Steam nozzle

Steam Nozzle:
Nozzle type, Nozzle Efficiency, Critical Pressure ratio, Metastable flow

1. STEAM NOZZLE Steam Nozzle - The steam nozzle is a passage of varying cross-section by means of which a part of the enthalpy of steam is converted into kinetic energy as the steam expands from a higher pressure to a lower pressure. Therefore, a nozzle is a device designed to increase the velocity of steam.

2. TECHNICAL TERMS:

3. TYPES AND SHAPES OF NOZZLES There are three types of nozzles Convergent nozzle Divergent nozzle Convergent-divergent nozzle Fig1: Convergent Nozzle Fig2: Divergent Nozzle Fig3: Convergent-Divergent Nozzle

4. 1 . Convergent Nozzle A typical convergent nozzle is shown in the Fig.1. I n a co n v e rge n t n ozz l e, t h e cr o s s s ec t i o na l a r e a decreases continuously from its entrance to exit. Fig.1. Convergent nozzle It is used in a case where the back pressure is equal to or greater than the critical pressure ratio.

5. 2 . Divergent Nozzle T he cr o s s s ec t i o na l a r e a o f d i v e rg e nt n ozz l e i n c r ea s es continuously from its entrance to exit. Fig.2.Divergent nozzle It is used in a case where the back pressure is less than the critical pressure ratio.

6. 3 . Convergent-Divergent Nozzle In this condition, the cross sectional area first decreases from its entrance to the throat and then again increases from throat to the exit. This case is used in the case where the back pressure is less than the critical pressure. Also, in present day application, it is widely used in many types of steam turbines. Fig.3. convergent-divergent nozzle

7. Nozzle Efficiency (or) Effect of Friction

8. Critical Pressure Ratio (P2/P1)

9. Metastable Flow (or) Supersaturated Flow