Research On Inner Flow Characteristics And Aeroacoustics Of Backward-Type Centrifugal Fan

Fan has been widely used in ventilation,mine,ship,vehicle and other fields,and its aerodynamic noise has attracted more and more attention.Accurate noise prediction is very important to reduce the noise of the ventilation system and prevent expensive noise reduction post-processing.In this paper,the flow characteristics and aeroacoustic performance of the open system consisting of the backward-type centrifugal fan and its attached pipes are mainly studied.A hybrid calculation method combining computational fluid dynamics(CFD)and computational aeroacoustics(CAA)is adopted to predict and study the aerodynamic noise of the backward-type centrifugal fan.Based on FW-H equation,the steady / transient flow field information of centrifugal fan is transformed into sound field information,and the sound propagation is calculated.(1)Using Proe,CFturbo and Spaceclaim software to establish a centrifugal fan three-dimensional model,computational fluid domain model and a complete set of experimental benches,design supporting processing drawings and produce fan and pipe samples,and successfully build a centrifugal fan experimental bench.(2)Fluent meshing software is used to divide the fan fluid domain grids including pipes.The performance of three turbulence models,realizable K – ε,SSA and LES,in the simulation of aerodynamic noise of fans is studied by using the FW-H equation built in fluent software.The results show that LES model has the highest accuracy.(3)Analyzed the gas flow characteristics inside the fan from multiple dimensions such as pressure,speed,temperature,vortex Q criterion and streamline,and found that the pressure gradient inside the fan changes significantly,the flow changes drastically,the temperature rises quickly,and the vorticity is high.There is a high degree of coincidence between the broken,streamlined,entangled and mixed area and the concentrated distribution of noise sources.(4)Using the controlled variable method,when studying the factors within a certain influence factor,keep other factors unchanged,and study the influence of grid type,structure simplification,and rotation domain processing method on the aerodynamic noise simulation of centrifugal fan one by one.(5)Simplify the structure of fan fluid domain,deal with the rotating domain by keeping the area of impeller outlet unchanged,divide the grid by using the grid generation technology of polyhedron grid,and adopt the grid based on Realizable k-e+LES+The hybrid calculation method of FW-H equation is used to study the aeroacoustic characteristics of centrifugal fans in pipeline and free space.It is found that the noise of centrifugal fans in pipeline is mainly eddy current noise,while the discrete noise of centrifugal fans in free space is obvious.