The hump characteristic is one of the main problems for the stable operation of pump turbines in pump mode.However,traditional methods cannot reflect directly the energy dissipation in the hump region.In this paper,3D...The hump characteristic is one of the main problems for the stable operation of pump turbines in pump mode.However,traditional methods cannot reflect directly the energy dissipation in the hump region.In this paper,3D simulations are carried out using the SST k-ω turbulence model in pump mode under different guide vane openings.The numerical results agree with the experimental data.The entropy production theory is introduced to determine the flow losses in the whole passage,based on the numerical simulation.The variation of entropy production under different guide vane openings is presented.The results show that entropy production appears to be a wave,with peaks under different guide vane openings,which correspond to wave troughs in the external characteristic curves.Entropy production mainly happens in the runner,guide vanes and stay vanes for a pump turbine in pump mode.Finally,entropy production rate distribution in the runner,guide vanes and stay vanes is analyzed for four points under the 18 mm guide vane opening in the hump region.The analysis indicates that the losses of the runner and guide vanes lead to hump characteristics.In addition,the losses mainly occur in the runner inlet near the band and on the suction surface of the blades.In the guide vanes and stay vanes,the losses come from pressure surface of the guide vanes and the wake effects of the vanes.A new insight-entropy production analysis is carried out in this paper in order to find the causes of hump characteristics in a pump turbine,and it could provide some basic theoretical guidance for the loss analysis of hydraulic machinery.展开更多
The understanding of hydraulic behavior in the hydro turbine requires the detailed study of fluid flow in the turbine. Previous methods of analyzing the numerical simulation results on the fluid machinery are short of...The understanding of hydraulic behavior in the hydro turbine requires the detailed study of fluid flow in the turbine. Previous methods of analyzing the numerical simulation results on the fluid machinery are short of intuitiveness on energy dissipation.In this paper, the energy dissipation was analyzed based on the entropy production theory. 3-D steady flow simulations and entropy production calculations of the reduced hydro turbine were carried out. The results indicated that the entropy production theory was suitable for evaluating the performance of the hydro turbine. The energy dissipation in the guide vanes area weighted nearly 25% of the whole flow passage, and mainly happened at the head and tail areas of the vanes. However, more than half the energy dissipation occurred in the runner, mostly at the leading edge of runner blade and the trailing edge of run-ner blade. Meanwhile, close to 20% of the energy dissipation occurred in the elbow. And it can be concluded that the method of entropy production analysis has the advantages of determining the quantity of energy dissipation and where the dissipation happens.展开更多
As the pump turbine tends to be operated with high head and high rotational speed, the study of stability problems becomes more important. The pump turbine usually works at operating conditions where the guide vanes e...As the pump turbine tends to be operated with high head and high rotational speed, the study of stability problems becomes more important. The pump turbine usually works at operating conditions where the guide vanes experience strong vibrations. However, most traditional studies were carried out based on constant GVO(guide vane opening) simulations. In this work, dynamic analysis on pressure fluctuation in the vaneless region of a pump turbine model was conducted using a dynamic mesh method in turbine mode. 3D unsteady simulations were conducted where GVO was closed and opened by 1° from the initial 18°. Detailed time domain and frequency domain characteristics on pressure fluctuation in the vaneless region under different guide vane rotational states compared with constant GVO simulations were investigated. Results show that, during the guide vanes oscillating process, the low and intermediate frequency components in the vaneless region are significantly different. The amplitudes of pressure fluctuation are higher than those with constant GVO simulations, which agree better with the experimental data. In addition, the pressure fluctuation increases when GVO is opened, and vice versa. It can be concluded that pressure fluctuation in the vaneless region is strongly influenced by the oscillating of the guide vanes.展开更多
The use of reversible pump turbines(RPT) within pumped storage power plants goes with prolonged periods of off-design operating conditions, which leads to the onset of operating mode-dependent instabilities. In order ...The use of reversible pump turbines(RPT) within pumped storage power plants goes with prolonged periods of off-design operating conditions, which leads to the onset of operating mode-dependent instabilities. In order to decrease the gravity of RPT flow instabilities and associated damages or even completely eliminate them, a deep understanding of its onset and development mechanism is needed. In line with this, the present study seeks to numerically investigate the onset and development mechanism of RPT unsteady flow structures as well as the evolutional characteristics of associated pressure pulsations throughout the RPT complete flow passage, under off-design conditions for three GVOs namely 17, 21, and 25 mm. The study results showed that low torque operating conditions and associated vaneless space back flow structures were the trigger of flow unsteadiness onset within the RPT vaneless space, the instabilities which grew to cause the S-shape characteristics appearance. Moreover, the runner flow unsteadiness was found to decrease with the GVO increase. On the other hand, the GVO increase worsened the pressure pulsation levels within RPT flow zones, where pressure pulsations within the vaneless space and flow zones in its vicinities were found to be the most sensitive to GVO changes.展开更多
基金Supported by National Key Technology R&G Program(Grant No.2012BAF03B01-X)Innovative Research Groups of National Natural Science Foundation of China(Grant No.51121004)
文摘The hump characteristic is one of the main problems for the stable operation of pump turbines in pump mode.However,traditional methods cannot reflect directly the energy dissipation in the hump region.In this paper,3D simulations are carried out using the SST k-ω turbulence model in pump mode under different guide vane openings.The numerical results agree with the experimental data.The entropy production theory is introduced to determine the flow losses in the whole passage,based on the numerical simulation.The variation of entropy production under different guide vane openings is presented.The results show that entropy production appears to be a wave,with peaks under different guide vane openings,which correspond to wave troughs in the external characteristic curves.Entropy production mainly happens in the runner,guide vanes and stay vanes for a pump turbine in pump mode.Finally,entropy production rate distribution in the runner,guide vanes and stay vanes is analyzed for four points under the 18 mm guide vane opening in the hump region.The analysis indicates that the losses of the runner and guide vanes lead to hump characteristics.In addition,the losses mainly occur in the runner inlet near the band and on the suction surface of the blades.In the guide vanes and stay vanes,the losses come from pressure surface of the guide vanes and the wake effects of the vanes.A new insight-entropy production analysis is carried out in this paper in order to find the causes of hump characteristics in a pump turbine,and it could provide some basic theoretical guidance for the loss analysis of hydraulic machinery.
