PERFORMANCE ANALYSIS OF ROCKET NOZZLE USING CFD

BY HATIM S R

31709114044

GUIDEMr. K. Arun (Ph. D)

AIM• Comparison of nozzle

configurations across different altitudes• Exhaust gas flows will be studied

using velocity contours• Specific Impulses will be

calculated

NOZZLE CONFIGURATIONS

•3 nozzle configurations:1. Ideal Nozzle2. 85% Bell Nozzle 3. 70% Bell Nozzle

NOZZLE CONFIGURATIONS

OPERATING CONDITIONS• Fluid – Air• Nozzle Material – Titanium• Chamber Pressure – 100 psia (or)

7.09275 bar• Temperature – 500 K

OPERATING CONDITIONS

• Ambient pressure will be varied• 4 different altitudes

1. Sea level – 1.01325 bar2. 5000m – 0.540 bar3. 10000m – 0.264 bar4. 20000m – 0.055 bar

CFD PARAMETERS

• Pressure-Coupled solver

• Spalart-Allmaras Turbulence Model

(used primarily in Aerospace application)

• Air – Ideal Gas Density

BOUNDARY CONDITIONS•Pressure Inlet – Combustion Chamber

•Pressure Farfield – Atmosphere

GEOMETRY OF IDEAL NOZZLE

MESH OF IDEAL NOZZLE

GEOMETRY OF 85% BELL NOZZLE

MESH OF 85% BELL NOZZLE

GEOMETRY OF 70% BELL NOZZLE

MESH OF 70% BELL NOZZLE

METHODOLOGY

• Input:1. Pressure: 100 psia or 7.09275 bar2. Temperature: 500 K3. Ambient Pressure

• Output:1. Velocity Contour2. Specific Impulse

Velocity Contour of Ideal Nozzle

• Sea Level - Ambient Pressure: 1.01325 bar• Nozzle is in overexpanded state, hence shocks are present

Velocity Contour of 85% Bell Nozzle

• Sea Level - Ambient Pressure: 1.01325 bar• Nozzle is in overexpanded state, hence shocks are present

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

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

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

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

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

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

Velocity Contour of 70% Bell Nozzle

• 10000m - Ambient Pressure: 0.264 bar• Nozzle is operating at design condition and therefore no

shocks are present

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

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

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

Specific Impulse

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