Hydroxyl tagging velocimetry (HTV) is generally used for velocity measurement especially in the high-temperature and high-velocity flow field. In this work, according to the monotonous change of OH fluorescence intensity with temperature, the relative temperature distribution could be observed from the intensity distribution along the hydroxyl fluorescence line. We could obtain the temperature along the photodissociation line by calibrating at two positions. In this way, HTV has the potential for simultaneously achieving velocity and temperature without adding extra diagnostic systems.

In view of the uncertainty in the calibration process of two-color plane laser-induced fluorescence (PLIF) temperature measurement, a new calibration method is proposed, in which the influence of fluorescence yield is considered. The calibration process was carried out at high and low temperature region, respectively. Then, the bias of thermometry results origin from quenching is restrained. This new calibration method is validated in a jet flame with temperature range of 1300–1800 K. Here, the temperature results from Coherent Anti-Stokes Raman scattering (CARS), single-point calibrated PLIF, and two-point calibrated PLIF are all acquired with the maximum standard errors of 13 K, 36 K, and 37 K, respectively. The temperature deviation between the average results from PLIF and Coherent Anti-Stokes Raman scattering (CARS) is 120 K and 10 K, when the two-point and one-point calibration methods are used. Therefore, the two-point calibrated PLIF is preferred in the combustion field, especially with a large temperature range and strong quenching coefficient.

This paper summarizes the direct observation of tagged hydroxyl within 200 µs after its formation in the temperature range of 294 K–891 K. We estimate the time and temperature frame of the coexistence of chemical reactions and diffusion based on analysis of the behavior of the tagging fluorescence spot of photodissociation hydroxyl. The reasons for the existence of chemical reactions and interactions between chemical reactions and diffusion are then analyzed. Theoretical and experimental identification of this frame can be explored for non-contact spectral measurements based on hydroxyl in a general flow field.