Machinery & Energetics (Apr 2023)
A study of electrothermomechanical converter for technological purposes with nonlinear changes in the loading and cooling medium
Abstract
Heavy temperature processes with high-temperature loads require optimisation of technological processes, ensuring high reliability and combining rotating parts of electric machines with actuators to achieve greater efficiency of electromechanical converters. The research aims to provide a theoretical justification and experimental confirmation of the effect of higher harmonics in the air gap under nonlinear changes in the temperature of the medium. The research is based on the basic principles of electrodynamics, heat and mass transfer, mathematical modelling by the finite element method, and experimental verification of multi-physical parameters. Based on the analysis of the differential equation for determining the increase in the surface temperature of a ferromagnetic rotor under conditions of nonlinear temperature changes in the environment surrounding the electromechanical converter, the regularities of the formation of the free and forced components of the instantaneous temperature values of the massive rotor are established. Depending on the mode of interaction between the load-cooling medium and the electromechanical part of the screw units, kinematic diagrams of single-mass and two-mass systems with variable or constant moments of inertia and stiffness were formed. According to the size of the electromagnetic system of the experimental sample, a mathematical model for studying thermal and electromagnetic processes was built. The regularities of the spatial distribution of the temperature of the screw electromechanical unit are determined. The spectra of higher harmonics of voltage and current in the frequency range from 0 to 50 kHz have been experimentally determined, which confirms the presence of the effect of generating higher harmonics when the temperature of the medium surrounding the rotor screw changes. The detected harmonic spectrum affects both the formation of the dynamics of the rotating system and additional thermal power while increasing the overall efficiency of the screw electromechanical converter. The practical value of the obtained results lies in the possibility of predicting the optimal indicators of interrelated electromagnetic and heat exchange processes in screw electromechanical converters for technological purposes
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