The meshing of total flow field is shown in Fig. 3. When meshes are more than 3,000,000 and the variation range of head is within 1 %, it is thought that mesh is independent. Under design condition, steady numerical simulation method is adopted to calculate pump head so as to minimize the impact of mesh size on computational accuracy.
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Due to the complex structure of computational domain in the internal flow field of the mixed-flow pump, unstructured meshing is adopted for impeller, guide vane and bending section, while structured meshing is adopted in the inlet section and outlet section, TGrid software is used in mesh interface of computational domain between impeller and guide vane for seaming, and local refinement is used in critical area. The total flow field comprises of inlet section, impeller, guide vane, bending section and outlet section. Based on previous researches, this paper carries out numerical simulation for internal flow of a mixed-flow pump under different guide vane thickness using Fluent software, researches the pressure pulsation characteristics of impeller inlet and outlet and the middle flow field of guide vane, and analyses the influence rules of guide vane thickness on pressure pulsation of a mixed-flow pump, thus to provide reference for the optimal design and stable operation of mixed-flow pumps. studied pressure pulsation characteristics of non-steady flow fields of an axial-flow pump using transient flow analysis theory related to time and LES method. Therefore they further verify the feasibility of numerical simulation method on the pressure pulsation research of centrifugal pumps. The results indicated that pressure pulsation amplitude under blade passing frequency can be successfully acquired within a large flow range using numerical simulation method. investigated the pressure fields of a centrifugal pump by tests and numerical simulations and compared their numerical results with tests. With the development of CFD technology in recent years, it is proved that gaining pressure pulsation mechanism of interior flow field through the research of interior unsteady flow characteristics of vane pump is one of the valid research methods.
However, for a long time, the researches have focused on the impact of unstable flow under off-design conditions on pump performance but neglected the performance degradation and damage of pumps caused by the rotor-stator interaction between impeller and guide vane. With the increase of capacity and size of single-machine, the fluid exciting vibration is becoming one of the severe issues for large mixed-flow pump units and other turbo-machinery such as wind turbine, whose operation stability and vibration problems have drawn more and more attention. Mixed-flow pumps are widely used in agricultural irrigation and drainage, municipal water supply and drainage, ships and warships water-jet propulsion, seawater desalinization system, circulating water system of thermal power generation, pumped-storage power station and nuclear power plants. Keywords: guide vane thickness, mixed-flow pump, pressure pulsation, numerical simulation. Therefore, appropriately reducing the thickness of guide vane is beneficial to the stability of the internal flow of guide vane. Compared with the thinning guide vanes, the pressure pulsation amplitude of the thicken guide vane increase 7.8 %. The thickness of the guide vane have less influence on pressure pulsation in the inlet of impeller, and have more influence on pressure pulsation in the middle of guide vane. The dominant frequency of pressure pulsation was approximate to the impeller blade passing frequency. The results show that the type of numerical simulation grid, turbulence model can accurately predict the internal flow characteristics of the mixed-flow pump. By setting pressure measurement points, the pressure pulsation characteristics in the impeller inlet, outlet and the middle of guide vane were discussed and the influence of the guide vanes’ thickness on pressure pulsation was analyzed. The unsteady flow field in a mixed-flow pump with different guide vane thicknesses was numerically simulated based on the standard k- ε turbulence model, the SIMPLE algorithm and the sliding mesh technique. The pressure pulsation is one of the key factors affecting instability operation and vibration of large mixed-flow pump units in pumped-storage power station.
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