Gas Dynamics of Variable Area Ducts

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Gas Dynamics of Variable Area Ducts

• P M V Subbarao
• Professor
• Mechanical Engineering Department
• I I T Delhi

Development of Efficient and Compact Passive
Devices.
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System of Equaions
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Combine conservation, state equations can
algebraically show
So we have three ways to change Mach number of a
flow area change (dA) friction f gt 0, same
effect as dA heat transfer heating, q gt 0,
like dA cooling, q lt
0, like dA
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Effect of Shape of duct on Flow
Pure shape effects
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Pure Shape Effects ..
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Subsonic Diffuser
Subsonic Nozzle
dA lt 0 M lt1 So, du gt 0 dp lt0
dA gt 0 M lt1 So, du lt 0 dpgt0
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Supersonic Nozzle
Supersonic Diffuser
dA gt 0 M gt1 So, du gt0 dplt0
dA lt 0 M gt1 So, du lt 0 dp gt0
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Generation of High Pressure from Supersonic
velocity
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Generation of Supersonic Velocity from Rest
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X 15 Hypersonic Research at the Edge of
Space
The X-15 was air launched from a B-52 aircraft at
about 45,000 ft and speeds upward of 500 mph.
The airplane first set speed records in the Mach
4-6 range with Mach 4.43 on March 7, 1961 Mach
5.27 on June 23, 1961 Mach 6.04 on November 9,
1961 and Mach 6.7 on October 3, 1967. It also
set an altitude record of 354,200 feet (67 miles)
on August 22, 1963, and provided an enormous
wealth of data on hypersonic air
flow. Aerodynamic heating, control and stability
at hypersonic speeds, reaction controls for
flight above the atmosphere, piloting techniques
for reentry, human factors, and flight
instrumentation.
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Intake at Design Altitude
p2
pthroat
p1
p2
p
p
p1
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At M1
Minimum Area A Also called throat
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Frictional Adiabatic Flow in A Variable Area Duct
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Constant Mach number frictional flow