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113-412: The Rolls-Royce RB3011 (previously designated RB2011 ) is a prototype propfan engine from Rolls-Royce plc . The design is also known as an "open rotor" engine. The RB3011 is designed for the 180–300 passenger aircraft (e.g. Boeing 737 or Airbus A320 ). The RB3011 was renamed from RB2011, because Rolls-Royce employees kept confusing the 2011 with the expected service entry date. Rolls-Royce bought

226-433: A gas turbine to drive an unshrouded (open) contra-rotating propeller like a turboprop, but the design of the propeller itself is more tightly coupled to the turbine design, and the two are certified as a single unit. El-Sayed differentiates between turboprops and propfans according to 11 different criteria, including number of blades, blade shape, tip speed, bypass ratio , Mach number , and cruise altitude . About

339-525: A swept wing . Since the inside of the propeller is moving slower in the rotational direction than the outside, the blade is progressively more swept back toward the outside, leading to a curved shape similar to a scimitar – a practice that was first used as far back as 1909, in the Chauvière two-bladed wood propeller used on the Blériot XI . (At the blade root, the blade is actually swept forward into

452-415: A turbojet , driving the fan of a turbofan , rotor or accessory of a turboshaft , and gear reduction and propeller of a turboprop . If the engine has a power turbine added to drive an industrial generator or a helicopter rotor, the exit pressure will be as close to the entry pressure as possible with only enough energy left to overcome the pressure losses in the exhaust ducting and expel the exhaust. For

565-409: A turboprop engine there will be a particular balance between propeller power and jet thrust which gives the most economical operation. In a turbojet engine only enough pressure and energy is extracted from the flow to drive the compressor and other components. The remaining high-pressure gases are accelerated through a nozzle to provide a jet to propel an aircraft. The smaller the engine, the higher

678-420: A turbopump to permit the use of lightweight, low-pressure tanks, reducing the empty weight of the rocket. A turboprop engine is a turbine engine that drives an aircraft propeller using a reduction gear to translate high turbine section operating speed (often in the 10s of thousands) into low thousands necessary for efficient propeller operation. The benefit of using the turboprop engine is to take advantage of

791-452: A turboshaft design. They supply: Industrial gas turbines differ from aeronautical designs in that the frames, bearings, and blading are of heavier construction. They are also much more closely integrated with the devices they power—often an electric generator —and the secondary-energy equipment that is used to recover residual energy (largely heat). They range in size from portable mobile plants to large, complex systems weighing more than

904-413: A buildup on the outside of the blades. Nickel-based superalloys boast improved strength and creep resistance due to their composition and resultant microstructure . The gamma (γ) FCC nickel is alloyed with aluminum and titanium in order to precipitate a uniform dispersion of the coherent Ni 3 (Al,Ti) gamma-prime (γ') phases. The finely dispersed γ' precipitates impede dislocation motion and introduce

1017-689: A decade after German aerospace engineers began exploring the idea of using swept wings to reduce drag on transonic speed aircraft, Hamilton Standard in the 1940s attempted to apply a similar concept to aircraft propellers. It created highly swept propeller blades with supersonic tip speeds, so that engines with exposed propellers could power aircraft to speeds and cruising altitudes only attained by new turbojet and turbofan engines. Early tests of these blades revealed then-unresolvable blade flutter and blade stress problems, and high noise levels were considered another obstacle. The popularity of turbojets and turbofans curtailed research in propellers, but by

1130-517: A few dozen hours per year—depending on the electricity demand and the generating capacity of the region. In areas with a shortage of base-load and load following power plant capacity or with low fuel costs, a gas turbine powerplant may regularly operate most hours of the day. A large single-cycle gas turbine typically produces 100 to 400 megawatts of electric power and has 35–40% thermodynamic efficiency . Industrial gas turbines that are used solely for mechanical drive or used in collaboration with

1243-575: A few years later with the emergence of contra-rotating propfans. In 1986, British engine maker Rolls-Royce used the term open rotor as a synonym for the original meaning of a propfan. This action was to delineate the propfan engine type from a number of ducted engine proposals at the time that had propfan in their names. By the 2000s, open rotor (OR) became a preferred term for propfan technology in research and news reports, with contra-rotating open rotor (CROR) also occasionally being used to distinguish between single-rotation propfans. As of 2015,

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1356-531: A fuel savings of 30 percent over an equivalent turboprop . They also revealed plans for propfans with power ratings of 14,100 and 30,200 hp (10,500 and 22,500 kW). Like the Progress D-236, the more powerful Progress D-27 propfan engine is a contra-rotating propfan with eight front blades and six back blades, but the D-27 has advanced composite blades with a reduced thickness-to-chord ratio and

1469-579: A gas turbine engine is its power to weight ratio. Since significant useful work can be generated by a relatively lightweight engine, gas turbines are perfectly suited for aircraft propulsion. Thrust bearings and journal bearings are a critical part of a design. They are hydrodynamic oil bearings or oil-cooled rolling-element bearings . Foil bearings are used in some small machines such as micro turbines and also have strong potential for use in small gas turbines/ auxiliary power units A major challenge facing turbine design, especially turbine blades ,

