THE BIRTH OF JET PROPULSION

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THE BIRTH OF JET PROPULSION

• P M V Subbarao
• Professor
• Mechanical Engineering Department

Another Beak Through Idea by an Individual.
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Working Principle of Propeller
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Aerofoil Theory of Propeller
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Anatomy of Propeller
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Capacity of Propeller
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Engines to drive propeller
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Need for Alternative Propulsion Method

• Dr. Hans von Ohain and Sir Frank Whittle are both
  recognized as being the co-inventors of the jet
  engine.
• Each worked separately and knew nothing of the
  other's work.
• Hans von Ohain is considered the designer of the
  first operational turbojet engine.
• Frank Whittle was the first to register a patent
  for the turbojet engine in 1930.
• Hans von Ohain was granted a patent for his
  turbojet engine in 1936.
• However, Hans von Ohain's jet was the first to
  fly in 1939.
• Frank Whittle's jet first flew in in 1941.

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Parallel Invention

• Doctor Hans Von Ohain was a German airplane
  designer who invented an operational jet engine.
• Hans Von Ohain, started the investigating a new
  type of aircraft engine that did not require a
  propeller.
• Only twenty-two years old when he first conceived
  the idea of a continuous cycle combustion engine
  in 1933.
• Hans Von Ohain patented a jet propulsion engine
  design similar in concept to that of Sir Frank
  Whittle but different in internal arrangement in
  1934.
• Hans Von Ohain joined Ernst Heinkel in 1936 and
  continued with the development of his concepts of
  jet propulsion.

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• A successful bench test of one of his engines was
  accomplished in September 1937.
• A small aircraft was designed and constructed by
  Ernst Heinkel to serve as a test bed for the new
  type of propulsion system - the Heinkel He178.
• The Heinkel He178 flew for the first time on
  August 27, 1939.
• The pilot on this historic first flight of a
  jet-powered airplane was Flight Captain Erich
  Warsitz.

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Think Different.

• A Royal Air Force officer.
• His first attempts to join the RAF failed as a
  result of his lack of height, but on his third
  attempt he was accepted as an apprentice in 1923.
• He qualified as a pilot officer in 1928.
• As a cadet Whittle had written a thesis arguing
  that planes would need to fly at high altitudes,
  where air resistance is much lower, in order to
  achieve long ranges and high speeds.

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• Piston engines and propellers were unsuitable for
  this purpose.
• He concluded that rocket propulsion or gas
  turbines driving propellers would be required.
• Jet propulsion was not in his thinking at this
  stage.
• By October 1929, he had considered using a fan
  enclosed in the fuselage to generate a fast flow
  of air to propel a plane at high altitude.
• A piston engine would use too much fuel, so he
  thought of using a gas turbine.
• After the Air Ministry turned him down, he
  patented the idea himself.

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• In 1935, Whittle secured financial backing and,
  with Royal Air Force approval, Power Jets Ltd was
  formed.
• They began constructing a test engine in July
  1936, but it proved inconclusive.
• Whittle concluded that a complete rebuild was
  required, but lacked the necessary finances.
• Protracted negotiations with the Air Ministry
  followed and the project was secured in 1940.
• By April 1941, the engine was ready for tests.
  The first flight was made on 15 May 1941.
• By October the United States had heard of the
  project and asked for the details and an engine.
• A Power Jets team and the engine were flown to
  Washington to enable General Electric to examine
  it and begin construction.

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• The Americans worked quickly and their XP-59A
  Aircomet was airborne in October 1942, some time
  before the British Meteor, which became
  operational in 1944.
• The jet engine proved to be a winner,
  particularly in America where the technology was
  enthusiastically embraced.

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The biggest aircraft
Powerplant 6 ZMKB Progress D-18 turbofans,
229.5 kN each
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The popular Biggest Aircrafts in the World
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The world's largest aircraft engine, the GE90-115B
Max. Thrust 569kN
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The fastest Aircraft

• X-15 is having a 4,520 mph world speed record.
• Fastest manned aircraft.
• Not only is the North American X-15 the fastest
  piloted aircraft ever, it is the highest flying.
• Thrust was obtained from one engine that produced
  313kN at maximum altitude.
• The North American X-15 was produced to explore
  the limits of sub-orbital supersonic flight.
• Three were produced. They flew a total of 199
  times.
• The X-15 first took to the sky on June 8, 1959.
  The last flight took place on Oct. 24, 1968. A
  200th flight was never made, even after several
  attempts.

