Assignment Assignment 1 AAB 30503 SEM JANUARY JANUARY 2015 2015
UNIVERSITI KUALA LUMPUR MALAYSIAN INSTITUTE OF AVIATION TECHNOLOGY J ANUARY - JUNE J UNE SEMESTER SEMESTER
GAS TURBINE ENGINE 1 (AAB (AAB 3050 30503) 3)
ASSIGNME NM ENT 1
GROUP
:
MEMBERS : 1)
2) __________________________ ________________ __________ : 3) __________________________ ________________ __________ : 4) __________________________ __________________________ : 5) __________________________ __________________________
:
SUBJECT
: GAS TURBINE ENGINE 1
LECTURER : MS. PUTERI NUR SYAZA WARDIAH
___________ ___________ ___________ ___________
CONTENTS 1.0
INTRODUCTI INTRODUCTION ON ......................................................... ........................................................................................... ............................................................ .......................... 3
1.1 2.0
HISTORY HISTORY OF TRENT 900 ........................................................... ............................................................................................. ........................................... ......... 4 ENGINE TYPE AND CONSTRUCTIO CONSTRUCTION N ......................................................... ........................................................................................ ............................... 9
2.1
ENGINE CHARACTER CHARACTERISTICS ISTICS ....................................................... ......................................................................................... ........................................ ...... 12
3.0 OPERATING PRINCIPLE AND APPLICATION OF TRENT 900 ENGINE ............................................. 30 3.1 OPERATING OPERATING PRINCIPLE PRINCIPLE....................................................... .......................................................................................... .................................................... ................. 30 3.1.1 INLET, FAN AND COMPRESSOR ........................................................................................ 32 3.1.2 COMBUSTIO COMBUSTION N SECTION SECTION .................................................................................... ................................................................................................... ............... 34 3.1.3 TURBINE TURBINE SECTION SECTION ....................................................... .......................................................................................... .................................................... ................. 35 3.1.4 EXHAUST EXHAUST SECTION SECTION ........................................................... ............................................................................................. ............................................... ............. 36 3.1.5 ACCESSORI ACCESSORIES ES SECTION SECTION ......................................................................................... .................................................................................................... ........... 37 3.3 OPERATING OPERATING LIMIT .............................................................................. ................................................................................................................ .................................... .. 37 3.3.1 THRUST THRUST RATING ..................................................... ........................................................................................ ......................................................... ...................... 38 3.3.2 TEMPERA TEMPERATURE TURE LIMIT ........................................................ .......................................................................................... .............................................. ............ 39 3.3.3 PRESSURE PRESSURE LIMIT ............................................................................... ............................................................................................................. .............................. 40 3.4 APPLICATIO APPLICATION N OF TRE TRENT NT 900 ......................................................... ........................................................................................... ......................................... ....... 42 3.4.1 MILITARY MILITARY ........................................................ .......................................................................................... ................................................................ .............................. 42
3.4.2 INDUSTRIAL INDUSTRIAL. ........................................................................................ ............................................................................................................... ....................... 43 3.4.3 COMMERCIAL AIRCRAFT .......................................................... ........................................................................................ .............................. 43 4.0 ADVANTAGES AND DISADVANTAGES ......................................................................................... 44
4.1
GENERALS GENERALS COMPARISO COMPARISON N ......................................................... ........................................................................................... ........................................ ...... 44
4.2
TRENT TRENT 900 VERSUS VERSUS GP7200................ GP7200.................................................. ..................................................................... ............................................ ......... 47
4.2.1
COMPARISON BETWEEN SPECIFICATIONS....... 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 FUTURE TRENDS TRENDS ........................................................ .......................................................................................... .......................................................... ........................ 50
5.1
................................................................................ ....................... 50 ACTIVE MAGNETIC MAGNETIC BEARINGS .........................................................
5.1.1
INTRODUCTION .......................................................... ............................................................................................ ......................................... ....... 50
5.1.2
WORKING PRINCIPLE. .................................................................................... ........................................................................................ .... 50
5.1.3
ADVANTAGES ADVANTAGES OF JET ENGINE ENGINE RUNNING ON ON MAGNETIC MAGNETIC BEARINGS ..... 51
5.2
THE MULTI-FUEL BLENDED WING BODY AIRCRAFT .......................................... .......................................... 52
5.3
............................................................................................. ............................................... ............. 53 HYBRID ENGINE ...........................................................
