Analysis Of Identification And Mechanism Of Vortex In Tandem Cascade

The pump is a machine for conveying fluid or making the fluid supercharged.With the rapid development of industry,the performance requirements of industrial pumps are higher and higher.Large volume,high lift,high efficien cy and small volume are the development directions of pumps.The asymmetry of the structure of the spiral pressure chamber generates a large radial force on the impeller when the impeller blade approaches the tongue.The spiral water chamber with a guide b lade has been invented to greatly reduce the radial force of the impeller.It is generally applied to a large single stage centrifugal pump to reduce the radial force of the impeller at the same time with high lift and high efficiency,so as to keep the pu mp stable.In this paper,through the numerical simulation of the two dimensional model pump,the internal flow field of the centrifugal pump is analyzed,and a series of vortex identification means,such as the vortex Q criterion,the flow line,the vecto r map and the pressure cloud,can be used to identify the two-dimensional vortex.The results show that a local high pressure region is formed at the leading edge of the guide vane,which is the main reason for the vortex generation in the guide vane channel.The inlet of the guide blade induced by high pressure pulsation produces two vortices in the opposite direction of rotation,because the two vortices occupy a large space in the guide vane channel,so they are called "channel vortices".The trailing edge of guide vane induces vortex generation,which is called "wake vortex" in this paper.When the tongue is impacted by the flow of the guide leaves,the whirlpool is generated on both sides of the tongue.This vortex has a significant influence on the downstream flow field after the shedding of the tongue.This vortex is called the "shedding vortex of the tongue." Subsequently,the article describes in detail the movement of three types of vortices and their interactions.In the second chapter,by changing the angle of stationary guide vane,the influence of different installation angles on the flow of vortex tongue is analyzed.In order to study the relationship between the installation angle of static guide vane and the efficiency and head of the centrifu gal pump,six different guide vane placement schemes are selected.The results show that the installation position of the guide blade has a great influence on the pump characteristics,and the pump's lift and efficiency are the highest when the tongue is l ocated between the guide vane outlet circumferential angle.When the guide vane is close to the tongue,the lift and efficiency of the pump are reduced to some extent.When assembling a spiral pressure chamber with a guide blade,the circumferential angle of the guide vane should be matched with the tongue.The location of guide vane has great influence on the hydraulic loss of volute,and has little effect on the performance and flow of impeller and guide vane.Finally,the effect of U cut on the inlet sid e of the guide vane on the pump performance is studied.It is known from the above that the flow field of guide vane and impeller is influenced greatly by the action of static and static interference,so by changing the gap between the guide vane and the i mpeller,the interference effect is reduced,and the effect on the external characteristics of the pump and the internal flow is explored.In the above paper,the optimal guide vane isolating tongue is located at the angle of =22.5 U,and the original mode l is taken as the original model.The research shows that the U shaped cutting on the inlet side of the guide blade has a significant influence on the external characteristics of the pump.Under the same flow,its lift is lower than the prototype pump,but the efficiency is higher than that of the prototype pump.Increase and increase the clearance of the guide vane impeller,the impact loss caused by the static and static interference and the hydraulic loss of the volute have been reduced,which makes the pump efficiency increase and the drop of the head is mainly due to the reduction of the power of the impeller.