Optimal Design Of Hybrid Magnetic Circuit Permanent-magnet Linear Generator For Thermoacoustic System

Thermoacoustic power generation technology is a novel thermoelectricity conversion technology which can use thermal energy produced by solar energy, industrial waste heat and combustion of any fuel to work. But the research on thermoacoustic energy power generation technology has focused on thermoacoustic engines at home and abroad, and the using of the acoustical power generated by thermoacoustic engines has also concentrated at room temperature and low temperature refrigeration system. Therefore there will be with great development potential and prospects in the research on thermoacoustic engines-driven generator. And how to convert sound energy into electrical energy efficiently is the core technology of the "sound-electricity" conversion.Firstly, based on the mechanical properties of the thermoacoustic engine, a new structure of the permanent-magnet linear generator is designed. The stator uses the rotating machine structure and the rotor uses the longitudinal crosswise hybrid magnetic circuit structure to solve the contradictions of motor's axial movement and magnetic field radial distribution. Combination of the computational method of permanent magnet rotating motor, permanent magnet linear motor and three-dimensional magnetic field calculation results, the electromagnetic program of permanent-magnet linear generator is calculated and the principal dimension of the motor is determined.Secondly, the magnetic field distribution of the motor is analyzed by using finite element software Ansoft. The analysis result by finite element method indicated that the motor achieves the conventional motor's electromagnetism load, and the influence of longitudinal magnetic field to the idling counter electromotive force is very small. Also the air gap length and the permanent magnet width influence on the permanent magnet flux and magnetic flux leakage is analyzed, provides a reference to this type of generator's optimization.Thirdly, the theoretical analysis of the cogging force is analyzed by using single-ended method, and the cogging force is calculated combine with three dimensional finite element analysis and Fourier series harmonic analysis. Then the cogging force is suppressed effectively by optimizing of the stator core length to make the permanent-magnet linear generator to start and run properly. Also the electromagnetic force under load is analyzed, the variation is obtained and make basis for the later system simulation.At last, the magnetic flux density changes and the harmonic of the stator teeth, the stator yoke and the rotor yoke are analyzed. The iron loss of motor is calculated by using the flux density wave method and the copper loss of motor is calculated by formula, so the efficiency of motor is determined finally. Also the different core material influence on the losses and efficient is analyzed and the iron core material for the permanent-magnet linear generator is determined.