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Course Overview

• This undergraduate level course teaches the
  principles of jet propulsion.
• The primary focus of the course is on the
  teaching of thermodynamics and Gas dynamics in
  aircraft engines.
• The course provides information that will enable
  the engineering analysis of
• ramjets and turbine engines and
• its separate components including inlets,
  nozzles, combustion chambers, compressors, and
  turbines.

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Course Objectives

• Students successfully completing MEL 341 will
  get
• A basic understanding of thermodynamic cycles of
  jet engines.
• A basic understanding of the rational behind
  several types of jet engines.
• A basic understanding of the compressible fluid
  flow in inlets and compressors and turbines.
• A basic understanding of the combustion physics
  in combustion chambers.
• The ability to analyze jet engines determine
  propulsion efficiency and design inlets and
  nozzles.

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Course Contents

• UNIT- I Propulsion
•  Aircraft Propulsion introduction -- Early
  aircraft engines -- Types of aircraft engines --
  Reciprocating internal combustion engines -- Gas
  turbine engines -- Turbo jet engine -- Turbo fan
  engine -- Turbo-prop engine
• Aircraft propulsion theory thrust, thrust power,
  propulsive and overall efficiencies -- Problems.
•  UNIT- II THERMODYNAMIC ANALYSIS OF IDEAL
  PROPULSION CYCLES
•  Thermodynamic analysis of turbojet engine
  Study of subsonic and supersonic engine models --
  Identification and Selection of optimal
  operational parameters. Need for further
  development Analysis of Turbojet with after
  burner.

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• Thermodynamic analysis of turbofan engine Study
  of subsonic and supersonic systems --
  Identification and selection of optimal
  operational parameters. Design of fuel efficient
  engines Mixed flow turbo fan engine Analysis
  of Turbofan with after burner.
• Thermodynamic analysis of turbo-prop engine
  Identification and selection of optimal
  operational parameters.

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UNIT III GAS DYNAMICS OF PASSIVE COMPONENTS OF
TURBO ENGINES

• FUNDAMENTALS OF GAS DYNAMICS Energy equation
  for a non-flow process -- Energy equation for a
  flow process -- The adiabatic energy equation --
  Momentum Equation --Moment of Momentum equation
  -- Stagnation Velocity of Sound --Stagnation
  Pressure -- Stagnation Density -- Stagnation
  State -- Velocity of sound -- Critical states --
  Mach number -- Critical Mach number -- Various
  regions of flow.
• ANALYSIS OF DIFFUSERS AND NOZZLES Introduction
  study of intakes for subsonic and supersonic
  engines -- Comparison of isentropic and adiabatic
  processes -- Mach number variation -- Area ratio
  as function of Mach numbers -- Impulse function
  -- Mass flow rates -- Flow through nozzles --
  Flow through diffusers Effect of friction --
  Analysis of intakes for supersonic engines
  intakes with normal shock oblique shocks
  Study of special supersonic nozzles and
  diffusers.

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UNIT IV STUDY OF COMPRESSORS

• Design and Analysis of compressors
  Classification analysis of centrifugal
  compressors velocity triangles design of
  impellers and diffusers analysis of axial flow
  compressor analysis of stage characterization
  of stage design of multistage axial flow
  compressor Performances analysis of centrifugal
  and axial flow compressors.
•  

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• UNIT V GAS DYNAMICS OF COMBUSTORS
•  Stoichimetry of combustion calculation
  air-fuel ratio gas dynamics of combustors
  thermal loading factors design and selection of
  combustors.
•  UNIT VI STUDY OF TURBINES
• Concept of gas turbine analysis of turbine
  stage velocity triangles and characterization
  of blades and stages Design of multistage axial
  flow turbine Performance analysis of turbines.
•  UNIT VI ADDITIONAL TOPICS
• Thermodynamic analysis real turbo engine cycles
  performance analysis and thermodynamic
  optimization.
•  Introduction to ramjets study of rocket
  engines study of missile engines.

