Tomographic laser absorption spectroscopy using Tikhonov regularization.

Area of Science:

• Combustion diagnostics
• Laser spectroscopy
• Optical diagnostics

Background:

• Few studies explore tunable diode laser absorption spectroscopy (TDLAS) in nonhomogeneous flames.
• Accurate temperature and species concentration measurements are crucial for combustion research.

Purpose of the Study:

• To investigate the performance of tomographic reconstructions using wavelength-modulated TDLAS in a McKenna burner flame.
• To validate TDLAS as a viable diagnostic tool for nonhomogeneous flame environments.

Main Methods:

• Utilized calibration-free wavelength modulation spectroscopy with second harmonic detection (WMS-2f) to probe water vapor.
• Employed a swept laser beam to acquire line-of-sight (LOS) absorption data at multiple radial locations.
• Applied Tikhonov regularized Abel inversion for tomographic reconstruction of radial profiles, suppressing noise amplification.

Main Results:

• Successfully reconstructed temperature and water vapor mole fraction profiles within the burner plume.
• Demonstrated accurate point-by-point calculations of temperature and mole fraction from spectral data.
• Validated the effectiveness of nonoptimal modulation depths and a least-squares approach for reconstruction.

Conclusions:

• Tunable diode laser absorption spectroscopy (TDLAS) with WMS-2f and Tikhonov regularized Abel inversion is a viable diagnostic tool for flame measurements.
• The developed technique enables accurate mapping of temperature and species concentration in nonhomogeneous combustion fields.
• This method provides valuable data for understanding and optimizing combustion processes.