| SPECIAL SECTION: FUNDAMENTAL AND APPLICATION OF MULTIPHASE FLOW IN ENERGY |
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Effect of air flow rate and rotational speed on vortices between neighboring blades in turbo air classifiers |
| FENG Lele, WU Yuxin, ZHANG Hai, ZHANG Yang, YUE Guangxi |
| 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 The flow field between neighboring blades strongly affects the gas-solid separation in air classifiers. The flow field between adjacent blades in a turbo air classifier was measured using a PIV (particle image velocimetry) system for various impeller rotational speeds and air flow rates. A coordinate transformation based algorithm was then used to analyze the relative motion between the particles and the blades. The relative tangential and radial velocity profiles at the blade passage inlet were also analyzed for various rotational speeds along with the changes of the vortex position and vorticity. As the rotational speed increases, the vortex first moves outwards and then inwards as the vorticity first increases and then decreases. The vortex position does not change much as the air flow rate increases, while the vorticity increases greatly. The overall separation efficiency first increases and then decreases as the rotational speed increases, while the cut size first decreases and then increases. These non-linear relationships correspond to the effect of the impeller rotational speed on the vortex position and the relative tangential velocity. The flow field analysis based on the coordinate transformation helps eliminate camera positioning errors and improves understanding of the gas-solid flow relative to the impeller.
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| Keywords
particle separation
particle image velocimetry (PIV)
algorithm
granular flow
vortex
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Issue Date: 27 April 2020
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2020,
Vol. 60
