Planar laser-induced fluorescence

There are many nonintrusive experimental tools available that can help scientists to develop a good picture of fluid dynamics and transport in chemical reactors. Laser Doppler velocimetry (LDV), particle image velocimetry (PIV) and sonar Doppler for velocity measurement, planar laser induced fluorescence (PLIF) for mixing studies, and high-speed cameras and tomography are very useful for multiphase studies. These experimental methods combined with computational fluid dynamics (CFDs) provide very good tools to understand what is happening in chemical reactors. 

Two-dimensional distributions of ground-state NO were detected by planar laser-induced fluorescence during the process of NO removal in a corona radical shower system in NO/dry air mixtures [57,58], The authors observed that the density of NO molecules decreased not only in the plasma region formed by the corona streamers and the downstream region of the reactor, but also in the upstream region of the reactor. They explained this behaviour by oxidation with ozone, which is transported upstream by electrohydrodynamic flow. 

Note that when solving the CFD transport equations, the mean velocity and turbulence state variables can be found independently from the mixture-fraction state variables. Likewise, when validating the CFD model predictions, the velocity and turbulence predictions can be measured in separate experiments (e.g., using particle-image velocimetry [PIV]) from the scalar field (e.g., using planar laser-induced fluorescence [PLIF]). 

Lozano, A., B. Yip, and R. K. Hanson. 1992. Acetone A tracer for concentration measurements in gaseous flows by planar laser-induced fluorescence. Experiments Fluids 13 369-76. 

The improvement in accuracy achieved by the complex closures compared to the simpler ones can also be questionable. Osenbroch ]67] and Mortensen ]60] successfully applied the combined particle image velocimetry (PIV)/planar laser induced fluorescence (PLIF) technique to measure the instantaneous velocity and reacting species concentration in mixing devices like a mixing channel, pipe, and multi-functional channel reactor. The measured... 

Figure 24 shows the evolution of the CN concentration field. A noticeable amount of CN is observed at t > 7 ms. The concentrations of CN are usually small, except in the secondary flame, thereby serving as a good indication of the flame position. Parr and Hanson-Parr [23] conducted pioneering measurements of the transient flame structure of RDX using both UV-visible absorption and non-intrusive planar laser-induced fluorescence (PLIF). The experiments were... 

Another technique used to study oxy-fuel burners is Chemically Sensitive-Planar Laser Induced Fluorescence (CS-PLIF) [15]. The CS-PLIF is a noninvasive, quantitative method for visualizing flow, mixing, and chemical reactions in complex geometries typical of commercial furnaces. The technique provides information on burner/bumer interactions, bumer/wall interactions, and burner interactions with the furnace flowfield/recir-culation pattern. 

Fig. 8.1 An image of an odor plume taken using planar, laser-induced fluorescence. This image reveals the instantaneous scalar structure of the plume. The image was captured from the outer layer of the momentum boundary layer of the plume. It is a horizontal image spanning a lateral and streamwise range it reveals the spatial patterns at a given vertical location. The color scale indicates the concentration of the odor in the plume concentrations are normalized by the source concentration Co and color coded as shown in the legend. From Grimaldi et al.. Journal of Turbulence, 2002, The relationship between mean and instantaneous structure in turbulent passive scalar plumes, vol. 3, pp. 1-24. Reproduced with the permission of the authors and Taylor and Francis Ltd. (www.tandf.co.uk/ioumals).

Cover design Image of an odor plume taken using planar, laser-induced fluorescence Concentration of the odor in the plume indicated by color. From Crimaldi etal., J. Turbul. 3 1-24, 2002. Reproduced with the permission of the authors and Taylor and Francis. (Chapter 8)... 

The laser-based techniques currently being used and developed include vibrational Raman scattering, coherent anti-Stokes Raman scattering (CARS), Rayleigh scattering, laser-induced fluorescence, and planar laser-induced fluorescence (PLIF). This is an active research field at various research establishments. Laser-induced fluorescence spectroscopy has been used to measure several combustion intermediates, for example, CH, C2, HCH, OH, NO, NO2, HNO, CO, halogenated hydrocarbons, and polycyclic aromatic hydrocarbons. 

Fuchs H, Winklhofer E. 2003. Fuel distribution in gasoline engines is monitored with planar laser-induced fluorescence . In Lambda Highlights 62. Lambda Phy-sik GmbH Gottingen 1-3. 

G. Kychakoff, R.D. Howe, R.K. Hanson, M.C. Drake, R.W. Pitz, M. Lapp, C.M. Penney Visualization of turbulent flame fronts with planar laser-induced fluorescence. Science 224, 382 (1984)... 

R.K. Hanson, J.M. Seitzman, P.H. Paul Planar laser-induced fluorescence imaging of combustion gases. Appl. Phys. B 50, 441 (1990)... 

Cross-correlation cameras are available with resolutions up to 2 k x 2 k pixels, and framing rates up to 30 Hz 8 bit cameras are sufficient for most purposes. However, 12 bit cameras are becoming common, especially for applications such as planar laser-induced fluorescence (PLIF), where extra sensitivity and dynamic range are required. 

Spray properties are mostly determined with optical measurement techniques. For the analysis of the droplet diameter Shadowgraphic methods, laser diffraction or Phase Doppler Anemometry (PDA) have been used elsewhere [1, 2, 11, 18]. Droplet velocities can be measured with Shadowgraphy, Particle Image Velocimetry (PIV), or PDA [1, 6, 19]. The determination of the spray temperature is possible with Global Rainbow Thermometry (GRT), Planar Laser Induced Fluorescence (PLIF), and Differential Infrared Thermography (DIT) [20-22]. 

Industrial Applications Fiber optic sensor for sol-gel material planar laser-induced fluorescence (PLIF) measurements in aqueous flows ... 

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