No abstract

The pump-turbine is the core component of a pumped storage power station. This paper considers an in-depth analysis of the rotor-stator interaction characteristics under computational fluid dynamics (CFD) and experimental measurements of pump-turbine with splitter blades used in a domestic pumped storage power station. The results show that as the guide blade opening increases, the rotor-stator interaction of the pump-turbine intensifies and the magnitude of the runner radial force and its pulsation amplitude as well as the magnitude of the guide blade water moment and its pulsation amplitude also increase. In addition, when the opening degree increases from 9.8° to 17.5°, the influence on the main frequency is mainly reflected in the phase change. While the opening degree increases from 17.5° to 24.8°, the influence on the main frequency is mainly reflected in the amplitude change. Moreover, the amplitude of 5fn at opening 9.8° and opening 24.8° is greater than the optimal opening 17.5°, indicating that deviation from the optimal opening will aggravate the difference of rotor-stator interaction between splitter blades and guide blades. In the paper, the influence of guide blade openings on the rotor-stator interaction between the splitter guide blade is studied, which provides a theoretical reference for the stable operation of the pump-turbine.

From the numerical calculations of a common centrifugal pump, the energy loss characteristics have been investigated by applying entropy generation theory to examine the loss due to the direct, turbulence, and wall friction dissipation rates. The turbulent and wall friction entropy dissipations contribute higher values compared with the direct entropy dissipation rate. The turbulent and wall friction entropy dissipations yielded 54.629% and 44.654%, respectively, at the design flow rate; however, the direct entropy dissipated the least of about 0.716%. This indication proves that these entropy variables affect the irreversible energy losses produced. Meanwhile, the entropy production rate distribution was compared with that pressure fluctuation and vortex characteristics and revealed that the region near the volute tongue interface is associated with high losses at all studied flow rates (0.8Qd, 1.0Qd, and 1.2Qd), especially under part-load conditions. The wall of the volute reveals maximum losses at different time steps at the design point. Furthermore, the trailing edge of the blade records the maximum pressure fluctuation, while the leading-edge records moderate intensities. Most regions in the pressure fluctuation intensity distribution reveal a common tendency with the entropy dissipated; thus, there is a high correlation between entropy production and pressure fluctuation. Moreover, the suction side of the impeller records the maximum entropy coefficient at the leading edge compared to the pressure side under the span view. This indicates that the suction side is also responsible for the high energy loss in the impeller flow passages and corresponds to the flow separation, which leads to vortex patterns recognized close to the hub of the blade. This study widens the assessment of the energy loss and can further contribute to the optimization of the hydraulic structures of centrifugal pumps.

The pumped hydro energy storage is the most effective way to store large-scale electricity and has been widely used in the world. As the key equipment in the pumped hydro energy storage, it is significant and urgent to improve the performance and operation stability of the pump-turbine. In this study, the effect of runners with and without splitter blade on the performances and inner flow characteristics of a pump-turbine in pump mode was analyzed by the method of numerical calculation. The results suggest that larger tangential velocity at runner outlet and higher pressure at the trailing edge of pressure side in splitter blade runner scheme contribute to higher head. The area of backflow at runner outlet, the highest values of entropy generation rate, and vorticity distribution in splitter blade runner scheme are well smaller than those in prototype runner without splitter blade, which is conducive to improving model performance.

The operation of water-jet propulsion can generate nonuniform inflow that may be detrimental to the performance of the water-jets. To reduce disadvantages of the nonuniform inflow, a rim-driven water-jet propulsion was designed depending on the technology of passive magnetic levitation. Insufficient understanding of large performance deviations between the normal water-jets (shaft) and permanent maglev water-jets (shaftless) is a major problem in this paper. CFD was directly adopted in the feasibility and superiority of permanent maglev water-jets. Comparison and discussion of the hydraulic performance were carried out. The shaftless duct firstly has a drop in hydraulic losses (1), since it effectively avoids the formation and evolution of the instability secondary vortex by the normalized helicity analysis. Then, the shaftless intake duct improves the inflow field of the water-jet pump, with consequencing the drop in the backflow and blocking on the blade shroud. So that the shaftless water-jet pump delivers higher flow rate and head to the propulsion than the shaft. Eventually, not only can the shaftless model increase the thrust and efficiency, but it has the ability to extend the working range and broaden the high efficiency region as well.