A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion . The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all the air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust .
173-784: The Rolls-Royce Trent is a family of high-bypass turbofans produced by Rolls-Royce . It continues the three spool architecture of the RB211 with a maximum thrust ranging from 61,900 to 97,000 lbf (275 to 431 kN ). Launched as the RB-211-524L in June 1988, the prototype first ran in August 1990. Its first variant is the Trent 700 introduced on the Airbus A330 in March 1995, then
346-504: A British Airways Boeing 777-236ER, operating as Flight 38 from Beijing to London, crash-landed at Heathrow Airport after both Trent 800 engines lost power during the aircraft's final approach. The subsequent investigation found that ice released from the fuel system had accumulated on the fuel-oil heat exchanger, leading to a restriction of fuel flow to the engines. This resulted in Airworthiness Directives mandating
519-438: A Trent 1000 fitted with composite fan blades and case, including bird strike trials. On 26 February 2014, Rolls-Royce detailed its Trent future developments. The Advance is the first design, which could be ready from the end of the 2020s and aims to offer at least 20% better fuel burn than the first generation of Trents. The Advance bypass ratio should exceed 11:1 and its overall pressure ratio 60:1. In previous Trents,
692-544: A 35% better efficiency gain. High-bypass turbofan The ratio of the mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as the bypass ratio . The engine produces thrust through a combination of these two portions working together. Engines that use more jet thrust relative to fan thrust are known as low-bypass turbofans ; conversely those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are of
865-435: A 454 kN (102,000 lbf) GE90-102B, while P&W offered its 436 kN (98,000 lbf) PW4098 and Rolls-Royce was proposing a 437 kN (98,000 lbf) Trent 8100 . Rolls-Royce was also studying a Trent 8102 over 445 kN (100,000 lbf). By December 1997, the -300X MTOW grew to 324,600 kg (715,600 lb). The 454 kN (102,000 lbf) Trent 8104 design was to be completed by June 1998, while
1038-404: A 6.4:1 bypass ratio and an overall pressure ratio reaching 40.7:1, it generates up to 413.4 kN (92,940 lbf) of thrust . In the early Trent 800 studies in 1990, Rolls-Royce forecast a growth potential from 85,000 to 95,000 lbf (380 to 420 kN) with a new HP core. By March 1997, Boeing studied 777-200X/300X growth derivatives for a September 2000 introduction: GE was proposing
1211-573: A 94.6 in (240 cm) fan. By September 1992, three were rebuilt as Trent 700 engines for the A330 with a 97.4 in (247 cm) fan. Rolls-Royce was studying a RB211 development for the Airbus A330 at its launch in June 1987. The Trent 700 was first selected by Cathay Pacific in April 1989, first ran in summer 1992, was certified in January 1994 and put into service in March 1995. Keeping
1384-516: A Trent 500 gearbox fitted), producing 36 MW for maritime applications. The current version is a turboshaft engine, producing 36 MW, using the Trent 800 core to drive a power turbine which takes power to an electrical generator or to mechanical drives such as waterjets or propellers. Amongst others, it powers the Royal Navy 's Queen Elizabeth -class aircraft carriers . This derivative
1557-794: A bypass ratio up to 8.5:1 in cruise. The Trent 900 powers the Airbus A380 , competing with the Engine Alliance GP7000 . Initially proposed for the Boeing 747-500/600X in July 1996, this first application was later abandoned but it was offered for the A3XX , launched as the A380 in December 2000. It first ran on 18 March 2003, made its maiden flight on 17 May 2004 on an A340 testbed, and
1730-511: A common core to lower development costs, and the three-shaft design provided flexibility, allowing each spool to be individually scaled. The engine family is named after the River Trent , a name previously used for the RB.50 , Rolls-Royce's first working turboprop engine; and the 1960s RB.203 , a 9,980 lbf (44.4 kN) bypass turbofan and the first three-spool engine, designed to replace
1903-434: A corresponding increase in pressure and temperature in the exhaust duct which in turn cause a higher gas speed from the propelling nozzle (and higher KE and wasted fuel). Although the engine would use less fuel to produce a pound of thrust, more fuel is wasted in the faster propelling jet. In other words, the independence of thermal and propulsive efficiencies, as exists with the piston engine/propeller combination which preceded
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#17327726070352076-419: A discordant nature known as "buzz saw" noise. All modern turbofan engines have acoustic liners in the nacelle to damp their noise. They extend as much as possible to cover the largest surface area. The acoustic performance of the engine can be experimentally evaluated by means of ground tests or in dedicated experimental test rigs. In the aerospace industry, chevrons are the "saw-tooth" patterns on
2249-419: A discordant nature known as "buzz saw" noise. All modern turbofan engines have acoustic liners in the nacelle to damp their noise. They extend as much as possible to cover the largest surface area. The acoustic performance of the engine can be experimentally evaluated by means of ground tests or in dedicated experimental test rigs. In the aerospace industry, chevrons are the "saw-tooth" patterns on
2422-410: A fixed total applied fuel:air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine. However, a high specific thrust turbofan will, by definition, have a higher nozzle pressure ratio, resulting in a higher afterburning net thrust and, therefore, a lower afterburning specific fuel consumption (SFC). However, high specific thrust engines have
2595-410: A fixed total applied fuel:air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine. However, a high specific thrust turbofan will, by definition, have a higher nozzle pressure ratio, resulting in a higher afterburning net thrust and, therefore, a lower afterburning specific fuel consumption (SFC). However, high specific thrust engines have
2768-585: A full-scale model was unveiled by Frank Whittle . In June 1989, the RB211-524L Trent was confirmed for the A330, rated at 74,000 lbf (330 kN). Rated at 65,000 lbf (290 kN) for the MD-11, the Trent made its first run on 27 August 1990 in Derby . By September 1992, the 94.6 in (240 cm) Trent 600 for the MD-11 was abandoned and prototypes were rebuilt as Trent 700 engines for
2941-426: A high dry SFC. The situation is reversed for a medium specific thrust afterburning turbofan: i.e., poor afterburning SFC/good dry SFC. The former engine is suitable for a combat aircraft which must remain in afterburning combat for a fairly long period, but has to fight only fairly close to the airfield (e.g. cross border skirmishes). The latter engine is better for an aircraft that has to fly some distance, or loiter for
3114-426: A high dry SFC. The situation is reversed for a medium specific thrust afterburning turbofan: i.e., poor afterburning SFC/good dry SFC. The former engine is suitable for a combat aircraft which must remain in afterburning combat for a fairly long period, but has to fight only fairly close to the airfield (e.g. cross border skirmishes). The latter engine is better for an aircraft that has to fly some distance, or loiter for
3287-416: A higher nozzle pressure ratio than the turbojet, but with a lower exhaust temperature to retain net thrust. Since the temperature rise across the whole engine (intake to nozzle) would be lower, the (dry power) fuel flow would also be reduced, resulting in a better specific fuel consumption (SFC). Some low-bypass ratio military turbofans (e.g. F404 , JT8D ) have variable inlet guide vanes to direct air onto
3460-416: A higher nozzle pressure ratio than the turbojet, but with a lower exhaust temperature to retain net thrust. Since the temperature rise across the whole engine (intake to nozzle) would be lower, the (dry power) fuel flow would also be reduced, resulting in a better specific fuel consumption (SFC). Some low-bypass ratio military turbofans (e.g. F404 , JT8D ) have variable inlet guide vanes to direct air onto
3633-624: A higher thrust for better takeoff performance. The 767-400ERX was dropped in 2001 to favor the Sonic Cruiser . When Boeing launched the 747-8 in November 2005, it was exclusively powered by the General Electric GEnx . The Rolls-Royce Trent 1000 is one of the two engine options for the Boeing 787 Dreamliner , competing with the General Electric GEnx . It first ran on 14 February 2006 and first flew on 18 June 2007 before
