| Local axial fans are widely used in the energy field,and noise pollution affects the health of workers and nearby residents.The noise pollution of the axial fan is mainly the aerodynamic noise of the air inlet and the radiated noise of the casing.At present,the control of the noise of the axial fan is mainly based on the passive noise reduction method,mainly focusing on the optimization of the internal mechanism of the muffler,that is to say Increase the muffler channel and change the sound propagation path.However,the noise reduction method that reduces the wind speed in the collecting area by optimizing the air inlet,thereby reducing the aerodynamic noise of the air inlet,has received little attention.Based on this,in this paper,taking noise reduction and low resistance as constraints,a ring air inlet muffler device is designed,and the numerical simulation calculation of the internal flow field and noise of the muffler is carried out.The main research contents and conclusions of this paper are as follows:(1)A three-dimensional model is established,and simulation schemes for different air volumes are set.The simulation results of the internal flow field of the radial annular air inlet muffler show that the resistance loss of the radial annular air inlet device is small(when the air volume is 977.18m~3/min,the resistance loss is 79.26Pa),the velocity distribution is large in the inner side and small in the outer side,and the smaller numerical difference reflects that the velocity distribution is more uniform.(2)The sound field simulation calculation of the physical model of the fan duct and the fan duct model equipped with the radial annular air inlet muffler device were carried out by Virtual.Lab Acoustics software.The noise has been well controlled,and the overall noise is kept at about 81d B,and the noise reduction effect is more obvious as the frequency increases.The low frequency 500Hz and 750Hz frequency bands are reduced by about 8d B,and the1750Hz and 2000Hz frequency bands are significantly reduced by 12d B and 14d B respectively.(3)Based on the above research results,a radial annular air inlet muffler device was fabricated in equal proportions.According to the national standard GB/T 2888-2008"Measurement Method for Noise of Fans and Roots Blowers",the measurement plan for the aerodynamic noise of the air inlet and the radiated noise of the casing was compiled,and the counter-rotating axial flow fan with and without radial ring muffler was carried out.Noise comparison measurement test,obtained the noise sound pressure level and spectrum distribution at different positions and symmetrical positions,the main conclusions are as follows:(1)The average sound pressure level of the 7 measuring points arranged at the XY cross-section of the air inlet of the counter-rotating axial flow fan is 101.8 d B(A),and the noise is large in the middle and small in the periphery;the average noise sound pressure of the 9measuring points of the casing The noise level is smaller than that of the air inlet,at 91.1d B(A),and the noise is in the order of the front end is larger,the middle is the second,and the rear end is the smallest.(2)The average sound pressure value of the noise at the 6 measuring points of the air inlet of the annular air inlet silencing counter-rotating axial flow fan is 82.5 d B(A),and the average sound pressure value of the noise at the 9 measuring points of the casing is 83.5 d B(A),which are lower than Occupational exposure for 8 hours,workplace noise allowable standard is85d B(A)noise occupational hygiene standard,and the noise reduction effect of the annular air inlet muffler is remarkable. |
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