I am left with one special turbine which is the revolutionary cause to Kaplan Turbine. I guess, you came to know about the turbine, i.e. Francis Turbine. Francis Turbine is a water type turbine. It was developed by James. B. Francis of University of Lowell, Massachusetts. As I have said earlier, the names of the machines or equipment is named under the person who invented it. The same way this turbine is named after him as Francis Turbine. Sir Francis, while studying the Boyden turbine, got an interest to redesign and increase the efficiency. He achieved the efficiency of astonishing 88% from 66% of Boyden Turbine. This turbine is an inward flow reaction turbine which combines both radial and axial flow concepts. Now-a-days, these turbines are most commonly used as they can operate till 2000 ft heads.
The Francis Turbines are mostly and primarily used for electrical power production. It produces the power output in the range of 10 to 750 megawatts. Further experimenting, Francis developed the mixed flow type reaction turbine which later became an American standard. He stands the first place in the Alumni of University of Massachusetts, Lowell in USA and later on, his work on turbines was published as “The Lowell Hydraulic Experiments “in 1855.
Its Operation is also very simple. It is a type of reaction turbine in which the working fluid comes to turbine under very extreme and immense pressure and so the energy is extracted by the moving turbine blades and vanes from the working fluid. We know the Newton’s Third law. For every action there is an equal and opposite reaction. So a part of energy is wasted by the fluid because of all the pressure variations occurring in the blades of the turbine. This is also known as Degree of Reaction. The remaining part of energy is extracted as power from the turbine. At the exit of the water, it acts on the spinning cup shaped runner, which leaves at low velocity and low swirl too, thereby with little kinetic and potential energy remained.
In the above Paragraph, we see the energy from the water is not utilized to the top. Francis turbine converts energy from water at high pressure heads which are not so easily available. So a turbine which helps even at low heads are to be invented and during this phase Kaplan was introduced. It will be introduced and briefly explained in the next post. Now let us see some advantages and disadvantages of Francis Turbine.
Advantages of Francis Turbine
- It is mostly used turbine all over the world as its efficiency is greater than all other turbines.
- There is an effective use of water pressure and velocity.
- It is now an American Standard Turbine.
- Its efficiency is nearly 94% when used to the Everest.
Disadvantages of Francis Turbine
- Its cost is very high.
- Its operation is simple but the design is very complex.
- Large number of moving parts are present.
- Its maintenance and repair is difficult task and expensive too.
- It is applicable to medium head levels only.