| At present,submersible axial flow pumps are widely used in flood control projects,power plant circulating water projects and water transfer projects due to the advantages of easy installation and smooth operation.The design approach is to apply the excellent axial flow pump hydraulic model to the submersible axial flow pump,but its pump hydraulic performance is significantly reduced.Therefore it is well worth studying to improve the hydraulic efficiency of submersible axial flow pumps.The 350ZQ-100 submersible axial flow pump studied in this paper is designed based on excellent axial flow pump geometric parameters with a specific speed of 1000,and the efficiency is also significantly lower compared to that of the axial flow pump.In this paper,CFD numerical simulation combined with orthogonal optimization method is used to optimize the design and flow field analysis of the impeller and guide vane of the submersible axial flow pump,and the influence of the changes of the geometric parameters of the impeller and guide vane on the hydraulic efficiency of the submersible axial flow pump is investigated by studying them,and finally an optimization scheme to improve the hydraulic efficiency of the 350ZQ-100submersible axial flow pump is obtained,which results in a significant improvement of the hydraulic efficiency of the pump;meanwhile,the external characteristic curves and the hydraulic efficiency of the submersible axial flow pump are compared with the optimized At the same time,the external characteristic curve and internal flow field of the model before and after the optimization are analyzed in depth for the reason of the reduction of the hydraulic efficiency of the submersible axial flow pump,which gives a reference for the improvement of the efficiency of the submersible axial flow pump.The main research of this paper is as follows:(1)According to the basic design parameters of 350ZQ-100 submersible axial flow pump,3D modeling,meshing and value simulation were carried out with relevant software,and the numerical simulation results were compared with the test results to verify the feasibility of numerical simulation calculation.And the numerical simulation calculation of three different impeller blade placement angle,and finally determine the highest efficiency under the design flow conditions without changing the blade placement angle,to verify the excellent axial flow pump blade placement angle geometry parameters applied to the 350ZQ-100 submersible axial flow pump is feasible.(2)To study the effect of changing different geometric parameters of impeller on the hydraulic efficiency of submersible axial flow pump,firstly,the size of impeller hub ratio was changed and four schemes with impeller hub ratio of 0.40,0.39,0.38 and 0.37 were selected,numerical simulation calculation was carried out for the four design schemes,and internal characteristics analysis was carried out for the four schemes,Finally,the impeller hub ratio was selected as the influencing force of submersible axial flow pump orthogonal optimization design.factors,with hub ratios of 0.40,0.38 and 0.37 as the optimized design levels;Secondly,the impeller blade exit angle was changed,and four schemes were designed by increasing the exit angle of five flow surfaces 0 degree,2 degree,3 degree and 4 degree respectively,and the numerical simulation calculation was carried out for the four schemes respectively,and finally the maximum efficiency was obtained under the design flow condition and high flow condition by increasing the impeller blade exit angle by 2 degree to meet the design head requirement,and the overall high efficiency zone was widened;Finally,the size of impeller blade grid density was changed,and four schemes were designed with blade grid density of 0.60,0.62,0.63 and 0.64,and numerical simulations were conducted for the four schemes respectively,and finally the impeller blade grid density was selected as the influencing factor for the orthogonal test design,and the impeller grid density of 0.60,0.62 and 0.64 was taken as the optimized design level.By increasing the axial spacing of the impeller and guide vane,four schemes were designed,namely,increasing 0 mm,5 mm,10 mm and 15 mm.Through numerical simulation of the four schemes and analysis of the obtained numerical simulation results,the maximum efficiency and head were obtained when the axial spacing was increased by 10 mm.And the internal characteristics of the four schemes were analyzed under the design flow conditions,and it was concluded that the energy dissipation in the flow channel of the guide vane of the 10mm increase scheme was the smallest,and the impeller and guide vane were the best match,and it could be seen that the optimal value of axial spacing of 30mm was different from the axial spacing of 20mm of the impeller and guide vane of the excellent axial flow pump with the same speed.