Mumbai University > Mechanical Engineering > SEM 6 > Thermal and Fluid Power Engineering

Marks: 5M

The main classification of water turbines depend upon the type of action of the water on the turbine. These are mainly categorized into two categories

1. Impulse turbine:

   In this case, the total potential energy of water is converted to kinetic energy in the nozzles. The impulse due to the high velocity jet coming out of the nozzles is used to turn the turbine wheel. The pressure inside the turbine is atmospheric. It is found suitable in when the available potential energy is high and flow available is comparatively low. E.g. Pelton wheel

2. Reaction Turbines:

   In these turbines, water enters the runner under pressure having some velocity head. While the water passes over the runner, its pressure is gradually converted into velocity head until its pressure is reduced to atmospheric pressure alongwith the change in K.E based on its absolute velocity.

These turbines are classified on various parameters:

Based on Direction of Flow of Water Through the Runner:

1. Radial flow:

   • Inward radial flow: E.g. Old francis turbine, Girard radial flow turbine, etc.
   • Outward radial flow: E.g Fourneyron turbine

2. Axial Flow Turbines:

   These are also called as parallel flow turbines. E.g Kaplan and propeller turbines

3. Mixed Flow Turbines:

   E.g Modern francis turbine

Based on Available Head and Discharge

Reaction turbines are used for low and medium heads.

1. Medium Head Turbines:

   60m-250m- Medium flow rate E.g. Modern Francis

2. Low Head Turbines:

   Head<60m- Large flow rates E.g. Axial flow Kaplan and propeller turbines.

Based on Specific Speed, Ns:

1. Pelton turbine, Ns=9 to 35
2. Francis turbine, Ns=50 to 250
3. Kaplan turbine, Ns=250 to 850

Based on position of Shaft

1. Horizontal shaft type
2. Vertical shaft type