What is a Francis Turbine?
A Francis Turbine is a type of reaction turbine in which inward flow (of water) is mixed.
Mixed flow means a combination of both axial and radial.
It is mainly used for electrical power generation.
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Operating parameters of Francis Turbine
Head: 40 m to 600 m
RPM: 75 to 1000
Power output: Few KW to 800 MW
Working principle of Francis Turbine
As discussed above, It is a type of reaction turbine.
A reaction turbine is a type of turbine in which the working fluid comes to the turbine under great pressure and the energy is extracted by the turbine blades from the working fluid (generally water).
Unlike Pelton turbine in which all the energy of the working fluid is transferred to the rotating wheel in a single impulse, in a Francis turbine energy transfer occurs gradually from inlet to outlet.
Parts of Francis Turbine
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As shown in above diagram of Francis turbine, below are its important parts.
- Turbine runner
- Runner cone
- Runner crown
- Runner Bucket
- Wearing rings or seal rings
- Facing plates or curb plates
- Spiral case or scroll case
- Stay vane
- Wicket gate
- Draft tube
- Discharge ring
- Turbine shaft
- Turbine guide bearing
- Wicket gate servomotors
- Servomotor connecting rod
- Wicket gate operating ring or shift ring
- Wicket gate link
- Wicket gate arm
- Packing box or stuffing box (Mechanical seals)
- Head cover
Applications of Francis Turbine
- It is one of the most efficient hydro-turbines
- It works over a wide range of head and flow rate
- It is one of the most widely used turbines used to generate electricity
Advantages of Francis turbine
- Its control is easy even with variable heads
- Very little change in efficiency with time
- It has small runner size
Disadvantages of Francis Turbine
- Its inspection is relatively difficult
- Problem of cavitation
- Water with dirt can create extreme problems to turbine
Below are some questions and answers related to the topic.
Who developed Francis Turbine?
James B. Francis developed Francis turbine.
What is the difference between Francis and Pelton turbine?
Pelton turbine is an impulse turbine while Francis is a reaction turbine.
What is the difference between Francis and Kaplan turbine?
Francis is a mixed flow turbine whereas Kaplan turbine is an axial flow turbine.