MULTIPARAMETER AND MULTIPOINT MEASUREMENTS

Laser-based diagnostic techniques, developed primarily within the comb ustion community, offer considerable promise for nonintrusive measurem ents in gaseous flows relevant to industry. In this paper, we review t wo diagnostic methods under development in our laboratory. The first t echnique allows simultaneous measurement of multiple parameters throug h analysis of the shape and shift of fully resolved absorption linesha pes. The light source is a tunable, narrow-linewidth semiconductor dio de laser, applied in the present case to either water vapor (1.39 micr ons) at combustion gas temperatures (to 1700 K) or to argon (800 nm) i n an atmospheric pressure plasma (at temperatures to 8000 K). Paramete rs inferred include, for water: temperature, pressure, velocity and sp ecies density; for argon, the parameters are electron density, kinetic temperature and the population temperature for the 4 s levels of argo n. The second diagnostic technique is planar laser-induced fluorescenc e (PLIF), which allows instantaneous measurements of a single paramete r at multiple points in the flowfield. The example application to be d iscussed is single-shot temperature imaging in a model scramjet flowfi eld using a two laser-two camera imaging scheme.