Hydraulic Turbine Working Principle
The hydraulic turbine is a motor device that is responsible for transforming kinetic energy into potential energy. It takes energy from a fluid, usually water, transforming it into rotating energy . This movement mobilizes a machine or an electric generator so that the rotating mechanical energy becomes electrical energy. Hydroelectric turbines are the fundamental piece of a hydroelectric power station.
What is a hydraulic turbine for?
The hydraulic turbine has the function of harnessing the energy of the fluid that passes through it to produce rotation energy. This dynamic energy is converted into electrical energy thanks to a generator that allows this energy modification.
Put simply: A hydraulic turbine serves to convert potential energy into kinetic energy and electrical energy. This mechanism is used by hydroelectric power plants to take energy from falls and water currents and obtain electrical energy.
How does a hydraulic turbine work?
The hydraulic turbine is fixed in a strategic place, where water flows or there is a fall of it. When the liquid passes through its mechanism, the rotor blades or vanes suffer a drop in the pressure that drives them and causes the turbine to spin.
As the medium moves faster, the pressure drop will be greater and the rotational speed higher. This rotation energy is captured by a generator or a machine that is responsible for transforming dynamic energy into electrical energy. You can see how a hydraulic turbine works here.
Parts of a hydraulic turbine
- Distributor: This is an element that does not move, it does not produce mechanical work and lacks angular velocity. It serves to accelerate the flow of water by completely or partially transforming potential energy into kinetic energy. The distributor directs the water to another component called the impeller and acts as a flow regulator. The shapes of the distributor can vary, in the action turbines it can be injector and in the reaction turbines it can be axial, semi axial or radial.
Rodete: The basic element of hydraulic turbines is known as impeller, wheel or rotor. This is essentially a disc that has a system of vanes, blades or spoons and is animated by a certain degree of angular velocity. The hydraulic energy that comes from the fluid or water jump is transformed into mechanical energy just in the impeller. It can be by acceleration and deviation or simply by the deviation of the liquid flow as it passes through the vanes.
Suction tube: It is a component almost always found in the reaction turbines, is installed after the impeller and has a divergent duct shape. It has a straight or angled shape and is responsible for rescuing the height between the rotor outlet and the level of the drain channel. It also recovers part of kinetic energy belonging to the residual fluid velocity at the rotor outlet. Eventually, the suction tube can be found in the action turbines in a cylindrical shape.
Housing: It is the component that is responsible for supporting and covering the parts of the turbine. In certain models, such as Kaplan and Francis, it has a spiral shape.
Types of hydraulic turbines
The hydraulic turbine is a subset of the turbo machines, so its classification is similar. They are divided taking into account the change in impeller pressure or the degree of reaction and according to the rotor design.
Hydraulic turbines according to the degree of reaction
Depending on how the turbine shaft is positioned, they can be vertical axis or horizontal axis turbines. They can also be classified according to the direction in which the fluid enters, so these can be:
Radial-axial turbines: It is when the fluid enters the rotor radially and then changes its direction and exits parallel to the rotary axis, that is, axially or in the same direction of the axis.
Axial turbines: The fluid will flow parallel or in the same direction of the axis of rotation.
Tangential Turbines: When the fluid hits the rotor in the periphery.
Hydraulic turbines according to their reactivity
This may be the most important classification of hydraulic turbines, they are two models: Action and reaction.
- Action: In this case, the fluid moves the turbine by directly hitting the rotor blades. In this particular case, it is necessary that there is a high drop of the fluid so that it hits strongly.
- Reaction: Here the fluid is going to move the impeller, not by blow, but by reaction caused by the exit of water on the rotor. It is necessary that there is a large flow of fluid so that you can push the water into the pipes, get out with a lot of pressure and move the rotor with force. In this case, the height does not matter so much, because the blades will not be hit directly. The important thing is that there is sufficient water flow.
Models of hydraulic turbines
Hydraulic turbines are presented in different models that integrate the characteristics mentioned above. Each type of turbine is used according to the need and the way in which the fluid is presented.
Kaplan turbine: It is a turbine of the axial type that, in addition, has the particularity of varying the angle of the blades while operating. It has been designed to be used in small waterfalls, but with large flows. It is a reaction turbine.
Propeller turbine: With adjustable valves, as in the previous case, but with the fixed vane angle. Instead of changing the angle, it is possible to change the speed of the impeller.
Pelton turbine: It is a turbine with the transverse flow, with partial admission. It is said that it has spoons instead of shovels or blades. They are designed for large waterfalls, but small flows. It is considered an action turbine.
Francis turbine: For mixed flow and reaction. There are elaborate designs that allow changing the angles of the pallets during operation. Work with jumps and medium flows.
Ossberger / Banki / Michell turbine: It is a turbine with free deviation, partial and radial admission. It is considered a slow speed turbine by the number of specific revolutions. It has been designed for medium jumps.
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