Aerodynamic Noise Simulation And Optimization Of Scroll Compressor

As a kind of high efficiency fluid machinery,scroll compressor is widely used in many fields,such as central air conditioning,new energy vehicles,variable frequency multi-connected,residential chiller,air source heat pump and so on,because of its compact structure,high efficiency and reliability.As an important part of the commercial air conditioning system,the noise phenomenon caused by airflow pulsation in other types of compressors still exists in the scroll compressor,and the noise reduction of the scroll compressor itself is still a key problem due to its unique motion structure.The noise of scroll compressor mainly comes from the mechanical noise,electromagnetic noise and aerodynamic noise.Because the aerodynamic noise accounts for a higher proportion in the noise,and there are few reports about the aerodynamic noise of scroll compressor at present,this paper mainly focuses on the study of aerodynamic noise.The internal flow field characteristics and noise radiation characteristics of the compressor were simulated and analyzed,and the optimization design of the compressor exhaust pipe diameter and scroll end parameters were carried out to reduce the noise.Firstly,the three-dimensional model of fluid domain of scroll compressor was established by Solid Works software,and the flow field and temperature field in the cavity were numerically simulated based on 2.5D dynamic mesh technology by ANSYSfluent software,and the fluid flow characteristics at the suction and discharge time,the pressure distribution in the cavity and the variation law of discharge pulsation at different speeds were revealed.The pressure field in the compressor cavity is centrosymmetric,the pressure distribution is uniform,and the extreme pressure difference is less than 4%;The velocity distribution is not uniform,and the velocity at the gap changes greatly,and the maximum velocity can reach 400m/s;The temperature distribution is not uniform,the maximum temperature difference is as high as 13%,and the temperature of the working chamber changes nonlinearly,and reaches the highest at the exhaust angle.At the same time,in the process of suction and exhaust,there are different degrees of vortex in the working cavity,and the vortex formed by gas reverse flow caused by pre-compression of suction cavity is obvious at the end of suction;At high rotating speed,the pressure extreme value changes greatly,and the fluctuation amplitude increases and the frequency decreases significantly.Secondly,based on the calculation results of the flow field,the frequency domain signals of the sound field are converted by Fourier transform.Combined with the sound analogy method of FW-H equation,the aerodynamic noise of scroll compressor is solved by using the acoustic module of ANSYSacoustics,and the distribution characteristics of the frequency curve of suction and exhaust noise are revealed.The spectrum distribution of different monitoring points at the suction hole has little difference and similar regularity,and reaches the minimum sound pressure at about1500 Hz;The frequency position of the noise peak and trough at the exhaust orifice is basically unchanged,and the exhaust noise sound pressure level tends to be relatively stable at the low frequency band,and on the contrary,the noise sound pressure fluctuates greatly and the radiated noise amount is higher at the high frequency band.On this basis,the variation of aerodynamic noise under different speed conditions was calculated and analyzed.The results show that the noise frequency range is mainly distributed in the range of 1000 Hz to 3000 Hz,in which the speed is proportional to the intensity of noise sound field.By comparing with the existing experimental data,the same trend of the noise spectrum curve at the scroll compressor discharge orifice is obtained,which verifies the correctness of the aerodynamic noise numerical simulation.Finally,based on the study of aerodynamic noise,the scroll compressor exhaust pipe diameter and scroll tooth end parameters are optimized,and the simulation calculation is carried out.After the optimization of the exhaust pipe diameter,the average noise sound pressure level is reduced by 4.5d B,and the total sound pressure level is reduced by about 6% compared with that before the optimization;The average sound pressure level(SPL)of the optimized scroll tip is reduced by 3.2d B,and the overall SPL is reduced by about 4% compared with that before optimization.By comparing the above two optimization schemes,it is concluded that compared with the optimization of scroll tooth end,the optimization of exhaust pipe diameter has more obvious effect on reducing noise.The results provide a design basis for the optimization analysis of aerodynamic noise of scroll compressor.