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Books References

• Jet Propulsion
• Flack, R.D.., Fundamentals of Jet Propulsion,
  Cambridge University Press, 2005.
• Baskharone, E.A., Principles of Turbomachinery
  in Air-Breathing Engines, Cambridge University
  Press, 2006.
• Kerrebrock J.L., Aircraft Engines and Gas
  Turbines, MIT Press, 1992.
• Mattingly, J.D., Elements of Gas Turbine
  Propulsion, McGraw-Hill Inc., 1996.
• Gas Dynamics
• Anderson, J.D., Modern Compressible Flow With
  Historical Perspective, McGrawHill, 2002.
• Zuker, R.D., and Biblarz, O.,Fundamentals of Gas
  Dynamics, John Wiley Sons Inc., 2002.
• Thompson, P. A. Compressible Fluid Dynamics.
  Maple Press Company, 1984.
• Saad, M.A.,Compressible Fluid Flow,
  Prentice-Hall, 1993.
• Liepmann, H., and A. Roshko. Elements of Gas
  Dynamics. John Wiley Publishers, 1957.

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Propulsion - Overview

• What is propulsion?
• The word is derived from two Latin words
• pro meaning before or forwards and
• pellere meaning to drive.
• Propulsion means to push forward or drive an
  object forward.
• A propulsion system is a machine that produces
  thrust to push an object forward.
• On airplanes, thrust is usually generated through
  some application of Newton's third law of action
  and reaction.
• A gas, or working fluid, is accelerated by a
  machine, and the reaction to this acceleration
  produces a force on the engine.

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Classification of Propulsion Systems
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Jet Propulsion

• Operating principle based on Newtons laws of
  motion.
• 2nd law - rate of change of momentum is
  proportional to applied thrust (i.e. F m a)
• 3rd law - every action has an equal and opposite
  reaction.

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Classification of Systems

• Only the practical thermo-chemical category will
  be considered further in this Course.
• This may be split into two main sub-categories
• Rockets (Solid or Liquid Propellant)
• Air Breathers (Ramjet, Turbojet , Turbofan
  Turboprop)
• along with a Hybrid Ram rocket.
• The fundamental operating principle common in
  all these cases is , that of jet or reaction
  propulsion, i.e. by generating high-velocity
  exhaust gases.

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Jet Characteristics

• Quantities defining a jet are
• cross-sectional area
• composition
• velocity.
• Of these, only the velocity is a truly
  characteristic feature and is of considerable
  quantitative significance.

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Jet Characteristics of Practical Propulsion
Systems
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Introduction to Rockets
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Solid Propellant Rocket - Basic Operating Features

• Four basic components
• motor case, nozzle, solid propellant charge,
  igniter.
• Propellant charge comprises combined fuel
  oxidizer.
• Gaseous combustion products fill void at high
  pressure (70 bar typically) and sustains
  combustion.
• Hot gases vent through convergent-divergent
  nozzle to provide high-speed (supersonic)
  propulsion jet.
• Gases generated and escape at fixed rate for
  steady operation by maintaining constant burning
  surface area.

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Solid Propellant Rocket for GW
Rapier

• Jet velocity 1500-2600m/s
• Most widely used in GW
• Short, medium range (lt 50 km)
• Simple, reliable, easy storage, high T/W

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Solid Rocket Features

• High propellant density (volume-limited designs).
• Long-lasting chemical stability.
• Readily available, tried and trusted, proven in
  service.
• No field servicing equipment straightforward
  handling.
• Cheap, reliable, easy firing and simple
  electrical circuits.
• But
• Lower specific impulses (compared with liquid
  rockets).
• Difficult to vary thrust on demand.
• Smokey exhausts (especially with composite
  propellants).
• Performance affected by ambient temperature.

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Liquid Propellant Rocket - Basic Operating
Features

• Fuel and oxidant tanked separately and delivered
  to combustion chamber at specific rates and
  pressures.
• Propellant flowrates (and hence thrust) variable
  upon demand.
• Disadvantages compared with solid propellant
  rockets
• increased complication
• Storage problems (usually LOX LH2 which must be
  maintained at very low temperatures)
• more costly
• reduced reliability.

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Liquid Propellant Rocket - Space

• Jet velocity 2000 - 3500m/s.
• Highest thrust, can be throttled.
• Long sustained flight (5mins).

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Space Transportation System (STS)
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Travel Cycle of Modern Spacecrafts
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Rentering Space Craft
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Major Knowledge Gains Through Gas Dynamics

• Simple principles of Gas Dynamics, it was showed
  that the heat load experienced by an entry
  vehicle was inversely proportional to the drag
  coefficient.
• The greater the drag, the less the heat load.
• Through making the reentry vehicle blunt, the
  shock wave and heated shock layer were pushed
  forward, away from the vehicle's outer wall.
• Since most of the hot gases were not in direct
  contact with the vehicle, the heat energy would
  stay in the shocked gas and simply move around
  the vehicle to later dissipate into the
  atmosphere.