Experimental investigation on the measurement performance of high-speed ultrasonic wave thermometry in ambient- and high-temperature environments

Abstract

This study proposes a high-speed (∼500 Hz), non-intrusive ultrasonic-based temperature measurement method and investigate its performance characteristics by conducting a static behavior measurement at ambient temperature and a dynamic behavior measurement from ambient temperature to 700 °C. In the ambient-temperature experiment, the optimal design of the ultrasonic wave propagation tube is verified by comparing the collected signal intensities. The high repeatability of the ultrasonic wave measurement method is verified with Pearson correlation coefficients of over 99.96 % among the received raw ultrasonic wave signals for every 0.002 s. In the dynamic high-temperature experiment, the measurement accuracy is validated by comparing the temperature deviation from the thermocouple temperature. In the fast-rising low-temperature region around 25–100 °C, a high error rate (>100 %) is obtained; therefore, a signal-denoising algorithm and four candidates of post-processing equations are applied to improve the ultrasonic wave thermometry accuracy. In the four candidate equations, the optimal post-processing method is determined to be the one that yields a linear fitting with slope and intercept obtained in Kelvin temperature. The accuracy of ultrasonic wave thermometry is verified with the time-weighted average and standard deviation of error rates being 1.09 % and 1.10 %, respectively, significantly lower than those of typical commercial thermocouples. As ultrasonic wave thermometry can only perform line-integral measurement and not point measurement, it can be effective for anomaly detection of steady operating systems like gas turbines and boilers for power generation. Thus, fast-responsive, line-integral ultrasonic wave thermometry can be a diagnostic tool to reduce the risk of combustion instability accidents or other problems caused by rapid temperature change.