CONTENTS1.0 INTRODUCTION.........................................................................................................................3

1.1 HISTORY OF TRENT 900..........................................................................................................4

2.0 ENGINE TYPE AND CONSTRUCTION...........................................................................................9

2.1 ENGINE CHARACTERISTICS...................................................................................................12

3.0 OPERATING PRINCIPLE AND APPLICATION OF TRENT 900 ENGINE...............................................30

3.1 OPERATING PRINCIPLE...............................................................................................................30

3.1.1 INLET, FAN AND COMPRESSOR...........................................................................................32

3.1.2 COMBUSTION SECTION.......................................................................................................34

3.1.3 TURBINE SECTION...............................................................................................................35

3.1.4 EXHAUST SECTION..............................................................................................................36

3.1.5 ACCESSORIES SECTION........................................................................................................37

3.3 OPERATING LIMIT......................................................................................................................37

3.3.1 THRUST RATING..................................................................................................................38

3.3.2 TEMPERATURE LIMIT..........................................................................................................39

3.3.3 PRESSURE LIMIT.................................................................................................................40

3.4 APPLICATION OF TRENT 900......................................................................................................42

3.4.1 MILITARY.............................................................................................................................42

3.4.2 INDUSTRIAL...................................................................................................................43

3.4.3 COMMERCIAL AIRCRAFT...........................................................................................43

4.0 ADVANTAGES AND DISADVANTAGES............................................................................................44

4.1 GENERALS COMPARISON.....................................................................................................44

4.2 TRENT 900 VERSUS GP7200.................................................................................................47

4.2.1 COMPARISON BETWEEN SPECIFICATIONS...................................................................48

4.2.2 ADVANTAGES TRENT 900 OVER GP 7200.....................................................................49

4.2.3 DISADVANTAGE TRENT 900 VERSUS GP 7200..............................................................49

5.0 FUTURE TRENDS......................................................................................................................50

5.1 ACTIVE MAGNETIC BEARINGS...................................................................................50

5.1.1 INTRODUCTION.......................................................................................................50

5.1.2 WORKING PRINCIPLE............................................................................................50

5.1.3 ADVANTAGES OF JET ENGINE RUNNING ON MAGNETIC BEARINGS......51

5.2 THE MULTI-FUEL BLENDED WING BODY AIRCRAFT............................................52

5.3 HYBRID ENGINE..............................................................................................................53

6.0 SUMMARY.....................................................................................................................................56

7.0 REFERENCES..................................................................................................................................58

1.0 INTRODUCTION

An aircraft engine is the component of the propulsion system for an aircraft that

generates mechanical power. A good engine must produce enough thrust to drive

the aircraft, high power-to-weight ratio, fuel efficient, quiet, easy to maintains and low

in cost. Big commercial aircraft like Airbus A380 must compensate to this feature to

become one of the leading and largest passenger airliners and therefore must has

an optimum engine to achieve it. Because of that, this report will focus on the “heart”

of this humongous aircraft which is the Trent 900 to know why it is chosen to driven

the Airbus A380, the largest commercial aircraft in the world.

For ease of understanding and future reference, we will divide this report into five

parts:

1. History

2. Engine Parts and Construction

3. Operating Principle

4. Advantages and Disadvantages

5. Future Trend

1.1 HISTORY OF TRENT 900

Rolls-Royce Trent 900 (T900) is manufactured by the British engine public

multinational holding company, Rolls- Royce Holdings. Rolls-Royce Limited is an

English company famously known for making cars and then, aero-engine

manufacturing company founded by Charles Stewart Rolls and Henry Royce Sir

Frederick on March 15, 1906 as a result of the partnership established in 1904.

Rolls-Royce Trent 900 is a series of turbofan engine, developed from the

RB211 and is one of the Trent engine families.

The Rolls-Royce RB211 is a type of high-bypass turbofan engines made by

Rolls-Royce plc and could generate 37,400 to 60,600 pounds-force (166-270

kilonewtons) thrust.

Originally developed for the Lockheed L-1011 Tristar, it entered service in

1972 and is the only engine to power this type of aircraft. This RB211 engine has

turn Rolls-Royce from a decent competitor in the aircraft engine industry into a world

leader. Already in the early 1970's engine has been calculated by the company to be

able to at least 50 years of continuous development.

Figure 1.1 Trent 900 Engine

When Rolls-Royce was privatised in April 1987, its share of the large civil

turbofan market was only 8%. Despite increasing sales success with the RB211,

General Electric and Pratt & Whitney still dominated the market. At that time, the

aircraft manufacturers were proposing new planes that would require unprecedented

levels of thrust. Furthermore the Boeing 777 and Airbus A330 were to be twin-

engined, and their airline customers were demanding that they be capable of

operating in the Extended-range Twin-engine Operations (ETOPS) environment at

the time of their initial introduction into service.

Rolls-Royce decided that to succeed in the large engine market of the future,

it would have to offer engines for every large civil airliner. In view of the enormous

development costs required to bring a new engine to market, the only way to do this

would be to have a family of engines based on a common core. The three-shaft

design of the RB211 was an ideal basis for the new family as it provided flexibility,

allowing the high-pressure (HP), intermediate-pressure (IP) and low-pressure (LP)

systems to be individually scaled. Rolls decided to launch a new family of engines,

which was formally announced at the 1988 Farnborough Airshow. Reviving a name

last used 30 years earlier, the new engine was named the Trent. The Trent name

had been used for two previous Rolls-Royce engines. The first Trent was the world's

first turboprop engine. The name was reused again in the 1960s for the RB203

bypass turbofan designed to replace the Spey. Rated at 9,980 lbf (44.4 kN) it was

the first three-spool engine, forerunner of the RB211 series, but it never entered

service.

Rolls-Royce has obtained significant sums of "launch investment" from the

British government for the Trent programmes, including £200 million approved in

1997 for Trent 8104, 500 and 600 and £250 million for Trent 600 and 900 in 2001.

No aid was sought for Trent 1000. Launch investment is repaid to the government by

a royalty on each engine sold.The basis for the Trent was the RB.211-524L, work on

which began in 1987.

Like its RB211 predecessor, the Trent uses a three-spool design rather than

the more common two-spool configuration. Although inherently more complex, it

results in a shorter, more rigid engine which suffers less performance degradation in

service than an equivalent twin-spool. The advantage three spools gives is that the

front-most fan (driven by the third, rearmost turbine) can be tuned to rotate at its

optimal (fairly low) speed; the two compressors are driven by the two other turbines

via their spools. The three spools are concentric, like a matryoshka doll.

All the engines in the Trent family share a similar layout, but their three-spool

configuration allows each engine module to be individually scaled to meet a wide

range of performance and thrust requirements. For example, the large 116-inch (290

cm) diameter fan of the Trent 900 keeps the mean jet velocity at take-off at a

relatively low level to help meet the stringent noise levels required by the Airbus

A380's customers. Similarly, core size changes enable the (High Pressure) turbine

rotor inlet temperature to be kept as low as possible, thereby minimising

maintenance costs. The overall pressure ratio of the Trent 800 is higher than the

700's despite sharing the same HP system and Intermediate Pressure turbine; this

was achieved by increasing the capacity of the IP compressor and the Low Pressure

turbine.

Trent engines use hollow titanium fan blades with an internal Warren-girder

structure to achieve strength, stiffness and robustness at low weight. The blades can

rotate at 3300 RPM with a tip speed of 1730 km/h, well above the speed of sound.

The single-crystal nickel alloy turbine blades are also hollow, and air is pushed

through laser-drilled holes in them to cool them because the gas temperature is

higher than the melting point of the blades. They each remove up to 560 kW from the

gas stream.

