Flow in open channel near draft tube outlet of low head turbine.

Rectangular sharp-crested weir used for flow measurement in flume is limited by the minimum head since head- discharge relation of clinging flow is different from free flow. Hydraulic characteristics of clinging flow under low head are studied via experiments associated with simulation in six rectangular sharp-crested weirs with different geometric parameters. The results show that head-discharge relation is stable under clinging flow; head relation between clinging and free flow is linearly correlated at the same discharge in a bistable regime, existing discharge formula of free flow can be applied to clinging flow by means of head transform; the pressure on downstream weir plate is negative, much less than atmosphere pressure, and flow regime can be judged based on the pressure. It is feasible to automatically measure large and small flow using the simplest weir without head limitation.

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Study on the Flow Field of an Undershot Cross-Flow Water Turbine

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.620.285 ◽

2014 ◽

Vol 620 ◽

pp. 285-291 ◽

Cited By ~ 1

Author(s):

Yan Rong Li ◽

Yasuyuki Nishi ◽

Terumi Inagaki ◽

Kentarou Hatano

Keyword(s):

Free Surface ◽

Flow Field ◽

Water Depth ◽

Open Channel ◽

Rotation Speed ◽

Cross Flow ◽

Water Turbine ◽

Low Head ◽

New Type ◽

Type Water

The purpose of this investigation is to research and develop a new type water turbine, which is appropriate for low-head open channel, in order to effectively utilize the unexploited hydropower energy of small river or agricultural waterway. The application of placing cross-flow runner into open channel as an undershot water turbine has been under consideration. As a result, a significant simplification was realized by removing the casings. However, flow field in the undershot cross-flow water turbine are complex movements with free surface. This means that the water depth around the runner changes with the variation in the rotation speed, and the flow field itself is complex and changing with time. Thus it is necessary to make clear the flow field around the water turbine with free surface, in order to improve the performance of this type turbine. In this research, the performance of the developed water turbine was determined and the flow field was visualized using particle image velocimetry (PIV) technique. The experimental results show that, the water depth between the outer and inner circumferences of the runner decreases as the rotation speed increases. In addition, the fixed-point velocities with different angles at the inlet and outlet regions of the first and second stages were extracted.

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Numerical Optimization of the Inlet Velocity Profile Ingested by the Conical Draft Tube of a Hydraulic Turbine

Journal of Fluids Engineering ◽

10.1115/1.4029837 ◽

2015 ◽

Vol 137 (7) ◽

Cited By ~ 5

Author(s):

Sergio Galván ◽

Marcelo Reggio ◽

Francois Guibault

Keyword(s):

Velocity Profile ◽

Flow Rate ◽

Numerical Optimization ◽

Draft Tube ◽

Velocity Profiles ◽

Plant Performance ◽

Swirl Number ◽

Inlet Velocity ◽

Turbine Performance ◽

Low Head

Past numerical and experimental research has shown that the draft tube inlet velocity is critically important to hydropower plant performance, especially in the case of low-head installations. However, less is known about the influence of flow parameters on turbine performance particularly swirl distribution. Based on the influence of draft tube flow characteristics on the overall performance of a low-head turbine, this research proposes a methodology for optimizing draft tube inlet velocity profiles as a new approach to controlling the flow conditions in order to yield better draft tube and turbine performance. Numerical optimization methods have been used successfully for a variety of design problems. However, addressing the optimization of boundary conditions in hydraulic turbines poses a new challenge. In this paper, three different vortex equations for representing the inlet velocity profile are applied to a cone diffuser, and the behavior of the objective function is analyzed. As well, the influence of the quantitative correlation between the swirling flow at the cone inlet and the analytical blade shape, flow rate, and swirl number using the best inlet velocity profiles is evaluated. We also include a discussion on the development of a flow structure caused by the inlet swirl parameters. Finally, we present an analysis of the influence of flow rate and swirl number on the behavior of the optimization process.

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