Analysis Of Internal And External Characteristics Of The Centrifugal Pump With The Impeller Of Columnar Passages And It’s Performance Improvement

Ultra-low specific speed centrifugal pump has broad application prospects in aerospace,metallurgy,petrochemical and civil industry and other fields,and its core component blade impeller has problems such as difficult processing and manufacturing,serious hydraulic loss and low efficiency,while the centrifugal pump with the impeller of columnar passages provides an opportunity to save mold manufacturing costs and improve the efficiency of ultra-low specific speed centrifugal pump.In order to understand the complex unsteady flow characteristics in the impeller of columnar passages,a centrifugal pump with the impeller of columnar passages with a ratio of 17 speed was preliminarily designed based on the design method of partial flow pump,and the effects of different columnar passages types,different flow conditions and different columnar passages inlet area ratios on the hydraulic performance,flow field state and pressure pulsation of the centrifugal pump with the impeller of columnar passages were analyzed.The main contents and results are as follows:In the first place,under the design conditions,the influence of three columnar passages types of square hole,round hole and flat hole on pump performance were discussed.Based on the equal area of the hole type,the hydraulic model of three disc through-hole centrifugal pumps was preliminarily designed,and the detached eddy simulation(DES)turbulence model was used to simulate the full-flow field.The analysis found that the head of the round hole impeller was 0.5m higher than the square hole impeller and 0.56m higher than the flat hole impeller;compared with the square hole and the flat hole,the relative velocity change curve of each radius of the round hole was smoother with time;for the pressure pulsation at the entrance of the columnar passages,the round hole was reduced by 33%compared with the square hole,compared with the flat hole by 18%,for the pressure pulsation near the volute throat,the round hole was reduced b y 11%compared with the square hole and 5%lower than the flat hole,and the research results showed that the round hole performance was better than the square hole and the flat hole.In the second place,based on the optimal performance columnar passages,the change law of internal and external characteristics of the centrifugal pump with the impeller of columnar passages under multiple working conditions is studied.On the basis of the design conditions,5 working conditions,including 0.375Q_d,0.75Q_d,1.4Q_d,1.7Q_d,and 2.0Q_d,were selected for full-flow field numerical calculation.The analysis shows that with the increase of flow,the efficiency shows a trend of first rising and then falling,reaching a maximum(37.68%)around the 1.7 Q_d working condition.Within a certain range,the pump head is less sensitive to flow changes,showing the characteristics of variable flow and constant pressure.When the pump works in the small flow condition(Q<1.0Q_d),the inverse pressure gradient promotes the high-pressure fluid backflow to increase,and the pressure at the columnar passages inlet increases,which can improve the cavitation resistance of the impeller,but it will seriously affect the fluid flow into the columnar passages;When the pump works in a large flow condition(Q>1.0Q_d),although the return flow of high-pressure fluid is weakened,the work done by the Gorgholard force increases,which also increases the pressure at the columnar passages inlet;The presence of stall vortex greatly affects the performance of centrifugal pump with the impeller of columnar passages,resulting in different sensitivity of the columnar passages flow field to the volute throat under different working conditions,that is,the degree of fluctuation of the relative velocity curve in the columnar passages with time increases with the increase of the flow.With the increase of flow,the peak pressure pulsation at the entrance of the columnar passages and near the throat of the volute showed a trend of first rising and then falling,reaching a maximum near the 1.7Q_d working condition,the main reason for the pressure pulsation in the columnar passages was related to the stall vortex,and the main reason for the pressure pulsation near the volute throat was related to the impact of the columnar passages outflow fluid;when the traffic is constant the pressure pulsation in the columnar passages gradually decreased with the increase of radius,and the research results showed that the flow in the columnar passages tended to stabilize with the increase of radius.In the end,the optimization method of ultra-low specific speed centrifugal pump is used to explore the influence of columnar passages inlet and outlet area ratio on the performance of centrifugal pump with the impeller of columna r passages.Under the condition that other parameters remain unchanged,only the outlet area of the columnar passages was changed to design six impeller models,including introductory columnar passages(YCP0.49,YCP0.64,YCP0.81)and involuted columnar pas sages(YCP1.21,YCP1.44,YCP1.69),and the performance of YCP0.49,YCP0.64,YCP0.81,YCP1.21,YCP1.44,YCP1.69 model and non-diffusion columnar passages YDP1.0were analyzed and compared.The analysis found that the characteristics outside the pump were not sensitive to the change of columnar passages inlet and outlet area ratio.The stall vortex range in the columnar passages increases with the increase of the area ratio.The relative velocity curve of different radius in YCP1.0 columnar passages is smoother with time,and the pressure pulsation in the columnar passages is related to the relative velocity carried by the stall vortex,that is,the larger the relative velocity,the higher the peak pressure pulsation,and the results show that the performance of non-diffusion columnar passages is better than that of involute columnar passages and introductory columnar passages.Through the above research,it can not only deepen the understanding of the performance of the centrifugal pump with the impeller of co lumnar passages by technicians,but also provide corresponding reference for the optimization of the centrifugal pump with the impeller of columnar passages in engineering practice.