Numerical Simulation And Experimental Study On Mixing Flow Field Of Synchronous Rotor In Internal Mixer

At present, the internal mixer is widely used in rubber industry of intermittent mixing equipment. With rapid development of rubber industry and other polymer material industry, the performance of internal mixer is required higher and higher. The development of synchronous rotor mixer is exactly to meet the need of that requirement. The synchronous rotor mixer is widely accepted as one of the most advanced internal mixer. It has the outstanding advantage of uniform temperature distribution for mixing rubber, and it is appropriate for processing the mixing rubber of higher Uniformity. The rubber mixing process is very complex in internal mixer, which involved the problem of thermodynamics and rheology, etc. And polymer melt has one of the characteristic of the variable shear viscosity. These problems make the mathematical model establishment and analysis difficultly. Thus there are so many problems need to study for synchronous rotor mixer mixing process. In this paper, modern computer technology is used in 3D flow field simulation research for synchronous rotor mixer mixing process. This simulation research is helpful for searching the mixing mechanism of synchronous rotor mixer, improving mixing process and rotor structures. This research is also a useful exploration for optimizing the mixing process technique and producing high quality mixing rubber.In this paper, the mixing model of ST rotor is established firstly, this model is based on the rubber mixing rheological theory. Polyflow and mesh superposition technique are used in 3D numerical simulation. And pressure field, velocity field, viscosity field and dispersive mixing index are gained from this numerical simulation, where the dispersive mixing index is firstly introduced in rubber mixing numerical simulation. In order to verify the feasibility of mixing model, relevant rubber mixing experiments are did. The SXM-1L is used for main experiment machine for mixing experiment. Through changed formula, adjusted two rotors'initial relative position and rotate speed, different conditions mixing rubber are gained. In rubber mixing process, mixing temperature, pressure and power are collected. Through testing the Mooney viscosity, carbon black dispersion degree and physical properties, microscopic morphologic structure and physical properties are obtained. Finally this paper, results of simulation and experiments are analyzed combine with nogs expansion picture which verify the feasibility of mixing model in a certain extent again.Analyzing the pressure field, we know that pressure field distribute well in each two rotors'initial relative position of ST style rotors'mixing flow field, only on the top of short nogs'regions appear high pressure or lower pressure, and these regions can form a mass flow from high pressure region to lower pressure region. The mass flow is good for rubber exchanging between two rotors and power distribution. From the results of velocity field, we know two rotors'initial relative positions influence axial movement of mixing rubber. Axial velocity values are negative in blue region and this region forms to dead angle zone easily, not good for this region's rubber mix with others region rubber. Analyzing the viscosity field result, we see that rotate speed great influences to viscosity and formula has no influence to viscosity. As the rotate speed increase, average viscosity decrease and descent range becoming smaller. From the results of dispersive mixing index, we know shearing field is dominated in rubber mixing field and shearing is proportional to rotate speed. Which shearing action in 0°, 135°and 315°initial relative positions are weaker than in 45°, 225°and 270°positions. In the juncture zone between long nog and short nog, sheering action is the weakest. Formula has no influence to average dispersive mixing index.Analyzing the experiment results, we find the general trend between experiment result and the simulation result is close. Two rotors'initial relative positions can influence the uniformity and physical mechanical properties of mixing rubber. From analyzing the results of mixing experiments, we know that average dispersion lower in two rotors initial relative positions in 135°and 315°, but average dispersion well in 45°,225°and 270°. Average Mooney viscosity value decreases about 5%~6% when rotate speed increases 10r/min; shearing action improving is good for carbon black dispersion. From the dispersion degree of carbon black testing, it shows that average dispersion degree of carbon black is up to 6 level for all the tested mixing rubber and 7~8 level account for 62.5%. These shows synchronous rotor mixer is good for mixing rubber dispersion, rotate speed great influences to viscosity, and initial relative positions great influences to carbon black dispersion. When two rotors are placed in different initial position, carbon black dispersion can differ to about 2 levels. Definite stretching intension, tensile strength and break elongation are related to carbon black dispersion, physical mechanical properties are improved following with the carbon black dispersion increasing. Initial relative position is also great influence the physical mechanical properties of mixing rubber. Verifying the mixing simulation model of this paper is available in engineering application.