Design and Development of Draft Tube for Hydro Power Plant

Abstract

In the present edge it is the need of time to explore more and more of a renewal source of energy, one of them is hydro-energy. The hydropower plants of small to large scale may be used to accomplish the need of hydro-energy. Penstock, main inlet valve, distributer, guide vane, runner and draft tube are important parts of the hydro power plant which affects the efficiency. In hydro turbines, the function of draft tube is to create positive suction pressure utilizing unused kinetic energy at the exit of turbine runner and hence to increase the effective net head on turbine unit. In medium and low head reaction turbine the hydraulic draft tube is also responsible for a large proportion of the total hydraulic loss in the system. The design of the hydraulic draft tube is one of the most challenging task due to the interaction of many complex flow features, such as unsteadiness, turbulence, separation, streamline curvature, secondary flow, swirl, and vortex breakdown. In this dissertation, the design of draft tube for hydro power plant has been calculated considering all related parameters. 3D CAD model has been generated for the same using solid modeling software. Parametric modeling has been implemented to modify the dimensions of components by means of pro-program to reduce geometric modeling time in the redesign. The CFD analysis has been performed for finding the pressure and velocity distribution, which are matching with experimental readings. The draft tube design has been modified based on literature and manufacturing possibilities. Five different cases for draft tube model are proposed and compared to achieve maximum efficiency and pressure at outlet based on CFD analysis. The proposed case five design i.e. sharp heel draft tube is extended with radius at both sides, gives maximum outlet pressure as per analysis results compared to all other concepts.