1582-490: A hundred tonnes housed in purpose-built buildings. When the gas turbine is used solely for shaft power, its thermal efficiency is about 30%. However, it may be cheaper to buy electricity than to generate it. Therefore, many engines are used in CHP (Combined Heat and Power) configurations that can be small enough to be integrated into portable container configurations. Gas turbines can be particularly efficient when waste heat from

1695-418: A lesser extent, on cars, buses, and motorcycles. A key advantage of jets and turboprops for airplane propulsion – their superior performance at high altitude compared to piston engines, particularly naturally aspirated ones – is irrelevant in most automobile applications. Their power-to-weight advantage, though less critical than for aircraft, is still important. Gas turbines offer a high-powered engine in

1808-493: A more pronounced curvature at the leading edge . An engine that was launched in 1985, the D-27 delivers 14,000 hp (10,440 kW) of power with 27,000 lbf (119 kN) of thrust at takeoff. Two rear-mounted D-27 propfans propelled the Ukrainian Antonov An-180 , which was scheduled for a 1995 first flight and a 1997 entry into service. In January 1994, Antonov rolled out the first prototype of

1921-405: A pair of 12,000–13,000 shaft hp (8,900–9,700 kW) propfans or with two 25,000 lbf thrust (110 kN) UDF propfans. General resources Gas turbine A gas turbine or gas turbine engine is a type of continuous flow internal combustion engine . The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in

2034-584: A proof-of-concept aircraft by modifying its company-owned MD-80 , which is suited for propfans due to its aft fuselage-mounted engines (like its DC-9 ancestor), in preparation for the possible propfan-powered MD-91 and MD-92 derivatives and a possible MD-94X clean-sheet aircraft. They replaced the left side JT8D turbofan engine with the GE36. Test flights began in May 1987, which proved the design's airworthiness, aerodynamic characteristics, and noise signature. Following

2147-432: A propfan with a propeller diameter of 236 in (600 cm; 19.7 ft; 6.0 m) would theoretically produce almost 60,000 lbf (270 kN) of thrust. These sizes achieve the desired high bypass ratios of over 30, but they are approximately twice the diameter of turbofan engines of equivalent capability. For this reason, airframers usually design the empennage with a T-tail configuration in order to avoid

2260-532: A recovery steam generator differ from power generating sets in that they are often smaller and feature a dual shaft design as opposed to a single shaft. The power range varies from 1 megawatt up to 50 megawatts. These engines are connected directly or via a gearbox to either a pump or compressor assembly. The majority of installations are used within the oil and gas industries. Mechanical drive applications increase efficiency by around 2%. Oil and gas platforms require these engines to drive compressors to inject gas into

2373-461: A second, independent turbine (known as a power turbine ) that can be connected to a fan, propeller, or electrical generator. The purpose of the gas turbine determines the design so that the most desirable split of energy between the thrust and the shaft work is achieved. The fourth step of the Brayton cycle (cooling of the working fluid) is omitted, as gas turbines are open systems that do not reuse

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2486-462: A sudden onset, and it led to the concept of a sound barrier when first encountered in the 1940s. This effect can happen whenever the propeller is spun fast enough that the blade tips approach the speed of sound. The most effective way to address this problem is by adding blades to the propeller, allowing it to deliver more power at a lower rotational speed. This is why many World War II fighter designs started with two or three-blade propellers but by

2599-569: A threshold stress, increasing the stress required for the onset of creep. Furthermore, γ' is an ordered L1 2 phase that makes it harder for dislocations to shear past it. Further Refractory elements such as rhenium and ruthenium can be added in solid solution to improve creep strength. The addition of these elements reduces the diffusion of the gamma prime phase, thus preserving the fatigue resistance, strength, and creep resistance. The development of single crystal superalloys has led to significant improvements in creep resistance as well. Due to

2712-550: A very small and light package. However, they are not as responsive and efficient as small piston engines over the wide range of RPMs and powers needed in vehicle applications. In series hybrid vehicles, as the driving electric motors are mechanically detached from the electricity generating engine, the responsiveness, poor performance at low speed and low efficiency at low output problems are much less important. The turbine can be run at optimum speed for its power output, and batteries and ultracapacitors can supply power as needed, with

2825-425: Is also required to drive a helicopter rotor or land-vehicle transmission ( turboshaft ), marine propeller or electrical generator (power turbine). Greater thrust-to-weight ratio for flight is achieved with the addition of an afterburner . The basic operation of the gas turbine is a Brayton cycle with air as the working fluid : atmospheric air flows through the compressor that brings it to higher pressure; energy

2938-463: Is distinguished from the Otto cycle , in that all the processes (compression, ignition combustion, exhaust), occur at the same time, continuously. In a real gas turbine, mechanical energy is changed irreversibly (due to internal friction and turbulence) into pressure and thermal energy when the gas is compressed (in either a centrifugal or axial compressor ). Heat is added in the combustion chamber and

