A steam nozzle is a passage of varying cross section, which converts heat energy of steam into kinetic energy. The main use of a steam nozzle is in steam turbine, which produces a jet of steam with high velocity.
The smallest section of the nozzle is called throat. It may be noted that the steam enters the nozzle with a high pressure and negligible velocity. But leaves the nozzle with a high velocity and small pressure. The pressure, at which the steam leaves the nozzle is known as back pressure.
Moreover, no heat is supplied or rejected by the steam during flow through a nozzle. Therefore it is considered as adiabatic flow, and the corresponding expansion is considered as an adiabatic expansion. The expansion of steam in a nozzle follows the Rankine cycle. The following are the three types of nozzles.
- Convergent nozzle
- Divergent nozzle
- Convergent – divergent nozzle