FACTOID # 14: North Carolina has a larger Native American population than North Dakota, South Dakota and Montana combined.

 Home Encyclopedia Statistics States A-Z Flags Maps FAQ About

 WHAT'S NEW RELATED ARTICLES People who viewed "Turbofan" also viewed:

SEARCH ALL

Search encyclopedia, statistics and forums:

(* = Graphable)

Encyclopedia > Turbofan
Schematic diagram of high-bypass turbofan engine
CFM56-3 turbofan, lower half, side view.
Boeing 747 jet engine up close

A turbofan is a type of jet engine, similar to a turbojet. It essentially consists of a ducted fan with a smaller diameter turbojet engine mounted behind it that powers the fan. Part of the airstream from the ducted fan passes through the turbojet where it is burnt to power the fan, but the majority of the flow bypasses it, and very often produces most of the thrust.[1] Image File history File links Turbofan_operation. ... Image File history File links Turbofan_operation. ... A mounted CFM56 turbofan on display at MIT. . © 2005 joseph barillari File links The following pages link to this file: Turbofan CFM International CFM56 Categories: GFDL images ... A mounted CFM56 turbofan on display at MIT. . © 2005 joseph barillari File links The following pages link to this file: Turbofan CFM International CFM56 Categories: GFDL images ... CFM International CFM-56 series engines is a family of high-bypass turbofan engines made by CFM International and has a thrust range from 18,500 to 34,000 lbf (82 kN to 151 kN). ... Image:Jet engine intake. ... Image:Jet engine intake. ... A Pratt and Whitney turbofan engine for the F-15 Eagle is tested at Robins Air Force Base, Georgia, USA. The tunnel behind the engine muffles noise and allows exhaust to escape. ... Turbojets are the simplest and oldest kind of general purpose jet engines. ... A ducted fan is an arrangement of a propeller-driven aircraft where the propeller is mounted inside the fuselage, within a duct. ... For other uses, see Fan. ...

A few designs work slightly differently and have the fan blades as a radial extension of an aft mounted low pressure turbine unit.

All of the jet-engines used in currently manufactured commercial jet aircraft are turbofans. They are used commercially mainly because they are highly efficient, and relatively quiet in operation. Turbofans are also used in many military jet aircraft, and occasionally in other vehicles (e.g. jet-powered cars) where very high speeds and lower weight are needed. Ralph DePalma in his Packard 905 Special at Daytona Beach in 1919, courtesy Florida Photographic Collection For the album Land Speed Record by the band HÃ¼sker DÃ¼, see Land Speed Record (album). ...

In a turbojet, air enters an intake before being compressed to a higher pressure by a rotating (fan-like) compressor. The compressed air passes on to a combustor, where it is mixed with a fuel (e.g.' kerosene) and ignited. The hot combustion gases then enter a windmill-like turbine, where power is extracted to drive the compressor. Although the expansion process in the turbine reduces the gas pressure (and temperature), there is normally sufficient energy remaining to provide a high-velocity jet, as the exhaust gases expand to atmospheric pressure through the propelling nozzle. This process normally produces a net thrust opposite in direction to that of the jet. Unlike a reciprocating engine, a turbojet undertakes a continuous-flow process. Look up air in Wiktionary, the free dictionary. ... An intake is an air intake for an engine. ... Compressor has several meanings: A gas compressor is a mechanical device that takes in a gas and increases its pressure by squeezing a volume of it into a smaller volume. ... Kerosene or kerosine, also called paraffin oil or paraffin in British usage (not to be confused with the waxy solid also called paraffin wax or just paraffin) is a flammable hydrocarbon liquid. ... A Siemens steam turbine with the case opened. ... In thermodynamics, motive power is an agency, as water or steam, used to impart motion. ... Rocket Nozzle A nozzle is a mechanical device designed to control the characteristics of a fluid flow as it exits from an enclosed chamber into some medium. ...

The description given above is, strictly speaking, for a single spool (shaft) turbojet. After World War II, 2-spool (shaft) turbojets were developed to make it easier to throttle-back compression systems with a high design overall pressure ratio (i.e., combustor inlet pressure/intake delivery pressure). Adopting the 2-spool arrangement enables the compression system to be split in two, with a Low Pressure (LP) Compressor supercharging a High Pressure (HP) Compressor. Each compressor is mounted on a separate (co-axial) shaft, driven by its own turbine (i.e HP Turbine and LP Turbine). Otherwise a 2-spool turbojet is much like a single spool engine. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki TÅjÅ Casualties Military dead: 17,000,000 Civilian dead: 33,000...

Modern turbofans evolved from the 2-spool axial-flow turbojet engine, essentially by increasing the relative size of the Low Pressure (LP) Compressor to the point where some (if not most) of the air exiting the unit actually bypasses the core (or gas-generator) stream, passing through the main combustor. This bypass air either expands through a separate propelling nozzle, or is mixed with the hot gases leaving the Low Pressure (LP) Turbine, before expanding through a Mixed Stream Propelling Nozzle. Owing to a lower jet velocity, a modern civil turbofan is quieter than the equivalent turbojet. Turbofans also have a better thermal efficiency, which is explained later in the article. In a turbofan, the LP Compressor is often called a fan. Civil-aviation turbofans usually have a single fan stage, whereas most military-aviation turbofans have multi-stage fans. The axial flow compressor is an improvement on the centrifugal compressor previously used in turbine engines,though small and micro turbines use centrifugal compressors with relative advantages (in terms of pressure ratios achieveable per stage of compression). ... Turbojets are the simplest and oldest kind of general purpose jet engines. ... A Siemens steam turbine with the case opened. ...

Turboprop engines are gas-turbine engines that deliver almost all of their power to a shaft to drive a propeller. Turboprops remain popular on very small or slow aircraft, such as small commuter airliners, and military transports, such as the C-130 Hercules and P-3 Orion. A schematic diagram showing the operation of a turboprop engine. ... The Lockheed C-130 Hercules is a four-engine turboprop cargo aircraft and the main tactical airlifter for many military forces worldwide. ... The Lockheed P-3 Orion is a maritime patrol aircraft of numerous militaries around the world, used primarily for maritime patrol, reconnaissance, and anti-submarine warfare. ...

If the turboprop is better at moderate flight speeds and the turbojet is better at very high speeds, it might be imagined that at some speed range in the middle a mixture of the two is best. Such an engine is the turbofan (originally termed bypass turbojet by the inventors at Rolls Royce). Another name sometimes used is ducted fan, though that term is also used for propellers and fans used in vertical-flight applications. A schematic diagram showing the operation of a turboprop engine. ... This article is about the aircraft engine company. ... A ducted fan is an arrangement of a propeller-driven aircraft where the propeller is mounted inside the fuselage, within a duct. ...

The difference between a turbofan and a propeller, besides direct thrust, is that the intake duct of the former slows the air before it arrives at the fan face. As both propeller and fan blades must operate at subsonic inlet velocities to be efficient, ducted fans allow efficient operation at higher vehicle speeds. For other uses, see Propeller (disambiguation). ... For other uses, see Fan. ...

duct work on an A-7 Corsair — the decreasing diameter of the inlet duct slows incoming air.