(3)To study the effect of changing different variables of the geometry of the guide lobe section on the hydraulic performance of submersible axial flow pumps,design four schemes of 0.22,0.21,0.20 and 0.19 of guide vane blade densities,carry out numerical simulation calculation of the four schemes,through analyzing the internal flow field and external characteristic curves of the four schemes,finally select the guide vane blade grille densities as the impact factor on the design of orthotropic optimization of submersible axial flow water pumps,the guide vane blade grille By changing the number of guide vanes,four schemes are designed,namely 5 blades,6blades,7 blades and 8 blades,the models of the four schemes are numerically simulated and the external characteristic curves of the four schemes are analyzed,and the efficiency of the submersible axial flow pump under the design flow condition is the largest when the number of guide vanes is 8,which is also different from that of the excellent axial flow pump with 5 guide vanes at the same speed,considering that the dynamic and static interference between the guide vanes and impeller blades will affect the stable operation of the submersible axial flow pump.Interference will affect the stable operation of submersible axial flow pump,so choose the number of guide vane 5,7 and 8 three options in the design flow conditions of the internal characteristics of the analysis,the number of guide vane is 8 when the guide vane flow channel energy dissipation is the smallest.Therefore,according to the research results,the number of guide vanes is selected as the influencing factor for the orthogonal optimization design of submersible axial flow pump,and the number of 5,7 and 8 guide vanes is taken as the optimization level.(4)The influence of three different well bores on hydraulic efficiency of submerged axial flow pump is studied.The numerical simulation of right angle bend,equal diameter bend and gradually contracted bend is carried out.It is found that the hydraulic efficiency and head of submerged axial flow pump can be improved slightly by equal diameter bend.The area of high energy dissipation area in the well bore with equal diameter bend is obviously smaller than that of right angle bend and gradually contracted bend by means of turbulent energy distribution diagram in the well bore.It effectively improves the fluid flow state in the well bore and reduces the hydraulic loss of the fluid in the well bore.(5)The impeller hub ratio,impeller vane grid density,number of guide vanes and guide vane grid density are taken as the factors of the orthogonal optimization test,and nine parameter combination schemes are designed.The optimal combination obtained from the extreme difference analysis is compared with the optimal combination obtained from the orthogonal test table,and finally the design head is met while the maximum efficiency is achieved,and the combination that makes the submersible axial flow pump meet the design head and achieve the highest efficiency is obtained,namely,the impeller hub ratio is 0.37,the impeller vane grid density is0.62,the number of guide vanes is 7,the guide vane grid density is 0.21,compared with the excellent axial flow pump of the same speed the impeller hub ratio is reduced from 0.40 to 0.37;the impeller grid density is increased from It can be seen that the optimal geometric parameters of the submersible axial flow pump are different from those of the excellent axial flow pump with the same speed.Comparing the numerical simulation results of the model before and after optimization,it is found that the efficiency and head of the optimized model are higher than those of the pre-optimized model at all operating points,and the high efficiency zone is significantly widened,and the hydraulic efficiency of the submersible axial flow pump is improved.Under the small flow rate condition(875m~3/h),the optimized efficiency reaches 65.68%,which is 3.74%higher than that before optimization,and the optimized head is 6.3m,which is 0.26m higher than that before optimization,4.1%higher;under the design flow rate condition(1180m~3/h),the optimized efficiency reaches 80.01%,which is8.18%higher than that before optimization.The optimized head is 4.85m,which is0.73m higher than that before optimization,15%higher;under the high flow rate condition(1416m~3/h),the optimized efficiency reaches 68.02%,which is 5.91%higher than that before optimization,and the optimized head is 2.53m,which is 0.33m higher than that before optimization.Further comparing the changes of internal flow field before and after optimization,it can be found that the optimized model impeller blade pressure distribution is more reasonable,the high turbulent kinetic energy area is reduced,and the fluid energy loss is reduced;the high energy dissipation area inside the outlet extension section and guide vane flow channel is significantly improved,the overall flow channel is smoother and the fluid flow is stable. |
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