A reaction turbine is a rotating engine that harnesses the energy of fluids by utilizing Newton's Third Law of Motion, which states that every action has an equal and opposite reaction. The reaction turbine is designed to allow streams of pressurized fluid to turn the rotor. Usually, the fluid nozzles are attached to the rotor and face opposite the direction of rotation. As the fluid leaves the nozzle, the resulting reaction force causes the rotor to turn. The system takes advantage of the change in water pressure as it flows through the turbine.
Most reaction turbines generate electricity. Many even transmit that electricity into the energy grid. There are three main types of reaction turbines: propeller, kinetic, and Francis.
A propeller reaction turbine generally consists of a propeller, with three to six blades, that is situated in a tube. The water flow is controlled by wicket gates that are located upstream of the propeller. Most models of propeller reaction turbines feature fixed wicket gates, while a few models, including the Kaplan reaction turbine, feature adjustable wicket gates and rotor blades. The Kaplan turbine is typically used in specialized scenarios that require fine blade adjustments for efficient energy production.
Additional types of propeller reaction turbines include the bulb turbine, which typically consists of a turbine and generator that operates in the water stream. The straflo turbine is similar, except that the generator is placed on the exterior of the turbine. A tube turbine features a direct connection to the generator.
The Francis reaction turbine was invented by James B. Francis in 1848. It can be implemented either horizontally or vertically, depending on the application. Typically, there are two water contact stages in the Francis reaction turbine. As the water enters the top of the turbine, and when the water empties from the bottom of the turbine, energy is transferred, thereby resulting in the movement of the turbine. Generally, a Francis reaction turbine consists of a runner, several guide vanes, a scroll tube, wicket gates, and draft tube.
Kinetic reaction turbines utilize the kinetic energy in running water, rather than the potential energy, to generate electricity. Typically, these turbines are placed in rivers, tidal waters, or ocean currents to take advantage of the natural flow of water. They do not require additional infrastructure to operate, thus reducing the potential impact on the environment. The speed of the water flow dictates the specification of the kinetic turbine. Periods of flooding and drought typically need to be considered before a person implements a kinetic turbine system.