Bypass ratio (bypassed airflow to combustor airflow) is a parameter often used for classifying turbofans, although specific thrust is a better parameter. In aeronautical engineering, and jet engine design in particular, bypass ratio is a common measurement that compares the amount of air deliberately blown past the engine to that moving through the core. ... A ring of can type combustors circles the mid section of this gas turbine. ...

The noise of any type of jet engine is strongly related to the velocity of the exhaust gases. High-bypass-ratio (i.e., low-specific-thrust) turbofans are relatively quiet compared to turbojets and low-bypass-ratio (i.e., high-specific-thrust) turbofans. A low-specific-thrust engine has a low jet velocity by definition, as the following approximate equation for net thrust implies:

$F_n = dot m cdot (V_{jfe} - V_a)$

where:

$dot m = ,$intake mass flow
$V_{jfe} =,$ fully expanded jet velocity (in the exhaust plume)
$V_a =,$ aircraft flight velocity

Rearranging the above equation, specific thrust is given by:

$frac{F_n}{dot m} = (V_{jfe} - V_a)$

So for zero flight velocity, specific thrust is directly proportional to jet velocity. Relatively speaking, low specific thrust engines are large in diameter to accommodate the high airflow required for a given thrust.

Jet aircraft are often considered loud, but a conventional piston engine or a turboprop engine delivering the same power would be much louder. A schematic diagram showing the operation of a turboprop engine. ...

## Early turbofans

Early turbojet engines were very fuel-inefficient, as their overall pressure ratio and turbine inlet temperature were severely limited by the technology available at the time. The very first running turbofan was the Daimler-Benz DB 670 (aka 109-007) which was operated on its testbed on April 1, 1943. The engine was abandoned later while the war went on and problems could not be solved. Improved materials, and the introduction of twin compressors such as in the Pratt & Whitney JT3C engine, increased the overall pressure ratio and thus the thermodynamic efficiency of engines, but led to a poor propulsive efficiency, as pure turbojets have a high specific thrust/high velocity exhaust. is the 91st day of the year (92nd in leap years) in the Gregorian calendar. ... Year 1943 (MCMXLIII) was a common year starting on Friday (the link will display full 1943 calendar) of the Gregorian calendar. ... // Background YJ57-P-3 at USAF Museum The Pratt & Whitney J57 was a development of the T45 turboprop engine intended for the XB-52. ... Thermodynamics (from the Greek Î¸ÎµÏÎ¼Î·, therme, meaning heat and Î´Ï…Î½Î±Î¼Î¹Ï‚, dynamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ...

The original low-bypass turbofan engines were designed to improve propulsive efficiency by reducing the exhaust velocity to a value closer to that of the aircraft. The Rolls-Royce Conway, the 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, but were not disimilar to their military equivalents. The Rolls-Royce Conway was the first by-pass engine to go into service in the world. ... A turbofan engine with afterburner. ... This section does not cite its references or sources. ... The Spey is a low-bypass turbofan engine from Rolls-Royce that has been in widespread service for over 30 years. ...

The unusual General Electric CF700 turbofan engine was developed as an aft-fan engine with a 2.0 bypass ratio. This was derived from the T-38 Talon and the Learjet General Electric J85/CJ610 turbojet (2,850 lbf or 12,650 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 (4,200 lbf or 18,700 N). The CF700 was the first small turbofan in the world to be certificated by the Federal Aviation Administration (FAA). There are now over 400 CF700 aircraft in operation around 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. The General Electric J85 was a small single-shaft turbojet engine, capable of generating up to 4000 lbf (18 kN) of dry thrust. ... The Northrop T-38 Talon is a widely used US-built supersonic jet trainer. ... Learjet is a manufacturer of business jets for civilian and military use. ... The General Electric J85 was a small single-shaft turbojet engine, capable of generating up to 4000 lbf (18 kN) of dry thrust. ... FAA may refer to: Federal Aviation Administration in the United States Fleet Air Arm in the UK Royal Navy Fuerza Aérea Argentina in Argentina This is a disambiguation page &#8212; a navigational aid which lists other pages that might otherwise share the same title. ... Project Apollo was a series of human spaceflight missions undertaken by the United States of America (NASA) using the Apollo spacecraft and Saturn launch vehicle, conducted during the years 1961 â€“ 1975. ... Description Role: Research Aircraft Crew: one, pilot Dimensions Length: 22. ...

## Low bypass turbofans

Schematic diagram illustrating a 2-spool, low-bypass turbofan engine with a mixed exhaust, showing the low-pressure (green) and high-pressure (purple) spools. The fan (and booster stages) are driven by the low-pressure turbine, whereas the high-pressure compressor is powered by the high-pressure turbine

A high specific thrust/low bypass ratio turbofan normally has a multi-stage fan, 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 give sufficient core power to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the (HP) turbine rotor inlet temperature. Image File history File links Turbofan_operation_(lbp). ... Image File history File links Turbofan_operation_(lbp). ... Core power is a parameter used in aeroengine performance engineering to enable a comparison of the power capabilities of jet engine (e. ...

Imagine a retrofit situation where a new low bypass ratio, mixed exhaust, turbofan is replacing an old turbojet, in a particular military application. Say the new engine is to have the same airflow and net thrust (i.e. same specific thrust) as the one it is replacing. A bypass flow can only be introduced if the turbine inlet temperature is allowed to increase, to compensate for a correspondingly smaller core flow. Improvements in turbine cooling/material technology would facilitate the use of a higher turbine inlet temperature, despite increases in cooling air temperature, resulting from a probable increase in overall pressure ratio.

Efficiently done, the resulting turbofan would probably operate at 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). Specific fuel consumption, often shortened to SFC, is an engineering term that is used to describe the fuel efficiency of an engine design w/ a mechanical output. ...

A few low-bypass ratio military turbofans (e.g. F404) have Variable Inlet Guide Vanes, with piano-style hinges, to direct air onto the first rotor stage. This improves the fan surge margin (see compressor map) in the mid-flow range. The swing wing F-111 achieved a very high range / payload capability by pioneering the use of this engine, and it was also the heart of the famous F-14 Tomcat air superiority fighter which used the same engines in a smaller, more agile airframe to achieve efficient cruise and Mach 2 speed. // Introduction Each compressor (or fan) in a gas turbine engine has an operating map. ... A U.S. Air Force F-111 The General Dynamics F-111 Aardvark (the nickname was unofficial for most of its lifespan, but it was officially named Aardvark at its retirement ceremony for the United States Air Force) is a long-range strategic bomber, reconnaissance, and tactical strike aircraft. ... The Grumman F-14 Tomcat is a supersonic, twin-engine, two-seat, variable geometry wing aircraft. ...