The completely redesigned core turbo machinery delivers better performance,

noise and pollution levels than the RB211. So significant are the improvements that

Rolls-Royce fitted the Trent 700's improved HP system to the RB211-524G and -

524H, creating -524G-T and -524H-T respectively.

When the RB211 programme originally started, it was intended that none of

the compression system would require variable stators, unlike the American

competition. Unfortunately, it was found that, because of the shallow working line on

the Intermediate Pressure Compressor (IPC), at least one row of variable stators

was required on the IPC, to improve its surge margin at throttled conditions. This

feature has been retained throughout the RB211 and Trent series. Although the

original intent was not met, Rolls-Royce eliminated the need for many rows of

variable stators, with all its inherent complexity, thereby saving weight, cost and

improving reliability.

Versions of the Trent are in service on the Airbus A330, A340, A380, Boeing

777, and Boeing 787, and variants are in development for the forthcoming A350

XWB. The Trent has also been adapted for marine and industrial applications.

First run in August 1990 as the model Trent 700, the Trent has achieved

significant commercial success, having been selected as the launch engine for both

of the 787 variants (Trent 1000) note 1, the A380 (Trent 900) and the A350 (Trent

XWB). Its overall share of the markets in which it competes is around 40%. Sales of

the Trent family of engines have made Rolls-Royce the second biggest supplier of

large civil turbofans after General Electric, relegating rival Pratt & Whitney to third

position.

In keeping with Rolls-Royce's tradition of naming its jet engines after rivers,

this engine is named after the River Trent in the Midlands of England. Singapore

Airlines is currently the largest operator of Trents, with five variants in service or on

order.

Airbus had begun development of a larger successor to the Boeing 747, an

aircraft designated A3XX which was later to be launched formally as A380 and Rolls-

Royce has announced it would develop the Trent 900 to power the A380 in 1996.

The Trent 900 became the A380's launch engine when Singapore Airlines specified

the engine for its order for 10 A380s in October 2000 and swiftly followed by Qantas

in February 2001.

To build the Trent 900, Airbus has share their risk and revenue with seven

partners: Industria de Turbo Propulsores (low pressure turbine), Hamilton

Sundstrand (electronic engine controls), Avio S.p.A. (gearbox module), Marubeni

Corporation (engine components), Volvo Aero (intermediate compressor case),

Goodrich Corporation (fan casings and sensors) and Honeywell (pneumatic

systems). In addition, Samsung Techwin, Kawasaki Heavy Industries and

Ishikawajima-Harima Heavy Industries (IHI) are programme associates.

ON May 17 2004, T900 made the first flight with 340- 300 by replacing the

internal CFM56-5 port. The engine is certified by EASA on October 2009 and the

FAA gave their certification on December 4, 2006. In October 2007, Rolls-Royce

announced that T900 has resumed production after a 12-month suspension caused

by the delay in producing the A380. On September 27, 2007, British Airways has

chosen T900 to provide the thrust of their 12 A380 aircraft. This order provides share

of the A380 engine market to 52% at the end of February 2009. For A380 it comes in

two thrust rating 310 kN (70,000 lbf) and 320 kN (72,000 lbf) but was able to achieve

360 kN (81,000 lbf). It has a large number of technology inherited from the 8104

demonstrators with its 2.95 m (116 in) diameter, swept-back fan which provides

greater thrust for the same engine size and also about 15 percent lighter than

previous wide-chord blades. It is also the first member of the Trent family to have a

counter-rotating HP spool and use highly reliable core Trent 500. It is the only A380

engine that can be transported on a Boeing 747 cargo aircraft. Characteristics of the

engine has 2.95 m (116 in) diameter propeller struck the back of a larger terrace to

the same engine size and also about 15 percent lighter than the previous wide-chord

blade. Trent 900 is the first of the Trent family to have a contra-rotating HP spool

andusing highly reliable core Trent 500.

Goodrich FADECs is used as an engine controller on most Trent family while

Hamilton Sundstrand engine controller is used for Trent 900. Hamilton Sunsdtrand is

a United Technologies (UTC) company which is the parent company of Pratt &

Whitney who produce another engine for A380, GP7000 with the help of GE Aircraft

Engines. This kind of cooperation among competitors is common in the aircraft

industry as it provides for risk-sharing among them and variety in source countries,

which can be an important factor in the choice of the airline's airframe and

powerplant.

The Trent 900 will be the first Trent engine fitted with the advanced Engine

Health Monitoring (EHM) system based on QUICK Technology.

Rolls-Royce Trent 900 engines have many variants such as Trent 970B- 84

with £ 78,300. terrace use by Singapore Airlines, Lufthansa, China Southern Airlines

and Malaysia Airlines., Trent 972B- 84 (80 210 lbs. Used by Qantas), Trent 977B- 84

(83 840 lbs. Variants for A380-843F) and Trent 980- 84 (84 100 lbs.for the A380-941

variant).

2.0 ENGINE TYPE AND CONSTRUCTION

Rolls-Royce Trent 900 series turbofan engine is one that has been developed

from the RB211 and belongs to Trent engine family. Besides that, Trent 900 is a type

of turbofan engine or fanjet that utilized air-breathing jet engine that widely use in

aircraft propulsion. It consists of multi-blade ducted propeller driven by a gas turbine

engine. The word "turbofan" is derived obviously from "turbine" and "fan": turbo

refers to a gas turbine engine that convert mechanical energy from combustion, and

the fan is a ducted fan that used the mechanical energy from gas turbine to generate

forward thrust that accelerate air rearwards.

Therefore, all the air taken by turbofan engine passes through the engine

core, in a turbofan called bypasses air. Turbofan is a turbojet that being used to drive

a ducted fan, with both of those contributing to the thrust. How turbofan engine

work? The incoming air is accumulating by the engine inlet. Part of the air entering

through the fan and go through the core compressor and then the burner, where it is

mixed with fuel and combustion occur. The hot air passes through the core and fan

turbines and then out through exhaust nozzle, as in the basic turbojet. The rest of the

incoming air passes through fan and bypass, or go around the engine, such as air

through the propeller. Incoming air through the fan has slightly increased velocity

due to free flow. Thus, a turbofan engine gets it thrust both from the core and the

fan. The ratio of air that goes around the engine to the air that goes through the core

is called bypass ratio.

The Trent 900 engine consists of triple-spool high bypass ratio, axial flow,

turbofan with Low Pressure (LP), Intermediate Pressure (IP) and High Pressure (HP)

Compressors driven by separate turbines through coaxial shaft. The LP compressors

fan diameter is 2.95 m (116 in) with a swept fan blade and OGV’s to increase

efficiency and reduce noise. The combustion system utilizes single annular

combustor chamber. The LP and IP assemblies rotate independently anti-clockwise

direction; the HP assemblies rotate clockwise, when viewed from the rear of the

engine.

The Compressor and Turbine have the following features:

Compressor Turbine

Low Pressure – 1 stage (ccw) Low Pressure – 5 stages

Intermediate Pressure – 8 stages (ccw) Intermediate Pressure – 1 stage

High Pressure – 6 stages (cw) High Presssure – 1 stage

*ccw – counter-clockwise rotation, cw – clockwise rotation

The fan consists of 24 blades swept design that reduces the effects of the

shockwaves, as the tip of the fan rotates supersonically, making it lighter, quieter and

more efficient. Fan contaminant system used in Trent 900 is also the first to be

manufactured from Titanium and does not need the additional Kevlar wrap, making it

lighter and smaller.

At the engine core, the high pressure shaft rotates in the opposite direction to

the other two shafts, meaning the engine can be made lighter and more fuel efficient.

