| Submersible tubular pump is a new type of pump which combines submersible motor and tubular pump technology.It has the characteristics of low head and large flow.Its structure is compact and the total hydraulic loss of the flow passage is small.In recent years,submersible tubular pumps had been widely used in farmland irrigation,water supply and drainage diversion and municipal engineering.Due to the recent uneven precipitation,the safety and reliability of submersible tubular pumps had been greatly tested.Therefore,it is of great practical significance to study the hydraulic performance of submersible tubular pumps with high specific speed,to explore the stable operation range of submersible tubular pumps,to improve the replaceability of flow passage components and to improve their hydraulic efficiency.The main research work and achievements of this paper were as follows:1.Describing briefly the design procedure of impeller streamline method for tubular pump and building 3D modeling.The computational domain of n_s=1000model was meshed and the grid independence verification was carried out.The three-dimensional constant values were calculated based on N-S basic governing equation and standard k-?turbulence model,and the external characteristics and flow characteristics of internal flow field were analyzed.2.Designed the external characteristic test plan,purchased the test equipment,built the test-bed,carried out the external characteristic test,and counted the external characteristic test data of the pump.Comparisons between the data and the numerical results show that they were in good agreement,which showed that the CFD numerical simulation had accuracy and reference.3.By solving the problem of low actual lift of the original model,and the correction coefficient of circumferential velocity was put forward.For the n_s=1000tubular pump,the optimum circumferential velocity correction coefficient was based on 1.4.At the same time,variable circulation design was adopted to reduce the circulation at hub and increased the circulation at rim..4.Five schemes of hub ratio were designed,the main design parameters of impellers with different hub ratios were calculated separately.The numerical calculation of n_s=1000 submersible tubular pump model with five hub ratios and three flow conditions.The results of external characteristics were analyzed,and the internal flow field law under design conditions was studied.Determining the appropriate hub ratio of n_s=1000 tubular pump is 0.4 and 0.38.5.For n_s=1250 and n_s=1600 tubular pumps,the optimum circumferential velocity correction coefficients were 1.4 and 1.3.The main design parameters of impellers were calculated and analyzed by numerical simulation.The appropriate hub ratio of n_s=1250 model was 0.36 and 0.38,and the appropriate hub ratio of n_s=1600model was 0.36.6.Statistical analysis of the hydraulic performance of n_s=1000,1250 and 1600three kinds of high specific speed submersible tubular pumps showed that:the hub ratio was large,the high efficiency range was narrow,and the high efficiency range shifts to the small flow area;the larger the hub ratio,the larger the slope of the head performance curve,five groups of hub specific head performance curves coincide basically and the efficiency points were not different under design conditions.Reducing the hub ratio of tubular pumps can increase the head performance curve,the running efficiency of tubular pump was improved,however,when the hub ratio decreases excessively,the twist degree of the blade will increase,resulting in fluid flow disorder in the impeller,and resulting in a decrease in the efficiency of the tubular pump. |
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