## Afterburning turbofans

Since the 1970s, most jet fighter engines have been low/medium bypass turbofans with a mixed exhaust, afterburner and variable area final nozzle – the first afterburning turbofan was the Pratt & Whitney TF30. An afterburner is a combustor located directly upstream of the nozzle. When lit, prodigious amounts of fuel are burnt in the afterburner, raising the temperature of exhaust gases by a significant amount, 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 flow when the afterburner is lit. Afterburning gives a significant thrust boost for take off, transonic acceleration and combat maneuvers, but is very fuel intensive. Consequently afterburning can only be selected for relatively short proportions of a mission. The 1970s decade refers to the years from 1970 to 1979, also called The Seventies. ... A fighter aircraft is a military aircraft designed primarily for attacking other aircraft, as opposed to a bomber, which is designed to attack ground targets, primarily by dropping bombs. ... For other uses of afterburner, see Afterburner (disambiguation). ... The TF-30, produced by Pratt & Whitney was the worlds first afterburning turbofan. ...

Unlike the main combustor, where the integrity of the downstream turbine blades must be preserved, an afterburner can operate at the ideal maximum (stoichiometric) temperature (i.e. about 2100K(3780R)). At 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. However, high specific thrust engines have 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 only has to fight fairly close to the airfield (i.e cross border skirmishes) The latter engine is better for an aircraft that has to fly some distance, or loiter for a long time, before going into combat. However, the pilot can only afford to stay in afterburning for a short period, before his/her fuel reserves become dangerously low.

Modern low-bypass military turbofans include the Pratt & Whitney F119, the Eurojet EJ200 and the General Electric F110 and F414, all of which feature a mixed exhaust, afterburner and variable area propelling nozzle. Non-afterburning engines include the Rolls-Royce/Turbomeca Adour (afterburning in the SEPECAT Jaguar) and the unmixed, vectored thrust, Rolls-Royce Pegasus. The Pratt & Whitney F119-PW-100 with integrated vectorable thrust nozzles. ... Eurojet EJ200s The Eurojet EJ200 is a military turbofan, used as the powerplant of the Eurofighter Typhoon. ... The F110 is an afterburning turbofan produced by General Electric. ... The General Electric F414 is an afterburning turbofan engines in the 22,000 lbf (85 kN) class (static thrust). ... RAF Jaguars Adour The Adour jet engine is a two-shaft turbofan developed by Rolls-Royce/Turbomeca, a joint subsidiary of Rolls-Royce (UK) and Turbomeca (France). ... The SEPECAT Jaguar is an Anglo-French ground attack aircraft still in service with several export customers, notably the Indian Air Force and the Royal Air Force of Oman. ... This article or section does not cite its references or sources. ... Rolls-Royce Pegasus The Rolls Royce Pegasus is a turbofan engine manufactured by Rolls-Royce plc. ...

## High-bypass turbofan engines

Schematic diagram illustrating a 2-spool, high-bypass turbofan engine with an unmixed exhaust. The low-pressure spool is coloured green and the high-pressure one purple. Again, the fan (and booster stages) are driven by the low-pressure turbine, but more stages are required. A mixed exhaust is often employed nowadays

The low specific thrust/high bypass ratio turbofans used in today's civil jetliners (and some military transport aircraft) evolved from the high specific thrust/low bypass ratio turbofans used in such aircraft back in the 1960s. Image File history File links Turbofan_operation. ... Image File history File links Turbofan_operation. ...

Low specific thrust is achieved by replacing the multi-stage fan with a single stage unit. Unlike some military engines, modern civil turbofans do not have any 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 the engine must generate sufficient Core Power to at least drive the fan at its design flow and pressure ratio. Through improvements in turbine cooling/material technology, a higher (HP) turbine rotor inlet temperature can be used, thus facilitating a smaller (and lighter) core and (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 the average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio (5:1, or more, is now common).

Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improved blade aerodynamics reduces the number of extra compressor stages required. With multiple compressors (i.e. LPC, IPC, HPC) dramatic increases in overall pressure ratio have become possible. Variable geometry (i.e. stators) enable high pressure ratio compressors to work surge-free at all throttle settings.

Cutaway diagram of the General Electric CF6-6 engine

The first high-bypass turbofan engine was the General Electric TF39, built 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. 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. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... CF6 turbofan at the KLM engine shop The General Electric TF39 and CF6 family of high-bypass turbofan engines are the most popular large aircraft turbines in the world, powering civil and military widebodies from a variety of manufacturers. ... The Lockheed SR-71 was remarkably advanced for its time and remains unsurpassed in many areas of performance. ... The Lockheed C-5 Galaxy is a military transport aircraft designed to provide strategic heavy airlift over intercontinental distances. ... CF6 turbofan at the KLM engine shop The General Electric TF39 and CF6 family of high-bypass turbofan engines are the most popular large aircraft turbines in the world, powering civil and military widebodies from a variety of manufacturers. ... This is a test The Pratt & Whitney JT9D engine was the first high-bypass-ratio engine to power a wide-bodied aircraft. ... RB211 powered Lockheed L-1011 The Rolls Royce RB.211 family is a family of high-bypass turbofan aircraft engines made by Rolls-Royce capable of generating 37,400 to 60,600 pounds-force (166 to 270 kilonewtons) thrust. ... CFM56-3 CFM56, front view CFM International CFM-56 series engines is a family of high-bypass turbofan engines made by CFM International and has a thrust range from 18,500 to 34,000 lbf (82 kN to 151 kN). ... The Pratt & Whitney PW4000 is a family of high-bypass turbofan aircraft engines with certified thrust ranging from 52,000 to 99,040 lbf (230 to 441 kN). ... Rolls-Royce Trent 900 on A380 prototype Rolls Royce Trent is a family of high bypass turbofan engines manufactured by Rolls-Royce. ... GE90 NASA GE90 airflow simulation A GE90-115 mounted on the #2 pylon of GEs Boeing 747 flight test aircraft at the Mojave Airport in 2002 General Electric GE90 is a family of high-bypass turbofan engines built by GE-Aviation for the Boeing 777, with thrust ranging from... Boeing 787 The General Electric GEnx (General Electric Next-generation) is an advanced turbofan under development by GE Aircraft Engines for the Boeing 787 and Airbus A350. ... The Engine Alliance GP7000 (known as the GP7200 for a brief time period) is a new turbofan jet engine that will incorporate advanced technologies of proven wide-body products, originally from the worlds No. ...

High-bypass turbofan engines are generally quieter than the earlier low bypass ratio civil engines. This is not so much due to the higher bypass ratio, as to the use of a low pressure ratio, single stage, fan, which significantly reduces specific thrust and, thereby, jet velocity. The combination of a higher overall pressure ratio and turbine inlet temperature improves thermal efficiency. This, together with a lower specific thrust (better propulsive efficiency), leads to a lower specific fuel consumption.

For reasons of fuel economy, and also of reduced noise, almost all of today's jet airliners are powered by high-bypass turbofans. Although modern military aircraft tend to use low bypass ratio turbofans, military transport aircraft (e.g. C-17 ) mainly use high bypass ratio turbofans (or turboprops) for fuel efficiency. For the Lockheed aircraft with this designation, see C-17 Super Vega. ... A Turboprop or turboshaft engine is a type of gas turbine. ...

