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Analysis on Flow Features for Screw Feeder Based on Discrete Element Model

XUE Zhi-ping;BAI Xue-wei;ZHANG Bo;LIU Qing-yu;GAO Kun-feng;College of Engineering, Shenyang Agricultural University;College of Power Engineering, Chongqing University;  
To investigate the flow of milled corn stover inside the screw feeder, which was attached to a specific pelletizer, the EDEM package was employed for its convenience in discrete element analysis, the geometric model of screw feeder was built,and the contact model among corn particles was given in this paper. The approaches for generating particles were also discussed,then the flow features of biomass material in screw feeder were acquired with DEM simulation. HERTZ-MINDLIN no-slide contact model was engaged, acceleration of gravity was set as 9.81m·s~(-2), 25,000 straw particles were generated and simulated in given contact parameter. The results showed that the discontinuous biomass material flow fluctuated frequently. A typical outlet feeding wave was captured in T =13.80-14.30 s. The further analysis of flow state and velocity was conducted, the factors of particle density, particle size, wall friction coefficient and screw pitch as well as screw reamer inner diameter were analyzed individually. Particle density was 40, 80, 120kg·m~(-3), elapsed time of feeding was 21.37 s, 17.68 s and 15.01 s, respectively; particle size was 2mm, 1.8mm and 1.6mm; elapsed time was 17.68 s, 18.06 s and 19.37 s respectively; wall friction coefficient was 0.58,0.48 and 0.38; elapsed time was 17.68 s,16.03 s and 15.84 s respectively; screw reamer inner diameter was 50 mm, 60 mm and70mm; average flow rate of feeding was 16.73g·s~(-1), 12.61g·s~(-1)and 8.96g·s~(-1)in the 20 s simulation time. It turned out that the outlet velocity would be faster for the larger particle density and size, whereas the little impact was observed on powder flow.The smaller wall friction coefficient and screw reamer inner diameter, the larger screw pitch, would lead to faster outlet velocity and the wider falling area, and the flow appeared more violent. This work could provide some reference for the design and improvement of screw feeder with application to biomass pelletizer.
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