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Show 3.3.3 Laser-induced Fluorescence Laser-induced fluorescence (LIF) is a technique that uses laser light to excite specific molecules to higher electronic states. When these molecules fall back to the ground state, they emit photons at a specific wavelength. Measuring the number of photons emitted at a given wavelength yields information on the concentration and temperature of the species of interest. The major advantages of LIF are that it is species specific, provides a strong signal relative to excitation processes such as Raman scattering, and provides the capability of measuring several important combustion species such as the CR and OR radicals and the pollutant species NO. Although LIF is relatively well-established for turbulent reacting flows, a number of practical considerations complicate the quantitative application of LIF to these flows . Laser-induced fluorescence has been used previously to measure CR [6], OR [7] and NO [8]. Particularly when used for planar imaging, these measurements provide information on the spatial relationships between turbulent mixing, combustion and pollutant formation. CR provides an excellent qualitative marker for the flame zone since it is short-lived and appears only during the initial oxidation of hydrocarbon fuels. The OR molecule provides an indicator of where combustion is most intense and where the secondary heat release due to CO oxidation is occurring. In addition, OR provides an important measure of the radical pool concentrations (consisting of 0, OR and R), which is important to both combustion and pollutant formation chemistry. The measurement of NO, particularly where it is formed, is integral to reduction strategies for NOx control. 4.0 Conclusion This paper should give those interested sufficient background to write a work plan for the BERL. Keep in mind the capabilities, limitations and the time required for each diagnostic. Table 3 lists the diagnostic capabilities and the time required for each. A visit to BERL would give the reader a much better feel for the facility and is encouraged prior to submission of a proposal. Any questions can be addressed to: Neal Fomaciari Sandia National Laboratory PO Box 909 MS 9053 Livermore CA 94551-0969 Tel: (510) 294-2472 FAX: (510) 294-1004 -12- |