Because of the implied low mean jet velocity, a high bypass ratio/low specific thrust turbofan has a high thrust lapse rate (with rising flight speed). Consequently the engine must be over-sized to give sufficient thrust during climb/cruise at high flight speeds (e.g. Mach 0.83). Because of the high thrust lapse rate, the static (i.e. Mach 0) thrust is consequently relatively high. This enables heavily laden, wide body, aircraft to accelerate quickly during take-off and consequently lift-off within a reasonable runway length.

The turbofans on twin engined airliners are further over-sized to cope with losing one engine during take-off, which reduces the thrust by 50%. Modern twin engined airliners normally climb very steeply immediately after take-off. If one engine is lost, the climb-out is much shallower, but sufficient to clear obstacles in the flightpath.

The Soviet Union's engine technology was less advanced than the West's and its first wide-body aircraft, the Ilyushin Il-86, was powered by low-bypass engines. The Yakovlev Yak-42, a medium-range, rear-engined aircraft seating up to 120 passengers was the first Soviet aircraft to use high-bypass engines. Il-86 of Pulkovo Aviation Enterprise at St. ... The three engined Yakovlev Yak-42 was designed as a replacement for the twin engined Tupolev Tu-134 jet. ...

## Turbofan configurations

Turbofan engines come in a variety of engine configurations. For a given engine cycle (i.e. same airflow, bypass ratio, fan pressure ratio, overall pressure ratio and HP turbine rotor inlet temperature), the choice of turbofan configuration has little impact upon the design point performance (e.g. net thrust, SFC), as long as overall component performance is maintained. Off-design performance and stability is, however, affected by engine configuration.

As the design overall pressure ratio of an engine cycle increases, it becomes more difficult to throttle the compression system, without encountering an instability known as compressor surge. This occurs when some of the compressor aerofoils stall (like the wings of an aircraft) causing a violent change in the direction of the airflow. However, compressor stall can be avoided, at throttled conditions, by progressively:

1) opening interstage/intercompressor blow-off valves (inefficient)

and/or

2) closing variable stators within the compressor

Most modern American civil turbofans employ a relatively high pressure ratio High Pressure (HP) Compressor with several rows of variable stators to control surge margin. However, on the three-spool RB211/Trent the HP Compressor has a modest pressure ratio and can be throttled-back surge-free, without employing HP Compressor variable geometry. Rolls-Royce RB211 engine The Rolls Royce RB.211 family is a family of high-bypass turbofan aircraft engines made by Rolls-Royce capable of generating 37,400 to 60,600 pound (166 to 270 kN) thrust. ... Trent is the name of several Places: Trento in Italy, famous for the Roman Catholic Council of Trent Trent, Texas, USA Trent, South Dakota, USA Trent, Dorset, UK Trent, Germany, a municipality on the island of RÃ¼gen, Germany Rivers: River Trent in the UK, or one of several other...

### Single shaft turbofan

Although far from common, the Single Shaft Turbofan is probably the simplest configuration, comprising a fan and high pressure compressor driven by a single turbine unit, all on the same shaft. The SNECMA M53, which powers Mirage fighter aircraft, is an example of a Single Shaft Turbofan. Despite the simplicity of the turbomachinery configuration, the M53 requires a variable area mixer to facilitate part-throttle operation. The M53 is an afterburning turbofan engine developed for the Dassault Mirage 2000 fighter by Snecma. ...

### Aft fan turbofan

One of the earliest turbofans was a derivative of the General Electric J79 turbojet, known as the CJ805, which featured an integrated aft fan/low pressure (LP) turbine unit located in the turbojet exhaust jetpipe. Hot gas from the turbojet turbine exhaust expanded through the LP turbine, the fan blades being a radial extension of the turbine blades. This Aft Fan configuration was later exploited in the General Electric GE-36 UDF (propfan) Demonstrator of the early 80's. One of the problems with the Aft Fan configuration is hot gas leakage from the LP turbine to the fan. General Electric J79 General Electric J79 The General Electric J79 is an axial-flow turbojet engine built for use in a variety of fighter aircraft and bomber aircraft. ... General Electric GE-36 UDF Unducted Fan engine on a McDonnell Douglas MD-81 testbed The General Electric GE-36 engine was an experimental aeroengine, a hybrid between a turbofan and a turboprop, known as an Unducted Fan (UDF) or Propfan. ...

### Basic two spool

Many turbofans have the Basic Two Spool configuration where both the fan and LP turbine (i.e. LP spool) are mounted on a second (LP) shaft, running concentrically with the HP spool (i.e. HP compressor driven by HP turbine). The Rolls-Royce BR710 is typical of this configuration. At the smaller thrust sizes, instead of all-axial blading, the HP compressor configuration may be axial-centrifugal (e.g. General Electric CFE738), double-centrifugal or even diagonal/centrifugal (e.g. Pratt & Whitney Canada PW600). The BR700 family of engines was developed by BMW and Rolls-Royce plc through the joint venture company BMW Rolls-Royce to power regional and corporate jets. ... The General Electric CFE738 is a small turbofan engine aimed at the business/commuter jet market, and is used on the Dassault Falcon 2000. ... The PW600 family of extremely small turbofan engines is being developed by Pratt & Whitney Canada for use in very light jets. ...

### Boosted two spool

Higher overall pressure ratios can be achieved by either raising the HP compressor pressure ratio or adding an Intermediate Pressure (IP) Compressor between the fan and HP compressor, to supercharge or boost the latter unit helping to raise the overall pressure ratio of the engine cycle to the very high levels employed today (i.e. greater than 40:1, typically). All of the large American turbofans (e.g. General Electric CF6, GE90 and GEnx plus Pratt & Whitney JT9D and PW4000) feature an IP compressor mounted on the LP shaft and driven, like the fan, by the LP turbine, the mechanical speed of which is dictated by the tip speed and diameter of the fan. The high bypass ratios (i.e. fan duct flow/core flow) used in modern civil turbofans tends to reduce the relative diameter of the attached IP compressor, causing its mean tip speed to decrease. Consequently more IPC stages are required to develop the necessary IPC pressure rise. Overall Pressure Ratio is an engine cycle term used in Gas Turbine Engineering and is defined as the ratio of the stagnation pressure at combustor entry, to that at compression entry. ... CF6 turbofan at the KLM engine shop The General Electric TF39 and CF6 family of high-bypass turbofan engines are the most popular large aircraft turbines in the world, powering civil and military widebodies from a variety of manufacturers. ... NASA GE90 airflow simulation General Electric GE90 is a family of high-bypass turbofan engines built by General Electric for the Boeing 777, with thrust ranging from 74,000 to 115,000 lbf (329 to 512 kN). ... Boeing 787 The General Electric GEnx (General Electric Next-generation) is an advanced turbofan under development by GE Aircraft Engines for the Boeing 787 and Airbus A350. ... This is a test The Pratt & Whitney JT9D engine was the first high-bypass-ratio engine to power a wide-bodied aircraft. ... A Pratt & Whitney 4098 thrust engine for advanced Boeing 777 models at Boeings Future of Flight museum The Pratt & Whitney PW4000 is a family of high-bypass turbofan aircraft engines with certified thrust ranging from 52,000 to 99,040 lbf (230 to 441 kN). ...

