Two-line laser-induced fluorescence imaging of vibrational temperatures in a NO-seeded flame
Two-dimensional temp. fields are measured in lean and sooting flames by means of two-color laser-induced fluorescence (LIF) imaging that uses seeded NO. Vibrational thermometry is performed by the probing of different vibrational ground-state levels. Spectral properties of the excited transitions within the A 2S+-X2P system are well known from previous studies. The energy difference of 1974 cm-1 between the (0,0)Q1 + P21(33.5) and the (0,2)O12(5.5) lines offers great sensitivity in the temp. range that is relevant for combustion processes. Excitation is possible by use of a tunable KrF excimer laser on its fundamental (248 nm) and Raman shifted (in H2, 225 nm) wavelengths. An excitation scheme for instantaneous two-line measurements by use of a single laser is developed. The possibility of single-shot measurements is discussed.
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