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Jet engines and other gas turbine engines are often uprated by adding a zero-stage, sometimes written '0' stage, [1] to the front of a compressor. [2] At a given core size, adding a stage to the front of the compressor not only increases the cycle overall pressure ratio, but increases the core mass flow. A further uprating may be done by adding another stage in front of the previously-added zero stage, in which case the new one may be known as a zero-zero stage.
Zero-staging is also combined with other modifications to provide increased thrust or lower turbine temperature. [3] It may be required for an existing aircraft weight increase, or for a new application, as shown by the following examples.
A comparison with other ways of uprating an existing engine without drastically redesigning the engine shows for a particular case, e.g. the Rolls-Royce/SNECMA M45H, the thrust could have been increased by 25% with a zero-staged l-p compressor or 10% with either an improved HP turbine or with water injection. [4]
A 15-stage Rolls-Royce Avon powered the Lightning F.1. A zero-stage, together with a new turbine, was added (total 16 stages) for the Caravelle III. A zero-zero stage was added (total 17 stages) for the Caravelle VI. [3]
The 7-stage Snecma Atar D was used in the Mystere II. A zero-stage was added (total 8 stages) for the E and G used in the Vautour and Super Mystere B.2. A zero-zero stage (total 9 stages), together with a 2-stage turbine was added for the Atar 8 and 9 used in the Mirage III. [5]
The Rolls-Royce/Snecma Olympus 593 started with a 6-stage LP compressor. As the Concorde increased in weight during the design phase the take-off thrust requirement increased. The engine was given a zero-stage to the compressor, a redesigned turbine and partial reheat. [2]
Examples of zero-staging for land-based gas turbines are the aeroderivative GE LM2500+ [6] and the heavy-duty GE MS5002B. [7] An alternative to zero-staging used by some OEMs is supercharging the compressor with a fan driven by an electric motor. [8]
Zero-staging is demonstrated by the following relationship:
where:
core mass flow =
core size =
core total head pressure ratio =
inverse of core total head temperature ratio = i.e. ()
core entry total pressure =
core entry total temperature =
So basically, increasing increases .
On the other hand, adding a stage to the rear of the compressor increases overall pressure ratio, and decreases core size, but has no effect on core flow. This option also needs a Turbine with a significantly smaller flow capacity to drive the compressor.
Zero-staging a compressor also implies an increase in shaft speed:
where:
HP Shaft Speed =
HP Compressor "Non-Dimensional" Speed (based on Exit Total Temperature) =
HP Compressor Exit Total Temperature =
So if the "Non-Dimensional" Speed of the original compressor is to be maintained, increasing increases . This implies an increase in both the blade and disc stress levels.
If the original shaft speed is maintained, then the increase in pressure ratio and mass flow from adding the zero stage will be severely reduced.
Although the above equations are written with zero-staging an HP compressor in mind, the same approach would apply to an LP or IP compressor.
A jet engine is a type of reaction engine, discharging a fast-moving jet of heated gas that generates thrust by jet propulsion. While this broad definition may include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an internal combustion air-breathing jet engine such as a turbojet, turbofan, ramjet, pulse jet, or scramjet. In general, jet engines are internal combustion engines.
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.
The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and a turbine. The compressed air from the compressor is heated by burning fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s.
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 . 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 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.
A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.
The Rolls-Royce Pegasus is a British turbofan engine originally designed by Bristol Siddeley. It was manufactured by Rolls-Royce plc. The engine is not only able to power a jet aircraft forward, but also to direct thrust downwards via swivelling nozzles. Lightly loaded aircraft equipped with this engine can manoeuvre like a helicopter. In particular, they can perform vertical takeoffs and landings. In US service, the engine is designated F402.
The Eurojet EJ200 is a military low-bypass turbofan used as the powerplant of the Eurofighter Typhoon. The engine is largely based on the Rolls-Royce XG-40 technology demonstrator, which was developed in the 1980s. The EJ200 is built by the EuroJet Turbo GmbH consortium. The EJ200 is also used in the Bloodhound LSR supersonic land speed record attempting car.
