Lieblein J. and Zelen A. conducted a study of the fatigue life of deep groove ball bearings. This study was based on data of 4948 bearings as obtained from 5 companies and 213 test groups. Among these data is a detail...Lieblein J. and Zelen A. conducted a study of the fatigue life of deep groove ball bearings. This study was based on data of 4948 bearings as obtained from 5 companies and 213 test groups. Among these data is a detailed test report #3183, lot 73, consisting of 23 failed bearings. This report states that the Weibull slope of this group is 2.23, meaning that this distribution is mono sloped. These test data were plotted by the author on a bilinear scale plane, of endurance life versus bearing number and proved to be distinctly bi sloped. This basic difference prompted a wide study resulting in several new findings and set the grounds for a new analysis method.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
文摘Lieblein J. and Zelen A. conducted a study of the fatigue life of deep groove ball bearings. This study was based on data of 4948 bearings as obtained from 5 companies and 213 test groups. Among these data is a detailed test report #3183, lot 73, consisting of 23 failed bearings. This report states that the Weibull slope of this group is 2.23, meaning that this distribution is mono sloped. These test data were plotted by the author on a bilinear scale plane, of endurance life versus bearing number and proved to be distinctly bi sloped. This basic difference prompted a wide study resulting in several new findings and set the grounds for a new analysis method.
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.
