ABSTRACT
Reaction turbine runners are designed to make use of both the pressure energy and kinetic energy of the water flow. The inlet structure, consisting of a spiral casing and a wicket gate with guide vanes designed to introduce swirl or circulation as the water enters the runner, typically transforms only a part of the hydraulic pressure into kinetic energy as the water passes through it. As a result, the flow velocity at the runner inlet is relatively low for reaction turbines compared to impulse turbines. The runner converts the remaining pressure head to kinetic energy and ultimately transforms both the pressure and velocity of the water into mechanical power. To extract the maximum power from the available head, hydraulic pressure is often below atmospheric when the water exits the runner. This is accomplished through the use of a draft tube, described in Section 11.2.
