terminate at a temperature-sensing thermocouple junction inside the measuring head
Implementation Method 2
the probe body has internal passages for circulation of a coolant fluid therein
Implementation Method 3
coolant can be circulated within the probe
Data Source
AI summary
A high temperature measurement probe comprises an elongate probe body having a measuring head which in use is located in a hot fluid flow. The probe further comprises a thermocouple extending along the interior of the probe body to terminate at a temperature-sensing thermocouple junction inside the measuring head. The probe body has internal passages for circulation of a coolant fluid therein. The measuring head contains a channel, one end of the channel forming an inlet for receiving hot fluid from the hot fluid flow and another end of the channel forming an outlet for discharging the hot fluid received at the inlet. Between the inlet and the outlet a section of the channel extends along the length direction of the probe body. The thermocouple runs along the section of the channel with the thermocouple junction proximate the upstream end of the section.