The Detent Force Calculation And Structural Optimization Of Tubular Permanent Magnet Linear Machine In Thermoacoustic Generation System

As thermoacoustic power generation technology is the emphasis of promising energy research,the mechanical resonant state dominates the output power of thermoacoustic power generation system.The calculation and analysis on the detent force of linear machine is the basis of mechanical resonance.On the premise of determining the topology of linear machine,the detent force characteristic of linear generator employed in thermoacoustic power generation system is analyzed in this thesis,besides,the sinusoidal property of the detent force and the no-load back EMF waveform is selected as the optimized objective.On the condition of high-frequency and short-stroke of thermoacoustic power generation system(TAPGS),tubular permanent magnet linear machine(TPMLM)is employed as the main component of the electro-acoustic conversion in TAPGS.According to the original design perspective of the typical rotary motor,the initial topology of TPMLM is determined.The magnetic field distribution of slotless-primary TPMLM is calculated through the equivalent magnetizing circuit method,the analytic models on cogging effect and end effect are established by Schwarz-Christoffel Transform subsequently,on the basis of which,the analytical results of air-gap magnetic induction intensity is deduced.The Maxwell tensor method is applied to model the analytic equation of the detent force,and the equation of the detent force is derived ultimately.The three-dimensional finite element method simulation of TPMLM is modeled in Ansoft to solve the detent force and no-load back EMF.Three sorts of advanced transformed structure of TPMLM are proposed in this thesis,that is the double-slots structure,the installed structure and the back-iron structure.The fundamental amplitude and harmonic distortion rate of the no-load back EMF are stood as the constraint condition,the property,feasibility and applicability of these structures are contrasted and analyzed.Total harmonic distortion(THD)is introduced in this part as the criterion of optimization analysis,considering a sinusoidal waveform is imperative in TAPGS,the fundamental amplitude,the harmonic content and THD of no-load back EMF among the proposed transformed structures are compared and analyzed respectively.Based on the problem that the detent force features hump-shaped,an advanced improvement is proposed.The comprehensive optimization on TPMLM is brought out in this thesis,the concretecontent of optimization comprises the dimensions of the “?” primary,the axial length of PM installed on the secondary,the circumferential number of the primary core unit and the limit displacement of the secondary.The obtained conclusion,through the comprehensive optimization,provides experience and reference to the design and optimization of TPMLM.The harmonic content of the detent force and the no-load back EMF is extremely low to the configuration of this topology,thus,the proposed topology is compatible to high-frequency short-stroke condition.