Figure 1.2 Trent blade of turbofan engine

Figure 1.3 Swept fan blades

Figure 2.20 Rolls-Royce Trent 900 4th generation fan blade – the most complicated aerodynamic structure on the A380. (1.07 metres long, 14 kg, pure titanium, “honeycomb” hollow wide chord,

supersonic swept

2.1 ENGINE CHARACTERISTICSGENERAL CHARACTERISTICS

Type: Three-shaft high bypass ratio (8.7–8.5) turbofan engine

Length: 5,477.5 mm (215.65 in) tip of spinner minus rubber tip to Tail Bearing

Housing Plug Mount Flange

Diameter: 2.95 m (116 in) LP compressor fan

Dry weight: 6,246 kg (13,770 lb.)

Components

Compressor: Single stage LP (CCW), Eight-stage IP compressor (CCW),six-

stage HP compressor (CW)

Combustors: Single annular combustor

Turbine: Single-stage HP turbine, single-stage IP turbine, five-stage LP

turbine

Performance

Maximum thrust: 334–374 kN or 75,000–84,000 lb. take-off (5min)

Overall pressure ratio: 37–39

Thrust-to-weight ratio: 5.46–6.11 (assuming 6,246 kg (13,770 lb.) mass /

weight of engine and certified to 334–374 kN or 75,000–

84,000 lb. of thrust)

EQUIPMENT

Trent 900 engine certification stated that the engine has been approved for

used with Aircelle Thrust Reverser Unit (TRU) at the inboard engine positions (part

numbers ASE 0010-XX-0 for the left hand installation and ASE 0050-XX-0 for the

right hand installation). Whilst, for Fixed Fan Duct (FFD) in the outboard engine

positions (part numbers ASE 5010-XX-0 for the left hand installation and ASE 5050-

XX-0 for the right hand installation). The Thrust Reverser Unit (TRU) and Fixed Fan

Duct (FFD) actually do not form part of the engine design and must be certified as

part of the aircraft part design.

DIMENSIONS

Generally, this engine measurement as table shown below:

Dimension Total

Overall Length (mm) 5477.5 (215.65 in)

Maximum Diameter (mm) 3944

Dry engine weight (kg) 6246 (13770 lbs.)

Length – measured from tip of spinner minus rubber tip to Tail Bearing Housing

Plug Mount Flange

Diameter – around centre line, inc. VFG cooler not includes drains mast.

Weight – not including fluids and Nacelle EBU

ENGINE BUILD THEORY

Module 01 low pressure (LP) compressor rotor

Fan disc on its shaft driven by the LP turbine

Dovetail slots machined into the disc locate the fan blades

Trent engines have between 20 and 26 fan blades, with 20 on the Trent 1000

Module 02 intermediate pressure (IP) compressor

The front bearing housing holds the roller bearings for locating the LP and IP

compressors

The IP compressor is an assembly of discs and blades into a drum

The latest Trent uses weight-saving blisks to improve engine efficiency

Module 03 intermediate case intercase

Sits between the IP compressor and the HP compressor

Internal hollow struts provide access for oil tubes, cooling air and the gearbox

drive shaft

Houses the location bearings for each shaft

Module 04 high pressure (HP) system

Consists of the inner casing, HP compressor, combustion system and HP

turbine

Trent 700, Trent 800 and Trent 500 have co-rotating HP systems

All Trents, from the Trent 900 onwards, operate a contra-rotating HP system

Figure 2.1 Blisks used in Trent engine

Module 05 intermediate pressure (IP) turbine

Consists of the turbine casing, blades, vanes, turbine disc, shaft and the roller

bearings for HP and IP shafts

Nozzle Guide Vanes (NGVs) are mounted into the casing

LP stage 1 vanes contain thermo-couples for measuring gas temperature

Module 06 high speed gearbox (HSGB)

Mounted onto the LP compressor case and driven by the internal gearbox

housed in the Intercase

Provides drive to accessories including fuel, oil, hydraulic pumps and

electrical generators for the aircraft

The drive speed provided by the gearbox can be as high as 15,000rpm

Module 07 low pressure (LP) compressor fan case

The largest module is formed through the assembly of cylindrical casings and

the ring of outlet guide vanes

The forward case is designed for fan containment

Both casings contain acoustic linings to reduce noise levels

Module 08 low pressure (LP) turbine

Bolted discs with blades form the LP turbine rotor

The LP turbine drives the fan through the LP turbine shaft

The Trent 900 LP turbine provides 80,000 horsepower, the equivalent of

around 1000 family car

CONSTRUCTION MATERIAL

1) COLD SECTION

For construction of compressor cases, inlet cases and accessory cases, aluminum

and magnesium alloys are extensively used where lowest heat and moderate

strength is the primary consideration. These materials have approximately 30-40

percent the weight of steel.

For fan cases, fan blades, compressor blades and compressor disk

manufacturing, aluminium alloy are used due to its low density, high specific strength

and corrosion resistance characteristics.

In the compressor high pressure stages, nickel-chromium alloys, referred to

as stainless steel and nickel-base alloys are often used. Epoxy-resin materials have

been developed for cold section construction of cases and shroud rings where lower

strength is permissible and light weight is the major consideration.

2) HOT SECTION

For this section, a variety of high strength to weight materials has been

developed, often referred as super alloys. These alloys have a maximum

temperature limit of 2000℃ when uncooled and 2600℃ when cooled internally.

Super alloys were developed for use in high temperature areas where oxidation

resistance is needed and where high thermal, tensile and vibratory stresses present.

Figure 2.2 Aluminium and magnesium

Super alloys are complex mixtures of many critical metals such as nickel, chromium,

cobalt, titanium, tungsten, carbon and others metallic elements.

ENGINE INLET DUCT

The air entrance or flight inlet duct is usually identified as Engine Station

Number One and normally considered to be part of the airframe, not part of the

engine.

Understanding the function of the inlet and its importance to engine

performances makes it a essential part of any discussion on turbofan engine design

and construction.

The turbofan engine inlet must provide a uniform supply of air to the

compressor if the engine is to enjoy stall-free compressor performance. Inlet duct

must also create as little drag as possible. In addition, the use of inlet cover is

recommended to promote cleanliness and to prevent corrosion and abrasion.

Figure 2.3 Trent 900 engine inlet

Figure 2.3 Divergent duct inlet

Trent 900 used subsonic inlets duct that has fixed geometry and divergent

shape. A diverging duct progressively increases in diameter from front to back as

shown in figure above. This kind of duct is sometimes referred to as an inlet diffuser

because of its effect on pressure. Air enters this duct will reduced in velocity and

increased in static pressure. Added pressure increase engine efficiency and produce

most compression for best fuel economy. Inlet of Trent 900 is the short duct design

of a high bypass turbofan engine.

Engine Inlet Vortex Dissipator

Trent 900 inlets have a tendency to form a vortex between ground and flight

inlet. The suction by the fan creating the vortex is strong enough to lift water and

debris such as sand, small stones, nuts, bolts, and others, from the ground and

direct it into the engine, causing serious compressor damage.

To dissipate the vortex, a small jet of compressor discharge air is directed at

the ground under the inlet from a discharge nozzle located in the lower part of the

engine flight cowl as figure below.

Figure 2.5 Trent 900 vortex dissipater

The system generally activated by a landing-gear switch which opens a valve

in line between engine compressor bleed port and the dissipator nozzle whenever

the engine is operating and weight is on the main landing gear.

COMPRESSOR

Compressor Type Axial flow

Low Pressure Compressor Stage 1 (Fan)

Intermediate Pressure Compressor Stages 8

High Pressure Compressor Stages 6

Triple-spool axial flow compressor has been used in Trent 900 for the

operational flexibility that provide engine with the feature of high compression ratios,

quick acceleration and better control of stall characteristics

Figure 2.6 Inner section of compressor case

The axial flow compressor has two main components, the rotor and stator. A

rotor and following stator make up a stage, and several stages are combined to

make up the complete compressor. Each rotor consists of a set of blades fitted into a

disk, which move air rearward through each stage. For compressor section in Trent

900, blades of each stage are bulb root fitted and secured with a pin, lock tab or

lock-wire.

