Optimal design and experiment of long axis centrifugal pump based on differ head

Abstract: In order to make a long axis centrifugal pump have the characteristics of high-efficiency under different conditions, this article investigated the optimization design of a 500GJC-32.3×3 long axis centrifugal pump. We calculated the parameters of a long axis centrifugal pump impeller according to the traditional method, optimization design of 7 parameters: impeller inlet diameter, blade number, blade wrap angle, blade outlet angle, impeller outlet width, impeller outlet with a mean diameter and impeller outlet tilt angle were done by using the orthogonal design method. With the result of an orthogonal test method studied by range analysis, we obtained the primary and secondary order of the impeller geometric parameters which affect the head and efficiency of a long axis centrifugal pump. The primary and secondary order of the factors affecting the efficiency of the design point is blade number > blade outlet angle> impeller outlet width> impeller outlet tilt angle> blade wrap angle> impeller outlet with a mean diameter > impeller inlet diameter, The primary and secondary order of the factors affecting the head of the design point is > blade outlet angle > impeller outlet tilt angle > impeller outlet with a mean diameter > blade wrap angle > impeller outlet width > impeller inlet diameter, According to the orthogonal results, what is needed to get the final optimal combination are as follows: impeller inlet diameter is 345mm, blade number is 6, blade wrap angle is105°, blade outlet angle is 25°, impeller outlet width is 75mm, impeller outlet with a mean diameter is 550mm, impeller outlet tilt angle is 25°. Based on results of the orthogonal design, considering the affections of primary and secondary order of the factors on the efficiency and head, using the control variable method, greater impact parameters on pump performance must be chosen to optimize. Ignoring the effect of the blade number, 6 blades were selected. Then, we changed the unlimited blade number theoretical head of impeller shroud and unlimited blade number theoretical head of impeller hub on the basis of a head difference theory, controlled the secondary parameters unchanged, and then changed blade outlet angle to make all streamlines have the same limited blade number theoretical head. Five different impellers were designed according to the above method, 3D models of different impellers were made by using Pro/E software, models were meshed by using ICEM software, and different impellers were numerically simulated by using ANSYS CFX software. Through comparing the simulation results, we found that the impellers based on the head difference theory had good hydraulic performance, and that an appropriate head coefficient of impeller hub can get the best hydraulic performance. When the appropriate head coefficient is equal to 1.1, a long axis centrifugal pump can get better hydraulic performance. Through the optimization, a better set of parameters were obtained, 3D models were made on the basis of parameters, and the flow field of a long axis centrifugal pump was analyzed by using .numerical simulation technology. By comparing numerical results with experimental results, the result indicated that the two results share the same trend, and the maximum errors of head, efficiency, and axis rate were 4.02%, 5.58% and 3.59% respectively, and when the pump was operating under conditions of (0.8-1.2) times designed rate of flow, the errors of head, efficiency, and axis rate are relatively small. The experimental results showed that when the pump was operating at the designed rate of flow, its head was above 97m, its efficiency was above 82%, the highest efficiency point was 83.22% which occurred at about 1.1 times designed rate of flow, and the curves had a wider high efficiency range and non overload specialty. Therefore, this type of long axis centrifugal pump can meet the design requirements, operate smoothly with high efficiency in both high flow period and drought period, decrease matching motor power and reduce one-time cost. Therefore, the results provide a certain reference for the optimum design of a long axis centrifugal pump.