| This research was supported by National Science and Technology Support Project of China(2015BAD20B01) et al. As an important part of water conservancy, pumping system plays a more and more critical role in the human transformation of nature as well as in the field of inter basin water transfer project, urban water supply and drainage, industrial water supply, et al. These years, with the construction of much more large water projects, pumping system with unidirectional outlet and inlet passages cannot fulfill the need of various projects, like large water transfer projects which contain irrigation and drainage of extra large flood years. Therefore, more attention is paid to the vertical axial flow pumping system with reversible inlet and outlet passages, and because of the advantages of their compact structure, space saving and low cost et al. these pumping systems are rapidly applied in the irrigation and drainage fields. Generally, pumping system efficiency to a large degree is decided by the hydraulic performance of passages, and now those studies about internal flow characteristics of two-way passages are not comprehensive, which hinder the performance improvement of two-way passages pumping system, so it is meaningful to analyze the effect of two-way passages on axial flow pumping system. Besides, there will be strong flow turbulence in outlet passage when two-way passages pumping system is operating, and pump shaft exposed in outlet passage will bear unbalanced radial force, which will cause pump shaft and system vibration, even bearing and packing abrasion, thus it is important to analyze the unsteady internal flow of pumping system as well as the hydraulic vibration.The main research contents and conclusions of this paper are as follows:1. Two models with the same impeller and guide-vanes were selected to be researched for the first time, which were called pump section and pump system with reversible passages respectively. SST k-ω turbulent model was chosen to do the unsteady simulation. And three monitoring points were then setting on the plane of impeller inlet and guide-vanes outlet, the interface of impeller and guide-vanes to predicate pressure fluctuation of internal unsteady flow between two models. The comparison of performance curve on simulated and experimental data of two pump models was acquired and analyzed. It shows that both of calculated head and efficiency of the axial flow pump have a good agreement with the experimental results, which indicates that the calculation is reasonable for hydraulic characteristics of this axial flow pump and can be used to perform detail analysis. Besides, the head and efficiency of pumping system are basically lower than that of pump section. Moreover, there are more vortexes in reversible passages with more unsteady flow and stronger pressure fluctuation intensity, and the fluctuation amplitude in the pumping system is larger than that in pump section, and it is revealed that reversible passages have strong influence near guide-vanes outlet but has little effect on pressure fluctuation near impeller inlet.2. Because of the shape of the two-way passages, unsteady flow is easy produced in impeller inlet which will cause impeller vibration, and the impeller vibration will affect the internal flow of pumping system. A coupled solution of flow field and structural response of impeller was firstly established by two-way coupling method to study the effect of FSI(Fluid-structure Interaction)of impeller on flow field in pumping system with two-way passages. The distribution on flow field in pumping system and the pressure on impeller blades were analyzed, compared with the calculated results without FSI. The analysis results indicate that after FSI, the pressure and vorticity gradient in the outlet of two-way inlet passage increase respectively, and the velocity in pressure side of blades increases which results in the change of vortex position near diffuser vane. Besides, the pressure difference between pressure side and suction side of impeller blades decreases with head of pumping system dropping.3. After studying the internal flow change of pumping system under the coupling response of impeller and flow, the distribution of stress and deformation of impeller were further investigated based on above coupling method.The analysis results show that axial force changes periodically with the rotation of impeller, and the maximum equivalent stress is mainly distributed near the hub, and the maximum deformation is mainly distributed in the interaction between leading edge and flange. With the flow rate increasing, the maximum equivalent stress and the maximum deformation of impeller decrease gradually. In addition, the equivalent stress of 4 monitoring points located at leading edge and trailing edge of impeller are studied. The contrast results show that on the impeller, the equivalent stress in leading edge is much higher than that in trailing edge.4. In this research, the above two-way passages vertical pumping system is still used to establish a combined calculation for turbulent flow and structure response of pump shaft for the first time by the same two-way coupling method. The static pressure and velocity distributions in outlet passage, pressure fluctuation and TKE(Turbulence Kinetic Energy) distributions on plane of diffuser outlet were analyzed, compared with the results without FSI. It shows that the area of bigger static pressure in outlet passage increases, and few changes are found on velocity distribution. The phrase of pressure fluctuation on plane of diffuser outlet changes obviously with the fluctuation intensity increasing. On the condition of small flow rate, TKE on plane of diffuser outlet grows with FSI, while few changes on the condition of design and big flow rate. In addition, good agreement of pumping system performance between simulation and experimental results illustrates the reliability of calculation. Overall, the flow field distribution has changed after FSI, thus FSI simulation can better show the real flow field for axial-flow pumping system with two-way passages. |
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