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RAJLAKSHMI ENGINEERING COLLEGE

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Comprehend the thermodynamic processes occurring in a gas turbine ... exhaust gasses past Mach 1. More complex engines can actually use a tertiary ... – PowerPoint PPT presentation

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Title: RAJLAKSHMI ENGINEERING COLLEGE


1
RAJLAKSHMI ENGINEERING COLLEGE
  • DEPARTMENT OF AERONAUTICAL ENGINEERING
  • AE-1304
  • PROPULSION-1

2
UNIT-1
  • FUNDAMENTALS OF GAS TURBINE ENGINES

3
INTRODUCTION
  • Comprehend the thermodynamic processes occurring
    in a gas turbine
  • Comprehend the basic components of gas turbine
    engines and their basic operation
  • Comprehend the support systems associated with
    gas turbine engines

4
ADVANTAGES OF GTEs
  • Weight reduction of 70
  • Simplicity
  • Reduced manning requirements
  • Quicker response time
  • Faster Acceleration/deceleration
  • Modular replacement
  • Less vibrations
  • More economical

5
DISADVANTAGES OF GTEs
  • Many parts under high stress
  • High pitched noise
  • Needs large quantities of air
  • Large quantities of hot exhaust (target)
  • Cannot be repaired in place

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14
BRAYTON CYCLE
  • Unlike diesels, operate on STEADY-FLOW cycle
  • Open cycle, unheated engine
  • 1-2 Compression
  • 2-3 Combustion
  • 3-4 Expansion through Turbine and Exhaust
    Nozzle
  • (4-1 Atmospheric Pressure)

15
BASIC COMPONENTS
16
NUMBERING OF TURBINE ENGINES
intake compressor burner
turbine afterburner (AB) nozzle (n)
(diffuser)
(e.g., turbofan)
17
COMPRESSOR
  • Supplies high pressure air for combustion process
  • Compressor types
  • Radial/centrifugal flow compressor
  • Axial flow compressor

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COMPRESSOR
  • Radial/centrifugal flow
  • Adv simple design, good for low compression
    ratios (51)
  • Disadv Difficult to stage, less efficient
  • Axial flow
  • Good for high compression ratios (201)
  • Most commonly used

20
THE THRUST EQUATION
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FACTORS AFFECTING THRUST
  • PRESSURE
  • TEMPERATURE
  • DENSITY
  • HUMIDITY
  • ALTITUDE
  • FORWARD VELOCITY

24
METHODS OF THRUST AUGMENTATION
  • AFTER BURNING
  • INJECTION OF WATER ALCOHOL MIXTURE
  • BLEED BURN CYCLE

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26
UNIT-II
  • SUBSONIC SUPERSONIC INLETS FOR JET ENGINES

27
INTRODUCTION
  • Inlets are very important to the overall jet
    engine performance will greatly influence jet
    engine thrust output.
  • The faster the airplane goes the more critical
    the inlet duct design becomes.
  • Engine thrust will be high only if the inlet duct
    supplies the engine with the required airflow at
    the highest possible pressure.

28
  • The nacelle/duct must allow the engine to operate
    with minimum stall/surge tendencies permit wide
    variation in angle of attack yaw of the
    aircraft.
  • For subsonic aircraft, the nacelle shouldnt
    produce strong shock waves or flow separations
    should be of minimum weight for both subsonic
    supersonic designs.
  • For certain military applications, the radar
    cross sectional control or radar reflectance is a
    crucial design requirements.

29
  • Inlet ducts add to parasite drag skin friction
    viscous drag) interference drag.
  • It must operate from static ground run up to high
    aircraft Mach number with high duct efficiency
    at all altitude, attitudes flight speeds.
  • It should be as straight smooth as possible
    designed such a way that Boundary layer to be
    minimum.
  • It should deliver pressure distribution evenly to
    the compressor.

30
  • Spring loaded , blow-in or such-in-doors are
    sometimes placed around the side of the inlet to
    provide enough air to the engine at high engine
    rpm low aircraft speed.
  • It must be shaped such a way that ram velocity is
    slowly smoothly decreases while the ram
    pressure is slowly smoothly increases.

31
DUCT EFFICIENCY
  • The duct pressure efficiency ratio is defined as
    the ability of the duct to convert the kinetic or
    dynamic pressure energy at the inlet of the duct
    to the static pressure energy at the inlet of the
    compressor without a loss in total pressure . It
    is in order of 98 if there is less friction
    loss.

