in an impulse turbine entire pressure energy is converted in
to kinetic energy as in case of a pelton turbine where the
nozzle does this..
In a reaction turbine only a part of the pressure energy is
converted to kinetic energy as in case of Francis and kaplan
in case u want to know more pls refer Hydraulic Machines by
Modi And Seth...
Impulse turbine works on the principle of Newton's second
law of motion.
Reaction turbine works on the principle of Neewton's third
law of motion"For every action there is an equal and
The main difference between reaction and impulse turbine is
that reaction turbine operates on newtons third law of
motion that is when steam leaves the rotor blades at an
angle the turbine is pushed towards opposite direction and
to a certain extent static pressure impulse is also
utilised for the movement.
Where as in impulse turbine only kinetic head of steam is
responsible for movemement of turbine.that is movement of
turbine takes place in direction of impact and not opposite
to the impact as was the case with reaction turbines.
In impulse turbine, the drop in pressure of steam takes
place only in nozzles and not in moving blades. This is
obtained by making the blade passage of constant cross-
- In this type, the drop in pressure takes place in fixed
nozzles as well as moving blades.
- The pressure drop suffered by steam while passing through
the moving blades causes a further generation of kinetic
energy within these blades, giving rise to reaction and add
to the propelling force, which is applied through the rotor
to the turbine shaft.
- The blade passage cross-sectional area is varied
impulse turbine works on the principle of impulse ie., a
force acting for a short period of time and the fluid flows
across the vane but reaction turbine works on recative
forces i.e., due to force of the high velocity fluid, the
vane tends to rotate in the opposite direction e.g the lawn
sprinkler works on reative forces