  The application of tunable diode laser absorption spectroscopy (TDLAS) to
flames with non-homogeneous temperature and concentration fields is an area
where only few studies exist. Experimental work explores the performance of
tomographic reconstructions of concentration and temperature profiles from
wavelength-modulated TDLAS measurements within the plume of an axisymmetric
McKenna burner. Water vapor transitions at 1391.67 nm and 1442.67 nm are probed
using calibration free wavelength modulation spectroscopy with second harmonic
detection (WMS-2f). A single collimated laser beam is swept parallel to the
burner surface, where scans yield pairs of line-of-sight (LOS) data at multiple
radial locations. Radial profiles of absorption data are reconstructed using
Tikhonov regularized Abel inversion, which suppresses the amplification of
experimental noise that is typically observed for reconstructions with high
spatial resolution. Based on spectral data, temperatures and concentrations are
calculated point-by-point. Here, a least-squares approach addresses
difficulties due to modulation depths that cannot be universally optimized due
to a non-uniform domain. Experimental results show successful reconstructions
of temperature and concentration profiles based on two-transition,
non-optimally modulated WMS-2f and Tikhonov regularized Abel inversion, and
thus validate the technique as a viable diagnostic tool for flame measurements.