32
RAM RECOVERY POINT
  • The ram recovery point is that aircraft speed at
    which the ram pressure rise is equal to the
    friction pressure losses or that aircraft speed
    at which the compressor inlet total pressure is
    equal to the outside ambient air pressure.
  • A good subsonic duct has 257.4 km/h.

33
SINGLE ENTRANCE DUCT
34
SUBSONIC DUCTS
35
VARIABLE GEOMETRY DUCT FOR SUPERSONIC A/C
36
NORMAL SHOCK RELATION
37
OBLIQUE SHOCK RELATIONS
38
BOUNDARY LAYER
39
UNIT-III
  • COMBUSTION CHAMBERS

40
COMBUSTION CHAMBER
  • Where air fuel are mixed, ignited, and burned
  • Spark plugs used to ignite fuel
  • Types
  • Can for small, centrifugal compressors
  • Annular for larger, axial compressors (LM 2500)
  • Can-annular for really large turbines

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45
UNIT-IV
  • NOZZLES

46
INTRODUCTION
  • The primary objective of a nozzle is to expand
    the exhaust stream to atmospheric pressure, and
    form it into a high speed jet to propel the
    vehicle. For air breathing engines, if the fully
    expanded jet has a higher speed than the
    aircraft's airspeed, then there is a net rearward
    momentum gain to the air and there will be a
    forward thrust on the airframe.

47
  • Many military combat engines incorporate an
    afterburner (or reheat) in the engine exhaust
    system. When the system is lit, the nozzle throat
    area must be increased, to accommodate the extra
    exhaust volume flow, so that the turbo machinery
    is unaware that the afterburner is lit. A
    variable throat area is achieved by moving a
    series of overlapping petals, which approximate
    the circular nozzle cross-section.

48
  • At high nozzle pressure ratios, the exit pressure
    is often above ambient and much of the expansion
    will take place downstream of a convergent
    nozzle, which is inefficient. Consequently, some
    jet engines (notably rockets) incorporate a
    convergent-divergent nozzle, to allow most of the
    expansion to take place against the inside of a
    nozzle to maximise thrust. However, unlike the
    fixed con-di nozzle used on a conventional rocket
    motor, when such a device is used on a turbojet
    engine it has to be a complex variable geometry
    device, to cope with the wide variation in nozzle
    pressure ratio encountered in flight and engine
    throttling. This further increases the weight and
    cost of such an installation.

49
  • The simpler of the two is the ejector nozzle,
    which creates an effective nozzle through a
    secondary airflow and spring-loaded petals. At
    subsonic speeds, the airflow constricts the
    exhaust to a convergent shape. As the aircraft
    speeds up, the two nozzles dilate, which allows
    the exhaust to form a convergent-divergent shape,
    speeding the exhaust gasses past Mach 1. More
    complex engines can actually use a tertiary
    airflow to reduce exit area at very low speeds.
    Advantages of the ejector nozzle are relative
    simplicity and reliability. Disadvantages are
    average performance (compared to the other nozzle
    type) and relatively high drag due to the
    secondary airflow. Notable aircraft to have
    utilized this type of nozzle include the SR-71,
    Concorde, F-111, and Saab Viggen

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51
NOZZLE
52
1-D ANALYSIS OF GAS
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54
MASS FLOW RELATION
55
UNIT-V
  • COMPRESSORS

56
  • Compressor
  • Draws in air compresses it
  • Combustion Chamber
  • Fuel pumped in and ignited to burn with
    compressed air
  • Turbine
  • Hot gases converted to work
  • Can drive compressor external load

57
COMPRESSOR
  • Controlling Load on Compressor
  • To ensure maximum efficiency and allow for
    flexibility, compressor can be split into HP LP
    sections
  • Vane control inlet vanes/nozzle angles can be
    varied to control air flow
  • Compressor Stall
  • Interruption of air flow due to turbulence

58
USE OF COMPRESSED AIR
  • Primary Air (30)
  • Passes directly to combustor for combustion
    process
  • Secondary Air (65)
  • Passes through holes in perforated inner shell
    mixes with combustion gases
  • Film Cooling Air (5)
  • Insulates/cools turbine blades

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60
VELOCITY TRIANGLE
61
  • THANK U
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