Study On Flow Characteristics Of Axial Flow Fan With Diffuser

The use of fans is widespread throughout the national economy and occupies a significant share of national production life.Early fan's design is according to the actual demand,through long-term engineering and technical personnel engaged in the work of related draw up the design scheme,and analyzes the program calculation,after adjustment for related production entity prototype fan.With the continuous upgrading of computers,computational fluid mechanics has also made great progress,and new technologies have been developed in the design of fans.The calculation process of specific parameters of the impeller blades and the rear diffuser vanes of fan is complicated,and the forming process of three-dimensional blades is complicated.Therefore,this paper uses the self-made Visual C++ program to calculate the spatial curve coordinates of different leaf height sections of the blade,the data imported into the three-dimensional modeling software of the blade forming curve automatically,avoiding the drawing of a large number of points in the modeling process,reducing a lot of the workload.Numerical simulation is carried out for axial flow fans with rear diffuser vanes and not under different flow conditions.The results show that whether it is with the rear diffuser vanes axial flow fan or without rear diffuser vanes axial flow fan,when the flow is close to zero,the total pressure reaches a maximum value.When the flow rate is relatively small,the total pressure is relatively high,and the efficiency is obviously not high.When the flow rate increases,the total pressure of the fan decreases.When the flow continues to increase,the total pressure rises slightly,and the efficiency reaches the highest value.At this time,the fluid streamlines are evenly distributed along the height of the leaf.This situation usually occurs during the best working conditions.When the flow rate increases again,the total pressure of the fan decreases,and the overall efficiency also decreases.Therefore,it can be seen that when the flow deviates from a certain range of optimal working conditions,there will be flow losses,which will reduce the efficiency of the fan.In the axial fan in which the same parameters of the impeller and the rear diffuser vanes have the same parameters and different numbers of vanes,the fluid passes through the high-speed rotating blade,and due to the effect of inertia,it flows through the curved vanes behind the non-rotating vanes.For rear diffuser vane number is less,the cascade of the relatively small string section of impeller,the fluid flow in the rear diffuser flow path,the affected by the effect of blade is small,to eliminate the winding through high-speed rotating blade speed not too big effect.Rear diffuser vane by the increase in the number,the blade is consistency to increase,so the flow of the fluid resistance increases,the total blade area of the diffuser is also increasing at the same time,which means that the friction area is increased,fluid loss increases,and the fan efficiency increases,the whole machine performance degradation.Fans whose blade width is inversely proportional to the number of blades,in the case of small flow conditions,the smaller the number of rear diffuser blades,the fan total pressure is higher,is due to the smaller number of diffuser blades with the big width of the diffuser vane,the fluid in the rear diffuser flow passage,the effect of winding speed are generated from the high-speed rotating blade basically eliminated,so the total pressure is relatively high.However,no matter the number of diffuser wheel blades,the total surface area of the diffuser vane blades is basically the same,and the surface friction loss is equivalent,so the efficiency is not much different.As the flow rate increases,the more blades there are,the greater the flow resistance and surface frictional resistance of the fluid,and the greater the degree of influence,resulting in a significant reduction in the total pressure and efficiency of the fan.