Abstract
A spontaneous vibrational Raman scattering technique is developed for simultaneous measurements of temperature and multi-species (C02 O2, CO, N2, CH4, H20, H2, and OH) concentrations in premixed methane - air flames. The Raman spectra and spectral background are obtained using a narrowband tunable KrF excimer laser working at 248 nm and a spectrometer combined with an intensified CCO camera. Optimal tuning of the narrowband KrF excimer laser (248.632 nm) for minimization of OH A2Σ_X2П and 02 B3Σu- X3Σgfluorescence interference is determined from fluorescence excitation spectra. Laser emission spectra are made to ensure that the optimum wavelength of the laser is within a good locking region. Natural fluorescence spectra (without laser excitation) are used to determine the gate time of the ICCO camera. Measured Raman spectra demonstrate that single-pulse concentration and temperature measurements, with only minimal fluorescence interference, are possible for turbulent premixed methane-air flames. A time-averaged temperature measurement technique is presented that matches the theoretical spectra to the measured N2 Stokes Raman spectrum. Methodologies for simultaneous temperature, major species, and OH concentration measurements in turbulent premixed flames are discussed.
Published Version
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