### Three spool

Rolls-Royce chose a Three Spool configuration for their large civil turbofans (i.e. the RB211 and Trent families), where the Intermediate Pressure IP compressor is mounted on a separate (IP) shaft, running concentrically with the LP and HP shafts, and is driven by a separate IP Turbine. Consequently, the IP compressor can rotate faster than the fan, increasing its mean tip speed, thereby reducing the number of IP stages required for a given IPC pressure rise. However, because the RB211/Trent designs have a higher IPC pressure rise than the American engines, the HPC pressure rise is less resulting in a shorter, lighter, more rigid engine. However, three spool engines are harder to both build and maintain. The greater rigidity means that there is less distortion of the engine casing under 'g' loads during flight, resulting in less blade tip rubbing and, therefore, a slower in-service deterioration of component performance and specific fuel consumption. Rolls-Royce RB211 engine The Rolls Royce RB.211 family is a family of high-bypass turbofan aircraft engines made by Rolls-Royce capable of generating 37,400 to 60,600 pound (166 to 270 kN) thrust. ... Rolls-Royce Trent 900 on A380 prototype Rolls Royce Trent is a family of high-bypass turbofan engines manufactured by Rolls-Royce. ...

The Turbo-Union RB199 military turbofan also has a three spool configuration, and the Russian military Kuznetsov NK-321 has also. RB199s of Tornado F3 The Turbo Union RB199 is an aircraft jet engine designed and built jointly by Rolls-Royce, MTU and FiatAvio (now Avio). ... The Kuznetsov NK-321 is a military specification afterburning 3-spool low bypass turbofan jet engine which powers the Tupolev Tu-160 supersonic bomber, and was fitted to the later model Tupolev Tu-144 supersonic transport. ...

### Geared fan

As bypass ratio increases, the mean radius ratio of the fan and LP turbine increases. Consequently, if the fan is to rotate at its optimum blade speed the LP turbine blading will run slow, so additional LPT stages will be required, to extract sufficient energy to drive the fan. Introducing a reduction gearbox, with a suitable gear ratio, between the LP shaft and the fan, enables both the fan and LP turbine to operate at their optimum speeds. Typical of this configuration are the long established Honeywell TFE731 and the recent Pratt & Whitney Advanced Technology Fan Integrator (ATFI) demonstrator engine (now the Geared Turbofan). Honeywell TFE731-60 on a NASA test stand. ... Pratt & Whitney is an American aircraft engine manufacturer whose products are widely used in both civil and military aircraft. ... The Pratt & Whitney GTF is a high-bypass geared turbofan engine designed for and currently selected as the exclusive engine for the proposed 70 to 90 seat Mitsubishi MRJ regional jet. ...

## Cycle improvements

Consider a mixed turbofan with a fixed bypass ratio and airflow. Increasing the overall pressure ratio of the compression system raises the combustor entry temperature. Therefore, at a fixed fuel flow there is an increase in (HP) turbine rotor inlet temperature. Although the higher temperature rise across the compression system implies a larger temperature drop over the turbine system, the mixed nozzle temperature is unaffected, because the same amount of heat is being added to the system. There is, however, a rise in nozzle pressure, because overall pressure ratio increases faster than the turbine expansion ratio, causing an increase in the hot mixer entry pressure. Consequently, net thrust increases, whilst specific fuel consumption (fuel flow/net thrust) decreases. A similar trend occurs with unmixed turbofans.

So turbofans can be made more fuel efficient by raising overall pressure ratio and turbine rotor inlet temperature in unison. However, better turbine materials and/or improved vane/blade cooling are required to cope with increases in both turbine rotor inlet temperature and compressor delivery temperature. Increasing the latter may require better compressor materials.

## Thrust growth

Thrust growth is obtained by increasing core power. There are two basic routes available: Core power is a parameter used in aeroengine performance engineering to enable a comparison of the power capabilities of jet engine (e. ...

a) hot route: increase HP turbine rotor inlet temperature

b) cold route: increase core mass flow

Both routes require an increase in the combustor fuel flow and, therefore, the heat energy added to the core stream.

The hot route may require changes in turbine blade/vane materials and/or better blade/vane cooling. The cold route can be obtained by one of the following:

1. adding T-stages to the LP/IP compression
2. adding a zero-stage to the HP compression
3. improving the compression process, without adding stages (e.g. higher fan hub pressure ratio)

all of which increase both overall pressure ratio and core airflow. T-stages are used to increase overall pressure ratio and, for a given core size, the core mass flow. ... Jet engines are often uprated by adding a zero-stage to the front of a compressor. ...

Alternatively, the core size can be increased, to raise core airflow, without changing overall pressure ratio. This route is expensive, since a new (upflowed) turbine system (and possibly a larger IP compressor) is also required. Core size is a parameter used in aeroengine performance engineering to enable a size comparison between jet engine (e. ...

Changes must also be made to the fan to absorb the extra core power. On a civil engine, jet noise considerations mean that any significant increase in Take-off thrust must be accompanied by a corresponding increase in fan mass flow (to maintain a T/O specific thrust of about 30lbf/lb/s), usually by increasing fan diameter. On military engines, the fan pressure ratio would probably be increased to improve specific thrust, jet noise not normally being an important factor.

## Technical Discussion

1. Specific Thrust (net thrust/intake airflow) is an important parameter for turbofans and jet engines in general. Imagine a fan (driven by an appropriately sized electric motor) operating within a pipe, which is connected to a propelling nozzle. Fairly obviously, the higher the Fan Pressure Ratio (fan discharge pressure/fan inlet pressure), the higher the jet velocity and the corresponding specific thrust. Now imagine we replace this set-up with an equivalent turbofan - same airflow and same fan pressure ratio. Obviously, the core of the turbofan must produce sufficient power to drive the fan via the Low Pressure (LP) Turbine. If we choose a low (HP) Turbine Inlet Temperature for the gas generator, the core airflow needs to be relatively high to compensate. The corresponding bypass ratio is therefore relatively low. If we raise the Turbine Inlet Temperature, the core airflow can be smaller, thus increasing bypass ratio. Raising turbine inlet temperature tends to increase thermal efficiency and, therefore, improve fuel efficiency.
2. Naturally, as altitude increases there is a decrease in air density and, therefore, the net thrust of an engine. There is also a flight speed effect, termed Thrust Lapse Rate. Consider the approximate equation for net thrust again:

