jet prop 4

JET PROPULSION

Part 4

Types of Jet Engines

Turbo JetAvon, Olympus 593

Turbo Fan - Bypass Engines

SMALL BYPASS Spey, BR700MEDIUM BYPASS Pegasus, BR715, V2500LARGE BYPASS RB211, Trent Series

Turbo PropPROPELLER Dart, Tyne, BR715TP

Turbo Shaft

HELICOPTER Lycoming T55, GemRN SHIPS Marine SpeyPOWER GENERATION Industrial Spey & Trent

Engine Types

Flame almost goes out - no power – no thrust.

This is called: - COMPRESSOR SURGE

Rolls Royce Avon

Turbo Jet

17 Stage Compressor driven by a 3 stage turbine

With RPM (i.e. Thrust) changes, the airflow velocity does not change

in proportion to engine RPM

At low rpm the rear of the compressor cannot get rid of all the air from the front of the compressor

This can result in the rear end of compressor ‘choking’

So airblasts

forwards

Rolls Royce Avon

Turbo Jet

Air dumped overboard

Rear end of compressor ‘unchoked’

Rearward movement of air restored

Power restoredBUT

air dumped sideways out of the engine produces no thrust.

So a more efficient system was required

Rolls Royce Avon

Turbo Jet

‘Bleed’ valve

‘Excess’ air is dumped overboard through a valve

Turbo Jet

Single Shaft LayoutThe Olympus 593

driven byLow Pressure Compressor Low Pressure Turbine

driven byHigh Pressure Compressor High Pressure Turbine

The Two Shaft Layout

The Two Shaft Layout

Turbo JetThe Olympus 593

Compressor surges lessened

No wasted energy/thrust

Allows front end of compressor to slow down – move less airand

Allows rear end of compressor to speed up – move more air

Turbo Jet

The turbojet is the simplest and earliest form of gas turbine.

Used principally in high speed aircraft where its relatively low frontal area

and high jet velocity are advantages.

Examples are the Concorde supersonic transportand a variety of military aircraft including the Dominie/HS125.

Part of the air is compressed fullyand passes into the combustion chamber,

while the remainder is compressed to a lesser extent and ducted around the hot section.

Turbo FanLow Bypass Engine

Rolls Royce Spey Adour BR710 Series

Two shaft layout with Contra-rotating shafts

It has low pressure and high pressure AXIAL Flow Compressors

Turbo FanMedium Bypass Engine

Pegasus

Bypass flow to ‘Cold’ (front) Nozzles

Core flow to ‘Hot’(rear) Nozzles

Turbo FanHigh Bypass Engine

RB211 Series (Trent)

In service with RAF – Wide-body Tristar Tanker/Transport

Boeing 747 and later series, Airbus A330 and larger a/c

Three shaft layout – all rotate same direction

LP(Fan) Intermediate and HP AXIAL Flow Compressors

Turbo FanHigh Bypass Engine

RB211 Series (Trent)

Turbo FanTurbofan engines are loosely categorised by

the size of the bypass compared to the core flow. (The amount of air entering the core engine

compared to the bypass duct)which is called the Bypass Ratio.

The low bypass ratio is approximately 1:1.Half the air goes through the core or hot section,

the other half goes through the bypass.

Medium bypass engines have a 5:1 ratio,while high bypass have a ratio of 10:1 or more.

Turbo Fan

The turbofan (bypass) reduces overall jet velocity, giving better propulsive efficiency at lower speeds,

lower noise levels and improved specific fuel consumption,

features which make the turbofan ideal for both civil and military aircraft.

Examples are the Boeing 747 and 757, the Jaguar and Hawk, and the Tornado.

The Harrier has a variation of the turbofan.

Turbo PropRolls Royce Dart

Reduction Gearbox

Prop Shaft

Dart RDa6 = 2 stage turbine Dart RDa7 = 3 stage turbine

Turbine drives 2 stage CENTRIFUGAL Compressor and Propeller

Over 70 Marks of Engine – different power levels – 15 different aircraft

Fokker F27, Fairchild F27, Briguet Alize, (and P51 Mustang and Dakota!)

Turbo PropTyne

C160 Transall, Shorts Belfast, Brequet Atlantic, Avro Lincoln,Canadair CL44, Vickers Vanguard, Aeritalia 222.

1 Stage HP Turbine

9 Stage HP Compressor

3 Stage LP Turbine

6 Stage LP Compressor

Prop Shaft(via Reduction

Gearbox)

Reduction Gearbox

Turbo PropTyne

C160 Transall, Shorts Belfast, Brequet Atlantic, Avro Lincoln,Canadair CL44, Vickers Vanguard, Aeritalia 222.

1 Stage HP Turbine

9 Stage HP Compressor

3 Stage LP Turbine

6 Stage LP Compressor

Prop Shaft(via Reduction

Gearbox)

Reduction Gearbox

RR Allison T56-A-15

Turbo Prop

C130 Hercules

RR Allison T56-A-15

4 Stage Turbine

14 Stage HP Compressor

Turbine drives compressor and propeller

Output Shaft

Reduction Gearbox

Thrust Strut

Air Intake

Turbo Prop

The turboprop is basically a turbojetwith an extra turbine designed to absorb the energy

remaining in the gas stream after sufficient hasbeen removed to drive the compressor.

The turboprop is a very efficient power unit for relative low speed, low altitude aircraft.

Examples are the 748 and F27,and the Transall C-160 and Atlantic.

Turbo ShaftLycoming T55-GA-714

Boeing CH47 Chinook

Turboshaft with Free Power Turbine

Combining Transmission

Front Rotor Transmission

Rear Rotor Transmission

Turbo Shaft

The turboshaft is virtually a turboprop without a propeller.

The power turbine absorbs as much of the remaining gas energy as possible

and the residual thrust is very low.

The main use of the turboshaft is the helicopterand industrial and marine application, including power and pumping stations,

hovercraft and ships.

Examples are the Lynx, Chinook and the Sea King.

Which of these is a turbo jet engine?

Tyne

Spey

Pegasus

Olympus

Check Understanding

Which of the following features makes the turbofan ideal

for both civil and military aircraft?

The turbine absorbs as much of the gas energy as possible

Lower noise levels andimproved specific fuel consumption

Very efficient power unit for relative low speed, low altitude

It is ideal for high-speed,high-altitude aircraft

Check Understanding

Which of these is a turbo fan engine?

Tyne

Pegasus

Dart

Gem

Check Understanding

Which application or type of operation best suits the turbojet engine?

In low speed aircraftoperating at high altitudes

In high speed aircraft wherelow frontal area is an advantage

In low speed aircraft operating at low altitudes

In helicopters

Check Understanding

Which of these is a turbo prop engine?

Check Understanding

RB 211

Dart

Spey

Avon

Which of these statements applies to a turboprop engine?

It has one less turbinecompared to a turbojet

It has an extra turbinecompared to a turbojet

It is ideal for high-speed,high-altitude aircraft

It has a very highresidual thrust

Check Understanding

Which of these is a turbo shaft engine?

Tyne

Lycoming

RB 211

Trent

Check Understanding

JET PROPULSION

End of Presentation