Numerical Modeling of the Mixing of Highly Viscous Polymer Suspensions in Partially Filled Sigma Blade Mixers

This paper presents a non-isothermal, non-Newtonian Computational Fluid Dynamics (CFD) model for the mixing of a highly viscous polymer suspension in a partially filled sigma blade mixer. The model accounts for viscous heating and the free surface of the suspension. The rheological model is found by calibration with experimental temperature measurements. Subsequently, the model is exploited to study the effect of applying heat both before and during mixing on the suspension's mixing quality. Two mixing indexes are used to evaluate the mixing condition, namely, the Ica Manas-Zlaczower dispersive index and Kramer's distributive index. Some fluctuations are observed in the predictions of the dispersive mixing index, which could be associated with the free surface of the suspension, thus indicating that this index might not be ideal for partially filled mixers. The Kramer index results are stable and indicate that the particles in the suspension can be well distributed. Interestingly, the results highlight that the speed at which the suspension becomes well distributed is almost independent of applying heat both before and during the process.

ESTIMATION OF MECHANICAL LOAD ON RUBBER MIXING ROTORS BY USING A PARTIALLY FILLED FLOW SIMULATION IN CHAMBER

Mixing characteristics and mechanical loads of rubber-mixing rotors are considered to be the two most important factors in actual rotor design. For the design of highly reliable production mixers, there is a great need for a proper estimation method of mechanical load, such as radial force or rotation torque of the rotors. The mechanical load of tangential mixing rotors and surrounding flow are mainly discussed by using partially filled numerical flow simulation. Operational parameters of the mixing condition were set to be fill factor and rotor phase angle of two rotors rotating at an even speed. The Carreau model was applied to the shear rate dependence of viscosity. The volume-of-fluid method was used for free surface simulation. Both two-dimensional and three-dimensional simulations were carried out to discuss mechanical load and its fluctuation mechanisms. For the numerical results, radial force on rotors, pressure, and the velocity distribution around the rotors and their fluctuations are presented and discussed. It was found that the radial force of the rotors could be estimated using this kind of flow simulation, and the fluctuation phenomena could be explained by the movement of a high-pressure region between the front of the rotor wings and the chamber wall.

Numerical Optimization Simulation of Synchronous Four-Wing Rotor

The mixer is the most widely used batch mixing equipment in the rubber industry. The rotor is a core component and has a great impact on the mixing effect of the equipment. The current rotor structure design is done empirically, being tightly dependent on practical experience. This paper proposes a method for optimizing the rotor structure by using optimization algorithms combined with numerical simulation technology. Using MATLAB software, a parametric design program for synchronous rotors and a set of optimization programs for the particle swarm optimization (PSO) algorithm were written. The global distribution index was used as the fitness function to optimize the synchronous rotor configuration. A comparative analysis of the rotors before and after optimization shows that the optimization process is feasible, and the results are reliable. This provides new ideas for the design and development of mixer rotors.