Research On The Influence Of WFB Vertical Self-priming Pump Impeller On Self-priming Performance

As a special centrifugal pump,the self-priming pump has the characteristics of strong adaptability and convenient use,and is widely used in irrigation,mine drainage and other fields.The self-priming process of the self-priming pump is a complex gas-liquid two-phase flow process,which mainly includes: liquid inflow,gas-liquid mixing,gas-liquid separation,gas discharge,stable water delivery and other processes.There are many factors that affect the performance of the self-priming pump,such as: impeller spacing,impeller outlet range,impeller type,and volume of the liquid storage chamber.At present,the design of the self-priming pump is still in the semi-empirical and semi-theoretical stage,and research on the internal mechanism is rare,so the study of its internal mechanism has very high academic value and practical significance.This article takes WFB vertical self-priming pump as the research object,optimizes the design for the impeller,and combines the experiment and numerical simulation to study the influence of the impeller type and the impeller outlet width on the hydraulic performance and self-priming performance of the self-priming pump.The contents are as follows:(1)Taking the 100WFB-B2 vertical self-priming pump as the research object,the impeller parameters are optimized for design.The three impellers are divided into semi-open impellers and closed impellers with the same hydraulic parameters as the semi-open impellers,Closed impeller with smaller impeller outlet width.Through experiments and numerical simulations,explore the influence of impeller type and impeller outlet width on the hydraulic performance and self-priming performance of self-priming pump.(2)The three model pumps with different impellers were tested,and their heads,efficiency and other parameters were obtained.The results were converted into curves and the external characteristic curves were compared and analyzed.It was found that the efficiency of the closed impeller with the same parameters was better.And the efficiency is 8%-10% higher than semi-open impeller.When the outlet width of the impeller is converted,the efficiency of the pump will decrease.(3)The internal flow of the three model pumps was simulated with a single-phase flow constant value to obtain the head under different flow conditions.The numerical simulation results were compared with the heads obtained from the external characteristics test.The maximum error value of the three models in the simulation results was found to be 6.1%,within the acceptable range,to prove its simulation reliability,and analyze the influence of the type of impeller and the width of the impeller outlet on the pump performance from the pressure and speed distribution inside the pump cavity,the distribution inside the impeller and the speed streamline,and the results show that: The impeller type has a greater influence on the pressure distribution inside the pump cavity and a smaller influence on the speed distribution inside the pump cavity,and the influence of the impeller type on the hydraulic performance of the self-priming pump is greater than that of the impeller outlet width on the hydraulic performance of the self-priming pump.(4)Using the MIXTURE mixed model provided by CFX software,the unsteady gas-liquid two-phase numerical simulation of the self-priming process of three self-priming pumps equipped with different impellers was carried out.The import and export of most major flow components such as: impeller inlet The gas content of the outlet,volute outlet,outlet pipe outlet,etc.is monitored to obtain the curve of the gas content with time during the self-priming process,and the time of completion of the self-priming is judged according to the change state of the gas content of the outlet.The gas-liquid two-phase distribution cloud inside the pump cavity fully shows how the gas-liquid two-phase flow inside the pump cavity during the self-priming process.The self-priming process is divided into three stages: initial period of self-priming,mid-term of self-priming and last stage of self-priming.Among them,the main effect of the impeller on the self-priming process is the middle period of self-priming.The results show that the effect of the type of impeller on the gas-liquid mixing and separation speed during the self-priming process is smaller than that of the wide-ranging impeller outlet.Comparing the change curve of the gas content of the main overcurrent monitoring surface,it can be found that due to the larger contact surface between the semi-open impeller and the pump cavity,the air intake of the semi-open impeller is higher than that of the closed impeller,and when the outlet width of the impeller is appropriately reduced,the maximum gas content of the inlet will increase;when the width of the impeller outlet increases,the gas-liquid mixing and separation area increases,and the gas-liquid separation effect of the impeller is the best;from the overall outlet gas content change curve,the difference in closed impeller and semi-open impeller is small;decrease the width of the impeller outlet,the gas changes will be more smoothly,and the self-priming time is longer.From the perspective of self-priming performance,the impact of the impeller outlet width change is much greater than the impeller type change.