Numerical parametric study of a Kaplan turbine incorporated with a sub runner considering analysis of hydraulic dissipation
In this paper, a novel approach on Kaplan turbines, proposed and published in a US patent, has been investigated numerically using CFD tool. This approach includes the incorporation of an extra runner, called sub runner, into the main runner of a typical Kaplan turbine. The sub runner, consisting of...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-03-01
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| Series: | Results in Engineering |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2590123025002191 |
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| Summary: | In this paper, a novel approach on Kaplan turbines, proposed and published in a US patent, has been investigated numerically using CFD tool. This approach includes the incorporation of an extra runner, called sub runner, into the main runner of a typical Kaplan turbine. The sub runner, consisting of some blades, performs the task of passive control of the main runner blades' adjustment angle through a control mechanism, attached to the sub runner shaft and its blades, in case of altered operating condition. As a result of this, the main runner can operate at its optimum and maximum hydraulic efficiency at the changed operating condition. For this purpose, it is aimed to extract its underlying passive control logic through investigating the hydrodynamic behavior and flow characteristics within the overall turbine domain numerically, so that the safe and allowable region of the turbine operation is determined. The analysis has been carried out by considering two varying operating parameters i.e., sub runner angular velocity and blades adjustment angle at different on-cam flow rates. It was revealed that placing the sub runner at the bottom of the main runner will not be a practical solution at high angular velocities at low on-cam flow rates. This is due to the development of some unstable and transient flows between the two runners at these velocities, disrupting the sub runner energy extraction performance. Furthermore, overall hydraulic efficiency improvements of 41.7, 24.8, and 18.4 percent could be achieved under the designed adjustment angle of the blades at first, second, and third on-cam flow rates, respectively, by adding the sub runner to the main turbine. Therefore, more design considerations should be made in the minimization of the associated hydraulic losses. |
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| ISSN: | 2590-1230 |