4. SUPERSONIC COMBUSTION
What is a supersonic combustion?
• A supersonic combustion is a combustion where the
velocity of a combustion zone relative to unburned gas is
higher than the sound speed of the unburned gas.
• The shock waves formed by the vehicle forebody and the
engine inlets serves as the engine compressor section
while the engine exhaust and vehicle afterbody serve as
the expansion nozzle to generate thrust from the gases
burned in the combustor.
• The surface geometry would be chosen so that supersonic
flow would be maintained throughout the internal
passages of the engine avoiding large recovery of
temperature and pressure from the free stream air
6. WORKING OF A SUPERSONIC COMBUSTIO
• A ramjet operates by combustion of fuel in a stream of air
compressed by the forward speed of the aircraft itself, as
opposed to a normal jet engine, in which the compressor
section (the fan blades) compresses the air.
7. • The velocity is the main significant factor in recognition of
the main flow characteristics inside the combustion
chamber.
• In order to evaluate the various velocity conditions for
different gas species and temperatures, the Mach number
is introduced as the ratio of the gas velocity to the speed of
the sound as follows:
9. USAGE OF SUPERSONIC COMBUSTION
• This supersonic combustion are used in scram jets which
are abbreviated as supersonic combustion ram jets
• Fuel (typically hydrogen or some hydrocarbon) is injected
into the supersonic airstream and, hopefully, mixes, ignites,
and burns.
• Ejection of the high enthalpy gases through a nozzle
produces the desired thrust.
All these happens in a millisecond
11. ADVANTAGES OF SUPERSONIC
COMBUSTION
• Scramjet engine does not have to carry oxygen.
• No rotating parts makes it easier to manufacture
• Scramjet has a higher specific impulse (change in
momentum per unit of propellant) than a rocket engine
• Higher speed could mean cheaper access to outer space
in the future
13. DISADVANTAGES OF SUPERSONIC
COMBUSTION
• Due to the nature of their design, scramjet operation
is limited to near-hypersonic velocities
• Testing scramjet designs use extremely expensive
hypersonic test chambers or expensive launch vehicles,
both of which lead to high instrumentation costs.
• Lack of stealth technology
• Very high initial propulsion requirements
14. Conclusion
Provide a brief summary of your presentation.
Remind the audience what you covered in the previous slides.
