Comparison of NO and OH planar fluorescence temperature measurements in scramjet model flowfield

Abstract

The use of nitric oxide (NO) and the hydroxyl radical (OH) as temperature tracers, in a two-line planar laser-induced fluorescence technique, is examined in the context of a supersonic mixing and combustion flowfield. The temperature measurements were based on the sequential excitation of two transitions, either in the A implied by X (0,0) band of NO near 226 nm or the A implied by X (1,0) band of OH near 283 nm. The measurements were obtained for each species through the use of two lasers and two cameras, with each camera integrating signal induced from only one of the lasers. Both temporally resolved and frame-averaged temperature measurements of each species are presented. Additional results include simultaneous NO and OH visualizations, in which seeded NO marks the fuel jet fluid and nascent OH marks the reaction zones and convected combustion gases. A detailed temperature comparison shows good agreement in the common measurement regions and indicates that shot noise is the largest source of uncertainty. The comparison also illustrates the importance of a careful interpretation of the measurements, since, depending on the origin of the tracer and the degree of mixing, the measurements may be biased toward the fuel, freestream, or reactionmore » zone temperatures. 33 refs.« less