Flow Analysis in Asymmetric and Symmetric Bifurcation with Varied Layout: A Case Study of Daram Khola HEP

Abstract

A bifurcation is used whenever it is needed to divide the fluid flow into more than one turbines for power generation, taking the water from a single reservoir or head works. Bifurcation is one of the critical parts of a hydropower project which contributes to head loss in the penstock manifold. The design and layout of a bifurcation are determined by the available head of water, flow rate, geological constraints and fabrication and economic constraints. The design of a bifurcation can be done conventionally using analytical techniques, design codes and guidelines. Nowadays with the advancement of computing devices, computational methods along with relevant software applications can be used for the design process for more accurate results. In this study, a case of Daram Khola HPP has been considered where the layout of bifurcation is mainly constrained by the geological arrangement that are the axis of penstock pipe, axes of the two turbine inlets and the center to center distance between the two turbine inlets. First, an asymmetric bifurcation layout is developed which is modeled and analyzed to determine head loss and flow distribution pattern in the two branch pipes. Modeling is done in ANSYS SpaceClaim and fluid flow analysis incorporating Computational Fluid Dynamics is carried out in ANSYS Fluent. The asymmetric layout is revised by changing the angle of bifurcation to 45° and similar analysis are performed. These layouts are further revised by incorporating symmetric bifurcation with angle of bifurcation 60° and adding a bend pipe just upstream of the