Difference Between Impulse And Reaction Turbine
Comparison between impulse and reaction turbine
Impulse
Turbine
|
Reaction
Turbine
|
At the inlet only kinetic energy is available.
I.e. only momentum transfer.
|
At the inlet, both kinetic
and pressure energy are available.
|
Steam expands in the fixed
blade (which act as a nozzle) itself. The entire pressure drop occurs at
nozzles. Therefore, pressure remains constant while it passes over the
blades.
|
The steam expands continuously
in both fixed and the moving blades as it passed above them. Thus, the
pressure drop occurs in a gradual way during flow over both blades.
|
Water casing is not necessary.
|
Air-tight casing is
necessary.
|
Inlet pressure is higher
than outlet pressure.
|
|
In impulse turbine, flow
area of moving blade is constant, since there is no expansion of steam.
|
In reaction turbine, the moving
blade do have change in flow area (convergent type).They are shaped like
nozzle and accelerate the steam.
|
Blades are symmetrical about plane of turbine shaft. Therefore, the
manufacturing of blade is simple |
Blades are asymmetrical.
|
In impulse turbine, due to great pressure drop, the operating speed is
very high.
|
In the reaction, small pressure drop due to turbine, the operating is
low.
|
Due to high pressure drop on the nozzles, the number of stages are
less. The size of an impulse for the power output turbine is comparatively
small.
|
Due to the small pressure drop at each stage, the number of stages
are more for the same pressure drop as in impulse turbine. Therefore the size
of the reaction for the same output power turbine is large. Reaction turbines
are only multi-stage turbines.
|
Operate at high water head.
|
Operate at low water head. |
Less space per unit power
|
More space takes per unit power
|
Turbine Impulse is suitable for small powers generation. More
hydraulic efficiency
|
Reaction turbine is suitable for medium and higher powers generation.
|
Examples: Pelton wheel, Banki turbine
|
Examples: Kaplan turbine, Francis turbine, Fourneyron turbine. |
Read: Types of turbines