$F_n = m cdot (V_{jfe} - V_a)$

With a high specific thrust (e.g. fighter) engine, the jet velocity is relatively high, so intuitively one can see that increases in flight velocity have less of an impact upon net thrust than a medium specific thrust (e.g. trainer) engine, where the jet velocity is lower. The impact of thrust lapse rate upon a low specific thrust (e.g. civil) engine is even more severe. At high flight speeds, high specific thrust engines can pick-up net thrust through the ram rise in the intake, but this effect tends to diminish at supersonic speeds because of shock wave losses.
3. Thrust growth on civil turbofans is usually obtained by increasing fan airflow, thus preventing the jet noise becoming too high. However, the larger fan airflow requires more power from the core. This can be achieved by raising the Overall Pressure Ratio (combustor inlet pressure/intake delivery pressure) to induce more airflow into the core and by increasing turbine inlet temperature. Together, these parameters tend to increase core thermal efficiency and improve fuel efficiency.
4. Some high bypass ratio civil turbofans use an extremely low area ratio (less than 1.01), convergent-divergent, nozzle on the bypass (or mixed exhaust) stream, to control the fan working line. The nozzle acts as if it has variable geometry. At low flight speeds the nozzle is unchoked (less than a Mach Number of unity), so the exhaust gas speeds up as it approaches the throat and then slows down slightly as it reaches the divergent section. Consequently, the nozzle exit area controls the fan match and, being larger than the throat, pulls the fan working line slightly away from surge. At higher flight speeds, the ram rise in the intake increases nozzle pressure ratio to the point where the throat becomes choked (M=1.0). Under these circumstances, the throat area dictates the fan match and, being smaller than the exit, pushes the fan working line slightly towards surge. This is not a problem, since fan surge margin is much better at high flight speeds.
5. The off-design behaviour of turbofans is illustrated under compressor map and turbine map.
6. Because modern civil turbofans operate at low specific thrust, they only require a single fan stage to develop the required fan pressure ratio. The desired overall pressure ratio for the engine cycle is usually achieved by multiple axial stages on the core compression. Rolls-Royce tend to split the core compression into two with an intermediate pressure (IP) supercharging the HP compressor, both units being driven by turbines with a single stage, mounted on separate shafts. Consequently, the HP compressor need only develop a modest pressure ratio (e.g.~4.5:1). US civil engines use much higher HP compressor pressure ratios (e.g. ~23:1 on the General Electric GE90) and tend to be driven by a two stage HP turbine. Even so, there are usually a few IP axial stages mounted on the LP shaft, behind the fan, to further supercharge the core compression system. Civil engines have multi-stage LP turbines, the number of stages being determined by the bypass ratio, the amount of IP compression on the LP shaft and the LP turbine blade speed.
7. Because military engines usually have to be able to fly very fast at Sea Level, the limit on HP compressor delivery temperature is reached at a fairly modest design overall pressure ratio, compared with that of a civil engine. Also the fan pressure ratio is relatively high, to achieve a medium to high specific thrust. Consequently, modern military turbofans usually only have 5 or 6 HP compressor stages and only require a single stage HP turbine. Low bypass ratio military turbofans usually have one LP turbine stage, but higher bypass ratio engines need two stages. In theory, by adding IP compressor stages, a modern military turbofan HP compressor could be used in a civil turbofan derivative, but the core would tend to be too small for high thrust applications.

// Introduction Each compressor (or fan) in a gas turbine engine has an operating map. ... IF NECESSARY, DOUBLE CLICK ON THUBNAIL IMAGES TO GET A CLEARER VIEW Introduction Each turbine in a gas turbine engine has an operating map. ... GE90 NASA GE90 airflow simulation A GE90-115 mounted on the #2 pylon of GEs Boeing 747 flight test aircraft at the Mojave Airport in 2002 General Electric GE90 is a family of high-bypass turbofan engines built by GE-Aviation for the Boeing 777, with thrust ranging from...

## Recent developments in blade technology

The turbine blades in a turbofan engine are subject to high heat and stress, and require special fabrication. New material construction methods and material science have allowed blades, which were originally polycrystalline (regular metal), to be made from lined up metallic crystals and more recently mono-crystalline (i.e. single crystal) blades, which can operate at higher temperatures with less distortion. A Siemens steam turbine with the case opened. ... Materials science includes those parts of chemistry and physics that deal with the properties of materials. ... ]]s are polycrystalline. ...

Nickel-based superalloys are used for HP turbine blades in almost all of the modern jet engines. The temperature capabilities of turbine blades have increased mainly through four approaches: the manufacturing (casting) process, cooling path design, thermal barrier coating (TBC), and alloy development. It has been suggested that this article or section be merged with Superalloy. ... Thermal barrier coatings are layered systems applied to metallic surfaces, such as gas turbine or aero-engine parts operating at elevated temperatures. ... An alloy is a homogeneous hybrid of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ...

Although turbine blade (and vane) materials have improved over the years, much of the increase in (HP) turbine inlet temperatures is due to improvements in blade/vane cooling technology. Relatively cool air is bled from the compression system, bypassing the combustion process, and enters the hollow blade or vane. After picking up heat from the blade/vane, the cooling air is dumped into the main gas stream. If the local gas temperatures are low enough, downstream blades/vanes are uncooled and solid.

Strictly speaking, cycle-wise the HP Turbine Rotor Inlet Temperature (after the temperature drop across the HPT stator) is more important than the (HP) turbine inlet temperature. Although some modern military and civil engines have peak RITs of the order of 3300 °R (2840 °F) or 1833 K (1560 °C), such temperatures are only experienced for a short time (during take-off) on civil engines.

## Turbofan engine manufacturers

The turbofan engine market is dominated by General Electric, Rolls-Royce plc and Pratt & Whitney, in order of market share. GE and SNECMA of France have a joint venture, CFM International which, as the 3rd largest manufacturer in terms of market share, fits between Rolls Royce and Pratt & Whitney. Rolls Royce and Pratt & Whitney also have a joint venture, International Aero Engines, specializing in engines for the Airbus A320 family, whilst finally, Pratt & Whitney and General Electric have a joint venture, Engine Alliance marketing a range of engines for aircraft such as the Airbus A380. General Electric Aircraft Engines (GEAE) is the top supplier of aircraft engines in the world and offers engines for the majority of commercial aircraft. ... This article is about the aircraft engine company. ... Pratt & Whitney is an American aircraft engine manufacturer whose products are widely used in both civil and military aircraft. ... Snecma was one of the worlds leading aerospace corporations which merged with SAGEM to form SAFRAN. Snecma is now a subsidiary of the SAFRAN Group and previous Snecma subsidiaries have been reorganised within the wider group. ... Categories: Stub | Aircraft engine manufacturers | General Electric subsidiaries ... An Airbus A320-232 with V2500 engines IAE International Aero Engines AG is a ZÃ¼rich-registered joint venture formed in 1983. ... The Airbus A320 family of short-to-medium range commercial passenger aircraft are manufactured by Airbus S.A.S.. Family members include the A318, A319, A320, and A321, as well as the ACJ business jet. ... The Engine Alliance, a 50/50 joint venture between General Electric and Pratt & Whitney, was formed in August 1996 to develop, manufacture, sell, and support a family of modern technology engines for new high-capacity, long-range aircraft. ... The Airbus A380 is a double-deck, four-engine airliner manufactured by the European corporation Airbus, an EADS subsidiary. ...

