Three-line fluorescence thermometry of optically thick shock-tunnel flow

Abstract

Two-line fluorescence thermometry measurements based on excitation of the A-X (0, 0) band of nitric oxide were performed in the free-stream flow of a large-scale shock tunnel, the Arnold Engineering Development Center Impulse Facility. Because the flow is optically thick, effects of laser absorption must be taken into account. This can be accomplished by extending the two-line thermometry concept to three lines. We illustrate the three-line technique by combining two-line planar laser-induced fluorescence measurements from separate facility runs. The resulting free-stream temperature T(0) = 468 K ? 65 K is insensitive to assumptions regarding the laser propagation distance through the flow, the vibrational temperature of the flow, and the precise nature of the absorption line shape.

Free-Piston Shock Tunnel Test Technique Development: An AEDC/DLR Cooperative Program

“…However, spectral hole burning is significant for tunnel run conditions III and I, but at a level that is manageable by the theory from Ref. 32.…”

“…The first of these is the same as those used in Ref. 32, which discusses fluorescence thermometry in optically thick flow. HEG personnel supplied the HEG freestream parameters.…”

“…32, signal profiles and signal ratio profiles were calculated for the HEG-supplied freestream parameters. These profiles are to be compared with the experimental profiles from Figs.…”

“…32, an explicit estimate was made of the NO density and temperature for run condition III. This was accomplished by combining the measured PLIF signal ratios from Runs 454 and 455, both taken at condition III.…”

“…105 shows the results of a second extension to the theory in Ref. 32. Rather than assuming that the freestream flow has a top-hat NO density profile with a diameter of 55 cm, it is assumed that there is, in addition, a boundary layer, in which the NO density and temperature fall linearly from the (to-be-determined) freestream values to the values at the edge of the boundary layer (zero NO density and ambient temperature = 293K).…”