Measurement of two-dimensional temperature field using filtered Rayleigh scattering

Two-dimensional temperature measurements in reacting flows have been measured using Filtered Rayleigh Scattering (FRS). In FRS iodine is contained in an optical cell. An injection seeded Nd:YAG laser is tuned to an absorption line of iodine. The iodine filter is placed in front of an intensified CCD camera recording the scattered light. Scattering from solid surfaces and particles is strongly absorbed by the iodine, while much of the Doppler broadened Rayleigh scattering is transmitted by the filter. The gas temperature can be deduced from the measured transmission of the molecular Rayleigh scattering. Two different premixed flames were investigated, a hydrogen-air flame created using a Hencken burner and a methane-air flame. The accuracy of the FRS measurements was investigated by comparing FRS-derived temperatures with calculated values and temperatures recorded with coherent anti-Stokes Raman spectroscopy. For the hydrogen-air flames, the FRS method gave temperatures within 2% of the expected value (from measurement and/or calculation). Methane-air flames were investigated to demonstrate the effectiveness of FRS to measure to obtain `large field' two-dimensional temperature information in a buoyantly driven flame. An uncertainty analyses is given to show the strengths and weaknesses of the FRS technique for temperature measurements in combustion flows.