Screw feeders are extensively adopted in the food, plastics, mineral processing and agriculture industries as an efficient and economical method for conveying solid granular materials.
The drawdown flow pattern depends on the screw and hopper design, as well as the particle shapes and sizes being conveyed.
Compositional variations and quality issues in the outgoing stream are related to varying residence times that can arise due to non-uniform drawdown patterns.
Rocky DEM, our state-of-the-art Discrete Element Method (DEM) solver, is a powerful tool that can help engineers evaluate the influence of design on screw conveyor efficiency under different mass flow rates and speeds. By adjusting their designs and then simulating them in Rocky, engineers can improve product quality control and reduce power consumption and wear on their conveying equipment.
The first video shows a Rocky simulation of wood chips in a variable pitch screw feeder.
As the simulation progresses, the material can be seen being fed into the screw from primarily the back portion of the hopper while the material at the front of the hopper becomes stagnant. This uneven discharge is an issue common with this type of screw feeder design and has been extensively reported upon in literature.
Variable Pitch Feeder design shows an uneven distribution of the material out of the hopper, as indicated by the faster moving particles in the rear and the stagnant particles in the front of the hopper
The second video shows the same wood chips flowing through another feeder with a different kind of screw design.
The funnel shape of this cone screw is shown by Rocky to activate the entire length of this hopper’s discharge area, mitigating problems related to stagnant material in the rear that could affect bulk material quality.
Cone Screw Feeder design shows even distribution of material out of the hopper, as indicated by the faster moving particles spanning the entire bottom length of the hopper
A design engineer can optimize this design further by changing the screw pitch, adjusting the shaft diameter, modifying the casing diameter, and so on. Rocky DEM can, therefore, be a valuable tool to help improve screw feeder design, enhance drawdown control, and minimize power costs and wear upon the equipment.
Lucilla Almeida
CAE Specialist at ESSS, D.Sc.
Lucilla holds a BE (Chemical) undergraduate degree, an M.Sc. in Chemical Engineering and a Ph.D. in Nuclear engineering from the Federal University of Rio de Janeiro. She joined ESSS in 2008 and has spent 5 years focused on applying CFD to solve common engineering problems in the Oil and Gas industry, dealing with turbulent and multiphase flow simulations. Since 2013, she is an Application Engineer for Rocky DEM Business Unit, supporting users, working on consultancy projects and validating models implemented for the CFD-DEM coupling.
