دانلود گزارش کارورزی و کار آموزی

چکیده : 

Laboratory tests and discrete element method simulations were conducted to evaluate regions of validity

of two basic contact models to describe flow rate of rapeseeds through horizontal orifice. Rectangular

container of 50 by 50 mm cross section, 50 mm high, having hopper of 30 in inclination was used to hold

seeds. Bedding of 10,000 seeds was generated in preparatory container and then discharged through

square orifice of 12, 14 or 16 mm side to similar lower container. This was equipped with independent

floor supported on load cell to measure the weight of seeds during discharge of the upper container.

Rapeseeds of moisture content of 5.5% and 15% were used for testing. DEM simulations were performed

in geometrical setup similar to laboratory equipment using spherical particles with material parameters

of rapeseeds. Two contact models were used in simulations that were previously found to adequately

represent impact of dry and wet seeds against flat surface. In laboratory testing mass flow rates of dry

rapeseeds (5.5% M.C.) through the orifices were higher than that of wet (15% M.C.) seeds. In the simulations

no difference in mass flow rates of dry and wet seeds was found if the mass flow rates were calculated

as a sum of masses of particles falling into the receiving container per time unit. However,

difference in the mass flow rates was observed if they were calculated using sum of vertical forces

exerted by particles on walls and floor of receiving container. Simulations revealed that proposed contact

models reproduced well experimental results for slow particle flow but for higher flow rates the models

need to be improved by inclusion of dissipative term.