The energy conversion takes place through the turbine blades. A turbine consists of alternate rows of blades. This blades convert the chemical or thermal energy of working fluid into kinetic energy and then from kinetic energy to mechanical energy as rotation of the shaft.
There are two types of blade, fixed and moving blade. Moving blade is also two types.
One is impulse blade and another reaction blade.
A fixed blade assembly is very important for turbine blading. It is also known as diaphragm. The shape of the blade is the key to the energy conversion process. Since the fixed blades have a conversing nozzle shape, it is also called nozzles.
When steam is passed over the fixed blades, they increase the velocity of steam as an operation of nozzles. Here blades are converted the thermal energy of steam into kinetic energy by causing the steam to speed up and gain velocity.
Moving blade can be shaped in either of two ways: reaction shaped or impulse shaped. The shape of the blade determines how the energy is actually converted. Either type of moving blades or a combination of both can be attached to the shaft of the rotor on dices, called wheels as shown in the figure.
Along the outer rim of the blades is a metal band, called shrouding which ties the blades together. The moving blades convert the kinetic energy in the moving speed into the mechanical energy as rotor rotation.