Question

Which of the following hydraulic turbine has lowest specific speed: 
1. Kaplan turbine
2. Propeller turbine
3. Impulse turbine
4.

Answer 1

Correct Answer - Option 3 : Impulse turbine

Classification of turbines on the various basis is given in the table below:

Flow	Energy	Head	Specific speed	Example
Tangential	Impulse	High (300 m and above)	Low (0 – 60 RPM)	Pelton Wheel turbine
Radial	Reaction	Medium (30 m to 300 m)	Medium (60 – 300) RPM	Francis turbine
Axial	Reaction	Low (less than 30 m)	High
			(300 – 600) RPM	Propeller turbine
			(600 – 1000) RPM	Kaplan turbine

From the above table, it is clear that, impulse turbine has lowest specific speed.