The goal of this research is to develop advanced laser-based techniques for non-intrusive measurements relevant to air-breathing combustion. In general, the program emphasizes spectrally-resolved absorption using tunable laser sources and planar laser-induced fluorescence (PLIF), conducted using either near-infrared or ultraviolet laser sources. Detailed below is progress on the exploration of IR PLIF as a diagnostic for imaging IR-active gases and on the suitability of pentanone as an alternative flow tracer to acetone for PLIF imaging. Furthermore, a novel absorption sensor for NO2 at temperatures up to 1900 K has been developed, and continuing work is reported on the spectroscopy of high-pressure gases.

Progress is reported at the completion of two years of an interdisciplinary program to investigate and establish modern diagnostic techniques for application to reacting flows. Project areas include: (1) optical probes for species measurements employing tunable ultraviolet, visible and infrared laser sources; (2) coherent anti-Stokes Raman spectroscopy (CARS) for temperature and velocity measurements in a supersonic jet; (3) computed absorption tomography for species measurements in a plane; (4) particle sizing techniques, especially for rocket exhausts; (5) fast-response temperature monitor, based on line-reversal concepts; (6) quantitative flow visualization, including temporally and spatially resolved species measurements in a plane using laser-induced fluorescence; (7) multiple-point velocity visualization; (8) application of modern diagnostics to a two-dimensional reacting shear layer; (9) development of measurement techniques and a novel facility for investigations of droplet evaporation in turbulent flows; (10) holographic display techniques for 3-D visualization of flowfield data; (11) spatially resolved laser absorption spectroscopy using optical Stark shifting; and (12) fast-scanning dye laser for measurements of species, temperature and fundamental spectral parameters. (Author).

Advanced optical diagnostic techniques relevant to propulsion were investigated. The techniques studied were based on laser spectroscopy, with emphasis on spectrally-resolved absorption and laser-induced fluorescence (LIF). Laser sources included tunable cw near-infrared diode lasers and tunable (or fixed-wavelength) pulsed lasers operated at ultraviolet (UV) or infrared (IR) wavelengths. The cw lasers were spectrally narrow, allowing study of innovative diagnostics based on spectral lineshapes, while the pulsed lasers provided intense bursts of photons needed for techniques based on LIF. Accomplishments of note included: (1) development of a new imaging diagnostic based on infrared planar laser-induced fluorescence (IR PLIF), (2) investigations of quantitative ultraviolet (UV) PLIF of NO and CO2 in high-pressure combustion environments, (3) the development of a new temperature diagnostic using UV absorption of CO2 for high-temperature combustion environments, (4) development of advanced wavelength-multiplexed diode laser absorption sensing of non-uniform temperature distributions, gas temperature in scramjet flows, and tunable mid-IR-based fuel sensing, and (5) further development of quantitative tracers to image fuel distribution using ketones and the aromatic toluene. The full spectrum of results was published in thirty-eight papers in the AIAA and peer reviewed literature, seven PhD theses, and forty-three presentations and invited lectures.