| SPECIAL SECTION: FUNDAMENTAL AND APPLICATION OF MULTIPHASE FLOW IN ENERGY |
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Dispersion characteristics of typical non-spherical particles in a high-speed round jet |
| HUANG Wenshi, WU Yuxin, FENG Lele, ZHANG Man, ZHANG Yang |
| Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China |
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Abstract Moderate and intense low-oxygen dilution (MILD) combustion is appealing due to its uniform heat flux profile and low NOx emissions. The new generation of MILD coal combustion burners use high-speed jets with strong turbulent mixing. The dispersion of the coal particles in the high-speed jet is a key issue in such systems. There are many studies of the dispersion of spherical particles in particle-laden jets in the literature. However, the dispersion of fossil fuel particles, which are typically not spherical, differs from that of spherical particles, so the dispersion characteristics of these non-spherical particles in high-speed jets still deserves further study. This study used glass beads, glass powder and pulverized coal as the solid phase in a high-speed two-phase round jet for a wide range of Reynolds numbers. The particle concentrations, velocities and turbulent kinetic energy distributions were measured for various particle sphericities, sizes and jet velocities using laser phase-Doppler anemometry (PDA). The results show that the concentration, velocity and turbulent kinetic energy distribution characteristics of non-spherical particles are similar to those of smaller spherical particles. However, the non-spherical particle dispersion cannot be accurately characterized by just the Stokes number since the lift can strongly affect the particle dispersion. Non-spherical particles are more easily dispersed than spherical particles, mainly due to a significant increase in the radial turbulent kinetic energy. Increasing the jet velocity promotes the shear layer growth and radial dispersion of the particles and more strongly influences the non-spherical particle dispersion than the particle size or sphericity.
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| Keywords
particle-laden flow
high-speed jet
particle dispersion
sphericity
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Issue Date: 27 April 2020
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2020,
Vol. 60
