Abstract
An improved method for preventing vortex rope formation and alleviating the associated pressure fluctuations in turbine draft tubes is investigated using baffles in the draft tube to hinder the swirling flow emerging from a Francis turbine runner. A strong swirl produces flow instabilities and pressure fluctuations. Partial load operating conditions at the rated water head and three flow rates are taken into consideration. It is demonstrated using a computational fluid dynamics simulation that this method effectively eliminates the vortex rope, particularly when using four baffles. The amplitude of the pressure pulsation in the draft tube modified with four baffles was 0.42 times that in a traditional draft tube. The baffles were found to reduce the tangential velocity of the flow in the draft tube and consequently hinder the development of the fierce swirling flow. This type of decrease is more significant compared to the gradual decay due to viscous effects of the solid wall in a traditional draft tube. The conclusion was verified by the results of experiments conducted using a novel device. The measured increase in turbine efficiency exceeded 3% at the evaluated partial loading point, indicating improved economic performance of the turbine.
Highlights
Hydropower is a readily available source of renewable energy[1] and currently accounts for a significant portion of electricity generation worldwide.[2,3,4] The use of hydropower and other forms of renewable energy such as wind energy, solar energy and geothermal power are rapidly expanding due to their renewable properties and generation without aggravating the greenhouse effect.[5,6] the unpredictable and volatile nature of many renewable energy sources could have an adverse effect on the coordination of energy supply and demand and potentially lead to the tremendous instability of the electrical grid.[6]
In order to confirm the quality of the numerical methodology, simulation results of a Francis turbine with a conventional draft tube are compared with the numerical and experimental solutions under partial load obtained from previous literature
The use of baffles installed on the draft tube wall of a Francis turbine to control the development of the vortex rope was numerically and experimentally investigated
Summary
Hydropower is a readily available source of renewable energy[1] and currently accounts for a significant portion of electricity generation worldwide.[2,3,4] The use of hydropower and other forms of renewable energy such as wind energy, solar energy and geothermal power are rapidly expanding due to their renewable properties and generation without aggravating the greenhouse effect.[5,6] the unpredictable and volatile nature of many renewable energy sources could have an adverse effect on the coordination of energy supply and demand and potentially lead to the tremendous instability of the electrical grid.[6]. When hydropower plants are operated for peak regulation and frequency modulation, hydraulic turbines tend to operate over an extended. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, China. Advances in Mechanical Engineering range of regimes quite far from their best efficiency point (BEP), which can lead to unfavourable issues, including reduction in the overall efficiency of the turbine, rotor–stator interaction (RSI), cavitation, vortex breakdown, and severe vibration and noise.[4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
