1. Gas Dynamics for Design of Nozzles
P M V Subbarao
Professor
Mechanical Engineering Department
Better Geometrical Solutions to Convert Microscopic KE to Macroscopic Kinetic Energy to…..

2. Generation of Supersonic Velocity from Rest
Isentropic Nozzle:

3. Isentropic Nozzle at Design Exit Pressure
pexit-design
pthroat
pin
pin p p*
pexit-design

4. Typical flight mission profile & Nozzle Exit Conditions
Turn
Turn
Cruise
Climb in Altitude
Descent
Takeoff
Landing

5. Isentropic Nozzle under Designed Conditions

6. End Conditions of an Isentropic Nozzle

7. Local Properties in an Isentropic Nozzle

8. The Design Conditions of an Isentropic Nozzle

9. Isentropic Nozzle at Design Conditions
Under design conditions the gas pressure at the exit plane of the nozzle is applied back pressure.

11. Isentropic Convergent Nozzle
The compact Isentropic Nozzle:

12. Remarks on Isentropic Converging Nozzle Design
Length of the nozzle is immaterial for an isentropic nozzle.
Strength requirements of nozzle material may decide the nozzle length.
Either Mach number variation or Area variation or Pressure variation is specified as a function or arbitrary length unit.
A converging Nozzle Design attains maximum capacity when the exit Mach number is unity.

13. Full Capacity Converging Nozzle
pin P*
Can this be A basis for selection of altitude of flying?????

14. Typical flight mission profile & Nozzle Exit Conditions
Engine capacity
Thrust
Flight Velocity
Turn
Turn
Cruise
Climb in Altitude
Descent
Takeoff
Landing

15. Operational Characteristics of Isentropic C Nozzles
A converging passage designed to accelerate the a gas flow is considered for study.
The concern here is with the effect of changes in the upstream and downstream pressures
on the nature of the flow and
on the mass flow rate through a nozzle.
Four different cases considered for analysis are:
Converging nozzle with constant upstream conditions.
Converging-diverging nozzle with constant upstream conditions.
Converging nozzle with constant downstream conditions.
Converging-diverging nozzle with constant downstream conditions.

16. Pressure Distribution in Under Expanded Nozzle
At all the above conditions, the pressure at the exit plane of nozzle, pexit = pb.

17. Variation of in Exit Pressure1 1

18. Variation of in Mass Flow Rate1

19. Low Back Pressure Operation

20. Frictional Adiabatic Flow in A Variable Area Duct
Sonic Point : M=1

21. Throat Conditions
The capacity of Frictional throat is always lower than ideal throat!!!

22. The Real Nozzle for Sonic Flow
It is impossible to get a sonic flow with real converging nozzle.
The flow is always subsonic (transonic) at the throat.
A compact real converging nozzle can produce transonic jet.
A real nozzle for sonic exit is a CD Nozzle.

23. Ideal Convergent-Divergent Nozzle Under Design Conditions

24. Ideal Convergent-Divergent Nozzle with High Back Pressure
pb1< pin, but > p*
Pthroat > p*