A temporally resolved approach for measurement of two-dimensional temperature fields in reacting flows is experimentally investigated. The method, based on planar laser-induced fluorescence of the hydroxyl (OH) radical, is applicable in many combustion environments, including variable 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 H2–O2–Ar flows with a two-laser, two-image ratio scheme. A complete measurement system for producing accurate, effectively instantaneous temperature images is described; the system includes single-shot monitors for laser-sheet energy distributions and spectral profiles. Temperature images obtained with the OH A 2Σ+ ← X 2Π (1, 0) P1(7)–Q2(11) transition pair exhibit a systematic error of only 7% over the entire range of conditions, with the error most likely dominated by shot-to-shot fluctuations in the lasers’ spectral profiles. The largest error source in the instantaneous temperature images is photon shot noise. A group of OH transition pairs that provide good temperature sensitivity and strong signals for reduced shot-noise error over a range of flow-field conditions is also presented.
© 1994 Optical Society of AmericaFull Article | PDF Article
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