Study On The Relationship Between Aerodynamic Characteristics And Vibration Level Of Centrifugal Fan

The research of the low-noise centrifugal ventilator not only conforms to the requirements of the development of national economy and defense,but also facilitates the environmental protection and the promotion of the strategy for building a sustainable human society.In recent years,with the advancement of relevant technology,the understanding of the aerodynamic feature and the vibration and noise mechanism of the centrifugal ventilator,as well as the measures for controlling the vibration and noise,have been improved considerably.However,problems continue to surface with the deepening of the research.Firstly,reports about the mechanism and distribution of aerodynamic excitations associated with the centrifugal fan have rarely been found.Secondly,the majority of the studies undertaken on vibration and noise prediction of ventilators and the control strategies are related to fluid-solid coupling.The process is complex and time-consuming,and apparent error are perceivable with available research techniques and knowledge.Various and varying requirements of practical centrifugal ventilator products hinders quick obtainment of engineering application instructions.Aerodynamic excitation is one of the main factors influencing centrifugal ventilator vibration.The motivation of the presented work comes from practical engineering applications.The technical route covers computational fluid dynamics(CFD)analysis,flow measurement,vibration measurement,the correlation of aerodynamic characteristics and vibration.The aerodynamic excitation in the centrifugal ventilator is analyzed through numerical simulation and experiment,then vibration is introduced to explore the influence of aerodynamic factors on centrifugal ventilator vibration.The relationship between the aerodynamic characteristics of the centrifugal ventilator and vibration magnitude is deduced to provide a new reference for the design of low-noise centrifugal ventilator structure and vibration prediction.At a preliminary step,for the conventional centrifugal ventilator,a comparative study is performed to evaluate the effect of turbulence model,grid number and geometric model processing approach.Thus the most appropriate computational strategy is determined to provide a sound base for subsequent simulation and analysis.In consideration of the various impeller and volute tongue structures,a comparative simulation is conducted to describe the influence of local structure on ventilator performance from the aspects of overall performance and steady flow.The aerodynamic excitation characteristics of the centrifugal ventilator are analyzed to support subsequent qualitative analysis of the integrated effect of structure,aerodynamics characteristics and vibration.Then unsteady flow calculation and analysis are conducted based on steady simulation results.The purpose is to seek the mechanism of pressure fluctuation in the centrifugal ventilator and the variation tendency of pressure fluctuation at different positions.With respect to the conventional structure,pressure fluctuation simulation is performed to study the influence of blade profile and volute tongue,and the influence of local structure on aerodynamics excitation in the centrifugal ventilator.Through comparing variations of pressure fluctuation in different regions and with difference structures,the distributions of aerodynamic excitation in circumferential and axial directions in the centrifugal ventilator are anticipated to be elucidated,and the quantitative effect of structure on aerodynamic excitation will be explained as well.Further,the measurement of the inner flow of the conventional centrifugal ventilator is performed on the basis of numerical simulation.Flow velocity distribution,static pressure distribution and pressure fluctuations are obtained to validate numerical work and the experiment.It is proved that an agreement between numerical and experimental results in terms of overall tendency is achieved,and the largest deviation is less than 10%.A further analysis is carried out on pressure distribution and fluctuation at the inlet and outlet of the impeller,and in blade passage to provide a more reliable basis for exploring the relationship between the structure and aerodynamic excitations.As the final step of the study,vibration test is performed for the centrifugal ventilator.Both comparison and correlation are involved in treating pressure fluctuation measurement data,numerical results and the vibration test data associated with the conventional centrifugal ventilator.Thereby,the influence of aerodynamic excitation on the vibration of the ventilator casing,and typical location,typical frequency vibration characteristics exposed to such an excitation are obtained.With different impellers and volute tongue profiles,numerically obtained pressure fluctuations at typical positions and the vibration at corresponding positions are analyzed.Therefore,the relationship between the aerodynamic characteristics of the centrifugal ventilator and typical location,typical frequency vibration magnitude is established,providing reference guidance for the design of the low-noise centrifugal ventilator.