Steam turbines are generally classified on the basis of action of steam on moving blades. On the basis of this, steam turbines are divided into two categories.
These are:
- Impulse turbines
- Reaction turbines
Contents
Key Differences between Impulse and Reaction Turbines
| Impulse turbines | Reaction turbines |
|---|---|
| Steam is completely expanded in the stationary nozzles | Steam is partially expanded in the stationary nozzles |
| Pressure over the moving blades remains constant | Steam momentum causes reaction force on moving blades which sets motion in the rotor |
| Steam causes impulsive force | Steam causes a reaction force |
Working of Impulse Turbines
Steam is allowed to expand complete in the stationary nozzles. The pressure over the moving blades is forced to remain constant. As a result, the steam attains a high velocity and intrudes against the moving blades. An impulse force is created on moving blades which produced rotation in rotor.
Working of Reaction Turbines
Unlike impulse turbine, in a reaction turbine, the steam is not completely expanded, here the steam is partially expanded in the stationary nozzles, the remaining expansion takes place during its flow over the moving blades. As a result, the momentum of the steam causes a reaction force on the moving blades which sets the rotor in motion.