3051-402: Is examining various architectures to tackle the 150 seat-aircraft market. Within 15-50 group – named for specific fuel consumption reductions of 15–50% compared with current generation engines – there are various options based on technology availability and maturity. The open rotor design is known to have increased noise compared to normal turbofan engines, where noise is contained by

3164-677: Is reducing the creep that is induced by the high temperatures and stresses that are experienced during operation. Higher operating temperatures are continuously sought in order to increase efficiency, but come at the cost of higher creep rates. Several methods have therefore been employed in an attempt to achieve optimal performance while limiting creep, with the most successful ones being high performance coatings and single crystal superalloys . These technologies work by limiting deformation that occurs by mechanisms that can be broadly classified as dislocation glide, dislocation climb and diffusional flow. Protective coatings provide thermal insulation of

3277-642: Is slated for certification as an "integrated engine" instead of a traditional "propeller/engine" because of its airframe integration complexity. CFM planned for an aerodynamically three-dimensional rotor with 12 woven carbon-fiber composite blades. Aided by a smaller engine core, the CFM RISE engine would have a bypass ratio of 75. Turboprops have an optimum speed below about 450 mph (390 kn; 720 km/h), because propellers lose efficiency at high speed, due to an effect known as wave drag that occurs just below supersonic speeds. This powerful drag has

3390-412: Is then added by spraying fuel into the air and igniting it so that the combustion generates a high-temperature flow; this high-temperature pressurized gas enters a turbine, producing a shaft work output in the process, used to drive the compressor; the unused energy comes out in the exhaust gases that can be repurposed for external work, such as directly producing thrust in a turbojet engine , or rotating

3503-419: Is then ducted into the combustor section which can be of a annular , can , or can-annular design. In the combustor section, roughly 70% of the air from the compressor is ducted around the combustor itself for cooling purposes. The remaining roughly 30% the air is mixed with fuel and ignited by the already burning air-fuel mixture , which then expands producing power across the turbine . This expansion of

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3616-475: Is used, it is possible to use exhaust air from the turbine as the primary combustion air. This effectively reduces global heat losses, although heat losses associated with the combustion exhaust remain inevitable. Closed-cycle gas turbines based on helium or supercritical carbon dioxide also hold promise for use with future high temperature solar and nuclear power generation. Gas turbines are often used on ships , locomotives , helicopters , tanks , and to

3729-968: The Airbus A400M transport, Lockheed AC-130 and the 60-year-old Tupolev Tu-95 strategic bomber. While military turboprop engines can vary, in the civilian market there are two primary engines to be found: the Pratt & Whitney Canada PT6 , a free-turbine turboshaft engine, and the Honeywell TPE331 , a fixed turbine engine (formerly designated as the Garrett AiResearch 331). Aeroderivative gas turbines are generally based on existing aircraft gas turbine engines and are smaller and lighter than industrial gas turbines. Aeroderivatives are used in electrical power generation due to their ability to be shut down and handle load changes more quickly than industrial machines. They are also used in

3842-473: The Allison Engine Company in 1995, and has studied the Pratt & Whitney/Allison 578-DX propfan engine built in the 1980s. The engine has two contra-rotating rotors (fans) on the outside of the engine nacelle , either at the front of the assembly ("tractor") or at the rear ("pusher"). Both pusher and tractor open rotor designs form part of Rolls-Royce's long-term "15-50" vision, which

3955-566: The An-70 military transport aircraft, powered by four Progress D-27s attached to wings mounted to the top of the fuselage. The Russian Air Force placed an order for 164 aircraft in 2003 , later canceled. As of 2013, the An-70 was still thought to have a promising future as a freighter. Since the propeller component of the Progress D-27 is made by Russia's SPE Aerosila , however, the An-70

4068-602: The Armstrong Siddeley Double Mamba (ASMD) engines (both connected to a lone set of coaxial contra-rotating propellers) on the British Fairey Gannet anti-submarine aircraft. Both setups had four largely unswept blades in the front propeller and the back propeller. When the 1973 oil crisis caused petroleum price spikes in the early 1970s, interest in propfans soared, and NASA-funded research began to accelerate. The propfan concept

4181-528: The BMW 801 . This, however, also translated into poor efficiency and reliability. More advanced gas turbines (such as those found in modern jet engines or combined cycle power plants) may have 2 or 3 shafts (spools), hundreds of compressor and turbine blades, movable stator blades, and extensive external tubing for fuel, oil and air systems; they use temperature resistant alloys, and are made with tight specifications requiring precision manufacture. All this often makes

4294-493: The European Aviation Safety Agency (EASA) defined an open rotor concretely (but broadly) as "a turbine engine fan stage that is not enclosed within a casing"; in contrast, it had only a working definition of an open rotor engine (the more commonly used term for propfan in the 21st century), calling it "a turbine engine featuring contra-rotating fan stages not enclosed within a casing." The engine uses

4407-645: The GE36 UDF was meant to replace the CFM56 high-bypass turbofan that it produced with equal partner Snecma in their CFM International joint venture. In the 1980s the engine was initially uncompetitive against the International Aero Engines rival offering, the IAE V2500 . In December 1986, the chairman of Snecma declared that the in-development CFM56-5S2 would be the last turbofan created for

