| Direct cooling refrigerators are gradually replaced by frost free refrigerators in recent years for their defects of uneven cooling and frost of the inner wall.Frost free refrigerator works by the air cooling system,which is clean,cooling uniformity and free of frost,and increasingly favored by consumers.However,there are still some drawbacks such as high energy consumption and noise,which have been plaguing manufacturers and seriously affecting the quality of life of consumers.In this article,a combination of theoretical analysis,noise source test,flow field and sound field simulation analysis is used to study the generation of noise and the control of air cooling system in frost free refrigerator.Initially,the structure and working principle of the air cooling system in frost free refrigerator are expounded.The modal analysis is carried out to find that the vibration noise is smaller and only considers the aerodynamic noise produced by the air cooling system.On the basis of aeroacoustics and hydrodynamics,the noise control of the fan and the air cooling system is analyzed.Then,on the basis of theoretical analysis and according to the principle of decomposition test,the four-points method is used to test by LMS test system in three cases:running of the whole machine,compressor running alone and the fan is running alone.Through processing the test data,it is concluded that the air cooling system is the main noise source of the refrigerator,and the fan noise is mainly distributed in the frequency band of 80?100Hz and 160?2500Hz.After that,on the basis of theoretical analysis and noise source testing,the FLUENT software is used to analyze the flow field of the frozen air duct,the wide-band acoustic module is selected for near field acoustic calculation,and the FW-H acoustic module is used for far field acoustic calculation.The simulation and experimental data are basically consistent with the experimental data.It is feasible to use the method to simulate the refrigeration duct.Finally,on the basis of the noise theoretical analysis,noise source testing and simulation analysis,the simulation optimization of the frozen air duct is carried out,and the optimal results are obtained by comparing the optimization results:the upper outlet angle is 35 degrees,the middle outlet angle is 90 degrees,the downward outlet angle is 135 degrees,the fan blade number is 11,and the outlet installation angle is 36 degrees and the inner diameter of impeller is 68mm.In addition,the curved surface of the air duct is optimized and the new wind channel is set up and the numerical simulation of the flow field and sound field is carried out.The maximum sound power is 51.4dB and the air volume of the air duct is 53.8 CFM(1CFM?1.7m3/h)after optimized,which is lower than the original air duct noise by 2.1dB and the air volume is increased by 4.64 CFM,which proves that the optimization scheme is feasible. |
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