Research On Design And Performance Optimization Of Axial Fan Based On Equal-Variable Circulation

Axial fans are widely used in electric power,mining,petroleum,textile and other fields.With the increasing application of axial fans,the transformation of axial fan airfoil and blade aerodynamic shape has become an important method for improving the performance of axial fans.Based on the existing low-pressure axial fan design method,this paper proposes an equal-variable circulation design method by analyzing the work of the original blades.At the same time,the obtained blades are further optimized by means of forward sweep modification and blade tip selection.Numerical simulation and experimental methods are used to analyze the performance and flow of the designed blade.First,for traditional twisted blades,the performance and flow field information of the blades obtained by equal-variable circulation design,equal circulation design,and variable circulation design are compared horizontally.The advantages of equal-variable circulation design are analyzed in terms of pressure velocity field,axial velocity and blade load.The results show that the equal-variable circulation design can stably increase the total pressure of the blade,and the range of the total pressure is 20-40 Pa.Its efficiency is basically the same as other design methods,and the area of the high negative pressure area of the blade suction surface is large.The suction surface has a large airflow velocity and good suction performance.The outlet axial velocity is higher than that of the other two blades,and the average increase can reach 4%.The area of the high-load area is larger and it has stronger performance.Secondly,a forward-swept modification was made to the designed blade.In this paper,the aerodynamic performance of the blade is obtained by changing the forward sweep height and forward sweep angle of the blade.By comparing their performance parameters,it is found that the forward swept blade with the best aerodynamic performance can be obtained by sweeping forward 20° from 60% relative blade height.The analysis of the pressure and velocity field in the flow channel,the axial velocity distribution,the streamline on the top of the blade and the load show that the forwardswept blade obtained by the equal-variable circulation design has better aerodynamic performance based on the same forward-swept modification.In the calculated flow range,the total pressure of the equal-variable circulation design blades is increased by an average of 2.6%.In the design conditions,the equal-variable circulation design can increase the flow rate by 3.34% and the total pressure by 6.35%.In small flow conditions,the forward-swept modification effect is obvious,the tip of the forwardswept blade has no separation flow and has a more uniform load distribution,and the tip of the blade is powerful.Finally,the effect of tip clearance on the blade is discussed for the forward-swept blade with equal-variable circulation.This paper mainly analyzes the flow field in the tip clearance,the leakage,the separation state and the secondary flow near the clearance.The internal mechanism of the effect of blade tip clearance on performance is studied.As the tip clearance increases,the leakage area increases,which will cause the mechanical efficiency of the impeller to decrease.When the leakage area is the same,the working efficiency of the variable tip clearance is better than the equal tip clearance,and the tapered tip clearance has the highest efficiency,and the efficiency of the tapered tip clearance is similar to the efficiency of the equal tip clearance.