4520-731: The XT701 turboshaft developed for the Boeing Vertol XCH-62 heavy lift helicopter ). The engine used an eight-bladed, 9-foot diameter (2.7-metre; 110-inch; 270-centimetre), single-rotation Hamilton Standard SR-7 propfan. The test engine, which was named the Allison 501-M78, had a thrust rating of 9,000 lbf (40 kN). It was first operated in flight on March 28, 1987. The extensive test program, which cost about $ 56 million, racked up 73 flights and over 133 hours of flight time before finishing on March 25, 1988. In 1989, however,

4633-413: The specific volume of the gas increases, accompanied by a slight loss in pressure. During expansion through the stator and rotor passages in the turbine, irreversible energy transformation once again occurs. Fresh air is taken in, in place of the heat rejection. Air is taken in by a compressor, called a gas generator , with either an axial or centrifugal design, or a combination of the two. This air

Rolls-Royce RB3011 - Misplaced Pages Continue

4746-402: The testbed aircraft returned to the air from April 3 through April 14 to measure ground noise levels during flight. The engine was removed after that, and the aircraft was converted to a space shuttle training aircraft later that year. The GE36 Unducted Fan (UDF), from American engine maker General Electric (GE) with 35-percent participation from French partner Snecma (now Safran ),

4859-477: The #3 engine station of a Boeing 727-100 on August 20, 1986. The GE36 UDF for the 7J7 was planned to have a thrust of 25,000 pounds-force (110 kN), but GE claimed that in general its UDF concept could cover a thrust range of 9,000 to 75,000 lbf (40 to 334 kN), so a UDF engine could possibly match or surpass the thrust of the CF6 , GE's family of widebody engines at that time. McDonnell Douglas developed

4972-442: The 1960s, interest increased when studies showed that an exposed propeller driven by a gas turbine could power an airliner flying at a speed of Mach 0.7–0.8 and at an altitude of 35,000 feet (11,000 metres). The term propfan was created during this period. One of the earliest engines that resembled the propfan concept was the 4,710 pounds-force (21.0 kilonewtons) Metrovick F.5 , which featured twin contra-rotating fans—14 blades in

5085-594: The 1980s although it developed an open rotor design that was thought to be a finalist for the Irkut MS-21 narrowbody aircraft. The Rolls-Royce RB3011 engine would have a diameter of about 170 in (430 cm; 14 ft; 4.3 m) and require a 16,000 shaft hp (12,000 kW) gearbox . The European Commission launched an Open Rotor demonstration in 2008 led by Safran within the Clean Sky program funded with €65 million over eight years. A demonstrator

5198-457: The 1991 Paris Air Show , as a demonstration for the planned Yak-46 aircraft with twin propfan engines, which in its base 150-seat version would have a range of 1,900 nmi (2,200 mi; 3,500 km) and cruise at a speed of 460 kn (530 mph; 850 km/h; 780 ft/s; 240 m/s) (Mach 0.75). The Soviets claimed the D-236 had a true aerodynamic efficiency of 28 percent and

5311-500: The British budget airline easyJet introduced its ecoJet concept, a 150–250 seat aircraft with V-mounted open rotor engines joined to the rear fuselage and shielded by a U-tail. It unsuccessfully initiated discussions with Airbus, Boeing, and Rolls-Royce to produce the aircraft. A twin-engine aircraft carrying 100–150 passengers would require propfan diameters of 120–168 inches (300–430 cm; 10.0–14.0 ft; 3.0–4.3 m), and

5424-584: The CFM56 family, and that " There is no point in spending more money on turbofans. UDF is the future." The V2500 ran into technical problems in 1987, however, and the CFM56 gained major sales momentum. General Electric lost interest in having the GE36 cannibalize the CFM56, which went five years before it received its first order in 1979, and while "the UDF could be made reliable by earlier standards, turbofans were getting much, much better than that." General Electric added

5537-542: The Propfan Test Assessment (PTA) program, Lockheed-Georgia proposed modifying a Gulfstream II to act as in-flight testbed for the propfan concept, while McDonnell Douglas proposed modifying a DC-9 for the same purpose. NASA chose the Lockheed proposal. The Gulfstream II had a nacelle added to the left wing, containing a 6,000 horsepower (4,500 kilowatts) Allison 570 turboprop engine (derived from

5650-408: The UDF propfan type, which are rated by the amount of thrust they put out. The rule of thumb is that at sea level with a static engine, 1 shaft horsepower (750 watts) is roughly equivalent of 2 pounds-force (8.9 N) thrust, but at cruise altitude, that changes to about 1 pound-force (4.4 N) thrust. That means two 25,000 lbf thrust (110 kN) engines can theoretically be replaced with

5763-697: The UDF's blade technology directly into the GE90 , the most powerful jet engine ever produced, for the Boeing 777 . At the beginning of the 1990s, the Soviet Union / Russia performed flight tests on the Progress D-236 , a geared contra-rotating propfan engine based on the core of the Progress D-36 turbofan, with eight blades on the front propeller and six blades on the back propeller. One testbed

