Graphical-and-Analytical Method for Designing Reinforced-Concrete Scroll Casings of Water Turbines Based on Laws of Variation in Cross-Section Average Tangential Velocities

Abstract

A new graphical-and-analytical method for design of reinforced-concrete scroll casings with trapezoidal cross-sections of water turbines is proposed. This method generalizes the methods currently used to determine the trapezoidal cross-section dimensions of scroll casings, given the dimensions of their inlet cross-section. This method allows considering different laws of variation in the cross-section average tangential velocity along the scroll length: the velocity can increase, be constant, decrease, or vary differently within different sections of the scroll. The necessary formulas are derived by an analytical method. The design procedure is described by way of examples.