| With the accelerating pace of industrial development,deep-sea mineral resources collection has gradually become an important strategic goal for various countries,and the deep-sea mining system with the most prospect of commercial exploitation is the hydraulic lifting mining system with the lifting pump as the core power equipment.As a kind of solid-liquid two-phase flow pump,the medium conveyed by the lifting pump is relatively special,and the working environment is harsh and the operating conditions are complex and changeable.Therefore,this paper took a mining lifting model pump as the research object and carried out the study of the four-quadrant characteristics and the two-phase flow process in the pump in order to investigate the performance and internal flow mechanism of the pump under different working conditions and further enrich and improve the design methods and theories of the deep-sea mining lifting pump.The main work and achievements are as follows:1.A more detailed summary of deep-sea mining lifting pumps and the current research progress for solid-liquid two-phase flow pumps was presented,as well as the methods and results of existing research on hydro-mechanical four-quadrant characteristics.2.The basic theory and test design methods of pump quadrant characteristics were introduced,the existing pump quadrant characteristics test bench was improved,a test bench for simultaneous testing of solid-liquid two-phase pump quadrant characteristics and internal flow visualisation was redesigned and built,and a test program for the pump quadrant characteristics test bench was developed based on the Lab VIEW software platform.3.The four-quadrant characteristics of the pump were tested in clear water media and two-phase media,and the effects of variable speed conditions on the four-quadrant characteristics in clear water media and the effects of particle size and solid phase volume fraction on the four-quadrant characteristics in two-phase media were analyzed.The test results show that:(1)The trend of the four quadrant characteristic curve with flow rate is basically the same for different speed,particle size and solid phase volume fraction.(2)With the increase of flow rate,the head of the pump condition decreases continuously,the torque of the forward pump condition increases first and then decreases,the negative torque of the reverse pump condition increases gradually.In the runaway condition,the speed and negative head of the pump are positively correlated with the flow rate.(3)With the increase of particle size or the rise of solid phase volume fraction,the head of the pump condition decreases,the torque of the forward pump increases,the flow rate at the peak point becomes smaller,the negative torque of the reverse pump increases,the runaway condition is positively correlated with the flow rate.4.The solid-phase particle flow process in the guide vane of the lifting pump during operation under forward and reverse pump conditions and forward and reverse runaway conditions was captured by high-speed photography,respectively.The particle motion characteristics under different working conditions were analyzed.The results of analysis show that:(1)The particle motion in the first stage space guide vane and the second stage space guide vane are basically similar under each operating condition.(2)The particle flow in the guide vane is relatively smooth under the forward pumping condition and the forward runaway condition.(3)There are five typical particle motion states in the guide vane under the reverse pump condition and the reverse runaway condition,and there are 29.25% and 45.25% probability of backflow,vortex or collision in the guide vane respectively.(4)Among the four operating conditions,the number of collisions between the particles and the guide vane is the highest in the reverse pump condition,followed by the reverse runaway condition and the least in the forward pump condition.(5)The main location of the collision in the reverse pump and reverse runaway condition is the middle of the guide vane,and the main location of the collision in the forward runaway condition is the inlet of the guide vane.5.The unsteady numerical simulation of solid-liquid two-phase flow was carried out based on the coupled CFD-DEM model for the forward and reverse pump conditions and forward and reverse runaway conditions of the model pump,and the solid-liquid two-phase flow law in the pump under different conditions was further analyzed based on the calculation results.The numerical simulation results show that:(1)The particles can pass through the two-stage components well under all operating conditions except for the reverse pump condition where there is a large amount of blockage before the particles enter the inlet of the first-stage impeller.(2)The average velocity of particles under forward pump conditions is the highest,reaching 2.34 m/s;the highest velocity of particles under forward runaway is the highest,reaching 20.97m/s.(3)The particle trajectory in the pump under the reverse pump condition is the most complicated compared with the other three working conditions,and the maximum particle trajectory wrap angle in the impeller reaches 651 degrees.(4)Under different working conditions,the liquid-phase flow structure in the guide vane will change to different degrees with the rotation of the impeller,and the liquid-phase flow structure in the guide vane is the main cause of the motion state of all kinds of particles,among which the flow structure in the high-speed zone of the liquid phase has the greatest influence on the motion state of the particles.(5)In the forward pump condition and forward runaway condition,the flow state in the high speed area of liquid phase is uniform and stable,so the particle passability in both conditions is better.In the reverse pump condition and reverse runaway condition,there are different scales of liquid-phase vortex and flow separation in the guide vane,which makes the particles in these two conditions have more backflow,vortex and collision. |
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