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#17327726070353806-550: A joint EASA/FAA certification on 7 August 2007 and service introduction on 26 October 2011. The 62,264–81,028 lbf (276.96–360.43 kN) engine has a bypass ratio over 10:1, a 2.85 m (9 ft 4 in) m fan and keeps the characteristic three-spool layout of the Trent series. The updated Trent 1000 TEN with technology from the Trent XWB and the Advance 3 aims for up to 3% better fuel burn , it first ran in mid-2014,
3979-502: A late 2018 demonstrator based on a Trent XWB-97 within the high temperature turbine technology (HT3) initiative. The core will be combined with a Trent XWB-84 fan and a Trent 1000 LP turbine for mid-2017 ground testing. The Advance3 demonstrator was sent from the Bristol production facility to the Derby test stand in July 2017 to be evaluated till early 2018. The demonstrator began initial runs at Derby in November 2017. In early 2018,
4152-547: A lean burn combustor and unshrouded HP turbine and a variable-geometry IP turbine. Hispano Suiza's new accessory gearbox, Goodrich 's new distributed control system, and Techspace Aero's new oil system were also fitted. After flight tests in 2014 of CTi fan blades with a titanium leading edge and carbon casing, they had indoor and outdoor tests in 2017, including crosswind , noise and tip clearance studies, flutter mapping, performance and icing conditions trials. In late 2018 Rolls-Royce has ground tested its ALPS demonstrator:
4325-590: A long time, before going into combat. However, the pilot can afford to stay in afterburning only for a short period, before aircraft fuel reserves become dangerously low. The first production afterburning turbofan engine was the Pratt & Whitney TF30 , which initially powered the F-111 Aardvark and F-14 Tomcat . Low-bypass military turbofans include the Pratt & Whitney F119 , the Eurojet EJ200 ,
4498-414: A long time, before going into combat. However, the pilot can afford to stay in afterburning only for a short period, before aircraft fuel reserves become dangerously low. The first production afterburning turbofan engine was the Pratt & Whitney TF30 , which initially powered the F-111 Aardvark and F-14 Tomcat . Low-bypass military turbofans include the Pratt & Whitney F119 , the Eurojet EJ200 ,
4671-485: A low mean jet velocity at take-off to lower the Airbus A380 noise. At the McDonnell Douglas MD-11 program launch at the end of 1986, it was only offered with GE CF6 -80C2 or PW4000 engines, but Rolls-Royce was studying to propose the 747-400 's RB211 -524D4D rated at 58,000 lbf (260 kN). By June 1988, Rolls-Royce was investing over $ 540 million to develop the uprated RB-211-524L with
4844-503: A new 95 in (240 cm) fan up from 86 in (220 cm) for the -524G/H and a fourth LP turbine stage up from three, targeting 65,000 to 70,000 lbf (290 to 310 kN). Rated at 65,000 lbf (290 kN), the Trent made its first run on 27 August 1990 in Derby . By July 1991, the MD-11 Trent was abandoned after the demise of Air Europe , its only customer. By February 1992, there were four Trent 600 engines with
5017-401: A pound of thrust, more fuel is wasted in the faster propelling jet. In other words, the independence of thermal and propulsive efficiencies, as exists with the piston engine/propeller combination which preceded the turbojet, is lost. In contrast, Roth considers regaining this independence the single most important feature of the turbofan which allows specific thrust to be chosen independently of
5190-488: A power rig simulating loading conditions in flight, sized for 15–80 MW (20,000–107,000 hp) gear systems; and recruited 200 engineers. The ratio of the initial test gear will approach 4:1 and thrust could be up to 440 kN (100,000 lbf). The test rig is an €84 million ($ 94 million) investment. In partnership with Liebherr , the 75 MW (100,000 hp) UltraFan gearbox was first run in October 2016. After
5363-403: A pure-jet of the same thrust, and jet noise is no longer the predominant source. Turbofan engine noise propagates both upstream via the inlet and downstream via the primary nozzle and the by-pass duct. Other noise sources are the fan, compressor and turbine. Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. Their noise
Rolls-Royce Trent - Misplaced Pages Continue
5536-403: A pure-jet of the same thrust, and jet noise is no longer the predominant source. Turbofan engine noise propagates both upstream via the inlet and downstream via the primary nozzle and the by-pass duct. Other noise sources are the fan, compressor and turbine. Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. Their noise
5709-497: A single-stage turbine, and a five-stage LP turbine. In July 1999, Boeing selected the General Electric GE90 over the Trent 8115 and P&W offer to power exclusively the longer-range 777s, as GE offered to substantially finance the jet development, for around $ 100 million. Rolls-Royce later dropped the Trent 8115 but continued to work on the Trent 8104 as a technology demonstrator. The Trent 500 exclusively powers
5882-569: A static thrust of 4,320 lb (1,960 kg), and had a bypass ratio of 6:1. The General Electric TF39 became the first production model, designed to power the Lockheed C-5 Galaxy military transport aircraft. The civil General Electric CF6 engine used a derived design. Other high-bypass turbofans are the Pratt & Whitney JT9D , the three-shaft Rolls-Royce RB211 and the CFM International CFM56 ; also
6055-424: A static thrust of 4,320 lb (1,960 kg), and had a bypass ratio of 6:1. The General Electric TF39 became the first production model, designed to power the Lockheed C-5 Galaxy military transport aircraft. The civil General Electric CF6 engine used a derived design. Other high-bypass turbofans are the Pratt & Whitney JT9D , the three-shaft Rolls-Royce RB211 and the CFM International CFM56 ; also
6228-473: A turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A bypass ratio of 6, for example, means that 6 times more air passes through the bypass duct than the amount that passes through the combustion chamber. Turbofan engines are usually described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition BPR
6401-473: A turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A bypass ratio of 6, for example, means that 6 times more air passes through the bypass duct than the amount that passes through the combustion chamber. Turbofan engines are usually described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition BPR
6574-421: A turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system. The thrust ( F N ) generated by a turbofan depends on the effective exhaust velocity of the total exhaust, as with any jet engine, but because two exhaust jets are present
6747-421: A turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system. The thrust ( F N ) generated by a turbofan depends on the effective exhaust velocity of the total exhaust, as with any jet engine, but because two exhaust jets are present
6920-496: A turbojet even though an extra turbine, a gearbox and a propeller are added to the turbojet's low-loss propelling nozzle. The turbofan has additional losses from its greater number of compressor stages/blades, fan and bypass duct. Froude, or propulsive, efficiency can be defined as: η f = 2 1 + V j V a {\displaystyle \eta _{f}={\frac {2}{1+{\frac {V_{j}}{V_{a}}}}}} where: While
7093-496: A turbojet even though an extra turbine, a gearbox and a propeller are added to the turbojet's low-loss propelling nozzle. The turbofan has additional losses from its greater number of compressor stages/blades, fan and bypass duct. Froude, or propulsive, efficiency can be defined as: η f = 2 1 + V j V a {\displaystyle \eta _{f}={\frac {2}{1+{\frac {V_{j}}{V_{a}}}}}} where: While
Rolls-Royce Trent - Misplaced Pages Continue
7266-704: A turbojet which accelerates a smaller amount more quickly, which is a less efficient way to generate the same thrust (see the efficiency section below). The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio . Engines with more jet thrust relative to fan thrust are known as low-bypass turbofans , those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are high-bypass, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofans on combat aircraft. The bypass ratio (BPR) of
