Draft Tubes of Water Turbines in Underground and Semi-Underground Powerhouses

Abstract

The effect of the centerline radius, bend angle, and diffuser length of high draft tubes in underground and semi-underground powerhouses on head losses is studied analytically. It is established that the dependence of the head losses on the diffuser length does not depend on the capacity, flow rate, and runner diameter of the water turbine; therefore, the diffuser length should be consistent with the construction conditions, but no greater than 35 – 40 m. The centerline radius r₀ of the elbow increases with its bend angle α.