### General Electric

GE Aircraft Engines, part of the General Electric Conglomerate, currently has the largest share of the turbofan engine market. Some of their engine models include the CF6 (available on the Boeing 767, Boeing 747, Airbus A330 and more), GE90 (only the Boeing 777) and GEnx (developed for the Airbus A350 & Boeing 787 currently in development) engines. On the military side, GE engines power many U.S. military aircraft, including the F110, powering 80% of the US Air Force's F-16 Vipers and the F404 and F414 engines, which power the Navy's F/A-18 Hornet and Super Hornet. Rolls Royce and General Electric are jointly developing the F136 engine to power the Joint Strike Fighter. General Electric Aircraft Engines (GEAE) is the top supplier of aircraft engines in the world and offers engines for the majority of commercial aircraft. ... â€œGEâ€ redirects here. ... American Airlines Boeing 767-300 at Gatwick Airport, England. ... The Boeing 747, sometimes nicknamed the Jumbo Jet,[4][5] is long-haul, widebody commercial airliner manufactured by Boeing in the United States. ... The Airbus A330 is a large-capacity, wide-body, medium-to-long-range commercial passenger airliner. ... NASA GE90 airflow simulation General Electric GE90 is a family of high-bypass turbofan engines built by General Electric for the Boeing 777, with thrust ranging from 74,000 to 115,000 lbf (329 to 512 kN). ... The Boeing 777 is an American long-range wide-body twin-engine airliner built by Boeing Commercial Airplanes. ... The General Electric GEnx (General Electric Next-generation) is an advanced turbofan under development by GE-Aviation for the Boeing 787. ... â€œA350â€ redirects here. ... The Boeing 787 Dreamliner is a mid-sized, wide-body, twin engine jet airliner currently in production by Boeing Commercial Airplanes and scheduled to enter service in November 2008. ... The F110 is an afterburning turbofan produced by General Electric. ... The F-16 Fighting Falcon is an American multirole jet fighter aircraft developed by General Dynamics and Lockheed Martin for the United States Air Force. ... A turbofan engine with afterburner. ... Boeing X-45C UCAV, which will utilize the F404 turbofan The General Electric F404 and F414 are a family of afterburning turbofan engines in the 10,500-22,000 lbf (85 kN) class (static thrust). ... The McDonnell Douglas (now Boeing) F/A-18 Hornet is a modern all-weather carrier-capable strike fighter jet, designed to attack both ground and aerial targets. ... The Boeing F/A-18E/F Super Hornet is a carrier-based fighter/attack aircraft that entered service in 1999 with the United States Navy. ... F136 The F136 is an advanced fighter engine being developed by General Electric/Rolls-Royce Fighter Engine Team specifically for the Joint Strike Fighter. ...

### CFM International

CFM International is a joint venture between GE Aircraft Engines and SNECMA of France. Categories: Stub | Aircraft engine manufacturers | General Electric subsidiaries ... Snecma was one of the worlds leading aerospace corporations which merged with SAGEM to form SAFRAN. Snecma is now a subsidiary of the SAFRAN Group and previous Snecma subsidiaries have been reorganised within the wider group. ...

They have created the very successful CFM56 series, used on Boeing 737 and Airbus aircraft. CFM56-3 CFM56, front view CFM International CFM-56 series engines is a family of high-bypass turbofan engines made by CFM International and has a thrust range from 18,500 to 34,000 lbf (82 kN to 151 kN). ... The Boeing 737 is an American short to medium range, single aisle, narrow body jet airliner. ... This article is about the airliner manufacturer. ...

### Pratt & Whitney

Pratt & Whitney is third behind GE and Rolls-Royce in market share. The JT9D has the distinction of being chosen by Boeing to power the original Boeing 747 "Jumbo jet". The PW4000 series is the successor to the JT9D, and powers some Airbus A310, Airbus A300, Boeing 747, Boeing 767, Boeing 777, and MD-11 aircraft. The PW4000 is certified for 180-minute ETOPS when used in twinjets. The first family has a 94 inch fan diameter and is designed to power the Boeing 767, Boeing 747, MD-11, and the Airbus A300. The second family is the 100 inch (2.5 m) fan engine developed specifically for the Airbus A330 twinjet, and the third family has a diameter of 112 inch designed to power Boeing 777. The Pratt & Whitney F119 and its derivative, the F135, power the United States Air Force's F-22 Raptor and the international F-35 Lightning II, respectively. Rolls Royce are responsible for the lift fan which will provide the F-35B variants with a STOVL capability. The F100 engine was first used on the F-15 Eagle and F-16 Fighting Falcon. Newer Eagles and Falcons also come with GE F110 as an option, and the two are in competition. Pratt & Whitney is an American aircraft engine manufacturer whose products are widely used in both civil and military aircraft. ... This is a test The Pratt & Whitney JT9D engine was the first high-bypass-ratio engine to power a wide-bodied aircraft. ... The Boeing Company (NYSE: BA, TYO: 7661) is a major aerospace and defense corporation, originally founded by William Edward Boeing. ... The Boeing 747, sometimes nicknamed the Jumbo Jet,[4][5] is long-haul, widebody commercial airliner manufactured by Boeing in the United States. ... A Pratt & Whitney 4098 thrust engine for advanced Boeing 777 models at Boeings Future of Flight museum The Pratt & Whitney PW4000 is a family of high-bypass turbofan aircraft engines with certified thrust ranging from 52,000 to 99,040 lbf (230 to 441 kN). ... The Airbus A310 is a medium to long-range widebody airliner manufactured by Airbus S.A.S. It was Airbus second model to be introduced, and is a shortened derivative of the A300. ... The Airbus A300 is a short to medium range widebody aircraft. ... Varig MD-11 The McDonnell Douglas MD-11 is a Widebody Trijet powered by three engines. ... ETOPS (Extended Twin-engine OPerationS) is an acronym for an International Civil Aviation Organization (ICAO) rule permitting newer twin-engined commercial air transports to fly routes that, at some points, are further than a distance of 60 minutes flying time from an emergency or diversion airport. ... The F119-PW-100 is an afterburning turbofan engine developed for the Lockheed Martin F-22 Raptor advanced tactical fighter by Pratt & Whitney. ... The F135 afterburning turbofan is the primary powerplant for the advanced, single-engine tactical F-35 Lightning II, being developed by Lockheed Martin. ... F-22 redirects here. ... The F-35 Lightning II is a single-seat, single-engine, stealth-capable military strike fighter, a multi-role aircraft that can perform close air support, tactical bombing, and air-to-air combat. ... STOVL is an acronym for Short Take Off and Vertical Landing. ... F-100 or F100 may refer to: The F-100 Super Sabre, a fighter aircraft formerly in the service of the United States Air Force, and in small numbers, with a number of NATO countries inluding France, and Denmark. ... The McDonnell Douglas (now Boeing) F-15 Eagle is an all-weather tactical fighter designed to gain and maintain air superiority in aerial combat. ... The F-16 Fighting Falcon is an American multirole jet fighter aircraft developed by General Dynamics and Lockheed Martin for the United States Air Force. ...