基金supported by the National Key Technology R&D Program of China(Grant No.2007BAA05B07)the National Natural Science Foundation of China(Grant No.51006026)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2012.072)
文摘The understanding of hydraulic behavior in the hydro turbine requires the detailed study of fluid flow in the turbine. Previous methods of analyzing the numerical simulation results on the fluid machinery are short of intuitiveness on energy dissipation.In this paper, the energy dissipation was analyzed based on the entropy production theory. 3-D steady flow simulations and entropy production calculations of the reduced hydro turbine were carried out. The results indicated that the entropy production theory was suitable for evaluating the performance of the hydro turbine. The energy dissipation in the guide vanes area weighted nearly 25% of the whole flow passage, and mainly happened at the head and tail areas of the vanes. However, more than half the energy dissipation occurred in the runner, mostly at the leading edge of runner blade and the trailing edge of run-ner blade. Meanwhile, close to 20% of the energy dissipation occurred in the elbow. And it can be concluded that the method of entropy production analysis has the advantages of determining the quantity of energy dissipation and where the dissipation happens.
基金supported by the National Key Technology R&G Program(Project No.2012BAF03B01-X)Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51121004)
文摘As the pump turbine tends to be operated with high head and high rotational speed, the study of stability problems becomes more important. The pump turbine usually works at operating conditions where the guide vanes experience strong vibrations. However, most traditional studies were carried out based on constant GVO(guide vane opening) simulations. In this work, dynamic analysis on pressure fluctuation in the vaneless region of a pump turbine model was conducted using a dynamic mesh method in turbine mode. 3D unsteady simulations were conducted where GVO was closed and opened by 1° from the initial 18°. Detailed time domain and frequency domain characteristics on pressure fluctuation in the vaneless region under different guide vane rotational states compared with constant GVO simulations were investigated. Results show that, during the guide vanes oscillating process, the low and intermediate frequency components in the vaneless region are significantly different. The amplitudes of pressure fluctuation are higher than those with constant GVO simulations, which agree better with the experimental data. In addition, the pressure fluctuation increases when GVO is opened, and vice versa. It can be concluded that pressure fluctuation in the vaneless region is strongly influenced by the oscillating of the guide vanes.
基金supported by the National Natural Science Foundation of China(Grant No.51606050)Chinese Postdoctoral Science Foundation(Grant No.2016M591527)+2 种基金Heilongjiang Postdoctoral Fund(Grant No.LBH-Z16057)Natural Science Foundation of Heilongjiang Province(Grant No.E2017038)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2019062)
文摘The use of reversible pump turbines(RPT) within pumped storage power plants goes with prolonged periods of off-design operating conditions, which leads to the onset of operating mode-dependent instabilities. In order to decrease the gravity of RPT flow instabilities and associated damages or even completely eliminate them, a deep understanding of its onset and development mechanism is needed. In line with this, the present study seeks to numerically investigate the onset and development mechanism of RPT unsteady flow structures as well as the evolutional characteristics of associated pressure pulsations throughout the RPT complete flow passage, under off-design conditions for three GVOs namely 17, 21, and 25 mm. The study results showed that low torque operating conditions and associated vaneless space back flow structures were the trigger of flow unsteadiness onset within the RPT vaneless space, the instabilities which grew to cause the S-shape characteristics appearance. Moreover, the runner flow unsteadiness was found to decrease with the GVO increase. On the other hand, the GVO increase worsened the pressure pulsation levels within RPT flow zones, where pressure pulsations within the vaneless space and flow zones in its vicinities were found to be the most sensitive to GVO changes.