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5876-722: The United States Federal Aviation Administration (FAA) Stage 4 regulations, which correspond to International Civil Aviation Organization (ICAO) Chapter 4 standards. A 2012 trade study projected that propfan noise would be 10–13 decibels quieter than allowed by Stage 4 regulations. Stage 5 noise limits reduce the limits by only seven effective perceived noise decibels ( EPNdB ), within the propfan noise envelope. The study also projected that open rotors would be nine percent more fuel-efficient but remain 10–12 decibels louder than turbofans. Snecma claimed that its propfan engines would have about

5989-456: The active species (typically vacancies) within the alloy and reducing dislocation and vacancy creep. It has been found that a coating of 1–200 μm can decrease blade temperatures by up to 200 °C (392 °F). Bond coats are directly applied onto the surface of the substrate using pack carburization and serve the dual purpose of providing improved adherence for the TBC and oxidation resistance for

6102-510: The addition of a ducted fan are called turbofans or (rarely) fan-jets. These engines produce nearly 80% of their thrust by the ducted fan, which can be seen from the front of the engine. They come in two types, low-bypass turbofan and high bypass , the difference being the amount of air moved by the fan, called "bypass air". These engines offer the benefit of more thrust without extra fuel consumption. Gas turbines are also used in many liquid-fuel rockets , where gas turbines are used to power

6215-710: The aircraft's planned (at the time) certification in the first quarter of 2015. The engine has been tested at the Aircraft Research Association in Bedford , Bedfordshire . Wind-tunnel testing has taken place at DNW in Marknesse in the Netherlands. It was hoped to reduce the fuel consumption of an aircraft, compared to those with normal turbofan engines, by up to 30%. This was the main reason for choosing this design of engine. Certification

6328-471: The amount of thrust per unit of blade surface area. A concept similar to wing loading , blade loading can be reduced by lowering the thrust requirement or by increasing the amount, width, and/or length of the blades. For contra-rotating propfans, which can be louder than turboprops or single-rotating propfans, noise can also be lowered by: Engine makers expect propfan implementations to meet community (as opposed to cabin) noise regulations without sacrificing

6441-401: The blade and offer oxidation and corrosion resistance. Thermal barrier coatings (TBCs) are often stabilized zirconium dioxide -based ceramics and oxidation/corrosion resistant coatings (bond coats) typically consist of aluminides or MCrAlY (where M is typically Fe and/or Cr) alloys. Using TBCs limits the temperature exposure of the superalloy substrate, thereby decreasing the diffusivity of

6554-494: The blades of the Hamilton Standard test propfan had a thickness-to-chord ratio that tapered from less than 20% at the spinner junction to 2% at the tips, and 4% at mid-span. Propfan blades had approximately half the thickness-to-chord ratio of the best conventional propeller blades of the era, thinned to razor-like sharpness at their edges, and weighed as little as 20 pounds (9.1 kg). (The GE36 UDF engine that

6667-428: The blades thereby reducing compressibility losses and designed to operate with a turbine engine and using a single stage reduction gear resulting in high performance". In 1982, the weekly aviation magazine Flight International defined the propfan as a propeller with 8–10 highly swept blades that cruised at a speed of 390–480 knots (450–550 miles per hour; 720–890 kilometres per hour), although its definition evolved

6780-420: The closely related form of the turbocharger . The turbocharger is basically a compact and simple free shaft radial gas turbine which is driven by the piston engine's exhaust gas . The centripetal turbine wheel drives a centrifugal compressor wheel through a common rotating shaft. This wheel supercharges the engine air intake to a degree that can be controlled by means of a wastegate or by dynamically modifying

6893-473: The compressor and the turbine with a compressed air store. In a conventional turbine, up to half the generated power is used driving the compressor. In a compressed air energy storage configuration, power is used to drive the compressor, and the compressed air is released to operate the turbine when required. Turboshaft engines are used to drive compressors in gas pumping stations and natural gas liquefaction plants. They are also used in aviation to power all but

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7006-513: The compressor/shaft/turbine rotor assembly, with other moving parts in the fuel system. This, in turn, can translate into price. For instance, costing 10,000  ℛℳ for materials, the Jumo 004 proved cheaper than the Junkers 213 piston engine, which was 35,000  ℛℳ , and needed only 375 hours of lower-skill labor to complete (including manufacture, assembly, and shipping), compared to 1,400 for

7119-444: The construction of a simple gas turbine more complicated than a piston engine. Moreover, to reach optimum performance in modern gas turbine power plants the gas needs to be prepared to exact fuel specifications. Fuel gas conditioning systems treat the natural gas to reach the exact fuel specification prior to entering the turbine in terms of pressure, temperature, gas composition, and the related Wobbe index . The primary advantage of

