Study On Blade Sweep Form And Rotor-stator Matching Of Low Pressure Axial Fan

With the development of economy,people’s living standard is gradually improving.The performance of axial fan is more demanding,and the reasonable matching and optimization research of rotors and stators in axial fans is the key to the design and development of axial flow fans.In this paper,a typical single-stage axial fan with guide vane mechanism(R+S type)is taken as the research object.Combining with numerical simulation,experiment and optimization,on the one hand,the effects of the three forms of blade skewing and sweeping on the performance and internal flow field of the fan are analyzed;on the other hand,based on the optimization method of multi-island genetic algorithm combined with ellipsoid-based neural network model,the rotor-stator matching optimization and analysis of the fan rear guide vane were carried out.(1)The model generated by the optimized and improved automatic pre-processing program is used to carry out the research.The numerical simulation results of the prototype are compared with the experimental results to verify the reliability of the numerical method.The internal flow conditions of the prototype impeller under three typical flow conditions are analyzed.It is found that the backflow and vortex exist on the pressure surface of the rotor blade under off-design conditions,and the distribution and development of the vortex in the rotor blade passage show certain regularity.(2)Three different forward sweeping forms of blade uniform-sweeping,root-sweeping and tip-sweeping are proposed and defined.Based on numerical simulation,the aerodynamic performance of fans with different sweeping forms and sweeping angles is analyzed.The performance results from calculation show that: blade root-sweeping reduces the fan performance in the whole flow range;tip-swept blade with appropriate sweeping angle is able to improve fan performance slightly and stabilize the total pressure and efficiency of the fan on the large flow side.Blade uniform-sweeping can effectively improve the performance of the fan,but the performance deteriorates seriously in the large flow side.(3)Internal flow characteristics of blades with different sweeping forms and sweeping angles are analyzed under design conditions.The analysis show that: sweeping forms have a great influence on static pressure of the blade surface,and the larger the sweeping angle is,the more obvious the variation trend of static pressure is;The root-swept blade intensifies the separation backflow near the trailing edge of the suction surface root,while the uniformswept blade inhibits it.The influence of sweeping forms on the velocity at different span on the inlet and outlet sections will cause the change of the pattern and intensity of trailing edge vortex near blade root;The horseshoe vortex at the leading edge of blade root and tip leakage vortex are both affected by sweeping forms and sweeping angle.(4)The matching optimization of the rear guide vane of the fan was carried out by the established optimization method.Under the design condition,the total pressure of the fan was increased by 5.91%,and the total pressure efficiency was increased by 6.30%.It was pointed out that the fan performance was most affected by the blade installation angle.After optimization,the negative flow incidence angel of the guide vane decreases,resulting the flow separation on the pressure surface of the guide vane is restrained and the pair-vortex on the leading edge of the pressure surface is eliminated.