Research On Aerodynamic Noise Control Of High Pressure Centrifugal Fan

High-pressure centrifugal fan is a typical fluid machine with a dynamic and static rotary device.In the city road sweeping vehicle upload system,high-pressure centrifugal fan connected to the outside and the sewage collection system to achieve pneumatic conveying function,is the core components of the sweepers.Because the high pressure centrifugal fan is often used in low density populated plant area and the equipment density area,the noise problem is easy to be neglected,but the noise of the fan in the city road sweeping vehicle seriously affect people's daily life,and the problem also becomes the restriction to enhance sweeper's product quality.Therefore,it is necessary to study how to make high-pressure centrifugal fans work efficiently and ensure good acoustic quality.The aerodynamic noise of centrifugal fan is a complex multi-physics coupling problem.The accurate solution of the flow field is the basis of acoustic simulation.In this paper,we first carry out the simulation process,through a series of boundary conditions,model structure and turbulence model comparison,to explore a relatively accurate flow field simulation process.For acoustic simulation,this paper uses a hybrid computational acoustics method based on the Lighthill acoustic analogy theory.After the transient flow field is periodically fluctuated,the sound source information is extracted,and the pressure pulsation data of the impeller and volute wall surface are obtained respectively.The surface acoustic information of the volute surface requires the data mapping method to cut the non-volute wall surface data.The main noise source of the centrifugal fan is the dipole source.The FW-H equation and the Lowson equation are used to convert the pressure pulsation into the dipole source information,and the acoustic characteristics of the blade and volute are analyzed separately.The influence of the volute on the radiation-noise of the impeller and its own noise contribution cannot be ignored.Considering the influence of the volute and focusing on dipole noise source of high-pressure centrifugal fan,fast multipole boundary element method is used to analyze the non-free sound field of the whole machine model.It is found that the noise of the impeller in the third order harmonic frequency cannot be propagated in the volute,and the blades and volute are all characterized by the middle and low frequency noise.The far-field noise radiation simulation results of the fan show that the noise propagation has a significant directivity.On the basis of fully revealing the flow field,aerodynamic performance and noise characteristics of the high pressure centrifugal fan,a new structure is proposed to improve the internal flow and the sound radiation state of the whole machine.The single blade model is abstracted to analyze the blade spoiler and the aerodynamic and acoustic characteristics of different blade structure fans based on the eddy visualization.The results show that several structures can effectively reduce aerodynamic noise on the basis of ensuring that the aerodynamic performance is not affected or even improved.By analyzing and revealing the flow field and sound field law of high pressure centrifugal fan systematically,this paper provides reference and guidance for aerodynamic noise prediction and noise reduction structure design of high pressure centrifugal fan.