| Centrifugal pumps are widely used in the petrochemical industry,shipbuilding industry,irrigation and other life and production fields.For the impeller,it is the core component for the energy conversion in the centrifugal pump and its performance directly affects the overall performances of the centrifugal pump.For the blade shape,it has a decisive influence on the hydrodynamic characteristics of the impeller.Therefore,in order to achieve the goal of improving the hydraulic performance of the centrifugal pump,on the basis of the original hydraulic design,the blade profile is modified to change the hydrodynamic load on the liquid surface.Based on the analysis of the mechanism of the impeller internal flow fields,computer aided design and numerical simulation are employed to research different combinations of vane wrap angle and blade outlet angle of the hydraulic design scheme of the centrifugal pump impeller.By numerical simulation,the optimized impeller has the features that liquid flow state is better and emergence of vortex,secondary flow and reflow unstable condition is selected,which is helpful to improve the design efficiency and reduce the research cost and development period.Single-stage single suction centrifugal pump KQW250-400 is selected as the research object.Due to the particular working environment of the building pump and its widely using scope,people have much higher demand for the work efficiency and service life.So,it has the higher requirements for the hydraulic performances of the centrifugal pump impeller.For the paper,based on the analysis of the main parameters of the impeller and the consideration of various influencing factors,vane wrap angle and blade outlet angle are changed to get five different improving schemes of the impeller.PCAD software is employed to get the two-dimensional hydraulic design diagram of the impeller.The three-dimensional entity model of the impeller is built and unstructured tetrahedral meshes are employed to discrete the computational domain of the centrifugal pump.To research the internal flow characteristics of centrifugal pump,based on standard ?-? turbulent model and SIMPLEC algorithm,performance curves which are correspond with five different centrifugal pump models in 0.6Qopt,0.8Qopt,1.0Qopt,1.2Qopt,1.5Qopt(Qopt is the designed flow rate)are given by numerical simulation.Internal static pressure,velocity,distribution characteristics of streamlines,turbulent kinetic energy and other physical quantities of the five improved impellers under different conditions are analyzed.Under the smaller flow rate 0.8Qopt,flow state of water is relatively disorder.Near the volute tongue,flow stall appears,which shows that control effects of the impeller to the flow is much poorer and energy losses are more severe.Under the bigger flow rate,the flow is uniform and energy loss is lower.Various factors are considered comprehensively.And vane wrap angle ?=26° and blade outlet angle ?2=24° are selected and employed ultimately,which indicates that the performance under this condition is the best.Under designed flow rate 550 m3/h,numerical simulation result of the head is 53.49 m,the efficiency is 87.66%,and the shaft power is 91.17 kW.And various performances have reached the designed requirements.According to the proportion of 1:1,3D mold model of the impeller is obtained by 3D rapid prototyping technology and 2Cr13 impeller is obtained by molten wax casting.Performance experiments of the original centrifugal pump model and centrifugal pump with the improved impeller are done in the performance test-bed.The tested results show that for the original centrifugal pump model,when the flow rate is 551.381m3/h,the head is 49.1m,the efficiency is 79.88%,and the shaft power is 92.319 kW.For the centrifugal pump model with the improved impeller,when the flow rate is 440.363 m3/h,the head is 55.48 m,the efficiency is 82.7% and the shaft power is 80.454 kW.When the flow rate is 550.823 m3/h,the head is 51.84 m,the efficiency is 85.65% and the shaft power is 90.794 kW.When the flow rate is 661.432 m3/h,the head is 47.02 m,the efficiency is 84.16% and the shaft power is 100.646 kW.Finally,under the designed flow rate,efficiency of the centrifugal pump with the improving impeller increases by 5.77% and the head increases by 2.74 m.For the centrifugal pump with the improved impeller,the overall efficiency is higher than the original centrifugal pump,higher efficiency area is wider and the overall performance of the centrifugal pump is improved.At the same time,the study will greatly improve the efficiency of the building pump,improve the economic efficiency and reduce energy consumption. |
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