7232-458: The core of the Snecma M88 military fighter engine, uses up to 12,200 horsepower (9 megawatts), provides a thrust of about 22,000 lbf (100 kN), and would cruise at a speed of Mach 0.75. Safran's future open rotor engine, however, would have a maximum diameter of almost 14.8 ft (4.50 m; 177 in; 450 cm). In 2007, the Progress D-27 was successfully modified to meet

7345-537: The direction of flow: Additional components have to be added to the gas generator to suit its application. Common to all is an air inlet but with different configurations to suit the requirements of marine use, land use or flight at speeds varying from stationary to supersonic. A propelling nozzle is added to produce thrust for flight. An extra turbine is added to drive a propeller ( turboprop ) or ducted fan ( turbofan ) to reduce fuel consumption (by increasing propulsive efficiency) at subsonic flight speeds. An extra turbine

7458-425: The early 2020s. In March 2018, GE Power achieved a 63.08% gross efficiency for its 7HA turbine. Aeroderivative gas turbines can also be used in combined cycles, leading to a higher efficiency, but it will not be as high as a specifically designed industrial gas turbine. They can also be run in a cogeneration configuration: the exhaust is used for space or water heating, or drives an absorption chiller for cooling

7571-600: The efficiency advantage. Some think that propfans can potentially cause less of a community impact than turbofans, given their lower rotational speeds. Geared propfans should have an advantage over ungeared propfans for the same reason. In 2007, the Progress D-27 was modified to meet the United States Federal Aviation Administration (FAA) Stage 4 regulations, which correspond to International Civil Aviation Organization (ICAO) Chapter 4 standards and were adopted in 2006. A 2012 trade study projected that noise from existing open rotor technology would be 10–13 decibels quieter than

7684-401: The end of the war were using up to five blades; as the engines were upgraded, new propellers were needed to more efficiently convert that power. Adding blades makes the propeller harder to balance and maintain, and the additional blades cause minor performance penalties due to drag and efficiency issues. But even with these sorts of measures, eventually the forward speed of the plane combined with

7797-435: The engine cycled on and off to run it only at high efficiency. The emergence of the continuously variable transmission may also alleviate the responsiveness problem. Turbines have historically been more expensive to produce than piston engines, though this is partly because piston engines have been mass-produced in huge quantities for decades, while small gas turbine engines are rarities; however, turbines are mass-produced in

7910-464: The engine duct. The forward rotor is larger in diameter than the rear rotor, to avoid problems with eddies from the forward rotor tips. The rotors are powered by the engine shaft via an epicyclic gearbox . The rotors produce a large amount of heat. In late 2008, the RB3011 was considered a contender for the powerplant of the Irkut MS-21 . Rolls-Royce felt it could develop and certify the engine before

8023-533: The entire engine from raw materials, including the fabrication of a centrifugal compressor wheel from plywood, epoxy and wrapped carbon fibre strands. Several small companies now manufacture small turbines and parts for the amateur. Most turbojet-powered model aircraft are now using these commercial and semi-commercial microturbines, rather than a Schreckling-like home-build. Small gas turbines are used as auxiliary power units (APUs) to supply auxiliary power to larger, mobile, machines such as an aircraft , and are

8136-407: The exhaust gases, or from ducted fans connected to the gas turbines. Jet engines that produce thrust from the direct impulse of exhaust gases are often called turbojets . While still in service with many militaries and civilian operators, turbojets have mostly been phased out in favor of the turbofan engine due to the turbojet's low fuel efficiency, and high noise. Those that generate thrust with

8249-525: The fore (front) fan and 12 blades in the aft (back) fan—at the rear of the engine and was first run in 1946. The blades, however, were mostly unswept. Other contra-rotating propeller engines that featured on common aircraft included the four powerful Kuznetsov NK-12 engines (each powering its own set of coaxial contra-rotating propellers) on the Soviet Union's Tupolev Tu-95 high-speed military bomber and Antonov An-22 military transport aircraft , and

8362-550: The hobby of engine collecting. In its most extreme form, amateurs have even rebuilt engines beyond professional repair and then used them to compete for the land speed record. The simplest form of self-constructed gas turbine employs an automotive turbocharger as the core component. A combustion chamber is fabricated and plumbed between the compressor and turbine sections. More sophisticated turbojets are also built, where their thrust and light weight are sufficient to power large model aircraft. The Schreckling design constructs

8475-420: The hot section and resin-transfer-molded composite fan blades. In addition to the rotor, the design includes a nonrotating set of variable-pitch stator blades that act as flow recovery vanes. The design increases the fan-pressure ratio and reduces rotor loading, increasing airspeed. The fan stage is to be powered by a high-speed booster compressor and a high-speed, low-pressure-shaft-driven front gearbox. The engine

8588-415: The initial designs needed to be based on the in-motion shape. With the help of computers, the blade designers would then work backward to find the optimal unloaded shape for manufacturing purposes. Hamilton Standard, the only large American manufacturer of aircraft propellers, developed the propfan concept in the early 1970s. Hamilton Standard tested numerous variations in conjunction with NASA . Under

