Redesign of Sharp Heel Draft Tube — Results from Tests in Model and Prototype

Draft tubes with a sharp heel are quite common in hydro power stations constructed 50 years ago. This design reduced both construction time and investment. We have shown that there is potential for increasing unit performance by a moderate modification of such draft tubes. The redesign has been done with the aid of model tests in a turbine rig. The new design has been installed in a 50 MW hydro unit and an efficiency improvement in the order of 0.5% has been verified through accurate measurements.