jet engine principle and operation

OBJECTIVESAt the end of this subject, the participants will have a general understanding of the following;

Technical definitions about powerplantsDifferent types of aircraft enginesThe basic principles involve in the operation of powerplantsThe different components of an aircraft engine and its operationThe different systems of an aircraft engine

OUTLINEIntroductionEngine ClassificationScientific PrinciplesComponents of a Gas Turbine EngineEngine SystemsProblem Solving

BackgroundAircraft Powerplant 20%ThermodynamicsInternal Combustion EngineReciprocating EngineJet EnginesATHODYDRocketGas Turbine Engine

INTRODUCTION

GAS TURBINE FUNDAMENTALS

History of jet engines150 BC - An Egyptian philosopher and mathematician, Hero, invented a toy (Aeolipile) that rotated on top of a boiling pot of water. This caused a reaction effect of hot air or steam that moved several nozzles arranged on a wheel. This works when one understands the Third Law of Motion - Every action produces a reaction ... equal in force and opposite in direction. 1232 - Chinese began to use rockets as weapons. The invention of gun powder uses the reaction principle to move rockets forward.1500 - Leonardo da Vinci drew a sketch of a device, the chimney jack, that rotated due to the effect of hot gases flowing up a chimney. It looked like a device that used hot air to rotate a spit. The hot air came from the fire and rose upward to pass through a series of fanlike blades that turned the roasting spit.

History of jet engines

History of jet engines1629 - Giovanni Branca developed a stamping mill, that used jets of steam to rotate a turbine that then, rotated to operate machinery. 1678 - Ferdinand Verbiest built a model carriage that used a steam jet for power.1687 - Sir Issac Newton announces the three laws of motion. These form the basis for modern propulsion theory. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors in this law the direction of the force vector is the same as the direction of the acceleration vector. For every action there is an equal and opposite reaction.

History of jet engines1791 - John Barber received the first patent for a basic turbine engine. His design was planned to use as a method of propelling the 'horseless carriage'. The turbine was designed with a chain-driven, reciprocating type of compressor. It has a compressor, a combustion chamber, and a turbine.1872 - Dr. F. Stolze designed the first true gas turbine engine. His engine used a multistage turbine section and a flow compressor. This engine never ran under its own power.1897 - Sir Charles Parson patented a steam turbine was used to power a ship.1914 - Charles Curtis filed the first application for a gas turbine engine.

History of jet engines1918 - General Electric company started a gas turbine division. Dr. Stanford A. Moss developed the GE turbosupercharger engine during W.W.I. It used hot exhaust gasses from a reciprocating engine to drive a turbine wheel that in turn drove a centrifugal compressor used for supercharging. 1920 - Dr. A. A. Griffith developed a theory of turbine design based on gas flow past airfoils rather than through passages. 1930 - Sir Frank Whittle in England patented a design for a gas turbine for jet propulsion. The first successful use of this engine was in April, 1937. His early work on the theory of gas propulsion was based on the contributions of most of the earlier pioneers of this field.

The specifications of the first jet engine were: Airflow = 25 pounds/sec Fuel Consumption = 200/gal/h or 1300 lb/h Thrust = 1000 lb Specific Fuel consumption = 1300/1000 = 1.3 lb/lb/h

History of jet engines1936 - At the same time as Frank Whittle was working in Great Britain, Hans von Ohain and Max Hahn, students in Germany developed and patented their own engine design.1939 (August) - The aircraft company Ernst Heinkel Aircraft flew the first flight of a gas turbine jet, the HE178.1941 - Sir Frank Whittle designed the first successful turbojet airplane, the Gloster Meteor, flown over Great Britain. Whittle improved his jet engine during the war, and in 1942 he shipped an engine prototype to General Electric in the United States. America's first jet plane was built the following year. 1942 - Dr. Franz Anslem developed the axial-flow turbojet, Junkers Jumo 004, used in the Messerschmitt Me 262, the world's first operational jet fighter.

Comparison between Jet engines and Reciprocating enginesThe main function of any airplane propulsion system is to provide a force to overcome the aircraft drag, this force is called thrust. Both propeller driven aircraft and jet engines derive their thrust from accelerating a stream of air - the main difference between the two is the amount of air accelerated. A propeller accelerates a large volume of air by a small amount, whereas a jet engine accelerates a small volume of air by a large amount.

Comparison between Jet engines and Reciprocating engines

DEFINITIONSPowerplant an aircraft engine and its component parts, and other parts necessary to properly install such engine in an aircraft, but not the propeller (if used).