COMBUSTION

Combustion section or burner, as it is called, consists basically of an outer

casing, an inner perforated liner, a fuel injection system and a starting ignition

system. The function of burner is to add thermal energy to the flowing gases, thereby

expanding and accelerating the gases into the turbine section.

Trent 900 used single annular combustion chamber that is the most common

configuration for through-flow, in which gases entering from compression are

immediately ignited and then pass directly into the turbine sections.

Figure 2.7 Stator and rotor of turbofan

Figure 2.8 Single annular combustor and its liner

The annular combustor takes air at the front and discharges it at the rear. It

consists of outer housing, containing only one liner. The perforated inner liner is

often referred to as a basket. Primary and secondary air provide for combustion and

cooling as in other combustion designs.

This annular combustor installed in Trent 900 is the most efficient design if we

consider the thermal efficiency versus weight and for its shorter length compared to

other types.

TURBINE

Figure 2.9 Turbine Section

Turbine Section No of stages

Low Pressure Turbine 5

Intermediate Pressure Turbine 1

High Pressure Turbine 1

The turbine section is bolted to the combustor and contains the turbine wheels

and turbine stators. Furthermore, turbine stators that engage under high heat and

high centrifugal loading conditions are fir-tree fitted. Turbine stators act as nozzles,

increasing velocity and decreasing pressure.

EXHAUST

Exhaust section of Trent 900 is located directly behind the turbine section and

is a convergent outer cone and an inner tail cone. The cone, sometimes referred to

as the turbine exhaust collector, collects the exhaust gases discharged from turbine

discharge and gradually converts them into a uniform wall of gases.

Tail cone shape acts to form a diffuser within the exhaust cone and the

resulting pressure build-up reduce turbulences downstream of the turbine wheel.

THRUST REVERSER

Trent 900 equipped with engine thrust reverser to:

Aid in braking and directional control during normal landing and to reduce

brake maintenance.

Provide braking and directional controls during emergency landings and

rejected take-offs.

In some aircraft to act as a speed brakes to increase the aircraft rate of

descent.

Back an aircraft out of a parking pot in what is called “power back” operation.

Figure 2.20 Exhaust section of Trent 900

Figure 2.11 Aerodynamic thrust reverser operations

A common method for operating this aerodynamic blockage type is a

pneumatic actuating system powered by compressor discharge pressure. Thrust

reverser provides approximately 20% of the braking force under normal runway

conditions. Reversers are capable of producing 35 to 50% of rated thrust in the

reverse direction.

ENGINE STATION

Engine manufacturer numbers the engine location either along the length of

the gas path or along the length of the engine for ease of identification purposes.

The station number start at either flight cowling inlet or engine inlet.

However, manufacturers do not always number engine stations the same

way. Engine symbols such as Pt and Tt are often used in conjunction with station

numbers. For example, to describe Pressure Total at Station-2 (inlet), Pt is used. To

describe Temperature Total at Station-7, the turbine outlet on a triple-spool engine,

Tt is used.

Figure 2.13 Engine station number on turbofan engine

DIRECTIONAL REFERENCES

For purpose of identifying engine construction points, or component and

accessory placement, directional references are used along with station numbers.

Figure 2.14 directional references

These references are described as forward at the engine inlet and aft at the

engine tailpipe, with a standard 12 hour clock orientation. The terms right- and left-

hand, clockwise and anticlockwise, apply as view from the rear of the engine looking

forward to the inlet.

BEARING

The main bearings of Trent 900 are either ball or roller anti-friction types. Ball

bearings ride in a grooved inner race and support the main engine rotor for both axial

(thrust) and radial (centrifugal) loads. The roller bearings put on a flat inner race

because of their greater surface contact area than the ball bearings.

Figure 2.15 (A) Roller type and (B) Ball type bearing

Figure 2.15 Location of bearing in Trent 900 engine

ACCESSORY

Figure 2.16 Main accessory gearbox location

Figure 2.17

(A) Main accessory gearbox positioned at 6 o’ clock

(B) Main accessory gearbox positioned at rear

Trent 900 driven external gearbox is the main unit of accessory section.

Accessory unit essential to the operation of engine, such as fuel pump, oil pump, fuel

control and starter and components such as hydraulic pumps and generators are

mounted on the main gearbox.

Fluids such as fuel, from the fuel control or fuel pump; engine oil, from the

main pump or scavenge oil pump; and hydraulic, from the hydraulic pump may be

leak into, or, from, the gearbox through the drive shaft seal. A system of seal drain

tubes connects to each drive pad and is normally routed to the bottom of the engine

cowling. The leakage is generally minute and presents little problem as it leaves the

drain point into the atmosphere.

The allowable leakage rate of the various fluids is listed in the manufacturer’s

maintenance instructions and is generally in the range of 5 to 20 drops per minute,

depending on the source of the leak.

NOISE SUPPRESSION

The Trent 900 engine is using acoustic liners. Acoustic liners in the nacelle

(engine housing) play an important role in reducing turbomachinery noise before it

escapes from the engine, converting acoustic energy into very small amounts of

heat. The manufacturers have used key manufacturing, materials and design

technologies to increase the effective acoustic areas in the nacelle without

increasing the overall nacelle length, and to enable acoustic liners to be employed

reliably in areas where the engine conditions are more extreme. Attention to detail is

important, and the zero-splice intake liner (which first entered service on the Airbus

A380 with our Trent 900 engine) has been very effective in reducing fan noise at

aircraft departure, far greater than might be expected for a relatively small increase

in acoustic liner area.

The Trent 900 engine also uses a 116 inch swept fan, a low NOx combustor

and a contra-rotating HP system which minimise emissions, noise and fuel

consumption, making the Trent 900 the most environmentally friendly engine

powering the Airbus A380.

Figure 2.18 100% a coustic inlet on Trent 900

Figure 2.19 Acoustic Liners

3.0 OPERATING PRINCIPLE AND APPLICATION OF TRENT 900 ENGINE

3.1 OPERATING PRINCIPLE

Trent 900 is a one type of turbofan engine. It is powered by a 3 spool high

bypass, axial flow, turbofan with low pressure, intermediate pressure, high pressure

compressors driven by separate turbines with through coaxial shafts. The figure 3.1

below shows the cross section of the Trent 900 engine.

Figure 3.1 Cross Section of Trent 900 Engine

From the figure 3.1 above, the Trent 900 engine is using triple spool or three

set of compressor and turbine. The compressor is consists of 1 stages of low

pressure compressor (LPC) or fan blades, 8 stages of intermediate pressure

compressor (IPC), and 6 stages of high pressure compressor (HPC). The turbine

section consists of 5 stages of low pressure turbine (LPT), 1 stages of intermediate

pressure turbine (IPT), and 1 stages of high pressure turbine (HPT). The speed of

rotors is defines as N1 for LP rotor, N2 for IP rotor and N3 for HP rotor. From the

figure 3.1, it is also stated that the rotation direction for the blade if view from the rear

is clockwise for HP rotor and counter clockwise for LP and IP rotor. This type of gas

turbine engine is using 3 ball bearings for axial and radial load and 5 roller bearings

for radials load only.

3.1.1 INLET, FAN AND COMPRESSOR

Figure3.2 Air inlet of Trent 900

During the operation of the Trent 900 engine, the first stages or section that

the air will flow through is the air inlet. Type of air inlet that use on the Trent 900 is

engine mounted inlet. The purpose of designing the air inlet is to recover as much of

the total pressure of the free airstreams and deliver this pressure to the compressor.

