Modified screw conveyor-mixers – Discrete element modeling approach

Theoretical Studies of the Interaction between Screw Surface and Material in the Mixer

Mixing is one of the most commonly used processes in food, animal feed, chemical, cosmetic, etc., industries. It is supposed to provide high-quality homogenous, nutritious mixtures. To provide appropriate mixing of materials while maintaining the process high efficiency and low energy consumption it is crucial to explore and describe the material flow caused by the movement of mixing elements and the contact between particles. The process of mixing is also affected by structural features of the machine components and the mixing chamber, speed of mixing, and properties of the mixed materials, such as the size of particles, moisture, friction coefficients. Thus, modeling of the phenomena that accompany the process of mixing using the above-listed parameters is indispensable for appropriate implementation of the process. The paper provides theoretical power calculations that take into account the material speed change, the impact of the material friction coefficient on the screw steel surface and the impact of the friction coefficient on the material, taking into account the loading height of the mixing chamber and the chamber loading value. Dependencies between the mixer power and the product degree of fineness, rotational speed of screw friction coefficients, the number of windings per length unit, and width of the screw tape have been presented on the basis of a developed model. It has been found that power increases along with an increase in the value of these parameters. Verification of the theoretical model indicated consistence of the predicted power demand with the power demand determined in tests performed on a real object for values of the assumed, effective loading, which was 65–75%.

Theoretical analysis and experiment of pressure distribution and pressure gradient of shield screw conveyor: Taking sandy soil as an example

The pressure distribution and pressure gradient characteristics of shield screw conveyor directly affect its normal function. Taking the conditioned soil microelements in the spiral tube as the research object, the pressure field distribution and pressure gradient theoretical calculation model of the shield screw machine were established based on the stress analysis and the mechanical equilibrium conditions at steady state and the influence parameters were analyzed. The correctness and validity of the proposed calculation model are verified by the experimental results of the indoor model machine. Under the condition that the conditioned soil is the plastic fluid paste, the conclusion that the pressure field and pressure gradient of the shield screw machine decrease linearly along the direction of the screw axis is also obtained.