The Rolls-Royce Olympus was the world's second two-spool axial-flow turbojet aircraft engine design, first run in May 1950 and preceded only by the Pratt & Whitney J57, first-run in January 1950. It is best known as the powerplant of the Avro Vulcan and later models in the Concorde SST.
The Europrop International TP400-D6 is an 11,000 shp (8,200 kW) powerplant, developed and produced by Europrop International for the Airbus A400M Atlas military transport aircraft. The TP400 is the most powerful turboprop in service using a single propeller; only the Kuznetsov NK-12 from Russia and Progress D-27 from Ukraine, using contra-rotating propellers, is larger.
The Rolls-Royce BR700 is a family of turbofan engines for regional jets and corporate jets. It is manufactured in Dahlewitz, Germany, by Rolls-Royce Deutschland: this was initially a joint venture of BMW and Rolls-Royce plc established in 1990 to develop this engine. The BR710 first ran in 1995. The United States military designation for the BR725 variant is F130.
The Snecma M88 is a French afterburning turbofan engine developed by Snecma for the Dassault Rafale fighter.
The SNECMA M53 is an afterburning turbofan engine developed for the Dassault Mirage 2000 fighter by Snecma. The engine is in service with different air forces, including the latest Mirage 2000-5 and 2000-9 multirole fighters.
A compressor map is a chart which shows the performance of a turbomachinery compressor. This type of compressor is used in gas turbine engines, for supercharging reciprocating engines and for industrial processes, where it is known as a dynamic compressor. A map is created from compressor rig test results or predicted by a special computer program. Alternatively the map of a similar compressor can be suitably scaled. This article is an overview of compressor maps and their different applications and also has detailed explanations of maps for a fan and intermediate and high-pressure compressors from a three-shaft aero-engine as specific examples.
A jet engine performs by converting fuel into thrust. How well it performs is an indication of what proportion of its fuel goes to waste. It transfers heat from burning fuel to air passing through the engine. In doing so it produces thrust work when propelling a vehicle but a lot of the fuel is wasted and only appears as heat. Propulsion engineers aim to minimize the degradation of fuel energy into unusable thermal energy. Increased emphasis on performance improvements for commercial airliners came in the 1970s from the rising cost of fuel.
The Rolls-Royce/SNECMA M45H is an Anglo-French medium bypass ratio turbofan produced specifically for the twin-engined VFW-Fokker 614 aircraft in the early 1970s.
A variable cycle engine (VCE), also referred to as adaptive cycle engine (ACE), is an aircraft jet engine that is designed to operate efficiently under mixed flight conditions, such as subsonic, transonic and supersonic.
The Lycoming ALF 502/LF 507 is a geared turbofan engine produced by Lycoming Engines, AlliedSignal, and then Honeywell Aerospace. The U.S. military designation for the ALF 502 is YF102.
The Rolls-Royce/Snecma Olympus 593 was an Anglo-French turbojet with reheat, which powered the supersonic airliner Concorde. It was initially a joint project between Bristol Siddeley Engines Limited (BSEL) and Snecma, derived from the Bristol Siddeley Olympus 22R engine. Rolls-Royce Limited acquired BSEL in 1966 during development of the engine, making BSEL the Bristol Engine Division of Rolls-Royce.
The General Electric Passport is a turbofan developed by GE Aerospace for large business jets. It was selected in 2010 to power the Bombardier Global 7500 and 8000, first run on June 24, 2013, and first flown in 2015. It was certified in April 2016 and powered the Global 7500 first flight on November 4, 2016, before its 2018 introduction. It produces 14,000 to 20,000 lbf of thrust, a range previously covered by the General Electric CF34. A smaller scaled CFM LEAP, it is a twin-spool axial engine with a 5.6:1 bypass ratio and a 45:1 overall pressure ratio and is noted for its large one-piece 52 in (130 cm) fan 18-blade titanium blisk.
The Rolls-Royce Olympus turbojet engine was developed extensively throughout its production run, the many variants can be described as belonging to four main groups.
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