Temperature determination in a shock tube using hydroxyl radical A-X band emission

Abstract

Temperature determination in a shock tube is one of the most important factors to understand the relevant flow physics inside. In the present study, the reservoir temperature determination in a shock tube using the ultraviolet emission spectra of hydroxyl radical (OH) A-X band was carried out. A radiation model for the OH A-X transition was developed, and it was validated using the benchmark data. Curve fit parameters, such as a peak-to-peak ratio and the absolute peak intensity of the P-branch, are proposed to evaluate the rotational temperature and the OH number density from the measured emission spectra. In the shock tube experiments, humid air from the atmosphere was employed as a test gas, and a small amount of the ultraviolet OH emission was measured behind the reflected shock wave. The measured spectrum was converted to the rotational temperature and the number density using the present model of the OH A-X emission. Then, the evaluated rotational temperature was compared with the calculated values of the reservoir condition behind the reflected shock wave. A good agreement was detected between the measured and the calculated temperatures, which are 4020 ± 290 K and 4110 ± 220 K, respectively. It was recognized that the reservoir temperature behind the reflected shock wave is well described by the present model of the OH A-X ultraviolet emission.