Theoretical Study On Volume Efficiency And Thermal Performance Of Linear Compressor Based On Numerical Analysis And Experiments

Linear compressor,as one of the most promising compressors,is widely used in industrial,military and civil fields.The compressor transforms the traditional reciprocating piston compressor's rotating motor and piston from crank-connecting rod driving structure to linear motor driving piston directly,and has the advantages of high efficiency,small size and compact structure.Therefore,it has been discussed and studied by many scholars at home and abroad.In recent years,with the successful development of high performance permanent magnet materials such as NdFeB,the dynamic magnetic linear compressor has become the most promising refrigeration compressor in the future.In this paper,the structure,working principle and process of the dynamic magnetic linear compressor are analyzed firstly,then the flow process of working substance in the compressor is simplified,and the thermodynamic model of the four processes of the dynamic magnetic linear compressor is established.The mechanical system is simplified to a two-mass and two-degreeof-freedom forced damped vibration model,and the dynamic model of the vibration system is established.The linear simplified model established by Cadman is used to linearize the gas force and friction force in the dynamic model.The magnetic circuit of the motor in the electromagnetic system is simplified and the electromagnetic force is obtained by using the principle of equivalent magnetic circuit.Then the voltage equation of the electromagnetic system and the dynamic equation of the vibration system are established to obtain the response results of the system.Finally,the vibration characteristics of the system are analyzed,and the influence of the vibration frequency on the working condition of the compressor is studied,which paves the way for the further research on the thermal performance of the dynamic magnetic linear compressor.Four main parameters affecting the volumetric efficiency of linear compressor are analyzed and calculated: volumetric coefficient,pressure coefficient,temperature coefficient and leakage coefficient.The volumetric efficiency,refrigeration capacity and consumption power of compressor are theoretically analyzed and calculated,and the main influencing factors are obtained.Based on the mathematic model of the linear compressor,the numerical simulation software MATLAB is used to simulate and calculate the volume efficiency,refrigeration capacity and consumption power of the linear compressor.The trend of the volume efficiency,refrigeration capacity and consumption power of the linear compressor with various factors is obtained,and some conclusions of the analysis are verified by the fluid simulation software Fluent.Finally,the performance test of linear frequency converter compressor FLA150 NBMA is carried out.The variation of volume efficiency,refrigeration capacity,input power and COP(refrigeration efficiency)with compression ratio,evaporation temperature,condensation temperature and frequency of the compressor is experimentally analyzed,and piston displacement under different input frequencies and spring stiffness is carried out.The experimental results show that the final results are basically consistent with the previous analysis,which shows that the mathematical model of dynamic magnetic linear compressor established and analyzed in the previous paper is basically accurate.