Aircraft engine an engine used or intended to be used for propulsion of aircraft and includes all parts, appurtenances and accessories thereof, other than propellers.

ENGINE CLASSIFICATIONSHeat EnginesEngines that convert heat energy to mechanical energyTYPES OF COMBUSTION ENGINES (HEAT ENGINES)1. External Combustion Engine2. Internal Combustion EngineTYPES OF INTERNAL COMBUSTION ENGINES1. Reciprocating Engines (RE)2. Jet EnginesReaction Engines Engines that generates thrust by its reaction to the flow in the opposite direction of a mass of air

TYPES OF JET ENGINESATHODYD = Aero-Thermodynamic DuctsRocketsGas Turbine Engines

TYPES OF JET ENGINESRamjeta jet engine in which fuel is burned in a duct with air compressed by the forward motion of the aircraft .

TYPES OF JET ENGINESPulsejeta ramjet engine in which air, admitted through movable vanes, mixes with fuel in the combustion chamber. The resulting explosion forces the vanes shut, causing a pulsating thrust.

TYPES OF JET ENGINESRocketan engine that carries both fuel and oxidizer that it burns in a combustion chamber, producing thrust by expelling the expanding hot gases through a nozzle.

TYPES OF JET ENGINESGas Turbine Enginean internal-combustion engine in which a turbine is turned by hot gases consisting of compressed air and the products of the fuels combustion.

Scientific PrinciplesNewtons Laws of MotionBernoullis PrincipleBoyles LawBrayton Cycle

JET PROPULSION PRINCIPLENewtons First Law of MotionA body will remain at rest unless a force acts on it.

THRUSTWhat is Thrust?

It is the force that pushes you deep into your seat as you speed down the runway for take-off.

It is the force that propels an airplane forward through the air.

JET PROPULSION PRINCIPLEHow is THRUST created?Balanced forces on an object prevent movement. If forces on an object are the same in all directions the object will not move.

JET PROPULSION PRINCIPLEUnbalanced forces cause an object to move.During operation, a jet engine pushes gases out of the exhaust nozzle. This makes an unbalanced force towards the front of the engine. Unbalanced forces cause jet engines to make thrust.

JET PROPULSION PRINCIPLENewton's 2nd Law of Motion states "Force equals mass accelerated (F = ma)."When a jet engine accelerates air (mass), it makes thrust (force).When a jet engine moves a small quantity of air, it makes a small quantity of thrust.When it moves a large quantity of air, it makes a large quantity of thrust.

JET PROPULSION PRINCIPLE

JET PROPULSION PRINCIPLENewton's 3rd Law of Motion states "Every action has an equal and opposite reaction."The ACTION is the jet exhaust going through the jet engine.The REACTION is the jet engines then moves forward.

JET PROPULSION PRINCIPLEJet engine thrust can be increased in two ways:increase the speed of exhaust gases.increase the quantity of exhaust gases.Increased engine thrust will make an aircraft fly faster or with more weight.

JET PROPULSION PRINCIPLEBernoullis Principle

Pressure is inversely proportional to velocity

JET PROPULSION PRINCIPLEBoyles LawPressure and Volume are inversely proportional as long as temperature is kept constant

JET PROPULSION PRINCIPLEBrayton Cycle

STANDARD DAY CONDITIONSStandard day conditions are used by engineers when calculating thrust rating.As air temperature increases, engine output decreases. As air temperature decreases, engine output increases.As air density increases, engine output increases. As air density decreases, engine output decreases.

STANDARD DAY CONDITIONS

TYPES OF GAS TURBINE ENGINES (GTE)TurbojetTurboshaftTurbopropTurbofan

TYPES OF GAS TURBINE ENGINES (GTE)TURBOJETa gas turbine engine in which the turbine extracts only the power required to drive the compressor and accessories necessary for continuous operation. The high velocity imparted to the exhaust gases by the exhaust nozzle provides the thrust for propulsion.

TYPES OF GAS TURBINE ENGINES (GTE)

TYPES OF GAS TURBINE ENGINES (GTE)TURBOSHAFTA gas turbine engine equipped with an output shaft driven by the turbine to drive a rotor, e.g., the main rotor of a helicopter.

TYPES OF GAS TURBINE ENGINES (GTE)TURBOPROPa turboshaft engine in which the output shaft drives a propeller.

TYPES OF GAS TURBINE ENGINES (GTE)TURBOFANa gas turbine engine that drives a shrouded fan and causes a portion of the fan airflow to bypass the gas turbine.

