Two - Field Coupling And Optimal Design Of Medium - Frequency Induction Heating In Pipeline

In order to improve the quality of the pipelines which are used to transport oil, natural gas and so on, the problems of the heat-treatment technology with medium frequency induction heating pipeline parameters optimization is studied. A magnetic and thermo coupling simulation model of pipeline medium frequency induction heating is established then the changing rule of the electromagnetic field, the internal eddy field and temperature field are analyzed. The influence of the main parameters in induction heating temperature field for heating efficiency are carried out, the guiding principle of the sensor design and process parameters improvement measures are discussed. The primary research works are as follows:At first, on the basis of the theory of electromagnetic field and heat transfer principle, a non-uniform heat source model of induction heating is established by applying the phasor method, which explains the problem of the uneven distribution of pipe heating temperature. At the same time the mathematical model of electromagnetic field and temperature field is establishment in induction heating with the introduction of magnetic vector potential.In the second step, the calculation model of pipeline and coil are built with considering the characteristics of pipeline’s medium frequency induction heat treatment, and the boundary conditions of electromagnetic field and temperature field are set up, the finite element meshing of the model is carried on. To simulate the change rule of temperature field, magnetic field, eddy current field in intermediate frequency induction heating process better, thermal physical parameters change with temperature is considered. This method is different from the traditional fixed value thermal physical parameters of the finite element analysis. On this basis, the heat affected zone of the electromagnetic field and temperature field are obtained. Then the influence of the temperature field in pipeline such as the medium frequency induction heating electric parameters (current and frequency) and coil structure parameters is analyzedFinally, the pipeline’s intermediate frequency induction heating experiment under the actual condition is carried out. According to the data obtained from the experiment we verify the accuracy of the simulation model. Then the law of the comprehensive income is used to guide the optimization design of medium frequency induction heating process parameters. The result shows that the effect of heating could be improved by the increased frequency, input current, increase the coil number of turns and reduce the air gap.