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AEROSPACE PROPULSION SYSTEM

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Airbreathing engine (propeller, turpoprop, turbojet, turbofan, ... F=thrust which would be produced by the thrust generator if the external flow are isentropic ... – PowerPoint PPT presentation

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Title: AEROSPACE PROPULSION SYSTEM


1
AEROSPACE PROPULSION SYSTEM
  • PROF. SEUNG WOOK BAEK
  • DIV. OF AEROSPACE ENGINEERING, KAIST, IN KOREA
  • ROOM Bldg. N7-2 3304
  • TELEPHONE 3714
  • http//procom.kaist.ac.kr
  • swbaek_at_kaist.ac.kr

2
Propulsion devices
devices which produce thrust for acceleration and
overcome external drag by generating rearward
momentum in one or more streams of gas
Airbreathing engine (propeller, turpoprop,
turbojet, turbofan, ramjet, scramjet) fluid
stream entering and leaving the propulsion
device Rocket engine (liquid and solid) ejection
of stored mass (fueloxidizer)
PROPULSION AND COMBUSTION LABORATORY
3
Airbreathing engines
  • release internal chemical energy combined with
    external oxidizer
  • chemical -gt thermal -gt kinetic energy
  • Engine components inlet, compressor (and fan),
  • combustor, turbine, afterburner and nozzle
  • Common performance measures
  • a compromise among specific thrust, specific
    impulse, thrust specific fuel consumption

PROPULSION AND COMBUSTION LABORATORY
4
Airbreathing engines
  • Thermal efficiency a ratio of the rate of
    kinetic energy generation to the rate of thermal
    (chemical) energy input
  • Propulsive efficiency a ratio of the useful
    power transmitted to the flight vehicle to the
    rate of kinetic energy generation
  • Afterburning increases the specific thrust at
    the high performance condition and allows use of
    a more fuel-efficient system for subsonic
    cruise.

PROPULSION AND COMBUSTION LABORATORY
5
Chemical rockets
  • release internal chemical energy combined with
    internal oxidizer
  • Solid propellant rockets
  • -relative simplicity
  • -weapon or strap-on booster rocket to very
  • large orbiting rockets
  • -increased propellant density with heavily
    aluminized solid propellant-very small cross
    section and reduced drag for low altitude

PROPULSION AND COMBUSTION LABORATORY
6
Chemical rockets
  • Solid propellant rockets
  • Design problem
  • -thrust level variation and rapid thrust
    termination
  • -screaming acoustic instability resilient
    propellant material-optimal cross-sectinal
    shapes that reduce wave reflection

PROPULSION AND COMBUSTION LABORATORY
7
Solid propellant rockets
  • Double-base propellants
  • -homogeneous propellant grain
  • -nitrocellulose type of gunpowder dissolved in
    nitroglycerin
  • -major ingredients are explosives and
    contribute to the functions of fuel, oxidizer
    and binder

PROPULSION AND COMBUSTION LABORATORY
8
Solid propellant rockets
  • Composite propellants
  • -heterogeneous propellant grain
  • -oxidizer crystals and powdered fuel
    (usually aluminum) held together in a matrix
    of synthetic rubber binder
  • -less hazardous to manufacture and handle
    than double-base propellants

PROPULSION AND COMBUSTION LABORATORY
9
Solid propellant rockets
  • Composite double-base propellants
  • -a combination of double-base and composite
    propellants
  • -usually crystalline oxidizer (ammonium
    perchlorate) and powdered aluminum fuel
    held together in a matrix of nitrocellulose- nitro
    glycerin

PROPULSION AND COMBUSTION LABORATORY
10
Chemical rockets
  • Liquid propellant rockets
  • -highly energetic liquid fuels and oxidizers in
    low pressure tanks
  • -variable thrust level capability
  • -pumps and associated piping lead to an
    increase in size and overall mass of the
    vehicle
  • Boiling points O2 -183 0C
  • H2 -253 0C
  • N2 -196 0C

PROPULSION AND COMBUSTION LABORATORY
11
Chemical rockets
  • Liquid propellant rockets
  • Design problem
  • -turbo pumps to supply the necessary
    fuel/oxidizer ratio
  • -variable nozzle to provide the maximum
    possible thrust for each altitude(maximum
    possible thrust occurs when the nozzle
    exhaust pressure is very near the ambient
    pressure
  • -base heating

PROPULSION AND COMBUSTION LABORATORY
12
Chemical rockets
  • Liquid propellant rockets
  • Design problem
  • Instabilities
  • -chugging-relatively low-frequency oscillation
    when combustion chamber pressure variations
    couple with the liquid fuel and oxidizer
    supply system-raising the fuel and oxidizer
    supply pressures-heavy piping and pump
    equipment

PROPULSION AND COMBUSTION LABORATORY
13
Chemical rockets
  • Liquid propellant rockets
  • Design problem
  • Instabilities
  • -screaming-acoustic instability indentified with
    the increase in the thermal output of fuel-
    oxidizer
  • -increase in pressure and temperature in the
    two phase region close to injector heads
  • -amplified to extreme levels by reflection form
    chamber walls-acoustic tiling

PROPULSION AND COMBUSTION LABORATORY
14
Non-chemical rockets
  • -required for very high energy missions for which
    the vehicle velocity change is very large
  • -energy supplied to a propellant through the
    thermal energy or radiative energy from a nuclear
    reactor and solar concentrator
  • -nuclear heated rocket, electrical rocket and
    etc.

PROPULSION AND COMBUSTION LABORATORY
15
Overall performance
  • Thrust reaction to the net force that the engine
    exerts on the fluid passing through it
  • Separate engine performance from effects of
    enclosure or airframe
  • Fthrust which would be produced by the thrust
    generator if the external flow are isentropic

PROPULSION AND COMBUSTION LABORATORY
16
Overall performance
  • Determine F in terms of engine parameters
  • Propulsive flow flow of the working fluid
  • External flow flow of fluid surrounding the
    thrust generator in a frame of reference fixed to
    the thrust generator

PROPULSION AND COMBUSTION LABORATORY
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