Study on Output Characteristics of an Undershot Water Turbine for Extra-Low Head

Abstract

In order to recover the small hydraulic energy in extra-low head but enough flow rate, the output characteristics of a semi-immersion type undershot water turbine was evaluated by the water funnel test. The momentum of the main flow was exchanged to the output power of the water turbine by the primary blade faced to the main flow. In the case of such kind of water turbine, it is effective to design the number of blades appropriately small number not to be impeded the conversion from the momentum of the main flow to the angular momentum of the primary blade. Furthermore, we clarified that when the pitch angle of the primary blade is designed to be perpendicular to the main flow, it is possible to effectively recover the small hydraulic energy of extra-low head.