With the development of large-capacity hydro turbines, the hydraulicinstability of hydro turbines has become one of the most important problems that affect the stableoperation of the hydro-electric units. The hydrauli...With the development of large-capacity hydro turbines, the hydraulicinstability of hydro turbines has become one of the most important problems that affect the stableoperation of the hydro-electric units. The hydraulic vibration and unstable operation of Francishydro turbines are primarily caused by the unsteady pressure pulsations inside draft tubes. Theforced rotating vortex core at the runner exit and the channel vortices inside Francis turbinerunners are origins of the unsteady pressure pulsations when operating at partial load. This paperbriefly analyzes the hydraulic instability of operation caused by the vortex core and channelvortices at partial load, then, presents a way to estimate the hydraulic stability by calculation ofthe flow behavior at the runner exit. The validity of estimation is examined by comparison withexperimental data. This will be helpful to evaluate the alternative design and predict the hydraulicstability for both the prototype and model hydro turbines.展开更多
Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation （LES） to investigate the spatial and temporal distributions of the turbulence when strongly distorted wak...Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation （LES） to investigate the spatial and temporal distributions of the turbulence when strongly distorted wakes in the inflow sweep over the passage, In a suitable consideration of the energy exchanging mechanism between the large and small scales in the complicated passage with a strong 3-D curvature, one-coefficient dynamic Sub-Grid-Scale （SGS） stress model was used in this article. The simulations show that the strong wakes in the inflow lead to a flow separation at the leading zone of the passage, and to form a primary vortex in the span-wise direction. The primary span-wise vortex evolves and splits into smaller vortex pairs due to the constraint of no-slip wall condition, which triggers losing stability of the flow in the passage. The computed pressures on the pressure and suction sides agree with the measured data for a working test turbine model.展开更多
文摘With the development of large-capacity hydro turbines, the hydraulicinstability of hydro turbines has become one of the most important problems that affect the stableoperation of the hydro-electric units. The hydraulic vibration and unstable operation of Francishydro turbines are primarily caused by the unsteady pressure pulsations inside draft tubes. Theforced rotating vortex core at the runner exit and the channel vortices inside Francis turbinerunners are origins of the unsteady pressure pulsations when operating at partial load. This paperbriefly analyzes the hydraulic instability of operation caused by the vortex core and channelvortices at partial load, then, presents a way to estimate the hydraulic stability by calculation ofthe flow behavior at the runner exit. The validity of estimation is examined by comparison withexperimental data. This will be helpful to evaluate the alternative design and predict the hydraulicstability for both the prototype and model hydro turbines.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50579025 and 90210005 ).
文摘Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation （LES） to investigate the spatial and temporal distributions of the turbulence when strongly distorted wakes in the inflow sweep over the passage, In a suitable consideration of the energy exchanging mechanism between the large and small scales in the complicated passage with a strong 3-D curvature, one-coefficient dynamic Sub-Grid-Scale （SGS） stress model was used in this article. The simulations show that the strong wakes in the inflow lead to a flow separation at the leading zone of the passage, and to form a primary vortex in the span-wise direction. The primary span-wise vortex evolves and splits into smaller vortex pairs due to the constraint of no-slip wall condition, which triggers losing stability of the flow in the passage. The computed pressures on the pressure and suction sides agree with the measured data for a working test turbine model.
