| YUE Ling-ling， LI Xing-you， CAI Meng-yin， WANG Pei-yong.Simulation and Experimental Verification of a New Time Constant Formula for Bare-wire Thermocouple[J].航空发动机,2024,50(3):128-136 |
| Simulation and Experimental Verification of a New Time Constant Formula for Bare-wire Thermocouple |
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| Key Words:bare-wire thermocouple CFD time constant junction heat transfer |
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| Abstract:In order to accurately determine the response time （time constant） of the thermocouple to measure the dynamic
temperature changes， a new time constant formula for thermocouple was derived based on energy conservation and considering convection，
radiation， and heat conduction at the thermocouple junction. Two parameters， α and e are involved in the time constant formula. The
parameter α related to the surface radiation was obtained by fitting the CFD（Computational Fluid Dynamics） simulated time constant of a
sphere under varying flow parameters； while the parameter e related to conduction was obtained by fitting the CFD simulated time constant
of an S-type thermocouple. The time constant formula was verified by simulation and experiment. The results show that under different
working conditions， compared with CFD simulation results， the errors of the formula are less than 20%. For a specific CFD simulation case
considering the combined effect of radiation and heat conduction， the time constant can be reduced to 33% of the case considering only
convection. Using an S-type thermocouple to measure the temperature of the standard high-temperature gas， the dynamic response curves
and the time constants of the thermocouple were obtained by loading the thermocouple and then removing the current. Compared with the
experimental data， the maximum error of the formula is -12%， demonstrating the high accuracy of the formula. |
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