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Introduction ( diapositiva 1) The Francis turbine is a type of water turbine. Francis turbines are the most common water turbine in use today. They operate in a water head from 40 to 600 m and are primarily used for electrical power production. Francis turbines are almost always mounted with the shaft vertical to isolate water from the generator. This also facilitates installation and maintenance. Aplicacion Francis turbines may be designed for a wide range of heads and flows. This, along with their high efficiency, has made them the most widely used turbine in the world. Francis type units cover a head range from 40 to 600 m, and their connected generator output power varies from just a few kilowatts up to 800 MW.[2] Large Francis turbines are individually designed for each site to operate with the given water supply and water head at the highest possible efficiency, typically over 90%. In contrast to the Pelton turbine, the Francis turbine operates at its best completely filled with water at all times. The turbine and the outlet channel may be placed lower than the lake or sea level outside, reducing the tendency for cavitation. In addition to electrical production, they may also be used for pumped storage, where a reservoir is filled by the turbine (acting as a pump) driven by the generator acting as a large electrical motor during periods of low power demand, and then reversed and used to generate power during peak demand. These pump storage reservoirs act as large energy storage sources to store "excess" electrical energy in the form of water in elevated reservoirs. This is one of a few methods that allow temporary excess electrical capacity

Partes A Francis turbine consists of the following main parts: Spiral casing: The spiral casing around the runner of the turbine is known as the volute casing or scroll case. Throughout its length, it has numerous openings at regular intervals to allow the working fluid to impinge on the blades of the runner. These openings convert the pressure energy of the fluid into momentum energy just before the fluid impinges on the blades. This maintains a constant flow rate despite the fact that numerous openings have been provided for the fluid to enter the blades, as the cross-sectional area of this casing decreases uniformly along the circumference. Guide or stay vanes: The primary function of the guide or stay vanes is to convert the pressure energy of the fluid into the momentum energy. It also serves to direct the flow at design angles to the runner blades. Runner blades:Runner blades are the heart of any turbine. These are the centers where the fluid strikes and the tangential force of the impact causes the shaft of the turbine to rotate, producing torque. Close attention in design of blade angles at inlet and outlet is necessary, as these are major parameters affecting power production.

Draft tube: The draft tube is a conduit that connects the runner exit to the tail race where the water is discharged from the turbine. Its primary function is to reduce the velocity of discharged water to minimize the loss of kinetic energy at the outlet. This permits the turbine to be set above the tail water without appreciable drop of available head.

14- 10 – 8 Ventajas y desventajas ventajas 

Su diseño hidrodinámico permite bajas perdidas hidráulicas, por lo cual se garantiza un alto rendimiento.  Su diseño es robusto, de tal modo se obtienen décadas de uso bajo un costo de mantenimiento menor con respecto a otras turbinas.  Junto a sus pequeñas dimensiones, con lo cual la turbina puede ser instalada en espacios con limitaciones físicas, también permiten altas velocidades de giro.  Junto a la tecnología y a nuevos materiales, las nuevas turbinas requieren cada vez menos mantenimiento.1 Desventajas

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No es recomendado para alturas mayores de 800 m, por las presiones existentes en los sellos de la turbina. Hay que controlar el comportamiento de la cavitación. No es la mejor opción para utilizar frente a grandes variaciones de caudal debido a que el rendimiento cae al disminuir el caudal de diseño, por lo que se debe tratar de mantener un flujo de caudal constante previsto, antes de la instalación

Origins Water wheels of different types have been used historically for more than 1,000 years to power mills of all types, but they were relatively inefficient. Nineteenth-century efficiency improvements of water turbines allowed them to replace nearly all water wheel applications and compete with steam engines wherever water power was available. After electric generators were developed in the late 1800s turbines were a natural source of generator power where potential hydro-power sources existed. In 1826 Benoit Fourneyron developed a high efficiency (80%) outward-flow water turbine. Water was directed tangentially through the turbine runner, causing it to spin. Jean-Victor Poncelet designed an inward-flow turbine in about 1820 that used the same principles. S. B. Howd obtained a US patent in 1838 for a similar design. In 1848 James B. Francis, while working as head engineer of the Locks and Canals company in the water wheel-powered textile factory city of Lowell, Massachusetts, improved on these designs to create more efficient turbines. He applied scientific principles and testing methods to produce a very efficient turbine design. More importantly, his mathematical and graphical calculation methods improved turbine design and engineering. His analytical methods allowed confident design of high efficiency turbines to precisely match a site's water flow and pressure (water head). https://www.ntnu.no/documents/381182060/1267681377/HYDRAULIC+TURBINES_Her mod+Brekke+-+2015.pdf/656e691a-f52f-4c0d-a6b1-eaf069c08ef5

paginas para ver https://www.gerenewableenergy.com/hydro-power/large-hydropower-solutions/hydroturbines/francis-turbine