Research And Optimization Design Of Clearance Flow In Low Specific Speed Multistage Pump

The low specific speed multistage pump is widely used in industrial production and has a large demand,while the low specific speed multistage pump has generally low efficiency and serious energy consumption.With the increasing demand of users for practicality and energy saving,the development of low specific speed multistage pumps has encountered difficulties.Non-uniform internal flow,multi-clearance,and multi-segment structural combination of low specific speed multistage pumps have always been the research difficulties.The performance of each stage affects the overall performance of the multistage pump and also affects the economics of the entire production.The choice of component parameters is more of a concern.Understanding the internal clearance flow and the impact of key structures on the pump is of great importance for improving its efficiency,optimizing design,and enhancing product competitiveness.through the understanding of the low specific speed multistage pump model and structure,the design process of the parameters of each flow section of the multistage centrifugal pump is given under the parameters,and the numerical analysis and test are carried out according to the model pump,Verify its reliability.Then consider the actual situation to add the clearance flow and analyze its internal flow field,consider the influence of return guide vane parameters on the multistage pump,and finally optimize the matching of the impeller and the guide vane by changing the parameters of the impeller and guide vane.The main contents and conclusions are as follows:According to the existing parameters,the structure of the pump is selected,the suction chamber,the impeller and the guide vane are designed,and the model is assembled and meshed to perform numerical simulation.The results show that the loss of the suction chamber is very small,and the angle of the tongue is not good for the inlet of the impeller;the distribution of the pressure and flow lines of the impeller and the guide vane is reasonable,and the impact loss and vortex exist in the guide vane.An open pump test rig was set up for testing and compared with numerical analysis values.The results show that the simulated value is generally higher than the experimental value,but the overall trend is consistent and the error is within 4%,which indicates that the numerical simulation is reliable.Analyze the gaps existing in the low specific speed multistage centrifugal pumps,and model them.The results show that there are leakage,pressure difference and rotational motion in the fluid in the clearance between the impeller chamber and the impeller guide vane;there is a small amount of exchange between the fluid on both sides of the impeller and vane running clearance;the H-Q&?-Q curve of the model pump with clearance is better than the original.The model pump's curve slightly decreased but not noticeable.12 sets of models with different gap sizes were established for numerical analysis.The results show that the larger the overall gap size is,the more unfavorable the performance of the multistage pump is;the degree of influence of all gaps on the performance of the multistage pump is:impeller ring gap>guide vane ring gap>impeller and guide vane gap;the leakage in the gap between the impeller ring and the guide vane ring is aggravated with the increase of the gap size;the volumetric efficiency and the estimation formula are calculated by numerical calculations.The resulting difference is within 4%,and it can be considered that the numerical simulation has good adaptability to the treatment of small gaps.The analysis of the internal flow field of the return guide vanes is focused on.The results show that the fluid velocity near the vane wall surface is slower and more inhomogeneous;there are vortices and impact losses in the return guide vanes;in the absence of the secondary impeller the unevenness at the inlet of the secondary impeller is accompanied by There is reflux.Change the number of return guide vanes,inlet diameter,inlet angle and outlet angle to establish multiple sets of models for analysis.The results show that when the number of vanes is small,the vortexes are easily formed at the outlet.With the increase of the number of vanes,the Head increases slightly.However,the efficiency of the pump increases first and then decreases;the diameter of the inlet vane increases,The internal flow is more inhomogeneous;an excessively large inlet angle has an adverse effect on the flow field at the outlet of the counter vanes;an appropriate reduction in the outlet angle of the counter vanes can improve the fluid flow conditions,increase the efficiency of the pump and obtain a declining characteristic curve.Orthogonal test method was used to analyze the model pump with four factors:blade number of impeller?Z_Y?,blade number of guide vanes?Z_D?,impeller blade outlet angle??₂?,and guide vane throat area?F₃?.The results show that the order of factors affecting the Head is:Z_D>Z_Y>F₃>?₂.The factors affecting the efficiency are ranked as?₂>Z_D>F₃>Z_Y.The multistage pump is analyzed and optimized under the best combination.The multistage pump optimized efficiency increased by 2%,Head increased by nearly 5m.