7439-704: A turbojet which accelerates a smaller amount more quickly, which is a less efficient way to generate the same thrust (see the efficiency section below). The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio . Engines with more jet thrust relative to fan thrust are known as low-bypass turbofans , those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are high-bypass, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofans on combat aircraft. The bypass ratio (BPR) of
7612-431: A type of airbreathing jet engine that is widely used in aircraft propulsion . The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all
7785-507: Is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed (hovering). For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The trade off between mass flow and velocity is also seen with propellers and helicopter rotors by comparing disc loading and power loading. For example,
7958-507: Is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed (hovering). For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The trade off between mass flow and velocity is also seen with propellers and helicopter rotors by comparing disc loading and power loading. For example,
8131-410: Is considerable potential for reducing fuel consumption for the same core cycle by increasing BPR.This is achieved because of the reduction in pounds of thrust per lb/sec of airflow (specific thrust) and the resultant reduction in lost kinetic energy in the jets (increase in propulsive efficiency). If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft
8304-410: Is considerable potential for reducing fuel consumption for the same core cycle by increasing BPR.This is achieved because of the reduction in pounds of thrust per lb/sec of airflow (specific thrust) and the resultant reduction in lost kinetic energy in the jets (increase in propulsive efficiency). If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft
8477-562: Is designed for power generation and mechanical drive, much like the Marine Trent. It delivers up to 66 MW of electricity at 42% efficiency. It comes in two key versions DLE (Dry Low Emission) and WLE (Wet Low Emission). The WLE is water injected, allowing it to produce 58 MW at ISO conditions instead of 52 MW. It shares components with the Trent 700 and 800. The heat from the exhaust, some 416–433 °C, can be used to heat water and drive steam turbines, improving efficiency of
8650-430: Is due to the speed, temperature, and pressure of the exhaust jet, especially during high-thrust conditions, such as those required for takeoff. The primary source of jet noise is the turbulent mixing of shear layers in the engine's exhaust. These shear layers contain instabilities that lead to highly turbulent vortices that generate the pressure fluctuations responsible for sound. To reduce the noise associated with jet flow,
8823-430: Is due to the speed, temperature, and pressure of the exhaust jet, especially during high-thrust conditions, such as those required for takeoff. The primary source of jet noise is the turbulent mixing of shear layers in the engine's exhaust. These shear layers contain instabilities that lead to highly turbulent vortices that generate the pressure fluctuations responsible for sound. To reduce the noise associated with jet flow,
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#17327726070358996-413: Is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption (SFC) with increasing BPR. BPR can also be quoted for lift fan installations where the fan airflow is remote from
9169-413: Is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption (SFC) with increasing BPR. BPR can also be quoted for lift fan installations where the fan airflow is remote from
9342-420: Is sufficient core power to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the inlet temperature of the high-pressure (HP) turbine rotor. To illustrate one aspect of how a turbofan differs from a turbojet, comparisons can be made at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific thrust). A bypass flow can be added only if
9515-420: Is sufficient core power to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the inlet temperature of the high-pressure (HP) turbine rotor. To illustrate one aspect of how a turbofan differs from a turbojet, comparisons can be made at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific thrust). A bypass flow can be added only if
9688-424: Is that combustion is less efficient at lower speeds. Any action to reduce the fuel consumption of the engine by increasing its pressure ratio or turbine temperature to achieve better combustion causes a corresponding increase in pressure and temperature in the exhaust duct which in turn cause a higher gas speed from the propelling nozzle (and higher KE and wasted fuel). Although the engine would use less fuel to produce
9861-411: Is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission. Unlike in the main engine, where stoichiometric temperatures in the combustor have to be reduced before they reach the turbine, an afterburner at maximum fuelling is designed to produce stoichiometric temperatures at entry to the nozzle, about 2,100 K (3,800 °R; 3,300 °F; 1,800 °C). At
10034-411: Is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission. Unlike in the main engine, where stoichiometric temperatures in the combustor have to be reduced before they reach the turbine, an afterburner at maximum fuelling is designed to produce stoichiometric temperatures at entry to the nozzle, about 2,100 K (3,800 °R; 3,300 °F; 1,800 °C). At
10207-524: The Airbus A330neo . When the 380 t (840,000 lb) MTOW A340-600 HGW first flew in November 2005, Airbus was studying an enhanced version of the larger A340 variants to enter service in 2011. It would better compete with the 777-300ER and its 8-9% lower fuel burn than the A340-600: improved General Electric GEnx or Trent 1500 engines would erode this by 6-7%. The Trent 1500 would keep
10380-479: The Bristol Olympus , and Pratt & Whitney JT3C engines, increased the overall pressure ratio and thus the thermodynamic efficiency of engines. They also had poor propulsive efficiency, because pure turbojets have a high specific thrust/high velocity exhaust, which is better suited to supersonic flight. The original low-bypass turbofan engines were designed to improve propulsive efficiency by reducing
10553-415: The Bristol Olympus , and Pratt & Whitney JT3C engines, increased the overall pressure ratio and thus the thermodynamic efficiency of engines. They also had poor propulsive efficiency, because pure turbojets have a high specific thrust/high velocity exhaust, which is better suited to supersonic flight. The original low-bypass turbofan engines were designed to improve propulsive efficiency by reducing
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#173277260703510726-474: The GE9X 's 340 cm (134 in). Higher bypass and lower fan pressure ratio induce low-speed fan instability that is remedied by variable-pitch blades instead of a variable area jet nozzle . Along with eliminating the thrust reverser, a short, slim nacelle is lighter and less draggy , but in reverse-thrust the flow is distorted, turning the nozzle into the bypass duct , and then partly reversed again into
10899-702: The General Electric F110 , the Klimov RD-33 , and the Saturn AL-31 , all of which feature a mixed exhaust, afterburner and variable area propelling nozzle. To further improve fuel economy and reduce noise, almost all jet airliners and most military transport aircraft (e.g., the C-17 ) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in
11072-460: The General Electric F110 , the Klimov RD-33 , and the Saturn AL-31 , all of which feature a mixed exhaust, afterburner and variable area propelling nozzle. To further improve fuel economy and reduce noise, almost all jet airliners and most military transport aircraft (e.g., the C-17 ) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in
11245-455: The Spey but never introduced. In 2019, Rolls-Royce delivered 510 Trent engines. Like its RB211 predecessor, the Trent uses a concentric three-spool design rather than a two-spool configuration. The Trent family keeps a similar layout, but each spool can be individually scaled and can rotate more closely to its optimal speed. The core noise levels and exhaust emissions are lower than those of
11418-775: The Trent 800 for the Boeing 777 (1996), the Trent 500 for the A340 (2002), the Trent 900 for the A380 (2007), the Trent 1000 for the Boeing 787 (2011), the Trent XWB for the A350 (2015), and the Trent 7000 for the A330neo (2018). It has also marine and industrial variants like the RR MT30 . Despite the RB211 success, the large civil turbofan market was dominated by General Electric and Pratt & Whitney , and Rolls-Royce share
