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March 27, 2020
A water hydro turbine is a rotary engine that takes energy from moving water. Water Turbines were developed in the nineteenth century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy source. They are also referred as Hydro Turbines or Hydraulic Turbines. Since All water sources vary, so do Water Turbines. These have been designed to suit different Situation.There are two types of water hydro turbine, the reaction water hydro turbine and the impulse water hydro turbine.
Reaction water turbines generate power from the combined action of pressure and moving water. Water flows through the turbine, changes pressure, velocity, and direction. The water flow generates pressure between the front and back of the blades, develops a reverse reaction force on the runner, and thus, forms rotation torque to rotate the runner. With these actions, energy contained in piped water is then converted into mechanical energy or electrical energy. The reaction turbine must be completely enclosed to contain the water pressure and the turbine must be fully submerged in the water flow. Reaction turbines are generally used for applications with lower head and higher flows than impulse turbines. There are four types of reaction turbines: The mixed flow type, the axial flow type, the oblique type, and the flow through type. The reaction turbines have an expansion section (the draft tube) at the exit. The function of the draft tube is to recover the kinetic energy of the flow at the exit of the runner and convert the kinetic energy into pressure to recover it. The kinetic energy recovery of the draft tube has a significant effect on the efficiency of the turbine.
Reaction Turbines - Reaction Turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow. Most Water Turbines in use are Reaction Turbines and are used in low (<30m/98ft) and medium (30-300m/98-984ft) head applications. In reaction turbine pressure drop occurs in both fixed and moving blades.
Only kinetic energy of water is used by the impulse turbine. Impulse turbines change the velocity of a high-pressure water jet. Before reaching the turbine blades, nozzles are used to convert the potential energy of high pressure water into kinetic energy. No pressure change occurs at the turbine blades, and the turbine does not require housing for operation. The high-pressure water jet pushes on the blades of the turbines. The direction of the flow is changed. The resulting change in momentum results in a force exerted on the turbine blades and leads to the turbine spinning. In impulse turbines, water is not required to fill the chamber of the turbine. Water flows through the impulse turbine and loses all pressure. The discharge water of the impulse turbine is normally at atmospheric pressure. Impulse turbines are generally suitable for high head, low flow rate applications. There are three types of impulse water turbines: Shear type, oblique type, and the combination of shear and oblique types.
Impulse Turbines - Impulse turbines change the velocity of a water jet. The jet advances on the turbine's curved blades which change the direction of the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy. Prior to hitting the turbine blades, the water's pressure (potential energy) is converted to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the turbine blades, and the turbine doesn't require a housing for operation. Impulse turbines are most often used in very high (> 300m/984ft) head applications.