Rotational CARS Thermometry in Sooting Flames

Abstract

Coherent anti-Stokes Raman scattering of pure rotational transitions, rotational CARS, is demonstrated as an efficient method for temperature determination in sooting flames. The dual broadband CARS approach was used to measure temperature profiles in premixed, sooting ethylene flames al atmospheric pressure by probing the nitrogen gas. The recorded spectra were of equally high quality in non-sooting and sooting flames with volume fractions of sool of up to 7 × 10 ⁻⁷cm³soot/cm³. The advantages of rotational CARS in comparison with several other techniques for the measurement of temperatures in sooting flames, and the general applicability of the technique to different combustion conditions, are discussed. Potential limitations in the application of rotational CARS to sooting flames that are more heavily sooting than the ones investigated in this study, are outlined.

Keywords:

• Laser diagnostics
• rotational CARS
• sooting flames
• temperature measurements