11591-520: The bypass ratio . The engine produces thrust through a combination of these two portions working together. Engines that use more jet thrust relative to fan thrust are known as low-bypass turbofans ; conversely those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are of the high-bypass type, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofan engines with bypass and core mixing before
11764-544: The flight envelope . An air pipe is produced by additive manufacturing and prototype components come from new suppliers. The Advance3 will survey bearing load, water ingestion, noise sources and their mitigation, heat and combustor rumble while blade-tip, internal clearances and adaptive control operation are radiographed in-motion to verify the thermo-mechanical modelling. The Boeing New Midsize Airplane needs falls in its thrust range. Advanced cooled metallic components and ceramic matrix composite parts will be tested in
11937-414: The -200X entry into service slipped to mid-2002. Higher thrust was obtained with new swept fan blades while keeping a 2.79 m (110 in) fan. The 104,000 lbf (460 kN) Trent 8104 first ran on 16 December 1998, and exceeded 110,000 lbf (490 kN) of thrust five days later, before two other engines would join by mid-1999. The swept fan blades produce 2-3% more flow at a given speed with
12110-421: The 1960s. Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use turboprops . Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired net thrust. The core (or gas generator) of
12283-421: The 1960s. Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use turboprops . Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired net thrust. The core (or gas generator) of
12456-534: The A330 with a 97.4 in (247 cm) fan. 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 . The UK government granted Rolls-Royce £ 450 million repayable launch investment , repaid with interest, to develop the RB.211 engine and the Trent family up to the Trent 900 . Rolls-Royce obtained £200 million for
12629-701: The ALPS programme. At the September 2017 International Society for Air Breathing Engines (ISABE) conference in Manchester, UK, Rolls-Royce's Chief Technology Officer Paul Stein announced it reached 52 MW (70,000 hp). In early 2018, a third gearbox was tested for endurance and reliability . The first gearbox was then disassembled for evaluation, confirming the component's performance predictions. In April 2018, Airbus agreed to provide aircraft integration and its nacelle and for flight testing, co-funded by
12802-633: The Advance3 core ran at full power. By early 2019, the engine had run over 100 hours. A standalone engine will test the ALECSys on ground before another will be flight tested . Indoor ground tests of the lean-burn combustor were concluded on a modified Trent 1000 in January 2018, before being sent to Manitoba for cold-weather trials in February 2018, covering start-ups and ice ingestion. Noise testing will follow on an outside rig, then flight tests in
12975-617: The European Union research programme Clean Sky 2. At the April 2018 ILA Berlin Air Show , flight testing was confirmed on Rolls-Royce's Boeing 747 -200. The demonstrator generated 310–360 kN (70,000–80,000 lbf) of thrust, exploiting current testing on the Advance 3 and the 52 MW (70,000 hp) gearbox. Fan diameter could be up to 356 cm (140 in), compared to the Trent XWB 's 300 cm (118 in) and
13148-527: The HP spool was similar in all models and the engine grew by increasing the intermediate pressure spool's work. The Advance reverses this trend and the load is shifted towards the high pressure spool, with a greater pressure ratio, up to 10 compressor stages compared to 6 on the Trent XWB and a two-stage turbine replacing the current single-stage. The IP compressor will shrink from the 8 stages of today's XWB to 4 and
13321-644: The IP turbine will be single- rather than of two stages. The Advance3 ground-based demonstrator includes lean burn , run before on a Trent architecture only; ceramic matrix composite (CMC) for turbine high-temperature capability in the first stage seal segments and cast-bond first stage vanes; hybrid ball bearings with ceramic rollers running on metallic races, required to manage high load environments inside smaller cores. Opened in 2016, R-R's $ 30 million CMC facility in California produced its first parts, seals, for
13494-462: The RB211. Hollow titanium fan blades with an internal Warren-girder structure achieve strength, stiffness and damage tolerance at low weight. To operate in temperatures above their melting point , cooling air is bled from the compressor through laser-drilled holes in the hollow turbine blades , made from a single-crystal of a nickel alloy and covered by thermal barrier coatings . Each turbine blade removes up to 560 kW (750 hp) from
13667-537: The Trent 500's 2.47 m (97.4 in) fan diameter and nacelle , with the smaller, advanced Trent 1000 core and a revised LP turbine for a bypass ratio increased from 7.5-7.6:1 to 9.5:1. The last A340 was delivered in 2011 as it was replaced by the updated A350XWB design. The Trent XWB was selected in July 2006 to power exclusively the Airbus A350 XWB . The first engine was run on 14 June 2010, it first flew on an Airbus A380 testbed on 18 February 2012, it
13840-532: The Trent ;8104, 500 and 600 variants in 1997, and £250 million for the Trent 600 and 900 variants in 2001, no aid was sought for Trent 1000 variant. New proposed planes required higher thrust and customers wanted the Boeing 777 and Airbus A330 twinjets to fly Extended-range Twin-engine Operations at introduction. Rolls-Royce decided to offer an engine for every large civil airliner, based on
14013-464: The aerospace industry has sought to disrupt shear layer turbulence and reduce the overall noise produced. Fan noise may come from the interaction of the fan-blade wakes with the pressure field of the downstream fan-exit stator vanes. It may be minimized by adequate axial spacing between blade trailing edge and stator entrance. At high engine speeds, as at takeoff, shock waves from the supersonic fan tips, because of their unequal nature, produce noise of
14186-464: The aerospace industry has sought to disrupt shear layer turbulence and reduce the overall noise produced. Fan noise may come from the interaction of the fan-blade wakes with the pressure field of the downstream fan-exit stator vanes. It may be minimized by adequate axial spacing between blade trailing edge and stator entrance. At high engine speeds, as at takeoff, shock waves from the supersonic fan tips, because of their unequal nature, produce noise of
14359-422: The afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume and increased flow rate when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but
14532-422: The afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume and increased flow rate when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but
14705-409: The afterburner. Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit. The turbofan was invented to improve the fuel consumption of the turbojet. It achieves this by pushing more air, thus increasing the mass and lowering the speed of the propelling jet compared to that of
14878-404: The air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust . The ratio of the mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as
15051-441: The aircraft is going forwards, leaving a very fast wake. This wake contains kinetic energy that reflects the fuel used to produce it, rather than the fuel used to move the aircraft forwards. A turbofan harvests that wasted velocity and uses it to power a ducted fan that blows air in bypass channels around the rest of the turbine. This reduces the speed of the propelling jet while pushing more air, and thus more mass. The other penalty
15224-474: The average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio. Bypass ratios greater than 5:1 are increasingly common; the Pratt & Whitney PW1000G , which entered commercial service in 2016, attains 12.5:1. Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improvements in blade aerodynamics can reduce
15397-426: The average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio. Bypass ratios greater than 5:1 are increasingly common; the Pratt & Whitney PW1000G , which entered commercial service in 2016, attains 12.5:1. Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improvements in blade aerodynamics can reduce
