Computational and Experimental Analysis of Conical Draft Tube's Effect on Conical Basin of Gravitational Water Vortex Turbine

This paper presents an insight into the performance of the Gravitational Water Vortex Turbine (GWVT), a type of Ultra-Low Head (ULH) turbine, with and without the implementation of draft tube. Till date, no attention has been given on the effect of draft tube on GWVT. A model of GWVT along with a conical basin is developed on CATIA v5, and then subjected to a series of computational studies on ANSYS 2020R2. A similar setup is constructed in which a straight divergent draft tube is installed at the exit of the conical basin. The numerical approach suggested that maximum efficiency of the setup in the former case was 72.0% at 53 RPM whereas the efficiency in the latter case was 79.0% at 65 RPM. The increase in the efficiency was calculated to be 9.72%. This conclusion was validated through experimental verification conducted at Himalaya College of Engineering, Chyasal on a pre-fabricated test-rig of capacity 480 L, where the maximum efficiency of 69.4% and 64.5% were obtained with and without the installation of the draft tube respectively. Consequently, an increase of 7.59% in the efficiency of GWVT as an effect of draft tube was observed experimentally. It can be concluded that draft tube plays a vital role in the efficiency of the Gravitational Water Vortex Turbine.