Trent 900 used subsonic inlets duct that has fixed geometry and has a divergent

shape as shown in figure 3.3. A diverging duct progressively increases in diameter

from front to back. Air that enters this duct will be reduced in velocity and increased

in static pressure.

Figure 3.3 Divergent shape of inlet duct

Trent 900 is a multiple spools type of engine which made of three shafts.

Then, each shaft has own set of compressor and turbine. Figure 3.4 is showing the

compressor section of Trent 900. The first compressor is low pressure compressor

or N1 compressor. The fan is the first stage compressor and is a LPC. The Trent 900

are equipped with 24 fan blades which is swept design to reduces the effect of

shockwaves, as the tip of fan blades are rotates supersonically, making it lighter

quieter and efficiently. Trent 900 is a high bypass engine, which means not all of the

airflow will go through the engine core. Trent 900 bypass ratio is 8.7:1, which is 8.7

kg of air passes around the combustion chamber through the ducted fan or the

engine core for every 1 kg of air passing through the combustion chamber. After the

air that goes through to the engine core will then pass through IP compressor or N2

compressor. From the figure 3.4 it can be seen that IP compressor comprise of 8

stages. At each stage the pressure of airflow will increase by ratio of 1.25:1. At this

part also the shape of the duct is convergent. This will allow the pressure of the

airflow to increase, the velocity to decrease and the temperature to increase. All of

these properties will help greatly in combustion process. After the airflow leaving the

N2 compressor, it will enter the HP or N3 compressor which is has 6 stages. The

process that occurs at N2 will repeat at this stage. After the airflow pass through N3

compressor it will enter the combustion chambers. The airflow will mix with fuel to

produce combustion process.

Figure 3.4 The compressor section of Trent 900

3.1.2 COMBUSTION SECTION

Combustion section is a place where the combustion will occur by igniting the

mixture of air and fuel. This section is a hot section located after the compressor

section. After the air is compress by the last stage of a compressor which is N3

compressor, the airflow will be reduce in velocity first before entering the combustion

section by means of diffuser. This diffuser is located at the last stage of compressor

section and before combustor inlet. For the Trent 900 engine, it uses the annular

type combustor as shown in figure 3.5.

Figure 3.5 Cross section of an annular combustor of Trent 900

Air and fuel flow through the annular combustor. The fuel is injected through

the fuel injector. Air is diffused around the outside of the combustion chamber,

slowing down the speed at which the air leaves the compressor would blow out the

flame were it to pass directly through. From the figure, blue shows the combustion

chamber feed air from the HPC. Some of air will enter into the combustion chamber,

whilst most of air directed around the combustion chamber for cooling purposes. The

white color is where the higher temperature occurs. This is because at white it is the

primary zone where the ignition of fuel and air mixture takes place. Before the air

that entering the combustor, it is first being swirl by the swirl vane then the fuel is

injected through the fuel. The gas temperatures within the combustor are above the

melting point of the nickel alloy walls. Fuel is burned in the combustion chamber at

temperatures of over 2000°C, about half the temperature of the sun. Cooling air and

thermal barrier coatings are therefore used to protect the walls and increase

component lives. At the dilution zone, dilution air is used to cool the gas stream

before entering the turbines.

3.1.3 TURBINE SECTION

After the hot gases leaving the combustion chamber, the high thermal air will

now entering the turbine section. The turbine will extract energy from the hot gas

stream that received from the combustor. In a turbofan this power is used to drive

the fan and compressor by means of drive shaft. As mentioned earlier there are

three parts of turbine, each part drive their compressor counterpart; i.e: HP turbine

will drive HP compressor. The first part of the turbine is the HP turbine. It has only

one stage and drive the HP compressor. HP turbine blades and nozzle guide vanes

are designed with cooling passages and thermal barrier coatings, to ensure long life

while operating at such high temperatures. Cooling air is taken from the compressor

and is fed around the combustor into the blades to cool the airfoils. Aft of it is IP

turbine, it drives IP compressor and also contain only one stage. The final stage of

turbine section is the HP turbine. Since HPT is the last stage the airflow pressure

and temperature both fall as it passes through the turbine. It will also affect the

velocity by reducing it. Therefore to prevent from this situation occurs the LP turbine

is equipped with five stages. This is because turbine blades will convert the energy

stored within the gas into kinetic energy. In conclusion, if the number of blades is

increasing, the higher amount of kinetic energy produces.

Figure 3.6 Cross section of turbine blade

Figure 3.7 Turbine section of Trent 900 engine

3.1.4 EXHAUST SECTION

After leaving the turbine, the air flow will now move to the exhaust section.

Exhaust provides air flow with the final boost velocity. Exhaust nozzles will be

mounted at the rear exhaust duct flanges. Trent 900 produces exhaust gas at

subsonic velocity, so the shaped of the exhaust will be convergent duct and this type

of shaped will increase the exhaust gas velocity thus produce thrust. This will be

achieved by reducing the diameter of the front back. As stated before Trent 900 is a

high bypass engine means there will be two gas streams emitted into the

atmosphere. High temperature gas is discharged by the turbines while the cold air

mass is moved rearward by the fan section (high bypass air from the compressor

N1). Both streams are channeled outboard through two coaxial nozzles.

Figure 3.8 Cross section of Exhaust section

3.1.5 ACCESSORIES SECTION

Accessories section is where the accessories of the engine are located.

Usually the accessories located around the engine. Engine accessories including

Electronic Engine Controller (EEC), starter, fuel pump and oil pump, while the

accessory set included hydraulic pumps and electric generators to power the cabin.

The power required to drive accessory is taken from the shaft main power of this

engine. Beveled gears shows in figure 3.10 are used to drive an accessory shaft

then turn the gears in an accessory gearbox. That accessory gearbox provides a

mounting location for each accessory. Because the engine is operated at high

speed, reduction gearing is needed to drive accessory at the right speed.

Figure 3.9 Bevel gears used to drive the gearbox

3.3 OPERATING LIMIT

Based on the TCDS that has been referring to, there will be 3 limitations during

operation of the engine which is temperature, pressure and maximum or minimum

permissible rotor speed.

3.3.1 THRUST RATING

The table below is showing the thrust rating for the Trent 900 – series. From the

table, it shows that the thrust produce by the engine on specific condition such as for

take-off (net) and equivalent bare engine take-off is increasing through the series of

engine, whilst the thrust calculated for maximum continuous (net) and equivalent

bare engine maximum continuous is remain constant.

Table 3.1 The ISA thrust rating (EASA, 2013)

This thrust rating was calculated by using basic formula which is shown below:

F=Ms(V 2−V 1)

g

F= force/thrust

m= mass flow rate

V2= air velocity at exhaust section

V1= air velocity at intake section

g= acceleration of gravity (32.2 ft/sec²)

3.3.2 TEMPERATURE LIMIT

3.3.2.1 Climatic Operating Envelope The engine may be operated in ambient pressure up to ISA +40°. At take-off

ratings, the Trent 970-84, 972-84, 977-84 and 980-84 are flat rated to ISA +15°C at

all altitudes, whilst Trent 970B-84, 972B-84 and 977B-84 are flat rated to ISA +10°C

at all altitudes.

3.3.2.2 Turbine Gas Temperature (TGT) – Trimmed (°C)Turbine Gas Temperature is measured by thermocouples positioned at the

1st stage Nozzle Guide Vane of the LP Turbine. Table below shows the TGT.

