civil - Applied Hydraulic Engineering: Turbines

Francis Turbine

   Posted On :  13.07.2016 06:09 pm
Francis Turbine

The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, MA. It is an inward-flow reaction turbine that combines radial and axial flow concepts.

Francis Turbine

 

The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, MA. It is an inward-flow reaction turbine that combines radial and axial flow concepts.

 

Francis turbines are the most common water turbine in use today. They operate in a head range of ten meters to several hundred meters and are primarily used for electrical power production.

 

. The inlet is spiral shaped. Guide vanes direct the water tangentially to the turbine wheel, known as a runner. This radial flow acts on the runner's vanes, causing the runner to spi n. The guide vanes (or wicket gate) may be adjustable to allow efficient turbine operation for a range of water flow conditions.

 

As the water moves through the runner, its spinning radius decreases, further acting on the runner. For an analogy, imagine swinging a ball on a string around in a circle; if the string is pulled short, the ball spins faster due to the conservation of angular momentum. This property, in addition to the water's pressure, helps Francis and other inward-flow turbines harness water energy efficiently. Water wheels have been used historically to power mills of all types, but they are inefficient.

 

Nineteenth-century efficiency improvements of water turbines allowed them to compete with steam engines (wherever water was available).

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. In 1848 James B. Francis, while working as head engineer of the Locks and Canals company  in    the  water-powered  factory  city  of  Lowell,          Massachusetts,  improved on  these designs to create a turbine with 90% efficiency. 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 exactly match a site's flow conditions.

 

The Francis turbine is a reaction turbine, which means that the working fluid changes pressure as it moves through the turbine, giving up its energy. A casement is needed to contain the water flow. The turbine is located between the high-pressure water source and the low-pressure water exit, usually at the base of a dam.

 

The inlet is spiral shaped. Guide vanes direct the water tangentially to the turbine wheel, known as a runner. This radial flow acts on the runner's vanes, causing the runner to spin. The guide vanes (or wicket gate) may be adjustable to allow efficient turbine operation for a range of water flow conditions.

 

As the water moves through the runner, its spinning radius decreases, further acting on the runner. For an analogy, imagine swinging a ball on a string around in a circle; if the string is pulled short, the ball spins faster due to the conservation of angular momentum. This property, in addition to the water's pressure, helps Francis and other inward-flow turbines harness water energy efficiently.

 

 




Tags : civil - Applied Hydraulic Engineering: Turbines
Last 30 days 111 views

​ReadOrRefer.in

OTHER SUGEST TOPIC