Combustion measurements based on optical diagnostics techniques, which allow noninvasive measurements of velocity, density, temperature, pressure, and species concentration, have recently become of major interest as tools not only for clarifying the combustion mechanism but also for validating the computational results for the combustion fields. In this study, the combustion characteristics of a pulverized coal flame are investigated using advanced optical diagnostics. A laboratory-scale pulverized coal combustion burner is specially fabricated. Velocity and shape of nonspherical pulverized coal particles, light emissions from a local point, and temperature in the flame are measured by shadow Doppler particle analyzer (SDPA), a specially designed receiving optics (multicolor integrated receiving optics, MICRO), and a two-color radiation pyrometer, respectively. The simultaneous measurement of OH planar laser-induced fluorescence (OH-PLIF) and Mie scattering image of pulverized coal particles is performed to examine spatial relation of combustion reaction zone and pulverized coal particle. The results show that the sizeclassified diameter and velocity of the pulverized coal particles in the flame can be measured well by SDPA. The measurements of the OH chemiluminescence and CH band light emission from a local point in the flame using MICRO and the simultaneous measurement of the instantaneous OH-PLIF and Mie scattering image of pulverized coal are effective for evaluating the pulverized coal flames and investigating their detailed flame structure.
The purpose of this study is to elucidate of the primary air combustion zone in pulverized-coal combustion by means of advanced laser-based diagnostics with high temporal and spatial resolutions. An open-type burner is fabricated to apply various optical measurement techniques. Detailed and overall evaluation is performed by applying various optical measurement techniques to the flame, such as the velocity and shape of nonspherical pulverized-coal particles, temperature, and light emissions from a local point in the flame. It is observed that the particle mean diameter increases as the distance from the burner increases, and this is found to be caused by the decrease in the diameters of small particles and the increase in the diameters of large particles, which result in the char reaction and the particle swelling due to devolatilization, respectively. The size-classified streamwise velocities of pulverized-coal particles in the central region of the jet exhibit the same magnitude, whereas those in the outer region are different depending on the particle size. The behavior is well explained in terms of the particle inertia.
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