Experimental study of thermocouple temperature measurement based on coherent anti-Stokes Raman spectroscopy

Abstract

In this paper, we mainly investigate the error of thermocouples in different combustion environments by comparing the measured temperatures by CARS (coherent anti-Stokes Raman spectroscopy). In the experiment, we build a set of broadband and unstable-resonator spatially enhanced detection CARS devices to achieve precise temperature measurement. By comparing the measured temperatures by CARS and thermocouples in an adiabatic environment, we find that the temperatures measured by both are well matched. In an open environment, we find that the measured temperature by thermocouples has large errors compared to that by CARS and literature temperature, which is primarily caused by thermal radiation, and there is an error of about 7% by using the double-thermocouple correction method, and we propose the measured temperature by CARS as the true value to correct the radiation error of thermocouples and use the least-squares method to fit the temperature curve, resulting in an error of only 0.83%. In addition, we realize a wide-range precise temperature detection from 1100 to 2100 K by CARS, and the relative standard deviation and the relative error in the whole experiments are less than 1.8% and 1.6%, respectively.