Performance Prediction for an Archimedes Screw Turbine Based on Hydrostatic Pressure “Second Report: In Case With Consideration of Losses”

Abstract

The Archimedes screw turbine differs considerably from other water turbines in terms of its structure. In this report, its unique losses are defined, and a calculation method for each loss is proposed. The larger the number of blades, the smaller is the water level difference between the upstream and the downstream sides of the blade. Therefore, if the blade tip clearance is constant, there is a reduction in leakage because of the decreasing pressure difference, and the discharge efficiency is increased. In addition, the boundary layers on the casing wall surface are scraped away by the blades. This causes loss, and a prediction method for shaft power is proposed, considering this loss. It was confirmed that the shaft power predicted using this method and the shaft power obtained experimentally are in good agreement over a wide range of rotational speeds, except for the low speed range.