Spatial averaging effects in CARS thermometry of a nonpremixed flame

Coherent anti-Stokes Raman scattering (CARS) allows nonintrusive in situ temperature measurements to be made in reacting flows with errors typically less than 50 K. When the temperature varies over the length of the CARS probe volume, however, the measured temperature is biased toward the cold side rather than reflecting the mean temperature or the temperature at the center of the volume. This paper details CARS measurements made on a Wolfhard-Parker slot burner to quantity these spatial averaging errors in nonpremixed flames. Results, using both analytical and experimental inputs to a CARS spectral fitting program, show that while spatial averaging errors are significant, they can be predicted accurately.