Theresearch Of Hydraulic Performance About Muiti-stage Centrifugal Pump

Multi-stage centrifugal pumps are widely used in every sector of the national economy. It is an effective way to save energy and reduce emission by improving the efficiency of the centrifugal pump. Since the structure of the centrifugal pump is complex and there are many constraining factors in the process of hydraulic design, it may be difficult to improve the overall efficiency of the centrifugal pump. Therefore, it has important theoretical and realistic significance in improving the technical level of the general pump industry by conducting simulation on the internal flow of the centrifugal pump, revealing the flowing mechanism and exploring the main components inside multi-stage centrifugal pump that results in the loss of energy and its influence on the performance of the pump.By using Turbo Grid, UG and ICEM, modeling and mesh generation were first conducted on the suction casing, impeller, guide vanes and final stage of the guide vane and the discharging casing of a5-stage centrifugal pump. Then, on the basis of the standard k-ε flow model, numerical calculations were conducted on the three dimensional incompressible flow fields inside the centrifugal pump at different flowing points; an analysis was made on the internal flow and the external characteristics of the multi-stage centrifugal pump and the influence of the suction casing and the guide vane on the back impeller were calculated respectively. According to the results of the calculation, the variation trend is found to be consistent by comparing the head curve, the efficiency curve with the experimental data curve. Besides, the calculated results of the head and the efficiency curves are larger than the actual test results. The error within the high efficient range did not reach out of7%. The main reason is that the computing model does not simulate the flow within gaps, thus calculation can not be done on the corresponding hydraulic loss and volume loss.The flow of the high efficiency range in the first stage is consistent with that of the second stage, which indicates that the cooperation between guide vanes is reasonable. Computational analysis was made on the energy loss of different flow passage components, showing that energy loss in the guide vanes is the largest, followed by the discharging casing. Through analysis on the flow, it is found out that the internal flow field of the passageway in the guide vanes is non-uniform with large-scale reflux and vortex, indicating that the vanes do not coordinate very well with the impeller and there may exist problems in the process of vane designing; the flow field of the discharging casing is also non-uniform with very serious vortex and flow separation phenomena, and furthermore, there exists peripheral speed at the outlet, which has certain impact on the energy recovery of discharging casing and increases the hydraulic loss. The analysis was also made on the influence of the suction casing and guide vanes on the back impeller regarding its hydraulic performance. According to the analysis results, it is showed that there exists hydraulic loss inside the suction casing and the guide vanes themselves, which further influences the performance of the back impeller. Among the two, the guide vanes have the largest influence on the back impeller.According to the research, it shows that the numerical calculation models and methods used in this paper can predict more accurately the internal flow field and the hydraulic performance of multi-stage centrifugal pumps. Such design is feasible, but it is also worth mentioning that there exist defects in the designing of the guide vanes and the discharging stage. So, improvement should be further made.