Numerical Simulation Of Axial Flow Fan And Analysis Of Aerodynamic Noise

The fan is mainly used for conveying gas impeller machinery,is widely used in various production sectors of the national economy,especially in the fields of mining,metallurgy,petroleum,chemical,aerospace,ship machinery,energy and vehicle engineering.As the petrochemical industry involved in the gas is often toxic,flammable,explosive medium,the requirements of the fan is more demanding,must be in the structure,operating conditions and safety precautions to ensure safe and reliable operation of the fan.Therefore,improving the distribution of internal flow field of the fan,improving the P-Q performance of the fan and reducing the aerodynamic noise of the fan are gradually paid more and more attention by the scholar.The research object of this article is axial-flow fan,using the commercial computational fluid software FLUENT14.5 of the axial-flow fan,the internal flow field in numerical calculation of the internal flow field distribution under different impeller speed fan,and fan performance curve change rule;Using the same numerical calculation method for analyzing the distribution of flow field in the fan,and analyze the different sizes of splitter blade of axial flow ventilator internal flow field distribution.Axial fan in the course of the operation is often accompanied by a strong noise,which is mainly composed of two parts:First,when the fan impeller rotates,the blades generate periodic noise,this noise is called rotation noise or blade noise;The second,when the air flows through the impeller flow channel,the air vortex disturbance noise generated by the separation of the surface layer and the wake flow phenomenon,which is called the vortex noise.This paper adopts Lighthill acoustic analogy method,and the combination of LES and FW-H mixed model,the three-dimensional unsteady numerical solution of the flow noise of axial fan,the impeller speed on the fan noise spectrum distribution and total sound pressure level;and to analyze the influence of splitter blades on the fan noise spectrum distribution and the overall sound pressure level the value of the.In order to provide theoretical basis for the design of axial fan and fan noise reduction.The numerical calculation shows that the static pressure of the pressure plane of the fan is much higher than that of the suction surface,the static pressure of the pressure surface is positive pressure,and the static pressure of the suction surface is negative pressure,which is the sign of the work of the impeller.The speed of the wheel is gradually increased in the axial direction,and the kinetic energy is also increased.While the static pressure along the axial direction is gradually reduced,static pressure can be converted into gas kinetic energy.In addition,since the impeller tail boundary flow is subjected to lateral pressure,the airflow is generated parallel to the boundary,resulting in secondary vortices at the tail of the fan impeller.When there are shunt leaves,the gas flows through the diversion channel,static pressure can be converted into gas kinetic energy,gas flow rate increases and static pressure decreases;As the size of the shunt blades narrows,the flow path between the impeller becomes wider and the gas flow rate decreases and the hydrostatic pressure rises again;In addition,the shunt blades can make the static pressure distribution in the fan more uniform and reduce the pressure pulsation,thus effectively suppress the gas and impeller suction surface of the flow separation phenomenon;can also weaken the impeller tail boundary flow caused by the lateral pressure caused by the secondary flow,greatly improve the wake disturbance at the end of the impeller.The total sound pressure level at the inlet of the fan is lower,which is mainly the rotation noise caused by the impeller rotation in the vicinity of the blade.The total sound pressure level at the outlet of the fan is higher,which is in the wake of the impeller flow and separation vortex flow region,the eddy current disturbances are intense,which with the basis of rotating noise,superimposed vortex noise.In addition,the shunt blade can reduce the flow resistance of the gas in the fan flow channel,make the suction side of the impeller low-energy zone static pressure rise,reduce the vortex generation and erosion of the impeller secondary wake,thereby reducing the eddy current noise;if the shunt blade size is too short,the static pressure near the suction surface of the impeller is lower than that of the splitter blade,and enhance the separation loss in the fan passage,impeller suction surface vortex became serious,and eddy current noise enhancement.