Below 50% HP speed, maximum during starts on the ground:

700

Maximum during relights in flight: 850

Maximum for take-off (5 min. limit): 900

Maximum Continuous (unrestricted duration): 850

Maximum over-temperature : 920

Table 3.2 The TGT

3.3.2.3 Fuel temperature (°C)The fuel temperature is taken as that in the Wing Tank. The minimum and

maximum fuel temperature and pressure are not measured on the engine and

therefore, not provided to the flight deck. However, the wing tank temperature is

available on the flight deck and it is assumed that there is negligible difference in

temperature between the tank and the engine inlet.

Minimum fuel temperature in flight : –54 or the fuel freeze point (whichever is the higher).

Maximum fuel temperature :

(i) On ground to top of climb : 55

(ii) At the top of descent : 50

3.3.2.4 Oil temperature (°C)Combined oil scavenge temperature -

Minimum for engine starting with Special Starting procedure: – 40

Minimum for engine starting with no Special Starting procedure: – 30

Minimum for acceleration to take off power: - 40

Maximum for unrestricted use: - 196

3.3.3 PRESSURE LIMIT

3.3.3.1 Fuel pressure (kPa)Minimum absolute inlet pressure (measured at the pylon interface): 34

Maximum pressure at inlet (measured at the pylon interface):

(i) Continuous : 276

(ii) Transiently : 690

(iii) Static : 345

3.3.3.2 Oil pressure (kPa)Minimum oil pressure:

(i) Ground idle to 70% HP rpm 172

(ii) Above 95% HP rpm 344

Maximum allowable Oil Consumption (l/hr): 0.46

3.3.3.3 Maximum / Minimum Permissible Rotor Speeds

The table below is showing the maximum or minimum permissible rotor speeds.

Table 3.3 Table of Rotor Speed

3.4 APPLICATION OF TRENT 900

3.4.1 MILITARY

Turbofan engine are usually used for making aircraft move or flying, in other

words to develop thrust. So a Trent 900 engine could certainly be used on a military

aircraft such as C17. But its use on ground or ship based platform would be limited.

However its Trent family’s, the Trent 800 has the uses on ground and ship based

platform. Example the uses of Trent 800 in military is MT30 gas turbine or also

known as Marine Trent. The MT30 has 80% parts commonality. Example of MT30

that powered on military ship is US Navy’s Freedom class Littoral Warfare ships and

the Zumwalt class destroyers (figure 3.12 and 3.13).

Figure 3.10 The Zumwalt class destroyers

Figure 3.11 US Navy’s Freedom class Littoral Warfare ships

3.4.2 INDUSTRIAL

Since the Trent 900 engine is designed to move large volumes of air through

its fan section so there is not a lot of practical use for that in an industrial area. Trent

has other engine designed for industrial uses such as pumping stations that run now

stop for several years, but those are turbo shaft and not turbo fan type power-plants.

3.4.3 COMMERCIAL AIRCRAFT

As you know that, the Trent 900 engine was first use to power the A380. This

commercial aircraft was power the A380, when Rolls-Royce companies was able to

announce that it would develop the Trent 900 to power the A380 by 1996. In October

2000, the Trent 900 became the A380’s launched engine when Singapore Airlines

specified the engine for its order for 10 A380s then followed by Qantas in February

2001. The A380 also powered by GE7000 engine.

Figure 3.12 A380 powered by Trent 900 engine

4.0 ADVANTAGES AND DISADVANTAGES

4.1 GENERALS COMPARISON

A gas turbine is also named with combustion turbine. It is a type of engine that

performs the combustion internally. It has the upstream rotating compressor coupled

to a downstream turbine, and combustor in between.

In an ideal gas turbine, the gasses will go through the three processes. An

isentropic compression, isobaric (constant pressure) combustion and an isentropic

(expansion). Today, gas turbine are one of the most widely used power generating

technologies. There are four types of gas turbine engine which is Turbojet,

Turboprop, Turbo shaft and turbo fan. Most of them using turbine to generate power.

Turbo jet is the first and simple design which produce all of its thrust from the

exhaust from the turbine section. However, because all of the air is passing through

the whole turbine, all of its must burn fuel. It is inefficient, and the solution is turbo

fan.

While turboprop is combination of turbojet and propeller. The turbine primarily

drives a propeller at the front of the engine. There is no cowl around the prop. Some

air enters the turbine, the rest does not. The propeller is geared to allow it to spin

slower than the turbine. Although this diagram shows only a single shaft, many

turboprops have two, with a high pressure shaft driving the compressor and a low

pressure shaft driving the propeller. Some engines such as the popular PT6 also

reverse

the flow

direction multiple

time.

Meanwhile, the turbofan is a jet

engine developed

from

Figure 4.1 Cross Section Turbojet Engine

Figure 4.2 Cross Section Turboprop Engine

combination of turbojet and turboprop. In a turbofan, the turbine primarily drives a fan

at the front of the engine. Most engines drive the fan directly from the turbine. There

are usually at least two separate shafts to allow the fan to spin slower than the inner

core of the engine. The fan is surrounded by a cowl which guides the air to and from

the fan. Part of the air enters the turbine section of the engine, and the rest is

bypassed around the engine. In high-bypass engines, most of the air only goes

through the fan and bypasses the rest of the engine and providing most of the

thrust. 

Turboprops are more efficient at lower speeds since the prop can move much

more air with a smaller turbine than the fan on a turbofan engine. Turboprops also

are efficient on the short-haul operation and the aircraft with turboprops requires only

shorter runway to achieve the required lift compared to other types.

Turbofan is the most efficient engine and most of the thrust is produced from

the bypass air. The efficiency of the engine mainly depends on the engine bypass

ratio. The cowl around the turbofan's large fan allows it to perform better than an

open propeller at high speeds, but limits the practical size of the fan.

Turbojet is mainly used on the fighter or acrobatic aircraft. These aircraft’s

thrust is further increased by the “after burner” installed at the nozzle of the engine.

At supersonic speeds, turbojets have more of a performance benefit. They develop

all of their thrust from the high velocity turbine exhaust, while turbofans supplement

that with the lower velocity air from the fan. Since the air from the fan is also not

compressed nearly as much as the core turbine flows, it is also harder to prevent the

flow from going supersonic and causing losses.

The noise from turbojet is produced from the high speed exhaust through the

ambient air, together with the noise from the core. Turbofan engines have several

features which is by pass air will keep the core noise inside the engine more silent;

more efficient operation significantly reduces noise caused by bad air flow round

sharp edges and such. Other than that, the bigger the fan, the slower it spins. The

slower it spins the less noise it makes.

The need of industry is to make aircraft move faster, its means that the

engine/propeller need to rotate faster too. Due to the limitation of propeller also has

limitation to certain speed of rotation, the propeller will be stall if it exceed 4000rpm

(thrust not be or slightly produced). The blade in the turbofan engine can also stall

but it can reach higher speed compared to the propeller so aircraft with turbofan can

go faster compared to aircraft which utilized turboprop.

The Concorde used turbojets because it was designed to cruise for long

periods at supersonic speeds. Modern fighter jet engines are turbofans, which

provide a compromise between efficiency and speed.

Turbo shaft, is the engine mainly used on the helicopter and the energy

comes out of the turbine is used by the rotor to achieve the required rpm.

4.2 TRENT 900 VERSUS GP7200

As generals, Trent 900 was developed by Rolls Royce company meanwhile

GP7200 were manufactured by Engine Alliance which it was a collaboration between

General Electric (GE) and Pratt & Whitney (PW) to produce an engine suitable for

Airbus A380-800 superjumbo even thought at first, GP7200 was planned to power

Boeing commercial airplane’s cancelled 747-500X/-600X due to lack of demand from

airliners.

