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

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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Performance and Flow Field of a Gravitation Vortex Type Water Turbine

International Journal of Rotating Machinery ◽

10.1155/2017/2610508 ◽

2017 ◽

Vol 2017 ◽

pp. 1-11 ◽

Cited By ~ 15

Author(s):

Yasuyuki Nishi ◽

Terumi Inagaki

Keyword(s):

Free Surface ◽

Flow Field ◽

Simple Structure ◽

Low Flow ◽

Flow Area ◽

Turbine Efficiency ◽

Water Turbine ◽

Low Head ◽

Type Water ◽

Turbine Output

A gravitation vortex type water turbine, which mainly comprises a runner and a tank, generates electricity by introducing a flow of water into the tank and using the gravitation vortex generated when the water drains from the bottom of the tank. This water turbine is capable of generating electricity using a low head and a low flow rate with relatively simple structure. However, because its flow field has a free surface, this water turbine is extremely complicated, and thus its relevance to performance for the generation of electricity has not been clarified. This study aims to clarify the performance and flow field of a gravitation vortex type water turbine. We conducted experiments and numerical analysis, taking the free surface into consideration. As a result, the experimental and computational values of the torque, turbine output, turbine efficiency, and effective head agreed with one another. The performance of this water turbine can be predicted by this analysis. It has been shown that when the rotational speed increases at the runner inlet, the forward flow area expands. However, when the air area decreases, the backward flow area also expands.

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Study on an Undershot Cross-Flow Water Turbine with Straight Blades

International Journal of Rotating Machinery ◽

10.1155/2015/817926 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 4

Author(s):

Yasuyuki Nishi ◽

Terumi Inagaki ◽

Yanrong Li ◽

Kentaro Hatano

Keyword(s):

Flow Field ◽

Output Power ◽

Cross Flow ◽

Open Channels ◽

Small Scale ◽

Hydroelectric Power ◽

Turbine Efficiency ◽

Water Turbine ◽

Low Head ◽

Hydroelectric Power Generation

Small-scale hydroelectric power generation has recently attracted considerable attention. The authors previously proposed an undershot cross-flow water turbine with a very low head suitable for application to open channels. The water turbine was of a cross-flow type and could be used in open channels with the undershot method, remarkably simplifying its design by eliminating guide vanes and the casing. The water turbine was fitted with curved blades (such as the runners of a typical cross-flow water turbine) installed in tube channels. However, there was ambiguity as to how the blades’ shape influenced the turbine’s performance and flow field. To resolve this issue, the present study applies straight blades to an undershot cross-flow water turbine and examines the performance and flow field via experiments and numerical analyses. Results reveal that the output power and the turbine efficiency of the Straight Blades runner were greater than those of the Curved Blades runner regardless of the rotational speed. Compared with the Curved Blades runner, the output power and the turbine efficiency of the Straight Blades runner were improved by about 31.7% and about 67.1%, respectively.

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Performance and Flow Field of Gravitation Vortex Type Water Turbine using Volute Tank

International Journal of Fluid Machinery and Systems ◽

10.5293/ijfms.2021.14.3.229 ◽

2021 ◽

Vol 14 (3) ◽

pp. 229-246

Author(s):

Yasuyuki Nishi ◽

Daichi Sukemori ◽

Terumi Inagaki

Keyword(s):

Flow Field ◽

Water Turbine ◽

Type Water

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Improvement of Torque Performance of a Vertical Axis Type Marine Turbine for a Water Current Generation System

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 3 ◽

10.1115/omae2010-20474 ◽

2010 ◽

Author(s):

Tomoki Ikoma ◽

Shintaro Fujio ◽

Koichi Masuda ◽

Chang-Kyu Rheem ◽

Hisaaki Maeda

Keyword(s):

Turbine Blades ◽

Angle Of Attack ◽

Cross Flow ◽

Vertical Axis ◽

Hydrodynamic Forces ◽

Water Current ◽

Current Channel ◽

Marine Current ◽

Water Turbine ◽

Type Water

This paper describes the possibility of an improvement of torque performance and hydrodynamic forces on a vertical axis type water turbine, used for marine current generating system. The water turbine analyzed here is based on a Darrieus turbine with vertical blades. We considered possibilities of controlling the angle of attack of blades in order to improve the starting performance and to reduce energy loss during the rotation of the turbine. We used blade-element/ momentum theory in order to investigate the variations appearing in torque performance when the angle of attack were controlled. We also proved the validity of our predictions of hydrodynamic forces on the blade and the turbine, made through CFD calculation, by comparing them with the results of corresponding model tests in a current channel. In the corresponding model test we investigated not only the hydrodynamic forces on the turbine with three fixed blades, but also the inline force and the cross-flow force on the rotating turbine with three blades. Regarding the cyclic pitching of turbine blades, results suggest that significant increase in average turbine torque is possible.

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