8701-564: The initial tests, a first-class cabin was installed inside the aft fuselage and airline executives were offered the opportunity to experience the UDF-powered aircraft first-hand. The test and marketing flights of the GE-outfitted demonstrator aircraft concluded in 1988, exhibiting a 30% reduction in fuel consumption over turbo-fan powered MD-80, full Stage 3 noise compliance, and low levels of interior noise/vibration. The GE36 would have

8814-435: The inlet air and increase the power output, technology known as turbine inlet air cooling . Another significant advantage is their ability to be turned on and off within minutes, supplying power during peak, or unscheduled, demand. Since single cycle (gas turbine only) power plants are less efficient than combined cycle plants, they are usually used as peaking power plants , which operate anywhere from several hours per day to

8927-617: The lack of grain boundaries, single crystals eliminate Coble creep and consequently deform by fewer modes – decreasing the creep rate. Although single crystals have lower creep at high temperatures, they have significantly lower yield stresses at room temperature where strength is determined by the Hall-Petch relationship. Care needs to be taken in order to optimize the design parameters to limit high temperature creep while not decreasing low temperature yield strength. Airbreathing jet engines are gas turbines optimized to produce thrust from

9040-550: The marine industry to reduce weight. Common types include the General Electric LM2500 , General Electric LM6000 , and aeroderivative versions of the Pratt & Whitney PW4000 , Pratt & Whitney FT4 and Rolls-Royce RB211 . Increasing numbers of gas turbines are being used or even constructed by amateurs. In its most straightforward form, these are commercial turbines acquired through military surplus or scrapyard sales, then operated for display as part of

9153-793: The maximum noise level allowed by the Stage 4 regulations; the newer Stage 5 noise limits (which replaced the Stage 4 regulations for larger aircraft in 2018 and mirrored the ICAO Chapter 14 noise standard established in 2014) are more restrictive than the Stage 4 requirement by only seven effective perceived noise decibels ( EPNdB ), so current propfan technology shouldn't be hindered by the Stage 5 standards. The study also projected that at existing technology levels, open rotors would be nine percent more fuel-efficient but remain 10–12 decibels louder than turbofans. Snecma , however, maintains that open-rotor tests show that its propfan engines would have about

9266-429: The maximum tip speed for the propeller blades of a conventional turbofan. That maximum blade tip speed would be kept constant despite wider or narrower propeller diameter (resulting in an RPM reduction or increase, respectively). Drag can also be reduced by making the blades thinner, which increases the speed that the blades can attain before the air ahead of them becomes compressible and causes shock waves. For example,

9379-400: The mixture then leaves the combustor section and has its velocity increased across the turbine section to strike the turbine blades, spinning the disc they are attached to, thus creating useful power. Of the power produced, 60-70% is solely used to power the gas generator. The remaining power is used to power what the engine is being used for, typically an aviation application, being thrust in

9492-467: The pioneer of modern Micro-Jets, Kurt Schreckling , produced one of the world's first Micro-Turbines, the FD3/67. This engine can produce up to 22 newtons of thrust, and can be built by most mechanically minded people with basic engineering tools, such as a metal lathe . Evolved from piston engine turbochargers , aircraft APUs or small jet engines , microturbines are 25 to 500 kilowatt turbines

9605-470: The propeller problems became fixable. Advances were made in structural materials, such as titanium metal and graphite and glass fiber composites infused with resin . These materials replaced aluminum and steel metals in blade construction, which allowed the blades to be made thinner and stronger. Computer-aided design was also useful in refining blade characteristics. Since the blades bend and deflect with higher power loading and centrifugal force ,

9718-531: The propfan concept for jetliners beyond the Boeing 787 and Airbus A350 XWB. For instance, Airbus patented aircraft designs with twin rear-mounted contra-rotating propfans. Rolls-Royce had the rear (pusher) configured RB.509-11 and front (tractor) configured RB.509-14 geared propfan designs, which produced 15,000–25,000 lbf thrust (6,800–11,300 kgf; 67–111 kN) using the gas generator from its XG-40 engine with 13,000 hp (9,700 kW) of shaft power. It became lukewarm on propfan technology in

9831-474: The purpose of using pulverized coal or finely ground biomass (such as sawdust) as a fuel. In the indirect system, a heat exchanger is used and only clean air with no combustion products travels through the power turbine. The thermal efficiency is lower in the indirect type of external combustion; however, the turbine blades are not subjected to combustion products and much lower quality (and therefore cheaper) fuels are able to be used. When external combustion

9944-670: The rotation rate of the shaft must be to attain the required blade tip speed. Blade-tip speed determines the maximum pressure ratios that can be obtained by the turbine and the compressor. This, in turn, limits the maximum power and efficiency that can be obtained by the engine. In order for tip speed to remain constant, if the diameter of a rotor is reduced by half, the rotational speed must double. For example, large jet engines operate around 10,000–25,000 rpm, while micro turbines spin as fast as 500,000 rpm. Mechanically, gas turbines can be considerably less complex than Reciprocating engines . Simple turbines might have one main moving part,

