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Research On Flow Characteristics Of Centrifugal Fan

Posted on:2019-07-10Degree:MasterType:Thesis
Country:ChinaCandidate:L WangFull Text:PDF
GTID:2382330548969685Subject:Vehicle engineering
Abstract/Summary:PDF Full Text Request
As a fluid machine,centrifugal fans are widely used in various fields because of their own characteristics.Centrifugal fans are large consumers of power in large machines.Thus it is possible to reduce energy consumption by increasing the efficiency of centrifugal fans.This is the main objective of fan optimization.At present,there are semi-empirical and semi-theoretical design methods for the design of centrifugal fans.For some important parameters affecting the efficiency of the centrifugal fan,the values of parameters are obtained by experience rather than accurate calculation.In this paper,ANSYS CFD software is used to numerically simulate the flow inside the centrifugal fan.The method to improve the efficiency of the centrifugal fan is studied by analyzing the velocity,static pressure and full pressure with different scroll widths and number of impeller blades.Firstly,the impeller,volute,collector and volute tongue of the centrifugal fan are aerodynamically designed according to the known parameters.The three-dimensional model of the backward-bending impeller centrifugal fan is drawn based on the parameters of the aerodynamic design using the CAD software Solidworks.Secondly,the model of the centrifugal fan is filled with fluid domain and is meshed with ANSYS Meshing software.The grid is controlled between 2.8 million and 3.5 million to save computer resources.In this paper,the SIMPLE algorithm and the second-order upwind scheme are used to discretize the control equations.Fluent is used as the solver.Finally,the result of the calculation is processed by the post-processing software CFD-POST.The efficiency of the fan is calculated by the torque of the centrifugal fan impeller.In the analysis process of the results,the effect of the width of the volute and the number of blades on the internal flow of the centrifugal fan is studied under the design flow.The flow characteristics of centrifugal fan are studied by analyzing the static pressure,full pressure,speed cloud diagram and speed vector diagram on different sections.The results show that internal flow of centrifugal fan is very complex.Back-flow is formed around the centrifugal fan impeller front cover and volute near-wall surfaces,which has a large effect on the efficiency of centrifugal fan.By calculating the efficiency of the centrifugal fan with different volute widths and different number of blades,it is found that the volute width of the centrifugal fan,that is,the volute of the volute,has a great influence on the total pressure efficiency of the centrifugal fan.The centrifugal fan has the highest efficiency when the volute width is 0.095 m.For a volute with a volute width of 0.095 m,,the change in the number of blades has little effect on the efficiency of the centrifugal fan when the flow rate is less than 0.25 m3/s,and the efficiency of the centrifugal fan increases gradually with the number of blades when the flow rate is greater than 0.25m3/s.Then,the internal flow of thecentrifugal fan under variable flow conditions was analyzed.The efficiency of the centrifugal fan increases firstly and then decreases with the increase of the flow rate.The total pressure and static pressure of the centrifugal fan decrease gradually with the increase of the flow rate.Conclusions and prospects of present study are presented at the end of this thesis.
Keywords/Search Tags:Centrifugal fan, Numerical Simulation, Fan efficiency, Volute width, number of leaves
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