| Thermoacoustic electric generation technology is a research hotspot in renewable energy sources field which features wide resources,high efficiency,compact structure and long service life.Thermoacoustic electric generation system(TAEGS)is mainly composed of thermoacoustic engine and linear generator.Transverse flux PM linear machine(TFPMLM)is adopted in TAEGS.As the restoring detent force produced by the end field of linear machine,mechanical resonance state of TAEGS is changed along with reduction of electrical output power.On the other hand,permeate flux leakge,which is unique problems of TFPMLM,can produce large loss.This dissertation concerntrates on the spatial magnetic filed of TFPMLM.And the electromagnetic-mechanical coupling parameters obtained through spatial magnetic field analysis are subtituded into the analytical model to analyze the operating characteristics of TAEGS.The main research contents are as followed.Combined with the operating characteristics of driving force in TAEGS,transverse flux PM linear machine is elected as the electromechanical energy conversion device to ensure the ouput of electrical power steady together with the synchronization resonance between TAEGS and linear machine.Compared with traditional linear machine,the advantages of TFPMLM are reliable structure and simple processing technique,while the axial slotless structure can improve the stability of the application in high frequency short stroke operation state.The detent force of TFPMLM is derived through the establishment of equivalent magnetic circuit via superposition method,and mechanical characteristics matching relationship between TAEGS and TFPMLM is analyzed through numerical analysis.As the different polarity of permanent magnets along transverse and axial direction,there is lack of research on the end magnetic field of TFPMLM,which presents as complex three-dimensional distribution.Spatial decoupling analysis of end magnetic field is presented to make decoupling calculation of axial end flux leakage which produces detent foce.On this basis,the equivalent stiffness factor calculation method of TFPMLM is presented to combine detent force of linear machine with mechanical charaticcteristics of the system,which ensure the steady output of electrical power,and provide theoretical basis of following research on operating characteristics and frequency-offset compensation.In order to improve power density of linear machine and to ensure compactness of the system,relatively high electrical and magnetic load of TFPMLM are engaged in.As different polarity along axial direction and influence of saturation,magnetic field of primary core features three-dimensional orthogonal magnetic distribution.Permeate flux leakage perpendicular to the main flux is generated in a minizone with higher eddy-current loss,which is difficult to detect.On this condition,analytical method of permeate flux leakage of TFPMLM is presented to calculate the permeate zone and magnetic induction intensity through the establishment of three-dimensional primary core equivalent magnetic circuit,on the basis of which,eddy-current loss of permeate flux leakage is calculated,and the ratio between iron loss and main flux density under different saturation levels is deduced.A design criterion of TFPMLM under consideration of iron loss and power density is presented.The equivalent electromagnetic damping factor of TFPMLM can be obtained through the equivalent calculation of eddy current loss formed by permeate flux leakage,which provides precise model parameter for the control of TAEGS oscillation-generation transition stage.The numerical derivation of permeate flux leakage and influence on permeate flux leakage under different saturation levels are verified through normalization calculation between main flux and permeate flux leakage.The state equations of working fluid in the loop of TAEGS are established to obtain the origin of thermo-acoustic-electrical energy and the effects on energy conversion and attenuation.Based on the similarity theory,the mechano-electro analogic model of TAEGS is proposed to realize the coupling analysis on TAEGS and linear machine.According to the calculation of linear machine's equivalent stiffness factor and electromagnetic damping factor,matching reactance of maximum output electrical power is obtained.Moreover,electromagnetic damping under different working conditions is obtained.The calculation method of system equivalent stiffness factor under state of impedance matching is presented subsequently.The research results provide theoretical foundation and novel research idea for the optimal design of TAEGS and TFPMLM. |
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