OH Vibrational Thermally-Assisted Laser Induced Fluorescence Temperature Measurements in Flames

Abstract

Thermally-assisted laser induced fluorescence temperature measurements using upward vibrational transfer from υ' = 0 to υ' = I in A² Σ+ OH have been demonstrated in premixed nitrogen diluted flames of acetylene, ethylene, and methane over a wide range of equivalence ratios. Detection of the (0-0) and (1-0) vibrational bands was used to determine the relative populations of υ' =0 and I from which temperature was calculated assuming a simple Iwo level model incorporating the effects of vibrational energy transfer and quenching. It was found that collisional effects that are a source of systematic error can be accounted for through a calibration procedure for each fuel type. The resulting accuracy of the measurement is better than I00K as determined through comparison with sodium line reversal temperature measurements in flames that ranged in temperature from 1700 K to 2700 K. Similar results using detection of the (0-1) and (1-0) vibrational bands in order to minimize self-absorption effects were also obtained. Single-shot measurements using 0.7 mJ of laser energy were also demonstrated with a lσ precision of 5%.

Key words:

• laser induced fluorescence (LIF)
• OH (Hydroxyl)
• flame temperature