Water ow stabilization using submerged weir for draft-tube reaction hydraulic turbine

Abstract

In turbine engineering, draft-tube downstream runs under extreme water ow pressure and velocity, causing vibration and pressure variation in di erent operation frequencies. The practical challenge of obtaining stabilized water ow is an ongoing domain of research. This paper investigates a proposition of applying a submerged weir at the downstream end of the draft-tube reaction turbine. The main goal of this research is to reduce variations in water ow pressure, velocity, and shear distribution in accordance with the effect of the upstream water level. Two types of turbines, including vertical Kaplan and Francis turbine units, are examined. ANSYS CFX software tool is used to build three-dimensionally (3D) numerical models for the Kaplan and Francis turbines by building a submerged weir at the outlet of the draft tubes based on three di erent height suggestions. The effect of the proposed submerged weir on the ow through these turbines is studied by considering the dimensions of their components including the penstock with inlets, spiral casing, shafts and blades, and the draft tube with outlets. The ndings of this research are signi cant enough to solve the problem of negative pressure pulsation in the draft tube of Kaplan and Francis turbines types.