2. AIM
• Comparison of nozzle
configurations across different
altitudes
• Exhaust gas flows will be studied
using velocity contours
• Specific Impulses will be
calculated
5. OPERATING CONDITIONS
• Fluid – Air
• Nozzle Material – Titanium
• Chamber Pressure – 100 psia (or)
7.09275 bar
• Temperature – 500 K
6. OPERATING CONDITIONS
• Ambient pressure will be varied
• 4 different altitudes
1. Sea level – 1.01325 bar
2. 5000m – 0.540 bar
3. 10000m – 0.264 bar
4. 20000m – 0.055 bar
7. CFD PARAMETERS
• Pressure-Coupled solver
• Spalart-Allmaras Turbulence Model
(used primarily in Aerospace application)
• Air – Ideal Gas Density
15. METHODOLOGY
• Input:
1. Pressure: 100 psia or 7.09275 bar
2. Temperature: 500 K
3. Ambient Pressure
• Output:
1. Velocity Contour
2. Specific Impulse
16. Velocity Contour of Ideal Nozzle
• Sea Level - Ambient Pressure: 1.01325 bar
• Nozzle is in overexpanded state, hence shocks are present
17. Velocity Contour of 85% Bell Nozzle
• Sea Level - Ambient Pressure: 1.01325 bar
• Nozzle is in overexpanded state, hence shocks are present
18. Velocity Contour of 70% Bell Nozzle
• Sea Level - Ambient Pressure: 1.01325 bar
• Nozzle is in overexpanded state, hence shocks are present
• Contours show a drastic decrease in velocity
19. Velocity Contour of Ideal Nozzle
• 5000m - Ambient Pressure: 0.540 bar
• Nozzle is still in overexpanded state, but the shocks are said
to have ‘progressed’ downstream of nozzle
20. Velocity Contour of 85% Bell Nozzle
• 5000m - Ambient Pressure: 0.540 bar
• Nozzle is operating at design condition as parabolic contour
has decreased the exit pressure to ambient pressure
21. Velocity Contour of 70% Bell Nozzle
• 5000m - Ambient Pressure: 0.540 bar
• Nozzle is still in overexpanded state & shocks converge
after a small distance showing that the thrust generated is
very low
22. Velocity Contour of Ideal Nozzle
• 10000m - Ambient Pressure: 0.264 bar
• Nozzle is operating at design condition as isentropic
expansion has decreased the exit pressure to ambient
pressure and therefore no shocks are present
23. Velocity Contour of 85% Bell Nozzle
• 10000m - Ambient Pressure: 0.264 bar
• Nozzle is still operating at design condition because of the
parabolic contour & therefore no shocks are present
24. Velocity Contour of 70% Bell Nozzle
• 10000m - Ambient Pressure: 0.264 bar
• Nozzle is operating at design condition and therefore no
shocks are present
25. Velocity Contour of Ideal Nozzle
• 20000m - Ambient Pressure: 0.055 bar
• Nozzle is operating at underexpanded state and exhaust
gas flow expands majorly outside of the nozzle
• The flow bends around the nozzle lip
26. Velocity Contour of 85% Bell Nozzle
• 20000m - Ambient Pressure: 0.055 bar
• Nozzle is operating at underexpanded state and exhaust
gas flow expands majorly outside of the nozzle
• The flow bends around the nozzle lip
27. Velocity Contour of 70% Bell Nozzle
• 20000m - Ambient Pressure: 0.055 bar
• Nozzle is operating at underexpanded state and exhaust
gas flow expands majorly outside of the nozzle
• The flow bends around the nozzle lip
29. Conclusion
• Ideal Nozzle has high specific impulse but increased
length leads to higher inert mass & area of cooling
• 85% Bell Nozzle has a good balance between specific
impulse & nozzle weight reduction and also operates
efficiently over a wider range of ambient pressures
• 70% Bell Nozzle has very low specific impulse
• Therefore 85% Bell Nozzle is suggested to be used as
nozzle configuration in industry
