In this paper,a new method of dynamic mesh based on two functional controls is used in the continuous guide vane closure,and the three-dimensional numerical simulation is carried out to investigate the transient flow ...In this paper,a new method of dynamic mesh based on two functional controls is used in the continuous guide vane closure,and the three-dimensional numerical simulation is carried out to investigate the transient flow characteristics for a Francis-type reversible pump-turbine in the turbine mode in the load regulation scenario,with the detached eddy simulation(DES)turbulent model.The transient flow characteristics during the closure of the guide vanes are illustrated by analyzing the signals of the mass flow,the torque and the pressure fluctuations in the frequency and time-frequency domains.It is shown by the simulated results that a continuous assessment of the transient flow characteristics during the guide vane closure may be made by using the new method of the dynamic mesh.Furthermore,the flow field analysis involves both the onset and the development of the unsteady phenomena progressively based on an organized guide vane closure law.The flow pattern in the return channel maintains a relatively stable flow field before the last stage of the closure,as compared with the unstable flow field in other domains.To identify the unit variation under the fluid-dynamical conditions,the influence of the three-dimensional unsteady flow structures in the passage is analyzed and its evolution during this transient process is characterized by the fluid-dynamics and the spectral analysis.展开更多
Influences of water head variations on the performances of a prototype reversible pump turbine are experimentally studied in generating mode within a wide range of load conditions(from 25% to 96% of the rated power). ...Influences of water head variations on the performances of a prototype reversible pump turbine are experimentally studied in generating mode within a wide range of load conditions(from 25% to 96% of the rated power). The pressure fluctuations of the reversible pump turbine at three different water heads(with non-dimensional values being 0.48, 0.71 and 0.90) are measured and compared based on the pressure data recorded in the whole flow passage of the turbine. Furthermore, effects of monitoring points and load variations on the impeller-induced unstable behavior(e.g. blade passing frequency and its harmonics) are quantitatively discussed. Our findings reveal that water head variations play a significant role on the pressure fluctuations and their propagation mechanisms inside the reversible pump turbine.展开更多
Reversible pump turbines are widely employed in the pumped hydro energy storage power plants. The frequent shifts among various operational modes for the reversible pump turbines pose various instability problems, e.g...Reversible pump turbines are widely employed in the pumped hydro energy storage power plants. The frequent shifts among various operational modes for the reversible pump turbines pose various instability problems, e.g., the strong pressure fluctuation, the shaft swing, and the impeller damage. The instability is related to the vortices generated in the channels of the reversible pump turbines in the generating mode. In the present paper, a new omega vortex identification method is applied to the vortex analysis of the reversible pump turbines. The main advantage of the adopted algorithm is that it is physically independent of the selected values for the vortex identification in different working modes. Both weak and strong vortices can be identified by setting the same omega value in the whole passage of the reversible pump turbine. Five typical modes（turbine mode, runaway mode, turbine brake mode, zero-flow-rate mode and reverse pump mode） at several typical guide vane openings are selected for the analysis and comparisons. The differences between various modes and different guide vane openings are compared both qualitatively in terms of the vortex distributions and quantitatively in terms of the areas of the vortices in the reversible pump turbines. Our findings indicate that the new omega method could be successfully applied to the vortex identification in the reversible pump turbines.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51909222).
文摘In this paper,a new method of dynamic mesh based on two functional controls is used in the continuous guide vane closure,and the three-dimensional numerical simulation is carried out to investigate the transient flow characteristics for a Francis-type reversible pump-turbine in the turbine mode in the load regulation scenario,with the detached eddy simulation(DES)turbulent model.The transient flow characteristics during the closure of the guide vanes are illustrated by analyzing the signals of the mass flow,the torque and the pressure fluctuations in the frequency and time-frequency domains.It is shown by the simulated results that a continuous assessment of the transient flow characteristics during the guide vane closure may be made by using the new method of the dynamic mesh.Furthermore,the flow field analysis involves both the onset and the development of the unsteady phenomena progressively based on an organized guide vane closure law.The flow pattern in the return channel maintains a relatively stable flow field before the last stage of the closure,as compared with the unstable flow field in other domains.To identify the unit variation under the fluid-dynamical conditions,the influence of the three-dimensional unsteady flow structures in the passage is analyzed and its evolution during this transient process is characterized by the fluid-dynamics and the spectral analysis.
基金supported by the National Natural Science Foundation of China(Grant No.51506051)the Fundamental Research Funds for the Central Universities(Grant No.JB2015RCY04)+2 种基金the Open Research Fund Program of Key Laboratory of Fluid and Power Machinery(Xihua University)Ministry of Education(Grant No.szjj-2017-100-1-001)the Open Research Fund Program of State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(Grant No.LAPS16014)
文摘Influences of water head variations on the performances of a prototype reversible pump turbine are experimentally studied in generating mode within a wide range of load conditions(from 25% to 96% of the rated power). The pressure fluctuations of the reversible pump turbine at three different water heads(with non-dimensional values being 0.48, 0.71 and 0.90) are measured and compared based on the pressure data recorded in the whole flow passage of the turbine. Furthermore, effects of monitoring points and load variations on the impeller-induced unstable behavior(e.g. blade passing frequency and its harmonics) are quantitatively discussed. Our findings reveal that water head variations play a significant role on the pressure fluctuations and their propagation mechanisms inside the reversible pump turbine.
基金Project supported by the National Key R&D Program of China(Project No.2018YFB0604304-04)the National Natural Science Foundation of China(Grant No.51506051)
文摘Reversible pump turbines are widely employed in the pumped hydro energy storage power plants. The frequent shifts among various operational modes for the reversible pump turbines pose various instability problems, e.g., the strong pressure fluctuation, the shaft swing, and the impeller damage. The instability is related to the vortices generated in the channels of the reversible pump turbines in the generating mode. In the present paper, a new omega vortex identification method is applied to the vortex analysis of the reversible pump turbines. The main advantage of the adopted algorithm is that it is physically independent of the selected values for the vortex identification in different working modes. Both weak and strong vortices can be identified by setting the same omega value in the whole passage of the reversible pump turbine. Five typical modes（turbine mode, runaway mode, turbine brake mode, zero-flow-rate mode and reverse pump mode） at several typical guide vane openings are selected for the analysis and comparisons. The differences between various modes and different guide vane openings are compared both qualitatively in terms of the vortex distributions and quantitatively in terms of the areas of the vortices in the reversible pump turbines. Our findings indicate that the new omega method could be successfully applied to the vortex identification in the reversible pump turbines.
