1) Impulse Turbine
Definition
An impulse turbine is a hydraulic turbine in which the entire energy of water is converted into kinetic energy before striking the turbine runner.

Principle
It works on Newton’s Second Law of Motion (change in momentum).
Water from a high head is converted into a high-velocity jet using a nozzle. This jet strikes the turbine blades (buckets), causing the runner to rotate. The pressure of water remains constant (atmospheric) while passing over the blades.

Example
Pelton wheel is the most common impulse turbine.

Applications
Used in high head (above 300 m) and low flow conditions
Installed in mountainous hydroelectric power plants
Suitable for small and large hydro power generation

2) Francis Turbine
Definition
The Francis turbine is a reaction turbine in which water flows radially inward and energy is transferred through both pressure and kinetic energy.

Principle
It works on the reaction principle.
Water enters the runner through guide vanes under pressure. As water flows over the blades, both pressure and velocity change, causing rotation. It operates fully submerged in water.

Inventor
Developed by James B. Francis.

Applications
Used for medium head (30–300 m) and medium flow
Most commonly used turbine in hydroelectric power plants
Suitable for large power generation stations

3) Kaplan Turbine
Definition
The Kaplan turbine is an axial-flow reaction turbine with adjustable blades.


Principle
It works on the reaction principle.
Water flows parallel to the shaft (axial flow). The blades are adjustable, allowing high efficiency even when water flow changes. Both pressure and kinetic energy help rotate the runner.

Inventor
Invented by Viktor Kaplan in 1913.

Applications
Used for low head (below 30 m) and high flow conditions
Ideal for river-based power plants
Used in dams and large irrigation projects