RAJLAKSHMI ENGINEERING COLLEGE

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RAJLAKSHMI ENGINEERING COLLEGE

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

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UNIT-1

• FUNDAMENTALS OF GAS TURBINE ENGINES

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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

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ADVANTAGES OF GTEs

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

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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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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)

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BASIC COMPONENTS
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NUMBERING OF TURBINE ENGINES
intake compressor burner
turbine afterburner (AB) nozzle (n)
(diffuser)
(e.g., turbofan)
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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

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THE THRUST EQUATION
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FACTORS AFFECTING THRUST

• PRESSURE
• TEMPERATURE
• DENSITY
• HUMIDITY
• ALTITUDE
• FORWARD VELOCITY

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METHODS OF THRUST AUGMENTATION

• AFTER BURNING
• INJECTION OF WATER ALCOHOL MIXTURE
• BLEED BURN CYCLE

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UNIT-II

• SUBSONIC SUPERSONIC INLETS FOR JET ENGINES

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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.

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• 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.

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• 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.

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• 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.

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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.

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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.

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SINGLE ENTRANCE DUCT
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SUBSONIC DUCTS
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VARIABLE GEOMETRY DUCT FOR SUPERSONIC A/C
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NORMAL SHOCK RELATION
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OBLIQUE SHOCK RELATIONS
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BOUNDARY LAYER
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UNIT-III

• COMBUSTION CHAMBERS

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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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UNIT-IV

• NOZZLES

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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.

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• 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.

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• 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.

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• 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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NOZZLE
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1-D ANALYSIS OF GAS
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MASS FLOW RELATION
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UNIT-V

• COMPRESSORS

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• 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

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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

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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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VELOCITY TRIANGLE
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• THANK U