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| Effects of number of blades on performance of waterwheel based on volume of fluid model |
| ZHAO Mengshang1, ZHENG Yuan2*, YANG Chunxia2, ZANG Wei1 |
| 1. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2. College of Energy and Electrical Engineering, Hohai University, Nanjing, Jiangsu 211100, China |
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Abstract Unsteady fluid flows around waterwheels in an open channel were simulated numerically in Fluent based on volume of fluid(VOF)model to study the waterwheel-based power generation device by utilizing micro-head in this paper. The SST k-ω two-equation turbulence model and sliding mesh were adopted to carry out unsteady flow simulations when the waterwheels were with different numbers of blades and at different rotational speeds. The results indicate that the 3-bladed waterwheel has the best optimal efficiency and the widest optimal efficiency zone. Since the local turbulent viscosity in the upstream of the 3-bladed waterwheel is larger, the range of influence generated by the waterwheel in the channel is smaller. For the 8-bladed waterwheel, however, the average turbulent viscosity in the upstream is fair, the range of the influence is larger. Under the same working condition, adding more blades can intensify the waterwheel blockage effect to the stream and elevate the average water level difference between upstream and downstream significantly, but suppress the fluctuation of water level difference. An increased average water level difference will reduce the waterwheel power-output, and the fluctuation of water level difference can affect adversely the operational stability of the waterwheel rotator system. Under the same working condition, increasing number of blades can suppress the fluc-tuation of torque but reduce the power-output. Torque fluctuation is due to the action of imbalanced moments experienced by the waterwheel in operation, which may result in severe vibration of the waterwheel structure and fatigue damage to the blades.
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Received: 05 August 2019
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