Numerical Prediction And Experiment Of Aerodynamic Noise Of An Impeller Blower

Impeller blowers are widely applied in the machinery which are used for processing forage,threshing grain,crushing returning of straw.When the impeller blowers are working,the materials after processing through mincing,rubbing and grinding are transported by the combination of the centrifugal force and the fast motion airflow produced by fast rotating blades.At present,the main problem of the impeller blowers is high noise,especially when impeller’s speed is fast.High noise may seriously affect the operator’s physical or mental health.Therefore,it is especially important to analyze the aerodynamic noise in order to effectively control the noise of the throwing impellers.The main work as follow:(1)The physical model of the passageway was set up using CATIA as3 D modeling software.Physical model was imported into pre-processing software ANSYS ICEM and meshed in the fluid grid.And,physical model was imported into pre-processing software Hyper Mesh and meshed in the boundary element for acoustic calculation.After that,fluid grid was imported into general CFD software ANSYS Fluent.The impeller blowers’ transient flow field were simulated by LES or DDPM at no-load or load respectively.The changing rule of the instantaneous pulse pressure in the flow field were obtained.And the rotating impeller’s time-domain pulse pressure data was outputted.(2)The aerodynamic noise of the impeller blower was simulated by using acoustic mix calculation method.The time-domain pulse pressure data of the rotating impeller was imported from ANSYS FLUENT to acoustics existing software LMS.Virtual Lab,and the radiation law of aerodynamic noise was calculated by indirect acoustic boundary element method.The sound pressure levels of the impeller blower under different frequencies were obtained.(3)The aerodynamic noise at inlet and outlet of the impeller blower has been tested with TES-1352 A programmable noise meter,INV3060 S signal acquisition analyzer,DASP V10 Analysis Software,and so on.And the results of numerical prediction were verified.On this basis,The effects of structure and working parameters on the aerodynamic noise of inlet and outlet were analyzed.It willprovide the basis for the design of the impeller blowers with low noise and high efficiency.The results showed that:(1)The error between test result and simulation was small.The error of outlet’s total SPL was 1.11 d B(A),and that of inlet’s total SPL was 0.5 dB(A).So,the numerical model of aerodynamic noise was reliable,and the simulation results were credible.(2)The total noise of the impeller blowers was mainly influenced by sound pressure level at 100 Hz and 400 Hz.The sound pressure level of inlet was mainly influenced by sound pressure level at 100 Hz,while 400 Hz level was the main influence factor for outlet.Compared with no-load,the total sound pressure level of inlet was increased,and the total SPL of outlet was reduced at load.(3)As the impeller’s rotational speed increased,the SPL of Impeller blowers increased significantly.In the working rotating speed range,the minimum SPL of aerodynamic noise appeared at 1700 r/min in both inlet and outlet.The SPL of inlet’s aerodynamic noise was smaller when rotating speed is 2700 r/min.(4)With paddles of backward slant + 5°,compared with common 0°,the SPL of inlet’s testing points would be reduced by 1.3 d B(A),and the SPL of outlet’s testing points would be reduced by 6 dB(A).When the number of paddle is 3,compared with other common number,the SPL is low.When inlet size was 200mm×160 mm,the noise of inlet side was relatively low.The SPL of impeller blowers’ noise reduced obviously when the height of the discharge tube increased.