2-T algorithm for temperature estimation in a non-uniform zone by line-of-site diode laser absorption spectroscopy

A new two-temperature (2-T) algorithm for an estimation of the temperatures in a non-uniform hot zone by absorption spectrometry with tunable diode lasers (TDLAS) is demonstrated in experiments with the Wolfhard-Parker burner. A laminar premixed flame of the burner has a planar structure with zones of relatively constant temperature and zones with pronounced temperature gradients. The temperature was evaluated by fitting the experimental absorption spectra of a H2O molecule by the linear combination of two single temperature spectra simulated using spectroscopic databases. The radiation of the two diode lasers generating in 7185 cm−1 and 7444 cm−1 spectral ranges crossed the flame in the direction along the slots at different heights above the burner. Temperature profiles of the flame obtained by fitting the line-of-sight TDLAS experimental spectra using a 2-T algorithm are compared with the local temperatures measured by coherent anti-Stokes Raman spectroscopy (CARS). The maximum and minimum temperatures estimated by the TDLAS and CARS coincide well if the line-of-sight optical path of the probing diode laser beam consists of a dominantly hot or dominantly cold layer.