15570-517: The characteristic three-shaft architecture of the RB211, it is the first variant of the Trent family. With its 97.4 in (247 cm) fan for a 5:1 bypass ratio , it produces 300.3 to 316.3 kN (67,500-71,100 lbf) of thrust and reaches an overall pressure ratio of 36:1. It competes with the GE CF6 -80E1 and the PW4000 to power the A330. The Trent 800 is one of the engine options for
15743-458: The demonstrator attained 90% core power, reaching a 450 psi (31 bar) P30 pressure at the rear of the HP compressor, while measuring bearing loads, changed by the different compressor arrangement. The lean burn combustor did not generate any rumble as further tests will cover water ingestion, noise , X-rays of the engine operating, and core-zone and hot-end thermal surveys . By July 2018,
15916-409: The early Boeing 777 variants. Launched in September 1991, it first ran in September 1993, was granted EASA certification on 27 January 1995, and entered service in 1996. It reached a 40% market share, ahead of the competing PW4000 and GE90 , and the last Trent-powered 777 was delivered in 2010. The Trent 800 has the Trent family three shaft architecture, with a 280 cm (110 in) fan. With
16089-448: The engine and doesn't flow past the engine core. Considering a constant core (i.e. fixed pressure ratio and turbine inlet temperature), core and bypass jet velocities equal and a particular flight condition (i.e. Mach number and altitude) the fuel consumption per lb of thrust (sfc) decreases with increase in BPR. At the same time gross and net thrusts increase, but by different amounts. There
16262-399: The engine and doesn't flow past the engine core. Considering a constant core (i.e. fixed pressure ratio and turbine inlet temperature), core and bypass jet velocities equal and a particular flight condition (i.e. Mach number and altitude) the fuel consumption per lb of thrust (sfc) decreases with increase in BPR. At the same time gross and net thrusts increase, but by different amounts. There
16435-427: The engine must generate enough power to drive the fan at its rated mass flow and pressure ratio. Improvements in turbine cooling/material technology allow for a higher (HP) turbine rotor inlet temperature, which allows a smaller (and lighter) core, potentially improving the core thermal efficiency. Reducing the core mass flow tends to increase the load on the LP turbine, so this unit may require additional stages to reduce
16608-427: The engine must generate enough power to drive the fan at its rated mass flow and pressure ratio. Improvements in turbine cooling/material technology allow for a higher (HP) turbine rotor inlet temperature, which allows a smaller (and lighter) core, potentially improving the core thermal efficiency. Reducing the core mass flow tends to increase the load on the LP turbine, so this unit may require additional stages to reduce
16781-416: The engine, from the gas generator, to a ducted fan which produces a second, additional mass of accelerated air. The transfer of energy from the core to bypass air results in lower pressure and temperature gas entering the core nozzle (lower exhaust velocity), and fan-produced higher pressure and temperature bypass-air entering the fan nozzle. The amount of energy transferred depends on how much pressure rise
16954-524: The exhaust velocity to a value closer to that of the aircraft. The Rolls-Royce Conway , the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern General Electric F404 fighter engine. Civilian turbofan engines of the 1960s, such as the Pratt & Whitney JT8D and the Rolls-Royce Spey , had bypass ratios closer to 1 and were similar to their military equivalents. The first Soviet airliner powered by turbofan engines
17127-458: The exhaust velocity to a value closer to that of the aircraft. The Rolls-Royce Conway , the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern General Electric F404 fighter engine. Civilian turbofan engines of the 1960s, such as the Pratt & Whitney JT8D and the Rolls-Royce Spey , had bypass ratios closer to 1 and were similar to their military equivalents. The first Soviet airliner powered by turbofan engines
17300-411: The fan is designed to produce (fan pressure ratio). The best energy exchange (lowest fuel consumption) between the two flows, and how the jet velocities compare, depends on how efficiently the transfer takes place which depends on the losses in the fan-turbine and fan. The fan flow has lower exhaust velocity, giving much more thrust per unit energy (lower specific thrust ). Both airstreams contribute to
17473-494: The fan nozzle. The amount of energy transferred depends on how much pressure rise the fan is designed to produce (fan pressure ratio). The best energy exchange (lowest fuel consumption) between the two flows, and how the jet velocities compare, depends on how efficiently the transfer takes place which depends on the losses in the fan-turbine and fan. The fan flow has lower exhaust velocity, giving much more thrust per unit energy (lower specific thrust ). Both airstreams contribute to
17646-450: The first fan rotor stage. This improves the fan surge margin (see compressor map ). Since the 1970s, most jet fighter engines have been low/medium bypass turbofans with a mixed exhaust, afterburner and variable area exit nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, large volumes of fuel are burnt in
17819-450: The first fan rotor stage. This improves the fan surge margin (see compressor map ). Since the 1970s, most jet fighter engines have been low/medium bypass turbofans with a mixed exhaust, afterburner and variable area exit nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, large volumes of fuel are burnt in
17992-479: The fleet accumulated 2.2 million flight hours. It is the most powerful among all Trent engines. The Rolls-Royce Trent 7000 powers exclusively the Airbus A330neo . Announced on 14 July 2014, it first ran on 27 November 2015. It made its first flight on 19 October 2017 aboard on the A330neo. It received its EASA type certification on 20 July 2018 as a Trent 1000 variant. It was first delivered on 26 November, and
18165-483: The fuel consumption of the turbojet. It achieves this by pushing more air, thus increasing the mass and lowering the speed of the propelling jet compared to that of the turbojet. This is done mechanically by adding a ducted fan rather than using viscous forces. A vacuum ejector is used in conjunction with the fan as first envisaged by inventor Frank Whittle . Whittle envisioned flight speeds of 500 mph in his March 1936 UK patent 471,368 "Improvements relating to
18338-496: The fuel used to move the aircraft forwards. A turbofan harvests that wasted velocity and uses it to power a ducted fan that blows air in bypass channels around the rest of the turbine. This reduces the speed of the propelling jet while pushing more air, and thus more mass. The other penalty is that combustion is less efficient at lower speeds. Any action to reduce the fuel consumption of the engine by increasing its pressure ratio or turbine temperature to achieve better combustion causes
18511-400: The gas generator cycle. The working substance of the thermodynamic cycle is the only mass accelerated to produce thrust in a turbojet which is a serious limitation (high fuel consumption) for aircraft speeds below supersonic. For subsonic flight speeds the speed of the propelling jet has to be reduced because there is a price to be paid in producing the thrust. The energy required to accelerate
18684-443: The gas inside the engine (increase in kinetic energy) is expended in two ways, by producing a change in momentum ( i.e. a force), and a wake which is an unavoidable consequence of producing thrust by an airbreathing engine (or propeller). The wake velocity, and fuel burned to produce it, can be reduced and the required thrust still maintained by increasing the mass accelerated. A turbofan does this by transferring energy available inside
18857-461: The gas stream. In April 1998, the RB211-524 HT was introduced for the 747-400 with the Trent 700 core, replacing the previous RB211-524G/H with 2% better TSFC , up to a 40% lower NOx emissions and a 50 °C cooler turbine. The Trent 800 LP spool rotates at 3300 rpm , its 110 in (279 cm) diameter fan tip travels at 482 m/s. The Trent 900 's 116 in (290 cm) fan keeps
19030-429: The gross thrust of the engine. The additional air for the bypass stream increases the ram drag in the air intake stream-tube, but there is still a significant increase in net thrust. The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed and gets closer to the ideal Froude efficiency . A turbofan accelerates a larger mass of air more slowly, compared to
