Abstract

Laser-based techniques are now widely accepted for nonintrusive probing of high-temperature gases. This paper describes progress in the development of two particular methods: laser-wavelength modulation spectroscopy and planar laser-induced fluorescence imaging. In the modulation spectroscopy, a single-frequency cw ring dye laser is rapidly scanned in frequency across a few cm⁻¹ to record fully resolved absorption line profiles. Both absorption and fluorescence recording are utilized, with the latter providing improved spatial resolution at the expense of quantitativeness for absolute species measurements. The line shape data provide an important source of collision-broadening coefficients, and experiments of this type have been carried out in flames, rf-excited atmospheric pressure plasmas, and shock-heated flows. When multiple lines are scanned, these data can be used to infer temperature at kilohertz repetition rates. The method of planar laser-induced fluorescence offers potential for instantaneous 2-D imaging of several flow-field parameters including species concentrations, temperature, velocity, and pressure. Recent work has been directed toward extending the method to new species, to supersonic flows, and to simultaneous determination of multiple flow-field parameters. Progress in the development of new measurement strategies and improved intensified camera systems is described.

© 1988 Optical Society of America