What is Francis Turbine and it's advantages & disadvantages ?

                       In this content, you can learn about introduction of Francis turbine and it's advantage & disadvantages.

          Francis Turbine

         Francis Turbine consists of scroll casing, guide vanes, runner and draft tube. It has fixed blades i.e. runner where water under pressure enters. The runner through number of guide vanes in radial direction and leave in axial direction. 

                            The runner blade convert hydraulic  energy into mechanical energy of rotation by reaction shaft is made of steel and connect turbine to the generator. At exit point water has some velocity and hence possess some energy is recovered by draft tube beyond exit of runner. 

   The hydraulic efficiency varies between 85-90%. It is medium head turbine. It works under medium discharge. It is radially inward or mixed flow turbine.

              Figure:- Francis Turbine runner

          Francis Turbine consists horizontal or vertical shaft. The runner blades of Francis turbine are not adjustable. The number of runner blades are(16 to 24). It is centripetal type. The specific speed of Francis turbine is in between 50 to 200 m.

  Advantage of Francis Turbine

Advantages of Francis turbine are as follows :-

(1) Head variation is easily controlled.

(2) When there is large variation in tail water level as compare to total head, operating head can utilized. 

(3) Economical as size of runner, generator and power plant required is small.

(4) Mechanical efficiency due to wear does not decrease as like pelton wheel.

(5) Ratio of maximum and minimum operating head may be two.

     Disadvantages of Francis Turbine

 Disadvantages of Francis turbine are as follows :-

(1) Sediment may wear high head turbine rapidly.

(2) Inspection and repair is tedious.

(3) More susceptible to water hammer effect.

(4) Cavitation problem is more.

(5) Efficiency is reduced if run below 50%of load.

Conclusion:-

 you have learnt about introduction of Francis Turbine and it's advantages and disadvantages.