Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe condition...Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps,particularly at low flow rates where backflow vortices form near the impeller inlet.This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump.Results show that backflow vortices form when the flow rate decreases to 0.59Q_(d).As the flow rate further declines,the backflow vortex progresses upstream,contracts,and rebounds.The flow rate range is divided into three stages:Stage Ⅰ with no backflow vortex,stage Ⅱ with initial vortex development extending upstream and relatively fragmented,and stage Ⅲ with vortex contraction and rebound forming a more coherent structure.Besides,backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 fb.They exhibit a three-dimensional spiral motion involving changes in axial length,self-rotation,and revolution around the pump axis,with an angular velocity of approximately half the impeller’s rotational speed.This work enhances insights into backflow vortex behaviors,which is essential for optimizing pump design and improving operational stability in challenging environments.展开更多
The hydraulic force on the reversible pump turbine might cause serious problems（e.g., the abnormal stops due to large vibrations of the machine）, affecting the safe operations of the pumped energy storage power plan...The hydraulic force on the reversible pump turbine might cause serious problems（e.g., the abnormal stops due to large vibrations of the machine）, affecting the safe operations of the pumped energy storage power plants. In the present paper, the hydraulic force on the impeller of a model reversible pump turbine is quantitatively investigated through numerical simulations. It is found that both the amplitude of the force and its dominant components strongly depend on the operating conditions（e.g., the turbine mode, the runaway mode and the turbine brake mode） and the guide vane openings. For example, the axial force parallel with the shaft is prominent in the turbine mode while the force perpendicular to the shaft is the dominant near the runaway and the turbine brake modes. The physical origins of the hydraulic force are further revealed by the analysis of the fluid states inside the impeller.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.U22B6010)supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.025GJHZ2022118FN)the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(Grant No.2021CXLH0003).
文摘Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps,particularly at low flow rates where backflow vortices form near the impeller inlet.This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump.Results show that backflow vortices form when the flow rate decreases to 0.59Q_(d).As the flow rate further declines,the backflow vortex progresses upstream,contracts,and rebounds.The flow rate range is divided into three stages:Stage Ⅰ with no backflow vortex,stage Ⅱ with initial vortex development extending upstream and relatively fragmented,and stage Ⅲ with vortex contraction and rebound forming a more coherent structure.Besides,backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 fb.They exhibit a three-dimensional spiral motion involving changes in axial length,self-rotation,and revolution around the pump axis,with an angular velocity of approximately half the impeller’s rotational speed.This work enhances insights into backflow vortex behaviors,which is essential for optimizing pump design and improving operational stability in challenging environments.
基金Project supported by the National Natural Science Foun-dation of China(Project No.51506051)
文摘The hydraulic force on the reversible pump turbine might cause serious problems（e.g., the abnormal stops due to large vibrations of the machine）, affecting the safe operations of the pumped energy storage power plants. In the present paper, the hydraulic force on the impeller of a model reversible pump turbine is quantitatively investigated through numerical simulations. It is found that both the amplitude of the force and its dominant components strongly depend on the operating conditions（e.g., the turbine mode, the runaway mode and the turbine brake mode） and the guide vane openings. For example, the axial force parallel with the shaft is prominent in the turbine mode while the force perpendicular to the shaft is the dominant near the runaway and the turbine brake modes. The physical origins of the hydraulic force are further revealed by the analysis of the fluid states inside the impeller.
