APPLICATION OF QUANTITATIVE 2-LINE OH PLANAR LASER-INDUCED FLUORESCENCE FOR TEMPORALLY RESOLVED PLANAR THERMOMETRY IN REACTING FLOWS

A temporally resolved approach for measurement of two-dimensional temp erature fields in reacting flows is experimentally investigated. The m ethod, based on planar laser-induced fluorescence of the hydroxyl (OH) radical, is applicable in many combustion environments, including var iable density flow fields. As a means of examining the accuracy of the technique, temperature images, from 1300 to 3000 K and 0.4 to 3 atm, have been acquired in shock-heated H-2-O2-Ar flows with a two-laser, t wo-image ratio scheme. A complete measurement system for producing acc urate, effectively instantaneous temperature images is described; the system includes single-shot monitors for laser-sheet energy distributi ons and spectral profiles. Temperature images obtained with the OH A 2 SIGMA+ <-- X 2PI (1, 0) P1(7)-Q2(11) transition pair exhibit a systema tic error of only 7% over the entire range of conditions, with the err or most likely dominated by shot-to-shot fluctuations in the lasers' s pectral profiles. The largest error source in the instantaneous temper ature images is photon shot noise. A group of OH transition pairs that provide good temperature sensitivity and strong signals for reduced s hot-noise error over a range of flow-field conditions is also presente d.