A SEMINAR ON A SEMINAR ON
TURBOFANTURBOFAN Presented by
PRADEEP A S
AGENDAAGENDA
IntroductionIntroduction Propulsion, ThrustPropulsion, Thrust Gas TurbinesGas Turbines Turbofan engine workingTurbofan engine working Types of TurbofanTypes of Turbofan Parts of turbofanParts of turbofan Turbofan benefitsTurbofan benefits
TURBOFANTURBOFAN
•Powered by gas turbine
•The combination of thrust produced from the fan & the exaust from the core is more efficient
•Efficient at subsonic speeds•Used in commercial jet aircraft
PROPULSIONPROPULSION
Jet propulsion is the thrust imparting Jet propulsion is the thrust imparting forward motion to an object as a reaction forward motion to an object as a reaction to the rearward expulsion of a high velocity to the rearward expulsion of a high velocity liquid or gaseous stream.liquid or gaseous stream.
Based on Newtons third law.Based on Newtons third law.For an aircraft to move, some kind of For an aircraft to move, some kind of
propulsion system is required.propulsion system is required.Turbofan engines serves the purposeTurbofan engines serves the purpose
THRUSTTHRUST
Equilibrium Reaction Action
Thrust•Jet – moves small mas of gas at high velocity
•Thrust is the force which moves the Aircraft through the air
•Thrust is used to overcome drag of an aeroplane
•This is generated by the aircraft through Some kind of propulsion system
HOW GAS TURBINE ENGINES HOW GAS TURBINE ENGINES WORK?WORK?
Pressurised gas spins the turbine
GAS TURBINE ADVANTAGESGAS TURBINE ADVANTAGES
Great power to weight ratioGreat power to weight ratio
Considerably smaller in sizeConsiderably smaller in size
Mechanical efficiency is highMechanical efficiency is high
Rotor blades operate at high speeds.Rotor blades operate at high speeds.
GAS TURBINE GAS TURBINE DISADVANTAGESDISADVANTAGES
ExpensiveExpensiveOperate at high speeds and high Operate at high speeds and high
temperaturetemperatureTend to use more fuel when they are idlingTend to use more fuel when they are idling
CHALLENGES
•Vibration problems are severe.•The design of rotor blades is a complex phenomenon
PROPULSION DEVICESPROPULSION DEVICES
JET ENGINE BASIC JET ENGINE BASIC OPERATIONOPERATION
Air enters through the Air enters through the intake ductintake duct Air compressed by passage through the Air compressed by passage through the compressorcompressor Mixed with fuel in the Mixed with fuel in the combustion chambercombustion chamber
Fuel is ignited, pressure and temperature raised. Fuel is ignited, pressure and temperature raised. Some of the pressure used to turn a Some of the pressure used to turn a turbine.turbine. Turbine shaft drives the compressor.Turbine shaft drives the compressor.
Hot high pressure air forced through a Hot high pressure air forced through a nozzle.nozzle. The reaction force is the engine thrust.The reaction force is the engine thrust.
GAS TURBINES-BRAYTON GAS TURBINES-BRAYTON CYCLECYCLE
BRAYTON CYCLEBRAYTON CYCLE
•1-2 Isentropic compression (in a compressor) •2-3 Constant pressure heat addition
•3-4 Isentropic expansion (in a turbine)
•4-1 Constant pressure heat rejection
Turbofan HistoryTurbofan History
In early jet engines, high velocity jet In early jet engines, high velocity jet exhaust mixing with surrounding air is exhaust mixing with surrounding air is major source of noisemajor source of noise
In 1960’s, low-bypass-ratio turbofans In 1960’s, low-bypass-ratio turbofans introducedintroduced
In 1967, NASA initiates acoustically In 1967, NASA initiates acoustically treated nacelle programtreated nacelle program
Engine ducts and inlets are lined with Engine ducts and inlets are lined with acoustic treatmentsacoustic treatments
Flight tested on Boeing 707 and DC-8Flight tested on Boeing 707 and DC-8Acoustic treatment proven effective and Acoustic treatment proven effective and
feasiblefeasibleEven greater jet noise reduction is Even greater jet noise reduction is
achievedachievedWith further reduction of jet noise, fan With further reduction of jet noise, fan
noise becomes major noise sourcenoise becomes major noise sourceGerman Daimler-Benz, the very first German Daimler-Benz, the very first
turbofan tested on April 1,1943turbofan tested on April 1,1943 Improved materials and twin compressors Improved materials and twin compressors
in the Pratt & Whitney JT3C enginein the Pratt & Whitney JT3C engine
How does turbofan engine work?How does turbofan engine work?
• The incoming air is captured by the inlet• The incoming air is compressed by the compressor• In the combustion chamber, the Compressed air is mixed with fuel and then ignited• The hot exhaust gases passes through the Core, fan turbines & then out of the nozzle • A turbofan gets thrust from both fan & the core• The ratio of air that goes around the engine & To the air that goes through the core is called BYPASS RATIO
TYPES OF TURBOFANTYPES OF TURBOFAN
Low bypass turbofanLow bypass turbofan
high bypass turbofanhigh bypass turbofan
Afterburning turbofanAfterburning turbofan
Low bypass turbofanLow bypass turbofan
• More fuel efficient than basic turbojets• A bypass flow can be introduced if the turbine inlet temperature is allowed to increase•To compensate for a Correspondingly smaller core flow•Better specific fuel consumption Can be achieved•Normally used in military aircraft
High bypass turbofanHigh bypass turbofan
A. Low pressure spoolB. High pressure spoolC. Stationary components1. Nacelle2. Fan3. Low pressure compressor4. High pressure compressor5. Combustion chamber6. High pressure turbine7. Low pressure turbine8. Core nozzle9. Fan nozzle
Low specific thrust/high bypass ratio Low specific thrust/high bypass ratio turbofans primarily used in civilian turbofans primarily used in civilian transport aircrafttransport aircraft
Multistage fan replaced by single stage Multistage fan replaced by single stage unitunit
Reducing core flow increases bypass Reducing core flow increases bypass ratio(5:1)ratio(5:1)
AFTERBURNING TURBOFANAFTERBURNING TURBOFAN
•An afterburner is a combustor located downstream of the turbine blades and directly upstream of thenozzle, which burns fuel from afterburner-specific fuel injectors•Raises the temperature of exhaust gases by a significant amount•Higher exhaust velocity• USED -To give significant thrust boost for take off - transonic acceleration -combat maneuvers •Fuel intensive
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