Laser methods for nonintrusive measurement of supersonic hydrogen-air combustion flowfields

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Abstract
Nonintrusive, laser-based optical techniques for measurement of supersonic hydrogen-air combustion flowfields are discussed. Shadowgraph visualization using a 35 mm camera or a high-framing-rate SP 2000 digital camera enables overall flowfield features to be studied. Spontaneous Raman scattering is used for major specie concentration and temperature measurement. Laser-induced iodine fluorescence provides a measure of the noncombusting fuel mole fraction distribution, using a broad-linewidth laser and a ratio of digital images. A narrow-linewidth, tunable laser is used to record a high resolution iodine spectrum, from which density, temperature and velocity are determined in the supersonic mixing flowfield. Similar techniques are being developed using both broad- and narrow-linewidth pulsed lasers and OH fluorescence for measurement in the supersonic flowfield with combustion.