19203-429: The gross thrust of the engine. The additional air for the bypass stream increases the ram drag in the air intake stream-tube, but there is still a significant increase in net thrust. The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed and gets closer to the ideal Froude efficiency . A turbofan accelerates a larger mass of air more slowly, compared to
19376-409: The high-bypass type, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofan engines with bypass and core mixing before the afterburner. Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit. The turbofan was invented to improve
19549-474: The hot nozzle to convert to kinetic energy. Turbofans represent an intermediate stage between turbojets , which derive all their thrust from exhaust gases, and turbo-props which derive minimal thrust from exhaust gases (typically 10% or less). Extracting shaft power and transferring it to a bypass stream introduces extra losses which are more than made up by the improved propulsive efficiency. The turboprop at its best flight speed gives significant fuel savings over
19722-474: The hot nozzle to convert to kinetic energy. Turbofans represent an intermediate stage between turbojets , which derive all their thrust from exhaust gases, and turbo-props which derive minimal thrust from exhaust gases (typically 10% or less). Extracting shaft power and transferring it to a bypass stream introduces extra losses which are more than made up by the improved propulsive efficiency. The turboprop at its best flight speed gives significant fuel savings over
19895-534: The initial set of low-speed fan rig tests and the casting of second-generation titanium aluminide IP turbine blades, the initial UltraFan demonstrator concept design was to be frozen in 2017. Tests simulated aircraft pitch and roll on an attitude rig in September 2016 to assess oil flow in the gearbox. The gearbox went through high-power tests in May 2017. The UltraFan was to be 300 cm (120 in) in diameter. Fan blades with titanium leading edges were evaluated under
20068-517: The intermediate compressor . The large fan could lead to gull-wing airframes. By July 2018, the UltraFan configuration was frozen. Detailed design and component manufacture, was set to enable 2021 ground tests. The 800 mm (2 ft 7 in) diameter planetary gearbox has five planet gears, is sized to power 110–490 kN (25,000–110,000 lbf) turbofans and amassed over 250 hours of run time by early 2019. In February 2019, introduction
20241-549: The larger A340-500/600 variants. It was selected in June 1997, first ran in May 1999, first flew in June 2000, and achieved certification on 15 December 2000. It entered service in July 2002 and 524 engines were delivered on-wing until the A340 production ended in 2011. Keeping the three spool architecture of the Trent family, it has the Trent 700 's 2.47 m (97.5 in) fan and a Trent 800 core scaled down. It produces up to 275 kN (61,900 lbf) of thrust at take-off and has
20414-548: 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. By June 2019, the Trent family had completed over 125 million hours. British Airways and Thai Airways are currently the largest operator of Trents, with four variants in service or on order, followed by Singapore Airlines and Cathay Pacific with three variants in service. On 17 January 2008,
20587-417: The mechanical power produced by the turbine. In a bypass design, extra turbines drive a ducted fan that accelerates air rearward from the front of the engine. In a high-bypass design, the ducted fan and nozzle produce most of the thrust. Turbofans are closely related to turboprops in principle because both transfer some of the gas turbine's gas power, using extra machinery, to a bypass stream leaving less for
20760-417: The mechanical power produced by the turbine. In a bypass design, extra turbines drive a ducted fan that accelerates air rearward from the front of the engine. In a high-bypass design, the ducted fan and nozzle produce most of the thrust. Turbofans are closely related to turboprops in principle because both transfer some of the gas turbine's gas power, using extra machinery, to a bypass stream leaving less for
20933-456: The need for a thrust reverser . Rolls-Royce planned to use carbon composite fan blades instead of its usual hollow titanium blades. The combination was expected to reduce weight by 340 kg (750 lb) per engine. The variable pitch fan facilitates low pressure ratio fan operability. Rolls-Royce worked with Industria de Turbo Propulsores to test ion plating (IP) turbine blade technologies. In Dahlewitz near Berlin, Rolls-Royce built
21106-423: The next couple of years after 2018. The UltraFan is a geared turbofan with a variable pitch fan system that promises at least 25% efficiency improvement. The UltraFan aims for a 15:1 bypass ratio and 70:1 overall pressure ratio. The Ultrafan keeps the Advance core, but also contains a geared turbofan architecture with variable-pitch fan blades. The fan varies pitch to optimise for each flight phase, eliminating
21279-483: The number of extra compressor stages required, and variable geometry stators enable high-pressure-ratio compressors to work surge-free at all throttle settings. The first (experimental) high-bypass turbofan engine was the AVCO-Lycoming PLF1A-2, a Honeywell T55 turboshaft-derived engine that was first run in February 1962. The PLF1A-2 had a 40 in diameter (100 cm) geared fan stage, produced
21452-411: The number of extra compressor stages required, and variable geometry stators enable high-pressure-ratio compressors to work surge-free at all throttle settings. The first (experimental) high-bypass turbofan engine was the AVCO-Lycoming PLF1A-2, a Honeywell T55 turboshaft-derived engine that was first run in February 1962. The PLF1A-2 had a 40 in diameter (100 cm) geared fan stage, produced
21625-539: The package. Besides Rolls-Royce, a leading packager of the Trent 60 is UK-based Centrax LTD, a privately owned engineering firm based in Newton Abbot, UK. 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 all three of the 787 variants ( Trent 1000 ), the A380 ( Trent 900 ) and the A350 ( Trent XWB ). Its overall share of
21798-414: The propulsion of aircraft", in which he describes the principles behind the turbofan, although not called as such at that time. While the turbojet uses the gas from its thermodynamic cycle as its propelling jet, for aircraft speeds below 500 mph there are two penalties to this design which are addressed by the turbofan. Firstly, energy is wasted as the propelling jet is going much faster rearwards than
21971-551: The replacement of the heat exchanger. This order was extended to the 500 and 700 series engines after a similar loss of power was observed on one engine of an Airbus A330 in one incident, and both engines in another. The modification involves replacing a face plate with many small protruding tubes with one that is flat. On 4 November 2010, a Qantas Airbus A380-842 (Registration VH-OQA), operating as Flight 32 en route from Singapore to Sydney, suffered an uncontained engine failure (explosion) in one of its four Trent 972-84. The cause
22144-467: The required thrust still maintained by increasing the mass accelerated. A turbofan does this by transferring energy available inside the engine, from the gas generator, to a ducted fan which produces a second, additional mass of accelerated air. The transfer of energy from the core to bypass air results in lower pressure and temperature gas entering the core nozzle (lower exhaust velocity), and fan-produced higher pressure and temperature bypass-air entering
22317-404: The same 2.8 m (110 in) fan, for an additional 10,000 lbf (44 kN) of thrust, while fan efficiency is 1% better. The HP compressor rotors and stators and the IP compressor stators were designed with 3D aerodynamics . As the 777-200X/300X grew to a MTOW of 340,500 kg (750,000 lb), thrust requirements drifted to 110,000–114,000 lbf (490–510 kN). The fan diameter
22490-399: The same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor. Bypass usually refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where
22663-399: The same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor. Bypass usually refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where
22836-452: The smaller TF34 . More recent large high-bypass turbofans include the Pratt & Whitney PW4000 , the three-shaft Rolls-Royce Trent , the General Electric GE90 / GEnx and the GP7000 , produced jointly by GE and P&W. The Pratt & Whitney JT9D engine was the first high bypass ratio jet engine to power a wide-body airliner. Turbofan#Three-spool A turbofan or fanjet is