CONTENTS 1.0
INTRODUCTI INTRODUCTION ON ......................................................... ........................................................................................... ............................................................ .......................... 3
1.1 2.0
HISTORY HISTORY OF TRENT 900 ........................................................... ............................................................................................. ........................................... ......... 4 ENGINE TYPE AND CONSTRUCTIO CONSTRUCTION N ......................................................... ........................................................................................ ............................... 9
2.1
ENGINE CHARACTER CHARACTERISTICS ISTICS ....................................................... ......................................................................................... ........................................ ...... 12
3.0 OPERATING PRINCIPLE AND APPLICATION OF TRENT 900 ENGINE ............................................. 30 3.1 OPERATING OPERATING PRINCIPLE PRINCIPLE....................................................... .......................................................................................... .................................................... ................. 30 3.1.1 INLET, FAN AND COMPRESSOR ........................................................................................ 32 3.1.2 COMBUSTIO COMBUSTION N SECTION SECTION .................................................................................... ................................................................................................... ............... 34 3.1.3 TURBINE TURBINE SECTION SECTION ....................................................... .......................................................................................... .................................................... ................. 35 3.1.4 EXHAUST EXHAUST SECTION SECTION ........................................................... ............................................................................................. ............................................... ............. 36 3.1.5 ACCESSORI ACCESSORIES ES SECTION SECTION ......................................................................................... .................................................................................................... ........... 37 3.3 OPERATING OPERATING LIMIT .............................................................................. ................................................................................................................ .................................... .. 37 3.3.1 THRUST THRUST RATING ..................................................... ........................................................................................ ......................................................... ...................... 38 3.3.2 TEMPERA TEMPERATURE TURE LIMIT ........................................................ .......................................................................................... .............................................. ............ 39 3.3.3 PRESSURE PRESSURE LIMIT ............................................................................... ............................................................................................................. .............................. 40 3.4 APPLICATIO APPLICATION N OF TRE TRENT NT 900 ......................................................... ........................................................................................... ......................................... ....... 42 3.4.1 MILITARY MILITARY ........................................................ .......................................................................................... ................................................................ .............................. 42
3.4.2 INDUSTRIAL INDUSTRIAL. ........................................................................................ ............................................................................................................... ....................... 43 3.4.3 COMMERCIAL AIRCRAFT .......................................................... ........................................................................................ .............................. 43 4.0 ADVANTAGES AND DISADVANTAGES ......................................................................................... 44
4.1
GENERALS GENERALS COMPARISO COMPARISON N ......................................................... ........................................................................................... ........................................ ...... 44
4.2
TRENT TRENT 900 VERSUS VERSUS GP7200................ GP7200.................................................. ..................................................................... ............................................ ......... 47
4.2.1
COMPARISON BETWEEN SPECIFICATIONS....... 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 FUTURE TRENDS TRENDS ........................................................ .......................................................................................... .......................................................... ........................ 50
5.1
................................................................................ ....................... 50 ACTIVE MAGNETIC MAGNETIC BEARINGS .........................................................
5.1.1
INTRODUCTION .......................................................... ............................................................................................ ......................................... ....... 50
5.1.2
WORKING PRINCIPLE. .................................................................................... ........................................................................................ .... 50
5.1.3
ADVANTAGES ADVANTAGES OF JET ENGINE ENGINE RUNNING ON ON MAGNETIC MAGNETIC BEARINGS ..... 51
5.2
THE MULTI-FUEL BLENDED WING BODY AIRCRAFT .......................................... .......................................... 52
5.3
............................................................................................. ............................................... ............. 53 HYBRID ENGINE ...........................................................
6.0 SUMMARY SUMMARY..................................................................................... ....................................................................................................................... ............................................ .......... 56 7.0 REFERENCE REFERENCES S ........................................................ ........................................................................................... ..................................................................... .................................... 58
Table of Contents & Group Members Tasks
Page No
3
4
9
Content
Assigned to
Introduction
Abdul Mu'izz Bin Abdul Munir
History or Background
Abdul Mu'izz Bin Abdul Munir
Abdul Mu'izz Bin Abdul Munir
Engine type and construction
30
Operating principle and application
44
Advantages and disadvantages
Muhammad Faiz Arif Bin Fauzi
Azri Safwan Bin Rusli
Future trend
Azri
56
Summary
All
58
References
50
Safwan Bin Rusli
Compiled by: All
All
1
Sign
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
Figur e 1.1 Trent 900 Engin e
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. 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 twinengined, 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 RollsRoyce 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 r est 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 t urbof an engine
Figur e 1.3 Sw ept f an blades
Figure 2.20 Roll s-Royce Trent 900 4th gener at ion f an blade –t he most compli cated aerodynami c st ructure on t he A380. (1.07 metr es long, 14 kg, pure tit anium, “honeycomb” hollow w ide chord, supersonic sw ept
2.1 ENGINE CHARACTERISTICS GENERAL 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 p ressure ratio: 37–39
Thrust-to-weight r atio: 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 5050XX-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 p ressure (LP) compressor ro tor
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 pressur e (IP) comp ressor
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
Figur e 2.1 Blisks used in Trent engine
Module 03 intermedi ate 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 pr essure (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
Module 05 intermediate pr essure (IP) turbi ne
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 hig h s peed 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 press ure (LP) comp ressor 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 p ressure (LP) turb ine
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.
Figure 2.2 Alumini um and magnesium
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.
Super alloys are complex mixtures of many critical metals such as nickel, chromium, cobalt, titanium, tungsten, carbon and others metallic elements.
ENGINE INLET DUCT
Figur e 2.3 Trent 900 engine inlet
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 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.
