Performance Analysis of Gravitational Water Vortex Turbine using OpenFOAM

Abstract

A Gravitational Water Vortex Turbine is a new development that extracts power from artificially formed water vortex when the water from open flow channel directed tangentially to a round basin and discharges through the hole provided at the bottom of the basin. This can harness hydro power in application range of low to ultralow head and median to low flows and has the unique feature of leaving positive environmental impact through the aeration of water as it passes through the turbine. However, the presence of free–surface vortex in the flow field complicates its design from conventional impulse and reaction turbines perspective due to vortex-blade interaction. Recent investigations have indicated that curved blade profiles are more efficient to harness the kinetic energy of the vortex. However, little amount of work has been done on the optimization of suitable runner for the free–surface vortex profile considering the vortex-blade interaction, the ratio of runner diameter to basin diameter (blade area) and its effect on torque and power output. In this study, the performance of Gravitational Water Vortex Turbine has been investigated nu merically using OpenFOAM. The effect of design parameters such as vortex-blade interaction, the ratio of runner diameter to basin diameter on the performance parameters such as effective head, torque, power and efficiency has been characterized. As a result, it is found out that a small blade size runner has higher rotational speed due to the strength of vortex was higher in the vicinity of air core but produces less torque. However, a large blade size runner has less rotational speed and high torque due to the nature of vortex tangential velocity field decrease with increasing radius and large blade area respectively. In addition, this work identified extending the size of runner blades to the far–field region resulting in reduction of power output. Therefore, the outcomes from this study will be helpful to design and establish performance analysis for the Gravitational Water Vortex Power Plant for a given flow and head of particular hydropower site. Moreover, it can also be used as pointer for the future generations of Gravitational Water Vortex Turbine technology.