23009-502: The sole requirement for bypass is to provide cooling air. This sets the lower limit for BPR and these engines have been called "leaky" or continuous bleed turbojets (General Electric YJ-101 BPR 0.25) and low BPR turbojets (Pratt & Whitney PW1120). Low BPR (0.2) has also been used to provide surge margin as well as afterburner cooling for the Pratt & Whitney J58 . Propeller engines are most efficient for low speeds, turbojet engines for high speeds, and turbofan engines between
23182-502: The sole requirement for bypass is to provide cooling air. This sets the lower limit for BPR and these engines have been called "leaky" or continuous bleed turbojets (General Electric YJ-101 BPR 0.25) and low BPR turbojets (Pratt & Whitney PW1120). Low BPR (0.2) has also been used to provide surge margin as well as afterburner cooling for the Pratt & Whitney J58 . Propeller engines are most efficient for low speeds, turbojet engines for high speeds, and turbofan engines between
23355-454: The speed of the propelling jet has to be reduced because there is a price to be paid in producing the thrust. The energy required to accelerate the gas inside the engine (increase in kinetic energy) is expended in two ways, by producing a change in momentum ( i.e. a force), and a wake which is an unavoidable consequence of producing thrust by an airbreathing engine (or propeller). The wake velocity, and fuel burned to produce it, can be reduced and
23528-547: The start of their deployment before being used in the static components of the second-stage HP turbine. The twin fuel-distribution system in the lean-burn combustor adds complexity with a sophisticated control and switching system and doubles the pipework but should improve fuel consumption and reduce NOx emissions. Hybrid ceramic bearings are newly configured to deal with loading changes and will cope with higher temperatures. More variable vanes in one IP and four HP compressor stages will be optimised for constant changes through
23701-536: The technology and materials available at the time. The first turbofan engine, which was only run on a test bed, was the German Daimler-Benz DB 670 , designated the 109-007 by the German RLM ( Ministry of Aviation ), with a first run date of 27 May 1943, after the testing of the turbomachinery using an electric motor, which had been undertaken on 1 April 1943. Development of the engine
23874-402: The technology and materials available at the time. The first turbofan engine, which was only run on a test bed, was the German Daimler-Benz DB 670 , designated the 109-007 by the German RLM ( Ministry of Aviation ), with a first run date of 27 May 1943, after the testing of the turbomachinery using an electric motor, which had been undertaken on 1 April 1943. Development of the engine
24047-497: The thrust equation can be expanded as: F N = m ˙ e v h e − m ˙ o v o + B P R ( m ˙ c ) v f {\displaystyle F_{N}={\dot {m}}_{e}v_{he}-{\dot {m}}_{o}v_{o}+BPR\,({\dot {m}}_{c})v_{f}} where: The cold duct and core duct's nozzle systems are relatively complex due to
24220-497: The thrust equation can be expanded as: F N = m ˙ e v h e − m ˙ o v o + B P R ( m ˙ c ) v f {\displaystyle F_{N}={\dot {m}}_{e}v_{he}-{\dot {m}}_{o}v_{o}+BPR\,({\dot {m}}_{c})v_{f}} where: The cold duct and core duct's nozzle systems are relatively complex due to
24393-673: The trailing edges of some jet engine nozzles that are used for noise reduction . The shaped edges smooth the mixing of hot air from the engine core and cooler air flowing through the engine fan, which reduces noise-creating turbulence. Chevrons were developed by GE under a NASA contract. Some notable examples of such designs are Boeing 787 and Boeing 747-8 – on the Rolls-Royce Trent 1000 and General Electric GEnx engines. Early turbojet engines were not very fuel-efficient because their overall pressure ratio and turbine inlet temperature were severely limited by
24566-606: The trailing edges of some jet engine nozzles that are used for noise reduction . The shaped edges smooth the mixing of hot air from the engine core and cooler air flowing through the engine fan, which reduces noise-creating turbulence. Chevrons were developed by GE under a NASA contract. Some notable examples of such designs are Boeing 787 and Boeing 747-8 – on the Rolls-Royce Trent 1000 and General Electric GEnx engines. Early turbojet engines were not very fuel-efficient because their overall pressure ratio and turbine inlet temperature were severely limited by
24739-428: The turbine inlet temperature is not too high to compensate for the smaller core flow. Future improvements in turbine cooling/material technology can allow higher turbine inlet temperature, which is necessary because of increased cooling air temperature, resulting from an overall pressure ratio increase. The resulting turbofan, with reasonable efficiencies and duct loss for the added components, would probably operate at
24912-428: The turbine inlet temperature is not too high to compensate for the smaller core flow. Future improvements in turbine cooling/material technology can allow higher turbine inlet temperature, which is necessary because of increased cooling air temperature, resulting from an overall pressure ratio increase. The resulting turbofan, with reasonable efficiencies and duct loss for the added components, would probably operate at
25085-425: The turbojet uses the gas from its thermodynamic cycle as its propelling jet, for aircraft speeds below 500 mph there are two penalties to this design which are addressed by the turbofan. Firstly, energy is wasted as the propelling jet is going much faster rearwards than the aircraft is going forwards, leaving a very fast wake. This wake contains kinetic energy that reflects the fuel used to produce it, rather than
25258-445: The turbojet, is lost. In contrast, Roth considers regaining this independence the single most important feature of the turbofan which allows specific thrust to be chosen independently of the gas generator cycle. The working substance of the thermodynamic cycle is the only mass accelerated to produce thrust in a turbojet which is a serious limitation (high fuel consumption) for aircraft speeds below supersonic. For subsonic flight speeds
25431-453: The turbojet. This is done mechanically by adding a ducted fan rather than using viscous forces. A vacuum ejector is used in conjunction with the fan as first envisaged by inventor Frank Whittle . Whittle envisioned flight speeds of 500 mph in his March 1936 UK patent 471,368 "Improvements relating to the propulsion of aircraft", in which he describes the principles behind the turbofan, although not called as such at that time. While
25604-476: The two flows may combine within the ducts, and share a common nozzle, which can be fitted with afterburner. Most of the air flow through a high-bypass turbofan is lower-velocity bypass flow: even when combined with the much-higher-velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity. Therefore, turbofan engines are significantly quieter than
25777-476: The two flows may combine within the ducts, and share a common nozzle, which can be fitted with afterburner. Most of the air flow through a high-bypass turbofan is lower-velocity bypass flow: even when combined with the much-higher-velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity. Therefore, turbofan engines are significantly quieter than
25950-418: The two. Turbofans are the most efficient engines in the range of speeds from about 500 to 1,000 km/h (270 to 540 kn; 310 to 620 mph), the speed at which most commercial aircraft operate. In a turbojet (zero-bypass) engine, the high temperature and high pressure exhaust gas is accelerated when it undergoes expansion through a propelling nozzle and produces all the thrust. The compressor absorbs
26123-418: The two. Turbofans are the most efficient engines in the range of speeds from about 500 to 1,000 km/h (270 to 540 kn; 310 to 620 mph), the speed at which most commercial aircraft operate. In a turbojet (zero-bypass) engine, the high temperature and high pressure exhaust gas is accelerated when it undergoes expansion through a propelling nozzle and produces all the thrust. The compressor absorbs
26296-400: The uprated RB-211-524L with a new 95 in (240 cm) fan up from 86 in (220 cm) for the -524G/H and a fourth LP turbine stage up from three, targeting 65,000 to 70,000 lbf (290 to 310 kN). At the September 1988 Farnborough Airshow , the 65,000–72,000 lbf (290–320 kN) -524L development was confirmed, estimated at £300 million, to power the MD-11 and A330 as
