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A SEMINAR ON

TURBOFANPresented by

Shishir Dhone

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AGENDA

Introduction

Propulsion, Thrust

Gas Turbines Turbofan engine working

Types of Turbofan

Parts of turbofan Turbofan benefits

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TURBOFAN

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

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PROPULSION

Jet propulsion is the thrust imparting

forward motion to an object as a reaction

to the rearward expulsion of a high velocity

liquid or gaseous stream.

Based on Newtons third law.

For an aircraft to move, some kind of

propulsion system is required.

Turbofan engines serves the purpose

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THRUST

Equilibrium Reaction Action

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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

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HOW GAS TURBINE ENGINES

WORK?

Pressurised gas spins the turbine

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GAS TURBINE ADVANTAGES

Great power to weight ratio

Considerably smaller in size

Mechanical efficiency is high

Rotor blades operate at high speeds.

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GAS TURBINE

DISADVANTAGES Expensive

Operate at high speeds and high

temperature

Tend to use more fuel when they are idling

CHALLENGES

Vibration problems are severe.

The design of rotor blades is a complex

phenomenon

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PROPULSION DEVICES

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JET ENGINE BASIC

OPERATION

Air enters through the intake duct

Air compressed by passage through the compressor

Mixed with fuel in the combustion chamber

Fuel is ignited, pressure and temperature raised.

Some of the pressure used to turn a turbine.

Turbine shaft drives the compressor.

Hot high pressure air forced through a nozzle.

The reaction force is the engine thrust.

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GAS TURBINES-BRAYTON

CYCLE

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Turbofan History

In early jet engines, high velocity jet

exhaust mixing with surrounding air is

major source of noise

In 1960s, low-bypass-ratio turbofans

introduced

In 1967, NASA initiates acoustically

treated nacelle program Engine ducts and inlets are lined with

acoustic treatments

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Flight tested on Boeing 707 and DC-8

Acoustic treatment proven effective and

feasible Even greater jet noise reduction is

achieved

With further reduction of jet noise, fannoise becomes major noise source

German Daimler-Benz, the very first

turbofan tested on April 1,1943 Improved materials and twin compressors

in the Pratt & Whitney JT3C engine

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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

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TYPES OF TURBOFAN

Low bypass turbofan

high bypass turbofan

Afterburning turbofan

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Low bypass turbofan

More fuel efficient than

basic turbojets

A bypass flow can be

introduced if the turbineinlet temperature is

allowed to increase

To compensate for a

Correspondingly smaller

core flowBetter specific fuel

consumption Can be

achieved

Normally used in military aircraft

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High bypass turbofan

A. Low pressure spool

B. High pressure spool

C. Stationary components

1. Nacelle

2. Fan

3. Low pressure compressor

4. High pressure compressor

5. Combustion chamber

6. High pressure turbine

7. Low pressure turbine

8. Core nozzle9. Fan nozzle

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Low specific thrust/high bypass ratio

turbofans primarily used in civilian

transport aircraft

Multistage fan replaced by single stage

unit

Reducing core flow increases bypass

ratio(5:1)

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AFTERBURNING TURBOFAN

An afterburner is a combustor

located downstream of the turbine

blades and directly upstream of the

nozzle, which burnsfuel from

afterburner-specific fuel injectorsRaises 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