| Rubber resource in our country is scarce, the contradiction between supply and demand is increasingly prominent, reclaimed rubber is the third rubber resources except for natural rubber and synthetic rubber. Promoting the development of reclaimed rubber industry is conducive to expanding rubber resources, it is an important measure to promote the development of circular economy and has important realistic and strategic significance. Plasticizing machine is the main production equipment of reclaimed rubber, the rubber polymer is heated to a certain temperature in the process of screw rotating and the plastic and regenerate is finished. Heating mode of coil winding electromagnetic induction heating is widely used in rubber plasticizing machine in current, the heat source is concentrated in outer surface of cylinder and internal rotor screw can not be heated. So the equipment has problems of large radial temperature difference, long preheating time, material uneven heating and material blocking. Because of the limitations of traditional heating methods and complexity structure of screw, the problem of rotating screw heating become the bottleneck of such equipments. Built-in bilateral electromagnetic induction heating technology is put forward in this paper; radial magnetic field of high frequency alternating is generated by the built-in electromagnetic winding, so the static cylinder and rotating screw are heated at the same time, the problem of rotating screw can not be heated is solved. The main research contents are as follows:Built-in bilateral electromagnetic induction heating technology is put forward, the basic structure is given and the mechanism of bilateral heating is deeply analyzed. Time-step finite element method is used to analysis eddy current distribution and flow of 50 kW rubber plasticizing machine heating by built-in bilateral electromagnetic induction heating technology. Combining with helix equation, the model of built-in bilateral electromagnetic induction heating system with rotor of screw structure is build and bilateral eddy power analytical expressions are derived, so the general relations between eddy heating power and parameters of system structure and other power parameters are clear and definite, and the analytic calculate results were compared with finite element calculate results to verify the accuracy of analytical expressions.The influence of winding structure on system heating power is analyzed, and analytical method is used to analyze equivalent current of travelling magnetic field generated by single phase and three-phase windings built-in cylinder. The influence of the winding mode and its distribution on the heating power is analyzed based on Fourier decomposition method. Based on the numerical analysis, the influence of axial section structure of core on eddy current flow and heating power is researched, and design basis of axial length of core and thickness of thread is given. Other parameters of the system such as winding slot structure air gap length, frequency and current intensity are analyzed, and the selection principle is given.Magnetic-thermal coupling analysis method is used to analysis the heating performance of rubber plasticizing machine heating by built-in bilateral electromagnetic induction heating technology, the preheating process of heating unit of rubber plasticizing machine is simulated and the preheating time and temperature rise curve is obtained. The radial temperature distribution and circumferential temperature distribution of plasticizing machine heating unit are calculated under different winding forms, and the rationality of structure of electromagnetic winding is verified by the uniformity of the temperature distribution. Built-in bilateral electromagnetic induction heating technology is compared with coil winding type electromagnetic induction heating technology in aspects, such as eddy current distribution, temperature distribution, preheat time and heating performance to verify the validity and superiority of bilateral heating technology.The flow characteristics and motion states of rubber polymer in spiral groove of plasticizing machine heating by bilateral electromagnetic heating technology is simulated, the velocity distribution, velocity vector, pressure distribution, shear rate and viscosity are obtained through the flow field analysis, and the flow characteristics and movement state of rubber polymer with non-Newtonian characteristic are studied. The mechanism of material viscosity on rotor surface is analyzed through the shear rate and viscosity distribution results, and the reasons of low viscosity of material on rotor surface heating by bilateral electromagnetic induction heating technology are analyzed. Based on the analysis of the flow field, the temperature distribution of cylinder, screw rotor and polymer of rubber plasticizing machine heating by bilateral electromagnetic heating technology are calculated, and the heat transfer process of rubber polymer is studied by means of tracing particle trajectories and polymer flow.Plasticizing machine units of built-in bilateral electromagnetic induction heating are designed and manufactured, and experiments were done to prove the validity of theory analyzed and the rationality of electricity parameters and structure parameters designed. Preheating and loading experiments were done on rubber plasticizing machine heating built-in bilateral electromagnetic induction heating technology, and the experiments data were compared with coil winding type to demonstrate the effectiveness of bilateral electromagnetic heating technology. Rubber of different batches produced by built-in bilateral electromagnetic induction heating rubber plasticizing machine were chosen randomly, and rubber mechanical performance analysis and Mooney viscosity test were carried out to verify the superiority of built-in bilateral electromagnetic heating technology compared with coil winding type. |
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