Robust Fitting of CARS Spectra for Temperature Measurement in Hostile Combustion Environments

As Coherent Anti-Stokes Raman Scattering (CARS) becomes actively applied in complex, hostile, and practical combustion systems, the trade-off between reliability and accuracy of CARS temperature measurement becomes important. Noise in the CARS signal can undermine detailed spectral fitting techniques, leaving calculated temperatures somewhat uncertain. This paper uses the CARS fitting code developed at Sandia National Laboratories (Palmer, 1989) to explore the robustness of “quick” fit, or integral fitting methods, as a technique for avoiding the difficulties in fine detail fitting of noisy CARS data. The theoretical temperature resolution from such integral fitting is much lower than for detailed calculations, but the reliability of the temperature can be significantly improved.