Flow Field Analysis And Noise Reduction Of Variable Flow Column Fan

With the continuous improvement of living standards of citizens and the requirements of energy conservation and environmental protection as well as the needs for some people who are sensitive to air in a closed environment,the use of fans is one of the necessary means for people to cool down in summer.However,noise generated by the use of fans has become a common problem,and the variable duct column fan studied in this dissertation can make importance and necessity of more prominent because of cross-flow fan and variable duct.In this dissertation,Fluent simulation software and Minitab software are used to simulate and analyze five factors that affect the noise of variable duct column fan,including number of blades,clearance of volute tongue,maximum angle of volute,clearance of outlet style and clearance of complement style,as well as design and analysis of DOE full-factor experiment.In this dissertation,the simulation model of variable duct cylindrical fan is established.Through the simulation calculation of Fluent software,two kinds of cross-flow wind turbines with 22 blades and 35 blades,concentric circular volute tongue with 2 mm clearance and inclined gradient volute tongue with 5 mm clearance,as well as concentric volute with 10 degree integral coverage angle of outlet and 51 degree volute with single coverage are considered.Two-dimensional cross-section analysis is carried out in different states,and three performance chart are output(i.e.static pressure nephogram,velocity vector diagram and power level distribution diagram).Qualitative conclusions are drawn from the analysis of the calculation results: the static pressure changes of 35-blade schemes of variable duct tubular wind turbine are smaller than those of 22-blade schemes.By contrast,the noise generated by 35-blade schemes of variable duct tubular wind turbine are larger than that generated by 22-blade schemes.Comparing with the concentric circle scheme with 2 mm volute tongue clearance,the peak intensity and distribution of noise in the scheme with 5 mm volute tongue clearance and variable angle inclination are reduced.The peak velocity and distribution of three states in the scheme with 51 degree widened volute scheme are less than those in the current state.It means that the restriction of widened volute scheme on the internal air flow of cross-flow fan is more reasonable,reducing considerably the disordered direction of the air flow,expecially for the outlet grate which improves the air flow direction obviously and makes it changeable.Eventually,the noise of the variable duct column fan in three states can be reduced by varying degrees.Following the qualitative result obtained,the DOE full-factor experimental design tool is used to test the prototype.Minitab software is applied to conduct two rounds of analysis after collecting the data.The first round of analysis shows there are two most significant factors affecting the noise difference of the variable duct column fan under the shaking head state,namely,clearance of the volute tongue,volute curve and cover angle,and then a regression equation of noise difference between these two factors is established.In the second round of analysis,there are three most significant factors affecting the noise value in the middle state obtained,namely,number of blades,clearance between the volute tongue,volute curve and covering angle,and then a regression equation of these three factors for the noise value is established as well.