Working of Impulse turbine:

The technique in which multiple system of rotors are keyed to a common shaft, in series and the steam pressure of jet velocity is absorbed in stages as it flows over the rotor blades, is termed as compounding. The velocity compounding is as shown in figure. Curtiz turbine is an example of this type of turbine. Three rings of moving blades (keyed to shaft) are separated by rings of fixed or guide blades. The rings of fixed blades are attached to the turbine casing which is stationary. The steam is expanded from the boiler pressure to the condenser pressure in the nozzle. The high velocity jet of steam 1^st enters the 1^st row of moving blades, where some portion of this high velocity is absorbed by this blade ring. The remaining being exhausted on the next ring of fixed blades. The fixed blades change direction of jet. The jet is in turn passed to the next ring of moving blades. This procedure is repeated as the steam flows over the remaining pairs of blades until practically whole of the velocity of the jet is absorbed.