Figur e 2.5 Trent 900 vort ex dissipat er
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
Figur e 2.6 Inner sect ion of compressor case
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 2.7 St at or and rot or of t urbof an
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 2.8 Single annul ar combustor and i t s 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 Turbi ne Section
Turbi ne Sectio n
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
Figur e 2.20 Exhaust sectio n of Trent 900
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 t urbine 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 2.11 Aerodynamic t hrust reverser operat ions
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 st at ion number on t urbof an 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 directi onal ref erences
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 lefthand, 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 t ype and (B) Ball t ype bearing
Figure 2.15 Locati on of bearing in Trent 900 engine
ACCESSORY
Figur e 2.16 Mai n accessory gear box locat ion
Figur e 2.17 (A) M ain accessory gearbox posit ioned at 6 o’ clock (B) M ain accessory gearbox positi oned 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.
Figur e 2.18 100% a coust ic inlet on Trent 900
Figure 2.19 Acoustic Liner s
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 Engi ne
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.
Figur e 3.4 The compr essor sect ion 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 combust or 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 sect ion of t urbine blade
Figure 3.7 Turbi ne 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 secti on of Exhaust secti on
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 igur e 3.9 Bevel Bevel gears used used to d rive riv e the th e 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 t he 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 calculated for maximum continuous (net) and equivalent equivalent bare engine maximum continuous is remain r emain constant.
Table 3.1 The The ISA thr ust rati ng (EASA, (EASA, 2013) 2013)
This thrust rating was calculated by using basic formula which is shown below: F=
Ms(V2 − V1) 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 3.3. 2.1 Cli Cli m at ic Oper Oper at in g Envelope 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 Tu r bi ne Gas Gas Temp er at ur e (TGT) (TGT) –Tr im m ed (° C)
Turbine Gas Temperature is measured by thermocouples 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 Tabl e 3.2 The TGT TGT
3.3.2.3 Fu el t emp er at ur e ( ° 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 Maximum fuel temperature
: –54 or the fuel freeze point (whichever is the higher).
:
(i) On ground to top of climb
:
55
(ii) At the top of descent
:
50
3.3.2.4 Oi l t em per at ur e ( ° 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 pr essur e (k Pa)
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 pr essur e (k Pa)
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 Maxim um / Min im um Per mi ssibl e Rotor Speeds
The table below is showing the maximum or minimum permissible rotor speeds.
Table 3.3 Table of Rot or 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).
Figur e 3.10 The Zumw alt class destroyers
Figur e 3.11 US Navy’ s Freedom class Lit t oral W arf are 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 pow ered 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.
Figure 4.1 Cross Secti on Turbojet Engi ne
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.
Figure 4.2 Cross Secti on Turbopr op Engine
Meanwhile, the turbofan is a jet engine developed from 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.
Figure 4.3 Cross Secti on Turbof an Engine
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 fro m airliners.
4.2.1
COMPARISON BETWEEN SPECIFICATIONS
Trent 900
GP 7200
General Specifications
General Specifications
Type : Three-spool high bypass ratio(8.7-8.5)
Type : Two-spool high-bypass ratio (8.8)
Length : 5.48m
Length : 4.74m
Diameter : 2.95m
Diameter : 3.16m
Dry Weight : 6,246kg
Dry Weight : 6,712kg
Components
Components
Compressor : 1 stage LPC, 8 stage IPC, 6
Compressor : 5 stage LPC, 9 HPC
stage HPC Combustor : Single Annular Combustor
Combustor : Single Annular Combustor Turbine : 2 stage HPT, 6 stage LPT
Turbine : 1 stage HPT, 1 stage IPT, 5 stage LPT Performance
Performance
Maximum Thrust : 344 to 357kN or 77000 to
Maximum Thrust : 36,980kgf, 363kN,
88000 lbf
81,500lbf
Overall Pressure Ratio : 37 to 39
Overall Pressure Ratio : 43.9
Thrust-to-weight ratio : 5.46 to 6.11
Thrust-to-weight ratio : 5.508
Ratings
Ratings
Maximum Take Off : 334.29-372.92 kN
Maximum Take Off : 332.437 kN or 74735 lbs
Maximum Continuous : 319.60 kN
Maximum Continuous : 326.81 kN
Table 4.1 Table of Specificat ion GP 7200 and Trent 900
4.2.2
ADVANTAGES TRENT 900 OVER GP 7200
Based 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 7200
In 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
Figur e 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 BL ENDED WING BODY AIRCRAFT During 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 Fut uristic BWB aircraft layout w it h LH2 tank and bi ofuel
5.3
HYBRID ENGINE Alternative 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 t he 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 Rot ating 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 turbi ne, 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 t he BWB wit h t he 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 REFERENCES Rolls-Royce. (3 February, 2015). Retrieved 10 March, 2015, from http://www.rollsroyce.com/customers/civil-aerospace/products/civil-large-engines/trent-900/trent-900infographic.aspx EASA. (2013). TYPE-CERTIFICATE DATA SHEET RB 211 T rent 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
