Start Date

2018 9:40 AM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

The occurrence of a vortex at an intake may lead to air-entrainment and reduce the discharge rate through the intake. Entrained air entering the high-speed penstock flow may cause serious damage to either the water conveyance system or the turbines in the hydropower station. As the submergence at the intake decreases, the vortex increases in power. At the critical submergence, the rotational velocity of the vortex reduces the pressure at the centre of the vortex sufficiently to result in a lowering of the water surface and the formation of an air-core that, at the limit, allows air to enter the intake. In this experimental research, the effect on the critical submergence of the intake shape and of geometrical parameters (length, height, mesh solidity and perforation diameter) of a cross-vane vortex inhibitor have been studied. Comparing the experimental results to a vertical pipe intake indicated that the critical submergence is somewhat reduced for an ogee-shape intake at low flow rates, and that the ogee intake with a cross-vane vortex inhibitor significantly reduces the critical submergence, the reduction increasing as Froude number decreases (for Fr = 0.5 to 3.2) with little dependence of the geometry of the cross-vanes (within the parameter range studied).

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May 17th, 9:40 AM

An Experimental Study of the Performance of an Ogee-Shaped Vertical Intake: Geometrical Parameters of Cross-Vane Vortex Inhibitor

The occurrence of a vortex at an intake may lead to air-entrainment and reduce the discharge rate through the intake. Entrained air entering the high-speed penstock flow may cause serious damage to either the water conveyance system or the turbines in the hydropower station. As the submergence at the intake decreases, the vortex increases in power. At the critical submergence, the rotational velocity of the vortex reduces the pressure at the centre of the vortex sufficiently to result in a lowering of the water surface and the formation of an air-core that, at the limit, allows air to enter the intake. In this experimental research, the effect on the critical submergence of the intake shape and of geometrical parameters (length, height, mesh solidity and perforation diameter) of a cross-vane vortex inhibitor have been studied. Comparing the experimental results to a vertical pipe intake indicated that the critical submergence is somewhat reduced for an ogee-shape intake at low flow rates, and that the ogee intake with a cross-vane vortex inhibitor significantly reduces the critical submergence, the reduction increasing as Froude number decreases (for Fr = 0.5 to 3.2) with little dependence of the geometry of the cross-vanes (within the parameter range studied).