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Multiscalar Point Measurements using Simultaneous Raman/Rayleigh/LIF Barlow, Robert 
In the Turbulent Diffusion Flame (TDF) laboratory, the combination of spontaneous Raman scattering, Rayleigh scattering, and laser-induced fluorescence (LIF) is used to obtain simultaneous point measurements of temperature and the concentrations multiple species. The major species (N2, O2, H2, H2O, CH4,CO2) are measured by spontaneous Raman scattering of light from two pulsed Nd:YAG lasers. Concentrations of OH and NO are measured using linear LIF. Here, the LIF signals are corrected for shot-to-shot variations in the Boltzmann fraction and collisional quenching rate, with corrections being based on the simultaneous measurements of major species and temperature. The concentration of CO is measured by two-photon LIF. This system is operated such that ionization of excited-state CO by a third photon is dominant over collisional quenching as a loss mechanism. This means that measurements are relatively insensitive to variations in the quenching rate within a turbulent flame. 
These multiscalar measurements provide a detailed characterization of the instantaneous thermochemical state in the laser probe volume. Additional scalar quantities describing the state of mixing, the progress of reaction, the degree of differential molecular diffusion, deviations from partial equilibrium, and even the rates of some reactions may be derived from the species and temperature measurements. The unique capabilities of the TDF lab have been used in fundamental studies of a wide variety of flames, including laminar, turbulent, nonpremixed, partially-premixed, and premixed flames. |
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