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  • INORGANIC AND PHYSICAL CHEMISTRY  (6)
  • INSTRUMENTATION AND PHOTOGRAPHY  (4)
  • 1
    Publication Date: 2011-08-19
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 1; 205-209
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  • 2
    Publication Date: 2011-08-18
    Description: Attention is given to the implementation of a novel reflective optics configuration in which the lens normally employed for focusing and crossing the input laser beams in Coherent Anti-Stokes Raman spectroscopy (CARS) is replaced by a spherical mirror, allowing large crossing angles to be obtained with a single focusing device and permitting the laser generation and collection equipment to be located on one side of the sample region. The experimental results obtained demonstrate the feasibility of mirror-based CARS in remote combustion diagnostics.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Applied Optics (ISSN 0003-6935); 22; July 1
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  • 3
    Publication Date: 2011-08-18
    Description: The linearity of an intensified silicon photodiode array multichannel detector is studied with coherent anti-Stokes Raman and other similar signals. Studies with diffuse and focused (spherically and cylindrically) signals resolved apparent saturation problems which limit the dynamic range of the detector. In addition, it has been shown that there is no short-range wavelength (473-532-nm) dependence on this saturation. Theoretical explanations for these phenomena are also included.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 23; 2369-237
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  • 4
    Publication Date: 2019-06-28
    Description: UV spontaneous vibrational Raman scattering and laser-induced predissociative fluorescence (LIPF) are combined and applied to a supersonic flame. For the first time, simultaneous measurements of temperature, major species (H2, O2, N2, H2O), and minor species (OH) concentrations are obtained with a 'single' excimer laser in a supersonic-lifted hydrogen-air diffusion flame. In the supersonic flame, a small amount of reaction occurs upstream of the lifted flame base, due to shock wave interactions and mixing with hot vitiated air. The strong turbulent mixing and high total enthalpy fluctuations lead to nonequilibrium values of temperature, and major and minor species concentrations. Combustion occurs farther downstream of the lifted region where slow three-body recombination reactions result in superequilibrium OH concentrations that depress the temperatures below their equilibrium values. Farther downstream, ambient air entrainment contaminates flame properties.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 91-2320
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  • 5
    Publication Date: 2018-12-01
    Description: Static-temperature measurements performed in a reacting vitiated air-hydrogen Mach-2 flow in a duct in Test Cell 2 at NASA LaRC by using a coherent anti-Stokes Raman spectroscopy (CARS) system are discussed. The hypersonic propulsion Test Cell 2 hardware is outlined with emphasis on optical access ports and safety features in the design of the Test Cell. Such design considerations as vibration, noise, contamination from flow field or atmospheric-borne dust, unwanted laser- and electrically-induced combustion, and movement of the sampling volume in the flow are presented. The CARS system is described, and focus is placed on the principle and components of system-to-monochromator signal coupling. Contour plots of scramjet combustor static temperature in a reacting-flow region are presented for three stations, and it is noted that the measurements reveal such features in the flow as maximum temperature near the model wall in the region of the injector footprint.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 6
    Publication Date: 2019-06-28
    Description: The flow field of an unconfined coaxial supersonic burner (SSB) was obtained numerically, using a CFD code. The explicit MacCormack algorithm, with point implicit treatment of chemistry source terms, was employed in the CFD code. Combustion of hydrogen and air was simulated by a two-step finite-rate combustion model whereas turbulence was accounted for by a Prandtl mixing length scheme. Boundary conditions and some important features of the numerical scheme were discussed. The qualitative features of the numerical solution were compared with those obtained by regular as well as schlieren photographs. General agreements of the CFD solution and the experimental photographs were observed.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 88-0095
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  • 7
    Publication Date: 2019-06-28
    Description: This paper describes a comparative study of temperatures measured with Coherent Anti-Stokes Raman Spectroscopy (CARS) and those using standard measurement techniques. CARS temperatures from nitrogen vibrational-rotational spectra have been obtained in a premixed hydrogen-air laboratory flame supported on a flat flame burner over a temperature range from about 1000 K to 2100 K. The techniques used for comparison were sodium line reversal, thin wire thermocouples and heat balance calculations. These studies show a good agreement over the entire temperature range studied.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 83-1482
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  • 8
    Publication Date: 2019-06-28
    Description: Simultaneous nitrogen number density and rotational-vibrational temperatures were measured in a turbulent diffusion flame with a Coherent Anti-Stokes Raman Scattering (CARS) instrument. The fuel jet was diluted with nitrogen (20 percent by volume) to allow temperature measurements across the entire jet mixing region. These measurements were compared with fluid dynamics computations. The CARS system incorporated a neodymium YAG laser, an intensified silicon photodiode array detector, and unique dynamic range enhancement methods. Theoretical calculations were based on a parabolic Navier-Stokes computer code. The comparison of these techniques will aid their development in the study of complex flowfields.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 84-1537
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  • 9
    Publication Date: 2019-07-13
    Description: In order to accurately determine the quantity of chlorophyll a in living algae by fluorescence spectrometry, either remotely or in the laboratory, the fluorescence excitation cross section must be known. Laboratory fluorescence studies of a number of different algae species representative of the various color groups were performed. These measurements indicate distinct maximum spectral excitation regions which differ from one color group to another. Within each color group, however, the fluorescent properties were nearly identical, regardless of species. These two key features - namely, the similarity of fluorescent properties within a color group, and the distinct spectral differences between color groups - make possible the simultaneous determination of chlorophyll a content of an unknown mixture of phytoplankton and the distribution of chlorophyll a among the various color groups.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Joint Conference on Sensing of Environmental Pollutants; Dec 10, 1973 - Dec 12, 1973; Washington, DC
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  • 10
    Publication Date: 2019-07-13
    Description: Phytoplankton biomass and diversity among various algal species are important for marine productivity assessments. The spatial heterogeneity of phytoplankton in coastal and estuarine environments complicates estimates of total biomass using conventional surface sampling techniques. Since synoptic or near-synoptic data can be quite useful in these studies, this area is a natural focal point for development of remote sensors. However, it is very difficult to sense phytoplankton density and diversity with spacecraft-borne passive sensors primarily because modulation in the signal due to phytoplankton is of the same order as that of atmospheric effects. The same sensors mounted on aircraft may be able to detect and quantify high concentrations of phytoplankton (blooms), but the current lack of knowledge about the spectral reflectance signatures of the major phytoplankton color groups rules out any diversity measurements by this type of sensor. An active fluorosensor mounted on a low-flying aircraft or helicopter is not limited by any of these constraints. A brief survey of the four currently active systems is presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: University of Michigan, International Symposium on Remote Sensing of Environment; Apr 23, 1979 - Apr 27, 1979; Ann Arbor, MI
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