26469-510: The use of two separate exhaust flows. In high bypass engines, the fan is situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail of the duct forming a low pressure ratio nozzle that under normal conditions will choke creating supersonic flow patterns around the core . The core nozzle is more conventional, but generates less of the thrust, and depending on design choices, such as noise considerations, may conceivably not choke. In low bypass engines
26642-510: The use of two separate exhaust flows. In high bypass engines, the fan is situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail of the duct forming a low pressure ratio nozzle that under normal conditions will choke creating supersonic flow patterns around the core . The core nozzle is more conventional, but generates less of the thrust, and depending on design choices, such as noise considerations, may conceivably not choke. In low bypass engines
26815-701: The world, with an experience base of over 10 million service hours. The CF700 turbofan engine was also used to train Moon-bound astronauts in Project Apollo as the powerplant for the Lunar Landing Research Vehicle . A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan behind inlet guide vanes, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to ensure there
26988-495: The world, with an experience base of over 10 million service hours. The CF700 turbofan engine was also used to train Moon-bound astronauts in Project Apollo as the powerplant for the Lunar Landing Research Vehicle . A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan behind inlet guide vanes, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to ensure there
27161-402: Was EASA certified in July 2016, first flew on a 787 on 7 December 2016 and was introduced on 23 November 2017. Corrosion -related fatigue cracking of IP turbine blades was discovered in early 2016, grounding up to 44 aircraft and costing Rolls-Royce at least £1354 million. By early 2018 it had a 38% market share of the decided order book. The Trent 7000 is a version with bleed air used for
27334-614: Was abandoned with its problems unsolved, as the war situation worsened for Germany. Later in 1943, the British ground tested the Metrovick F.3 turbofan, which used the Metrovick F.2 turbojet as a gas generator with the exhaust discharging into a close-coupled aft-fan module comprising a contra-rotating LP turbine system driving two co-axial contra-rotating fans. Improved materials, and the introduction of twin compressors, such as in
27507-446: Was abandoned with its problems unsolved, as the war situation worsened for Germany. Later in 1943, the British ground tested the Metrovick F.3 turbofan, which used the Metrovick F.2 turbojet as a gas generator with the exhaust discharging into a close-coupled aft-fan module comprising a contra-rotating LP turbine system driving two co-axial contra-rotating fans. Improved materials, and the introduction of twin compressors, such as in
27680-509: Was certified by the EASA on 29 October 2004. Producing up to 374 kN (84,000 lbf), the Trent 900 has the three shaft architecture of the Trent family with a 2.95 m (116 in) fan. It has an 8.5-8.7:1 bypass ratio and a 37–39:1 overall pressure ratio . In March 2000, Boeing was to launch the longer range 767-400ERX powered by 65,000–68,000 lbf (290–300 kN) engines, with deliveries planned for 2004. In July, Rolls-Royce
27853-488: Was certified in early 2013, and it first flew on an A350 on 14 June 2013. It keeps the characteristic three-shaft layout of the Trent, with a 3.00 m (118 in) fan, an IP and HP spool. The XWB-84 generates up to 84,200 lbf (375 kN) of thrust and the XWB-97 up to 97,000 lbf (431 kN). The engine has a 9.6:1 bypass ratio and a 50:1 pressure ratio . It had its first in-flight shutdown on 11 September 2018, as
28026-399: Was cleared for ETOPS 330 by 20 December. Compared to the A330's Trent 700 , the 68,000–72,000 lbf (300–320 kN) engine doubles the bypass ratio to 10:1 and halves emitted noise. Pressure ratio is increased to 50:1 and it has a 112 in (280 cm) fan and a bleed air system. Fuel consumption is improved by 11%. The MT30 (Marine Turbine) is a derivative of the Trent 800 (with
28199-421: Was delayed to 2027, to re-engine current aircraft, after full-scale ground tests in 2021. A variable-pitch fan or a more electric architecture would be needed beyond the 25% improvement over the Trent 800 , for the 2030s-2040s. A 100–500 kW (130–670 hp) integrated starter-generator on the shaft cold end would allow a smaller accessory drive . It could drive an aft-fuselage boundary layer suction fan for
28372-660: Was derived from the General Electric J85/CJ610 turbojet 2,850 lbf (12,700 N) to power the larger Rockwell Sabreliner 75/80 model aircraft, as well as the Dassault Falcon 20 , with about a 50% increase in thrust to 4,200 lbf (19,000 N). The CF700 was the first small turbofan to be certified by the Federal Aviation Administration (FAA). There were at one time over 400 CF700 aircraft in operation around
28545-431: Was derived from the General Electric J85/CJ610 turbojet 2,850 lbf (12,700 N) to power the larger Rockwell Sabreliner 75/80 model aircraft, as well as the Dassault Falcon 20 , with about a 50% increase in thrust to 4,200 lbf (19,000 N). The CF700 was the first small turbofan to be certified by the Federal Aviation Administration (FAA). There were at one time over 400 CF700 aircraft in operation around
28718-644: Was equally shared between the ANTLE demonstrator and the CLEAN program for longer term technology applications. The ANTLE program targeted reductions of 12% in CO 2 emissions, 60% in NO x emissions, 20% in acquisition cost, 30% in life cycle cost and 50% in development cycle, while improving reliability by 60%. The test phase ended by summer 2005. The ANTLE engine was based on a Rolls-Royce Trent 500 . Rolls-Royce Deutschland
28891-452: Was only 8% when it was privatised in April 1987. In June, Rolls-Royce was studying whether to launch a RB211-700 , a 65,000 lbf (290 kN) development for the Airbus A330 twin-jet, the long-range Boeing 767 and the MD-11 , derived from the 747-400 's -524D4D, with growth potential to 70,000 lbf (310 kN). By June 1988, Rolls-Royce was investing over $ 540 million to develop
29064-481: Was responsible for the high pressure compressor, Rolls-Royce UK for the combustion chamber and the high pressure turbine, Italian Avio for the intermediate pressure turbine, and ITP for the Low Pressure Turbine (LPT) and the external casing for an investment of €20.5 million, a 20% stake in the program. Volvo Aero was responsible for the rear turbine structures. It has a new 5 stage HP compressor ,
29237-587: Was the Tupolev Tu-124 introduced in 1962. It used the Soloviev D-20 . 164 aircraft were produced between 1960 and 1965 for Aeroflot and other Eastern Bloc airlines, with some operating until the early 1990s. The first General Electric turbofan was the aft-fan CJ805-23 , based on the CJ805-3 turbojet. It was followed by the aft-fan General Electric CF700 engine, with a 2.0 bypass ratio. This
29410-407: Was the Tupolev Tu-124 introduced in 1962. It used the Soloviev D-20 . 164 aircraft were produced between 1960 and 1965 for Aeroflot and other Eastern Bloc airlines, with some operating until the early 1990s. The first General Electric turbofan was the aft-fan CJ805-23 , based on the CJ805-3 turbojet. It was followed by the aft-fan General Electric CF700 engine, with a 2.0 bypass ratio. This
29583-405: Was to reach 2.9 m (114 in) to increase the thrust. By June 1999, the 8104 served as a basis for the proposed 115,000 lbf (510 kN) Trent 8115 , with a scaled core by 2.5% geometrically and 5% aerodynamically and a fan enlarged from 2.8 to 3.0 m (110 to 118 in), while keeping the Trent 800 architecture: an eight-stage IP compressor and a six-stage HP compressor both driven by
29756-536: Was to supply its Trent 600 for the 767-400ERX and Boeing 747X , while the European Union was limiting the Engine Alliance offer on quadjets. The 68,000–72,000 lbf (300–320 kN) Trent 600 was scaled from the Trent 500 with a swept fan diameter raised to 2.59 m (102 in) for a higher bypass ratio and lower fuel burn. Boeing offered the longer-range 767-400ERX with a higher MTOW and
29929-577: Was traced to an incorrectly manufactured oil feed stub pipe. For further details refer to the article on the Trent 900 . Between 1 March 2000 and 28 February 2005, the EU funded the EEFAE project, aiming to design and test two programs to reduce CO 2 by 12–20% and nitrous oxides by up to 80% from 2007/2008, with an overall budget of €101.6 Million including €50.9 from the EU and coordinated by Rolls-Royce plc . It
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