BASIC COMPONENTSInletCompressorCombustorTurbineExhaust NozzleAccessories

BASIC COMPONENTSDivision as Sections (according to function)Division as Modules (according to method of attachment)

INLETThe air inlet is designed to conduct incoming ram air to the compressor with minimal energy loss resulting from drag or ram pressure loss.The amount of air passing through the engine is dependent upon three factors:(1.)The compressor speed (rpm)(2.)The forward speed of the aircraft(3.)The density of ambient (surrounding) air.

COMPRESSORSThe compressor section's primary function is to supply air in sufficient quantity to satisfy the requirements of the combustion burners.A secondary function of the compressor is to supply bleed air for various purposes in the engine and aircraft.Airconditioning/Pressurization

COMPRESSORSWing Anti-Icing/Nacelle Anti-IcingPotable Water Tank PressurizationHydraulic Tank PressurizationCargo Compartment HeatingPneumatic Drive UnitsEngine StartingThrust Reverser Center Drive Unit

TYPES OF COMPRESSORSCentrifugal Flow CompressorsImpeller

Diffuser

CompressorManifold

TYPES OF COMPRESSORSAxial Flow Compressors

Axial Flow Compressor Velocity & Pressure Distribution

COMBUSTORThe combustion section houses the combustion process which raises the temperature of the air passing through the engine.The combustion process releases energy contained in the air-fuel mixture.The major part of the released energy is required at the turbine to drive the compressor.

COMBUSTORThe remaining energy creates the reaction or propulsion and passes out the rear of the engine in the form of a high-velocity jet.All combustion chambers contain the same basic elements:(1.)A casing.(2.)A perforated inner liner.(3.)A fuel injection system.(4.)Some means for initial ignition.

TYPES OF COMBUSTOR

TURBINESThe turbine transforms a portion of the kinetic (velocity) enemy of the exhaust gases into mechanical energy to drive the compressor and accessories. The turbine assembly consists of two basic elements the stator and the rotor, as does the compressor unit.

TURBINES

TYPES OF TURBINES

METHODS OF COOLING

EXHAUST SECTIONThe exhaust section direct the flow of hot gases rearward in such a manner as to prevent turbulence and at the same time impart a high final or exit velocity to the gases.

EXHAUST SECTION

ACCESSORIES SECTIONThe primary function is to provide space for mounting the accessories necessary for the operation and control of the engine. Generally, it also includes accessories concerned with the aircraft such as electric generators and fluid power pumps. The power for both the engine and aircraft accessories is extracted through a system of gearboxes and shafts.

ACCESSORIES SECTION

GEARBOX ASSEMBLIESInletGearbox

RadialDriveshaft

TransferGearboxHorizontalDriveshaft

AccessoryGearbox

Airbus A340 Accessory Drive Section

Engine SystemsFuel SystemLubrication SystemAir SystemCompressor Control SystemClearance Control SystemCooling SystemIgnition SystemStarting System

Engine SystemsThrust Reverser SystemEngine Control SystemEngine Indication System

Engine Fuel SystemsMainEngineControlAGBFuelPumpFuel Shut-off Valve

OIL SYSTEM

OIL SUMPS

COMPRESSOR CONTROL SYSTEM

Variable Bleed Valve & Variable Stator Vane System

ACTIVE CLEARANCE CONTROL SYSTEMDuring Engine Operation, especially during transients, casing-to-rotor clearances can change rapidly.Stator & rotor thermal responses are not the sameRotors tend to be heavier than stators, and require longer times to heat and to cool them.

ACTIVE CLEARANCE CONTROL SYSTEMStators are usually much more exposed to heating and cooling airflows than are rotors.To maintain close clearances during cruise, important for good cruise performance, efficiency and SFC, and to keep transient clearances satisfactory for good response, careful rotor-stator coordination has to be done.

ACTIVE CLEARANCE CONTROL SYSTEMCaseClearanceRotorBlade

Casing-to-Rotor Blade Clearance Variation During A Transient

ACTIVE CLEARANCE CONTROL SYSTEM

IGNITION SYSTEM

ENGINE STARTING SYSTEM

THRUST REVERSER SYSTEMThrust reverser supply the aircraft with reverser thrust, on the ground, to decrease the distance necessary to safely stop the aircraft.

TYPES OF THRUST REVERSERSTranslating Cowl Type

TYPES OF THRUST REVERSERSClam Shell Type

TYPES OF THRUST REVERSERSTurboprop Reverse Pitch

ENGINE CONTROL SYSTEM

FEEDBACK SYSTEM

ENGINE INDICATING SYSTEM

THE END