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A novel technique of spectroscopic imaging using a near-infrared (NIR) laser sheet beam was developed for visualization of liquid water in a proton-exchange membrane (PEM) sandwiched between two opaque electrodes set in a polymer electrolyte fuel cell (PEFC). In-plane two-dimensional distribution of water in the thin membrane was clearly visualized during the fuel cell operation. Under the condition of fuel feeding into the PEFC without humidification, water was generated by the fuel cell reaction in the whole electrode area. In contrast, under the condition of fuel feeding with humidification, the PEM got wet in the vicinity of a gas flow field locally. 10.1021/ac101525z

Addition of steam to a fame has important implications in the combustion process. The dissociation of the added steam (e.g., [H.sub.2]O [left and right arrow] H+OH, etc.) is one of the effects that contribute to the production of radical species, such as OH, H, and O, in the flame. In order to distinctly visualize two types of OH radicals produced from the fuel-air combustion reaction and that from the dissociation reaction with the added steam, we have developed a new method for planar laser-induced fluorescence spectroscopy in combination with isotope shift (herein called IS/PLIF spectroscopy). This technique has been applied to examine a methane-oxygen-nitrogen premixed flame. Two-dimensional fluorescence intensity distributions of OH radicals in the flames were monitored under three different conditions. They include without steam addition, with [H.sub.2]O steam addition, and with [D.sub.2]O steam addition. From the experimental data obtained under the three conditions, the distinction between the two types of OH radicals could be obtained. The results showed that steam addition reduced the total concentration of OH produced from the combustion and dissociation reactions and that the dissociation reaction of the added steam contributed to the production of OH. Furthermore, the results indicated that the percentage decrease in OH from fuel-air combustion reactions due to the temperature decrease effect with steam addition was almost independent of the equivalence ratio during combustion. In contrast, the percentage increase in OH produced from dissociation reaction with the steam depended on the equivalence ratio. [DOI: 10.1115/1.2056528]

Radiative heat transfer characteristics from the surface of a substance coated with a high-emissivity material have been examined from the measured two-dimensional (2D) temperature distribution using two-color thermometry principle. The technique utilized a charge coupled device camera and optical filters having either wide or narrow wavelength bandpass filters. The results obtained were compared to evaluate the accuracy of the temperature measurements. The 2D emissivity distributions were also derived from the measured 2D temperature distributions. The results indicate that the substrate coated with high-emissivity material exhibit high emission of radiation, resulting in effective cooling. The enhanced emissivity of materials also results in improved radiative heat transfer in heating furnaces and other high-temperature applications. The emissivity measured with the wide-bandpass filters increased with temperature. Atmospheric absorption, mainly due to humidity, made a negligible contribution to the total spectral intensity and to the temperature measurements. The small discrepancies are attributed to the dependence of emissivity on wavelength. Thus, the use of narrow-bandpass filters in thermometry is advantageous over the wide-bandpass ones.

To explore the possibility of flame control by magnetic force, the influence of four kinds of gradient magnetic fields on OH density distribution in a hydrogen-oxygen jet diffusion flame was investigated by numerically solving the equations of reactive gasdynamics and magnetism. Vertically decreasing (case 1), vertically increasing (case 2), horizontally decreasing (case 3), and horizontally increasing (case 4) gradients of magnetic field were considered as model configurations. According to the numerical analysis, because the mass density and the magnetic susceptibility of [O.sub.2] gas are much higher than those of other chemical species, the surrounding air containing a lot of [O.sub.2] gas is strongly influenced by the magnetic force, and the magnetically induced airflow changes the OH distribution in the flame indirectly. The direction and magnitude of the OH density change significantly depends on the configurations of the gradient magnetic field. Specifically, in cases 1, 3, and 4, the OH distribution migrated to the inside of the flame, but in case 2, it moved toward the outside. However, when the horizontally decreasing gradient of the magnetic field was set up near the burner outlet, as in case 3, the OH density change becomes largest among those in the four cases.