| Roto-jet pump is characterized by a low specific speed,high head,specific speed is generally in 5～30,belongs to the ultra-low specific rotation pump.Its high efficiency,smooth flow head curve and other very outstanding advantages,so that it can be a good substitute for high-speed pumps,multi-stage centrifugal pumps and reciprocating pumps and other traditional low specific speed pumps in the actual industrial production.As we all know,the impeller of the very low specific speed pump has a large radial size,a small impeller outlet width and other geometric characteristics,re sulting in a narrow impeller flow path,and the very low specific speed centrifugal pump efficiency is generally lower than the high specific speed centrifugal pump impeller efficiency.It follows that if a single-stage single-suction cyclone pump with the same flow rate,head and speed is designed as a two-stage single-suction cyclone pump,and the single-stage head of the two-stage single-suction cyclone pump is half the head of the cyclone pump,its specific revolution number is much larger than that of the single-stage single-suction cyclone pump,which is conducive to improving the efficiency of the pump.In this paper,based on the invention of two-stage single-suction rotary spray pump（Public（Announcement）No.CN110966206A）by members of this group,a two-stage single-suction rotary spray pump and a single-stage single-suction rotary spray pump with exactly the same flow rate,head and speed were designed,and a single-stage single-suction rotary spray pump was taken as the reference object.Through the test and numerical simulation of the cyclone pump used in the test bench,on the basis of verifying the accuracy of the simulation method,the performance advantages of the two-stage single-suction cyclone pump were studied,and on this basis,the flow field characteristics of the impeller and collector tube of the two-stage single-suction cyclone pump were studied;the focus was on the flow field characteristics,liquid flow circumferential velocity,radial velocity,axial velocity and pressure distrib ution law along the radial direction in the cyclone cavity at different flow rates.Explore the influence of different collector inlet diameters on the performance of two-stage single suction roto-jet pump,the main research content is as follows.（1）Carried out the design of two-stage single-suction cyclone pump and single-stage single-suction cyclone pump with identical flow rate,head and speed,and gave the main design process of the two types of cyclone pumps and the determination of key geometric dimensions.（2）Studied the performance of two-stage single-suction rotary spray pump and single-stage single-suction rotary spray pump respectively,comparing and analyzing the difference in performance between the two types of rotary spray pumps,the results show that the pump head is basically equal under the same flow conditions,the two-stage single-suction rotary spray pump has high efficiency,and the maximum difference in efficiency between the two reaches 11.59%,which occurs at the 1.2 Q operating point.In the design flow,two-stage single-suction rotary spray pump than single-stage single-suction rotary spray pump,head is basically equal,11.47%higher efficiency to verify the performance of two-stage single-suction rotary spray pump is much better than single-stage single-suction rotary spray pump.（3）The radial velocity coefficient,axial velocity coefficient,tangential velocity coefficient,pressure coefficient and other dimensionless parameters were introduced to calculate and analyze the distribution characteristics of axial velocity,radial velocity,tangential velocity and pressure in the first and second rotary chambers of the two-stage single suction roto-jet pump under different flow conditions.The results show that the axial velocity and radial velocity in the rotary cavity are less affected by the flow rate change,the axial velocity has limited effect on the axisymmetric flow in the rotary cavity,the most drastic fluctuation ofθ2 polar angle in the circumferential direction,followed byθ3 and the smallestθ1,and the pressure has a positive effect on improving the axial flow of liquid.Radial velocity in the Z<0.5 region radial velocity is less than or close to zero,while in the Z>0.5 region radial velocity is greater than zero,manifested in the characteristic axis surface that is counterclockwise rotation,the location of the velocity valley changes with the flow,the fluctuation of radial velocity in the secondary spin cavity is large.The tangential velocity in the cavity increases with the increase of radius,and the tangential velocity between the axial flow layers has no obvious velocity slip,in the region of S<1.05,the distribution of tangential velocity is approximately a primary function of radius,in the region of S>1.05,the velocity gradient becomes larger due to the influence of the wall of the spin shell.θ2 polar angle on the tangential velocity changes dramatically,and the maximum tangential velocity,θ3 second,θ1 smallest.The high pressure in the secondary spin cavity makes the tangential velocity variation in the secondary spin cavity more regular.The pressure in the cavity increases parabolically with the increase of the radius,and the pressure changes in the first and second cavities have the same trend and the same pressure increment.Under different flow conditions,the difference of pressure decreases with the increase of radius.θ2 pole angle has the smallest pressure,θ1 pole angle is 4.0%larger thanθ2 pole angle,θ3 pole angle is1.52%larger thanθ2 pole angle,and the pressure does not change much in different characteristic sections.The pressure in the secondary spin chamber varies significantly with flow rate,and the pressures at 0.6 Q and 1.4Q operating conditions are 102.88%and 91.55%of the design operating conditions,respectively,and the secondary spin chamber pressures are 231.26%,230.2%and 215.17%of the primary spin chamber under three different operating conditions,respectively.（4）For the influence of inlet diameter on the perfo rmance of two-stage single suction roto-jet pump,four different inlet diameters of 11mm,12mm,13mm,14mm collector tube were designed for combination,and the study of 16 groups of two-stage single suction roto-jet pump models showed that the flow characteristics in the collector tube are only related to the geometry of the collector tube,the size of the ambient pressure does not have much influence on the flow state in the collector tube,and the collector tube The inlet section of the collector is cond ucive to pressure conversion by appropriately increasing the diffusivity.With the increase of collector inlet diameter,regardless of the first and second stage collector,the location of the flow separation is more backward,and the pressure inside the c ollector as a whole tends to increase first and then decrease.d 1-2=12mm,d1-2=13mm when the inlet flow state is optimal,d1=13mm when the highest pressure inside the collector.There is uneven force in the secondary collector.The head and efficiency of m odel 13-13 are the highest among all models. |