## Extreme bypass jet engines

In the 1970s Rolls-Royce/SNECMA tested a M45SD-02 turbofan fitted with variable pitch fan blades to improve handling at ultra low fan pressure ratios and to provide thrust reverse down to zero aircraft speed. The engine was aimed at ultra quiet STOL aircraft operating from city centre airports. The M45SD-02 was a derivative of the Rolls-Royce/SNECMA M45H-01 turbofan, designed to demonstrate ultra-quiet engine technologies, needed for STOL aircraft operating from city centre airports. ... A Zenair CH701 STOL light aircraft Polish STOL light aircraft PZL-104M Wilga of Polish Border Guard at Radom Air Show in 2005. ...

In a bid for increased efficiency with speed, a development of the turbofan and turboprop known as a propfan engine, was created that had an unducted fan. The fan blades are situated outside of the duct, so that it appears like a turboprop with wide scimitar-like blades. Both General Electric and Pratt & Whitney/Allison demonstrated propfan engines in the 1980s. Excessive cabin noise and relatively cheap jet fuel prevented the engines being put into service. General Electric GE-36 UDF Unducted Fan engine on a McDonnell Douglas MD-81 testbed A propfan is a modified turbofan engine, with the fan placed outside of the engine nacelle on the same axis as the compressor blades. ...

## Terminology

Afterburner
extra combustor immediately upstream of final nozzle (also called reheat)
constant * (delta temperature)/[(blade speed) * (blade speed) * (number of stages)]
Bypass
airstream that completely bypasses the core compression system, combustor and turbine system
Bypass ratio
bypass airflow /core compression inlet airflow
Core
turbomachinery handling the airstream that passes through the combustor.
Core power
residual shaft power from turbine expansion to ambient pressure after deducting core compression power
Core thermal efficiency
core power/power equivalent of fuel flow
Dry
afterburner (if fitted) not lit
EPR
Engine Pressure Ratio
Fan
turbofan LP compressor
Fan pressure ratio
fan outlet total pressure/intake delivery total pressure
Gas generator
engine core
HPC
high pressure compressor
HP compressor
high pressure compressor
HPT
high pressure turbine
HP turbine
high pressure turbine
Intake ram drag
penalty associated with jet engines picking up air from the atmosphere (conventional rocket motors do not have this drag term, because the oxidiser travels with the vehicle)
IEPR
Integrated Engine Pressure Ratio
IPC
intermediate pressure compressor
IP compressor
intermediate pressure compressor
IPT
intermediate pressure turbine
IP turbine
intermediate pressure turbine
LPC
low pressure compressor
LP compressor
low pressure compressor
LPT
low pressure turbine
LP turbine
low pressure turbine
Net thrust
nozzle total gross thrust - intake ram drag (excluding nacelle drag, etc, this is the basic thrust acting on the airframe)
Overall pressure ratio
combustor inlet total pressure/intake delivery total pressure
Overall thermal efficiency
thermal efficiency * propulsive efficiency
Propulsive efficiency
propulsive power/rate of production of propulsive kinetic energy (maximum propulsive efficiency occurs when jet velocity equals flight velocity, which implies zero net thrust!)
SFC
Specific fuel consumption
Specific fuel consumption
total fuel flow/net thrust (proportional to flight velocity/overall thermal efficiency)
Static pressure
normal meaning of pressure. Excludes any kinetic energy effects
Specific thrust
net thrust/intake airflow
Thermal efficiency
rate of production of propulsive kinetic energy/fuel power
Total fuel flow
combustor (plus any afterburner) fuel flow rate (e.g. lb/s or g/s)
Total pressure
static pressure plus kinetic energy term
Turbine rotor inlet temperature
gas absolute mean temperature at principal (e.g. HP) turbine rotor entry

For other uses of afterburner, see Afterburner (disambiguation). ... In aeronautical engineering, and jet engine design in particular, bypass ratio is a common measurement that compares the amount of air deliberately blown past the engine to that moving through the core. ... Core power is a parameter used in aeroengine performance engineering to enable a comparison of the power capabilities of jet engine (e. ... The Integrated Engine Pressure Ratio (IEPR) is the ratio of the pressure at the core engine exhaust and fan discharge pressure compared to the intake pressure to the gas turbine engine. ... In aircraft design, overall propulsive efficiency is the efficiency, in percent, with which the energy contained in fuel is converted into propulsive energy. ... Specific fuel consumption, often shortened to SFC, is an engineering term that is used to describe the fuel efficiency of an engine design w/ a mechanical output. ... Specific fuel consumption, often shortened to SFC, is an engineering term that is used to describe the fuel efficiency of an engine design w/ a mechanical output. ... Specific Thrust is a term used in Gas Turbine Engineering to show the relative bulk of a jet engine (e. ... The thermal efficiency () is a dimensionless performance measure of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example. ...

## Other meanings

The Unicode standard includes a turbofan character, #274B, in the dingbats range. Its official name is "HEAVY EIGHT TEARDROP-SPOKED PROPELLER. ASTERISK. = turbofan"[3]. In appropriately-configured browsers, it should appear in the box on the right. The Unicode Standard, Version 5. ... This article is about the typesetters ornament. ...

## Notes and references

1. ^ [1]
2. ^ a b Actually a Bristol engine design taken on by Rolls-Royce when they took over Bristol
3. ^ Unicode.org

• Wikibooks: Jet propulsion
Wikimedia Commons has media related to:
Turbofan engines

Results from FactBites:

 Turbofan (238 words) The Turbofan spray head is a hydraulically driven air assisted atomiser which combines advanced Controlled Droplet Application technology with a powerful directed airblast for effective application in a wide variety of crops and cropping situations. Turbofan heads can be fitted to a variety of existing sprayer types, including axial fan airblast units and both tractor-mounted and self-propelled boom sprayers. The Turbofan head is available with a choice of easily interchangeable atomisers (either gauze mesh or stacked disc) in order to give optimal atomisation over a wide range of flow rates - between 0.25 and 8.0 litres per minute.
 ch10-3 (6601 words) The bypass ratio of a turbofan engine is defined as the ratio of the mass of air that passes through the fan, but not the gas generator, to that which does pass through the gas generator. For example, the efficiency of the turbofan with a bypass ratio of 1.4 increases from 8 percent to 27.5 percent as the Mach number is increased from 0.2 to 0.9. Comparison of the point with the curve for the high bypass ratio turbofan engine indicates that the efficiency of the fan engine is as high as that of the Wright engine at a Mach number twice that at which the Constellation cruised.
More results at FactBites »

Share your thoughts, questions and commentary here