What is Steam Nozzle | Types Of Steam Nozzle shapes

Introduction to Steam Nozzle ;

A steam turbine converts the energy of high-pressure, high temperature steam produced by a steam generator into shaft work. The energy conversion is brought about in the following ways:
1. The high-pressure, high-temperature steam first expands in the nozzles emanates as a high velocity fluid stream.
2. The high velocity steam coming out of the nozzles impinges on the blades mounted on a wheel. The fluid stream suffers a loss of momentum while flowing past the blades that is absorbed by the rotating wheel entailing production of torque.
3. The moving blades move as a result of the impulse of steam (caused by the change of momentum) and also as a result of expansion and acceleration of the steam relative to them. In other words they also act as the nozzles.

Flow Through Nozzles

  • A nozzle is a duct that increases the velocity of the flowing fluid at the expense of pressure drop.
  • A duct which decreases the velocity of a fluid and causes a corresponding increase in pressure is a diffuser
  • The same duct may be either a nozzle or a diffuser depending upon the end conditions across it. If the cross-section of a duct decreases gradually from inlet to exit, the duct is said to be convergent.
  • Conversely if the cross section increases gradually from the inlet to exit, the duct is said to be divergent.
  • If the cross-section initially decreases and then increases, the duct is called a convergent- divergent nozzle.
  • The minimum cross-section of such ducts is known as throat.
  • A fluid is said to be compressible if its density changes with the change in pressure brought about by the flow
  • If the density does not changes or changes very little, the fluid is said to be in-compressible. Usually the gases and vapors are compressible, whereas liquids are incompressible .

Shapes of nozzles

shapes of nozzle
shapes of nozzle

1. At subsonic speeds (Ma<1) a decrease in area increases the speed of flow.
2. In supersonic flows (Ma>1), the effect of area changes are different.

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