Two-line laser-induced fluorescence imaging of vibrational temperatures in a NO-seeded flame

摘要

Two-dimensional temperature 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 ~(2)Σ~(+)-X ~(2)II system are well known from previous studies. The energy difference of 1974 cm~(-1) between the (0,0)Q_(1)+P_(21)(33.5) and the (0,2)O_(12)(5.5) lines offers great sensitivity in the temperature 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 H_(2), 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.