4.2.1 COMPARISON BETWEEN SPECIFICATIONS

Trent 900 GP 7200

General Specifications

Type : Three-spool high bypass ratio(8.7-8.5)

Length : 5.48m

Diameter : 2.95m

Dry Weight : 6,246kg

General Specifications

Type : Two-spool high-bypass ratio (8.8)

Length : 4.74m

Diameter : 3.16m

Dry Weight : 6,712kg

Components

Compressor : 1 stage LPC, 8 stage IPC, 6

stage HPC

Combustor : Single Annular Combustor

Turbine : 1 stage HPT, 1 stage IPT, 5 stage

LPT

Components

Compressor : 5 stage LPC, 9 HPC

Combustor : Single Annular Combustor

Turbine : 2 stage HPT, 6 stage LPT

Performance Performance

Maximum Thrust : 344 to 357kN or 77000 to

88000 lbf

Overall Pressure Ratio : 37 to 39

Thrust-to-weight ratio : 5.46 to 6.11

Maximum Thrust : 36,980kgf, 363kN,

81,500lbf

Overall Pressure Ratio : 43.9

Thrust-to-weight ratio : 5.508

Ratings

Maximum Take Off : 334.29-372.92 kN

Maximum Continuous : 319.60 kN

Ratings

Maximum Take Off : 332.437 kN or 74735 lbs

Maximum Continuous : 326.81 kN

Table 4.1 Table of Specification GP 7200 and Trent 900

4.2.2 ADVANTAGES TRENT 900 OVER GP 7200Based on table above, it is clearly that, why the airliners choosing Trent 900

rather than GP7200. As per their general specifications, Trent 900 lighter than GP

7200 even the GP 7200 using less components but providing higher by pass ratio

which means more thrust will be generated. The issue is, the airliners will choose

which one will reduce the total weight of aircraft and at the same time providing

sufficient power to fly the Airbus A380. When there is more weight, more power will

needed, more fuel will be consumed and more cost will be generated.

From the components section, Trent 900 has 22 stages and same goes to GP

7200. The difference is just how much spool they used. Trent 900 used three spool

which will reduce the noise and of course it is more silent than GP 7200 and at the

same time the acceleration of Trent 900 more faster than GP 7200.

4.2.3 DISADVANTAGE TRENT 900 VERSUS GP 7200In compressor section, Trent 900 divided their stages more complex to

achieve more compression in increasing the pressure of air before entering the

combustion chamber, compared to GP 7200 which divided their stages to two spools

only, simpler construction but the efficiency of compression is much more better

compared to Trent 900. But In maintenance side, the simplicity of GP 7200 will help

the maintenance personnel in maintain the engine due to the GP 7200 easier to

maintain due to not too much work will be done on a simple construction rather than

Trent 900 which more complex and need more attention.

Second issue is, the price of the engine slightly higher than GP 7200. In 2000

Qantas were quoted a price of US$ 12.85 million per Trent 900. The price higher

because one engine produced from more than one country and company.

5.0 FUTURE TRENDS

5.1 ACTIVE MAGNETIC BEARINGS

5.1.1 INTRODUCTION

The new generation of aircraft engines will display has multiple applications,

offering fuel burn lower, lower production and lower noise levels. For example, LEAP

engines from CFM International and Pratt & Whitney PW1000G, they promises

maintenance costs equal to or better than existing engines. In this section, from the

research conducted, found that using active magnetic bearings by replacing the ball

bearing where existed in jet engines. It is will reduce the losses and service intervals

in jet engine to meet the goals of their maintenance costs.

Active magnetic bearings (AMB) have been successfully used in various

applications for several decades. They show great abilities to work under extreme

conditions, such as vacuum, high rotation speed or at high temperature. AMB are

used today in applications such as turbo-molecular pumps, turbo expanders, textile

spindles, machine tool spindles, hard disk drives and magnetically levitated vehicles

(MAGLEV). The idea here is to use magnetic bearings in aircraft jet engine.

5.1.2 WORKING PRINCIPLE

Figure 5.2.1 shows the basic components of a magnetic bearing and its

working principle. A rotor magnet is suspended by an electromagnet. To get control

of active players, position measured by the position sensor. Position signal is then

treated by a controller, which gives a current set point. This signal is then amplified

by the power amplifier, to obtain the necessary current generator. A closed-loop

control is realized and the system can be stabilized.

This single actuator allows lifting it along only one axis and only in one

direction. In the AMB system, some actuators are used to control the lifting rotor with

several degrees of freedom (DOF). The generator is usually arranged as a pair

facing each - other. This allows for interesting players in two opposite directions

along one axis

Figure 5.1

5.1.3 ADVANTAGES OF JET ENGINE RUNNING ON MAGNETIC BEARINGS

Current jet engine system supported by ball bearings and dampers, it is

limited in speed and temperature. In addition, these systems require complex

passwords secondary cooling and lubrication system is complicated. Significantly,

these components increase the weight of the airplane, the complexity and cost of a

single actuator allows lifting jet. This along only one axis and only in one direction. In

the AMB system, some actuators are used to control the rotor lift with few degrees of

freedom (DOF). Generators are usually arranged as a pair facing each - other. This

allows players to pull in two opposite directions along one axis

A way to develop and improve the jet engine is by develop it to more

electrical. The idea is to replace lubrication, hydraulic and pneumatic systems to a

single powerful electrical generator, and electrical components.

While, magnetic bearings can operate at high temperature, the entire system

can be dramatically improved. It is because there are no contacting parts in magnetic

bearings; the lubrication system can be eliminated. Studies have shown than a jet

engine with AMBs weights up to 5% less that the equivalent engine with

conventional bearings.

By removing lubrication in the bearings, oil emissions are reduced, which

provides direct environmental benefits. The removal of oil in the system makes it

more fire safe as well. It also will reduce the weight of the engine due to the hydraulic

and pneumatic systems was removed.

Since AMB are non-contact bearings, the friction losses are eliminated. This

provides a direct improvement in terms of kerosene consumption. Furthermore a

non-contact system avoids fatigue and wear, which occur with ball bearings. The

operating speed and the efficiency can be increased as well.

Magnetic bearing is an active system, thus it provides several advantages

over a passive one. The controller can compensate unbalance and control the rotor

behaviour actively at critical speeds. System monitoring is then possible by using the

AMB as a sensor, which provides indications about the changes in shaft dynamics.

This system diagnosis enables to reduce the maintenance cost by increasing the

intervals between engine services.

5.2 THE MULTI-FUEL BLENDED WING BODY AIRCRAFTDuring the past years, an innovative Blended Wing Body (BWB) configuration

has been studied by many researchers around the world including the “CleanEra”

group from TUDelft, and it seems to be a promising candidate to replace the existing

aircrafts. Instead of a separate fuselage with wings, an integration of body and wing

is used for the BWB (R.H, Liebeck, January-February 2004). A larger amount of

space available within the aircraft, thus making it possible to carry cylindrical fuel

tanks to store the cryogenic fuel. A novel way to overcome the storage problems of

the hydrogen is a multi-fuel BWB aircraft presented in Figure 5.2. The wings of a

BWB have sufficient room for storing LH2 tanks, without interfering with the

passenger section. Further away from the central line where wing thickness is

reduced, liquid biofuel can be stored.

Figure 5.2 Futuristic BWB aircraft layout with LH2 tank and biofuel

5.3 HYBRID ENGINEAlternative energy advances have been remarkable. However, new

technology, processes and products must be evaluated against the expense of

bringing them to market. With a difficult economy, limited budgets and engineering

resources, airplane manufacturers find it much more difficult to invest in developing

new technology during tough economic times. Unfortunately, this means innovation

can be delayed, perhaps when we need it most.

Electric motors are highly efficient, robust and do not lose power at higher

density altitudes. They are also quiet and emission free. Perhaps most important for

aviation, electric motors are relatively light weight. A 200-horsepower electric motor

weighs only one-third that of an equivalent horsepower internal combustion engine.

