| Linear compressor without crank linkage mechanism,the piston is directly driven by linear oscilating motor,low friction loss,long life oil-free or less oil lubrication can be achieved.According to the load change,the output of variable refrigerating capacity can be achieved by adjusting the piston stroke and working frequency,so as to achieve the purpose of energy saving and noise reduction.Therefore,the linear compressor has outstanding advantages in the field of household refrigeration.The free piston structure has no mechanical structure constraint in the motion direction,and the motion characteristics of piston are greatly affected by the compressor structural parameters and operating parameters.It is easy to cause a shortage of refrigeration capacity or non-ideal conditions such as cylinder collision,which affects the regulation performance of variable refrigeration capacity and the stability of system.Therefore,it is a key issue to be solved to effectively predict the performance of compressor through theoretical modeling,to provide a theoretical basis for the optimization of compressor design,and to realize the low cost and miniaturization of compressor through reasonable structural design,so that it can better meet the actual working conditions.In this paper,based on the moving magnetic linear compressor,combined with the compressor refrigeration conditions,the linear compressor resonant spring system,electromagnetic system,the dynamic characteristics of whole machine and other aspects are studied theoretically and experimentally.The specific research work is as follows:(1)A cylindrical arm spiral coil spring for linear compressor has been developed,which is made by spring wire and has low molding cost.Compared to the flexure spring with the same outside diameter,the axial stiffness to mass ratio of the coil spring can be increased by more than four times,and the maximum equivalent stress is reduced by 43%.Under the design amplitude,the fatigue life of the coil spring reaches more than 10~6 times.A spring profile design method based on Archimedean helix is given,a theoretical model of spring stiffness is constructed,and the error of theoretical model is verified by test to be less than 6.88%.(2)A cylindrical moving magnet linear oscilating motor is designed,the equivalent magnetic circuit model of motor is established,and the expression of electromagnetic thrust coefficient is given.A three-dimensional finite element model of motor is established,and the magnetic spring effect of motor is studied.It is concluded that the magnetic spring force of motor always pushes the moving deviation from the center position;the influence law of the radial offset and deflection of armature on the radial force and axial electromagnetic force of armature is revealed,and the permissible range of the radial offset and deflection of armature is given.(3)The kinetic model of whole linear compressor is established,which considering the magnetic spring effect of motor and the piston offset gap leakage sub-model.The effects of operating parameters on piston offset characteristics,leakage characteristics,and overall machine performance are investigated.Finally,some of models are validated by prototype tests,and the results show that the prediction accuracy of whole machine kinetic model considering the motor magnetic spring effect can be improved by more than 10%for the piston operating state.(4)Giving the calculation flow of linear compressor variable refrigeration capacity regulation performance.The effects of structural parameter matching(displacement and frequency,piston diameter and stroke),frequency regulation method and the size of series capacitor on the variable refrigeration capacity regulation characteristics of compressor and the nonlinear response characteristics of voltage-stroke are investigated.The results show that The combination of large displacement and low frequency is beneficial to the compressor output performance with maximum refrigerating capacity and variable refrigerating capacity,while the parameter combination of piston diameter and stroke should be reasonably selected after determining the priority of the two refrigerating capacity output modes;By changing the series capacitor to make the RLC resonant frequency higher than the piston resonant frequency,the nonlinear response characteristics of voltage stroke can be improved when the fixed frequency regulation is adopted.(5)A moving magnetic linear compressor equipped with a cylindrical arm spiral coil spring is designed,and a static thrust test rig and a dynamic performance test rig of motor are built to verify the accuracy of theoretical model and the feasibility of the cylindrical arm helical coil spring in dynamic operation.Through the refrigeration performance test,when the refrigeration capacity is adjusted from 100%to 50%of the maximum refrigeration capacity,the Coefficient of performance(COP)is only reduced by 12.88%,which verifies that the designed linear compressor can maintain a high cop while changing the refrigerating capacity output.Under the same working conditions,the maximum cop of the designed linear compressor is 1.32,which is 4.76%higher than that of the crank connecting rod compressor with similar displacement,which verifies the superior performance of the linear compressor.This paper has 95 figures,16 tables and 146 references. |
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