These features are certainly compelling. The critical question is how to efficiently get

energy to the electric motor. For that, it’s need a battery.

The system and architecture are different as compared to the conventional

turbofan engine. The hybrid engine uses several unique technologies like shrouded

contra-rotating fans, bleed cooling, dual hybrid combustion system (using hydrogen

and biofuel under flameless conditions to reduce CO2 and NOx emission

respectively). The hybrid engine will constitute a leap forward in terms of

environmental friendliness, will use advanced multiple fuels and will enable the

design of fuel-efficient Blended Wing Body (BWB) aircraft configurations. The

efficiency of BWB aircraft will be enhanced significantly due to embedded hybrid

engines using the boundary layer ingestion (BLI) method.

Figure 5.3 Schematic of the hybrid engine

The novel engine proposed is quite different than a conventional turbofan and

includes many breakthrough technologies. The various novel technologies involved

in the engine configuration are described as follows.

Boundary Layer Ingestion (BLI): this is a method of increasing the

propulsive efficiency of the engine by embedding the engine within the airframe such

that the engine can ingest the low velocity boundary layer flow of the aircraft,

reducing the engine ram drag. Also, the jet of the engine contributes to aircraft “wake

filling”, thus reducing the overall dissipation.

Counter Rotating Fans (CRF): The aircraft-engine integration of future BWB

aircraft presents unique challenges due to BLI. Such configurations also require that

engines be smaller in diameter to reduce the nacelle-wetted area. Thus, it can be

seen that the current trend of increasing bypass ratio and diameter of engines will

not be able to meet the requirements of future BWB class of aircraft. The proposed

hybrid engine with counter rotating fans has a smaller diameter and higher

propulsive efficiency for the same bypass ratio. Furthermore, since each stage of the

fan is less loaded than a single stage fan, a CRF can sustain more non-uniformities

in the flow generated due to BLI compared to a conventional architecture.

Bleed Cooling: With increasing pressure ratio, the temperature of bleed air

(the air that is used for cooling the hot section components like the turbine blades

and vanes) increases leading to the increase of the amount of bleed air required for

the hot components cooling. This increase has an adverse effect on the

thermodynamics of the gas turbine engine, reducing the efficiency of the cycle. The

cryogenic fuel used in the proposed hybrid engine is an excellent heat sink which

can be used for cooling the bleed air, therefore, reducing the amount of bleed air

required. Meanwhile, the temperature of the cryogenic fuels is increased which

reduces the use of combustion heat to increase its temperature, thus resulting in less

fuel consumption for a given temperature within combustion chamber.

The Hybrid Dual Combustion System: The proposed innovative hybrid

engine uses two combustion chambers as shown in Figure 5.3. The main combustor

operates on LH2/LNG while the second combustor (between HPT and LPT) uses

biofuel in the flameless combustion mode. Such a novel combustion system has

never been used before for aero-engines. There are several advantages of this

unique. Firstly, since the flammability limits of H2/Methane are wider than kerosene,

the combustion can take place at lean conditions, thus reducing NOx emissions

significantly compared to a conventional kerosene combustor. Secondly, the LH2

used for the first combustor can be used for cooling the bleed air (the features has

been mentioned in the previous session). Moreover, using LH2 in the first

combustion chamber will increase the concentration of water vapor and reduce the

concentration of O2 in the second combustion chamber, thus creating a vitiated

environment in which Flameless Combustion can be sustained. The implementation

of the flameless combustion can minimize the emission of CO, NOx, UHC and soot.

Additionally, the reduced emission of soot and UHC also reduces the amount of

nucleation centers available for condensation of water vapor in the plume, thus

reducing the contrail formation

6.0 SUMMARY

Trent 900 is a turbofan engine developed from RB211. Turbofans usually designed

with either two or three shafts configuration. Three-shaft design, the Rolls-Royce

pioneered over 50 years ago, has proven beneficial for various applications. The fan

module is the assembly of the fan disc, the low pressure (LP) fan shaft and the fan

blades. The compressor is made up of the fan and alternating stages of rotating

blades and static vanes. The compression system of a Trent engine comprises the

fan, eight intermediate pressure stages and six high pressure stages.. The annular

combustion chamber located within the casing structure.

Kerosene is introduced through the fuel injector to the front of the chamber. The

turbine is a compilation disc with blades attached to the turbine shaft, nozzle guide

vanes, casings and structure. Beside thrust, the engine also provides power for

engine and aircraft accessories.

The first part of the Trent 900 is the inlet and compressors. Inlet will recover as much

air as possible and deliver it to the compressors. The first part of the compressors is

the fan or Low Pressure (LP) compressor second part is Intermediate Pressure (IP)

compressor and finally High Pressure (HP) compressor. Each compressor have their

own set of blade called stage. When the airflow went through each stage of the

compressor the pressure will increase. The ratio of compression is 1.25:1.

After leaving the HP compressor the airflow will enter combustion chamber. Next the

airflow will went through 3 set of turbine section, that will drive the compressor and

just like compressor they have their own set of blade. The first set is HP turbine, next

is IP turbine and finally LP turbine. The airflow pressure and temperature both fall as

it passes through the turbine. It will also affect the velocity (velocity will decrease).

Therefore to remedy the situation the LP turbine is equipped with five stages, this is

because turbine blades will convert the energy stored within the gas into kinetic

energy. So the more blades there are, the higher the amount of kinetic energy will be

produced.

After passing through turbines the airflow will enter the exhaust section. The

convergence shaped of the exhaust section will cause the gas velocity to increase.

As mentioned earlier Trent 900 is a high bypass engine that means there will be two

gas streams vented to the atmosphere. High temperature gases are discharged by

turbine while a cool air mass is moved rearward by fan section (high bypass air from

N1 compressor). The two streams will be vented outboard through two coaxial

nozzles. The accessory section of Trent 900 is used to drive engine and aircraft

accessories. Beveled gears drive an accessory shaft to turn the gears in an

accessory gearbox. Because the engine operate at high speed, reduction gearing is

necessary to drive the accessories at the appropriate speed.

Figure 6.1 Comparison of the BWB with the Boeing777-200ER.

For future trends, the BWB aircraft is an environmentally friendly aircraft

burning cryogenic fuels (like LNG\LH2) and biofuels. It is preliminarily designed for

carrying around 300 passengers and flying 14000 km range. The comparison of the

layout of the BWB to the Boeing 777-200ER is provided in Figure 6.0. The shorter

and wider body of the aircraft makes it aerodynamically more efficient than a

conventional cylindrical body aircraft. Combined with the advanced hybrid engine,

the multi-fuel BWB is able to reduce CO2 emission by around 65% than a

conventional Boeing 777-200ER aircraft.

7.0 REFERENCESRolls-Royce. (3 February, 2015). Retrieved 10 March, 2015, from

http://www.rolls-royce.com/customers/civil-aerospace/products/civil-large-engines/trent-900/trent-900-infographic.aspx

EASA. (2013). TYPE-CERTIFICATE DATA SHEET RB 211 Trent 900 Series Engine. EASA.

R.H, Liebeck. (January-February 2004). Design of The Blended Wing Body Subsonic Transport. Journal of Aircraft, Vol. 41 No.1.

http://www.faqs.org/patents/app/20110138765

http://aviationblog.dallasnews.com/2010/11/some-background-on-the-trent- 9.htm/

http://www.rolls-royce.com/civil/products/largeaircraft/trent_900/

http://www.ainonline.com/aviation-news/dubai-air-show/2013-11-15/rollsroyce-continues-improve whole-trent-engine-family

http://grabcad.com/library/rolls-royce-trent-900-turbofan