10057-547: The rotational direction, to counter the twisting that is generated by the backward swept blade tips.) The Hamilton Standard test propfan was swept progressively to a 39-degree maximum at the blade tips, allowing the propfan to produce thrust even though the blades had a helical tip speed of about Mach 1.15. The blades of the GE36 UDF and the 578-DX have a maximum tip speed in rotation of about 750–800 ft/s (230–240 m/s; 510–550 mph; 820–880 km/h), or about half

10170-445: The rotational speed of the propeller blade tips (together known as the helical tip speed) will again result in wave drag problems. For most aircraft, this will occur at speeds over about 450 mph (390 kn; 720 km/h). A method of decreasing wave drag was discovered by German researchers in 1935—sweeping the wing backwards. Today, almost all aircraft designed to fly much above 450 mph (390 kn; 720 km/h) use

10283-626: The same 25,000 lbf (110 kN) thrust on the MD-92X, but the same engine would be derated to 22,000 lbf (98 kN) thrust for the smaller MD-91X. The MD-80 was also successfully flight tested in April 1989 with the 578-DX propfan, which was a prototype from the Allison Engine Company (at that time a division of General Motors ) that was also derived from the Allison XT701 and built with Hamilton Standard propellers. The engine program

10396-483: The same air. Gas turbines are used to power aircraft, trains, ships, electrical generators, pumps, gas compressors, and tanks . In an ideal gas turbine, gases undergo four thermodynamic processes: an isentropic compression, an isobaric (constant pressure) combustion, an isentropic expansion and isobaric heat rejection. Together, these make up the Brayton cycle , also known as the "constant pressure cycle" . It

10509-460: The same noise levels as its CFM LEAP turbofan engine, which entered service in 2016. Further reductions can be achieved by redesigning the aircraft structure to shield noise from the ground. For example, another study estimated that if propfan engines were used to power a hybrid wing body aircraft instead of a conventional tube-and-wing aircraft, noise levels could be reduced by as much as 38 EPNdB compared to ICAO Chapter 4 requirements. In 2007,

10622-409: The same noise levels as its CFM LEAP turbofan engine. In 2021, CFM International announced its Revolutionary Innovation for Sustainable Engines (RISE) development program to produce a single-stage, gear-driven propfan paired with active stators in a puller/tractor, configuration with flight tests to begin by 2025. The rotor was expected to be 12–13 ft (3.7–4.0 m) in diameter. The engine

10735-545: The size of a refrigerator . Microturbines have around 15% efficiencies without a recuperator , 20 to 30% with one and they can reach 85% combined thermal-electrical efficiency in cogeneration . Most gas turbines are internal combustion engines but it is also possible to manufacture an external combustion gas turbine which is, effectively, a turbine version of a hot air engine . Those systems are usually indicated as EFGT (Externally Fired Gas Turbine) or IFGT (Indirectly Fired Gas Turbine). External combustion has been used for

10848-503: The smallest modern helicopters, and function as an auxiliary power unit in large commercial aircraft. A primary shaft carries the compressor and its turbine which, together with a combustor, is called a Gas Generator . A separately spinning power-turbine is usually used to drive the rotor on helicopters. Allowing the gas generator and power turbine/rotor to spin at their own speeds allows more flexibility in their design. Also known as miniature gas turbines or micro-jets. With this in mind

10961-511: The substrate. The Al from the bond coats forms Al 2 O 3 on the TBC-bond coat interface which provides the oxidation resistance, but also results in the formation of an undesirable interdiffusion (ID) zone between itself and the substrate. The oxidation resistance outweighs the drawbacks associated with the ID zone as it increases the lifetime of the blade and limits the efficiency losses caused by

11074-595: The turbine engines high power-to-weight ratio to drive a propeller, thus allowing a more powerful, but also smaller engine to be used. Turboprop engines are used on a wide range of business aircraft such as the Pilatus PC-12 , commuter aircraft such as the Beechcraft 1900 , and small cargo aircraft such as the Cessna 208 Caravan or De Havilland Canada Dash 8 , and large aircraft (typically military) such as

11187-463: The turbine housing's geometry (as in a variable geometry turbocharger ). It mainly serves as a power recovery device which converts a great deal of otherwise wasted thermal and kinetic energy into engine boost. Turbo-compound engines (actually employed on some semi-trailer trucks ) are fitted with blow down turbines which are similar in design and appearance to a turbocharger except for the turbine shaft being mechanically or hydraulically connected to

11300-480: The turbine is recovered by a heat recovery steam generator (HRSG) to power a conventional steam turbine in a combined cycle configuration. The 605 MW General Electric 9HA achieved a 62.22% efficiency rate with temperatures as high as 1,540 °C (2,800 °F). For 2018, GE offers its 826 MW HA at over 64% efficiency in combined cycle due to advances in additive manufacturing and combustion breakthroughs, up from 63.7% in 2017 orders and on track to achieve 65% by

11413-473: The turbulent propwash adversely influencing the elevators and causing vibration issues therein. The propfans may be attached to the upper part of the rear fuselage . For the Rolls-Royce RB3011 propfan prototype, a pylon of about 8.3 ft (2.54 m; 100 in; 254 cm) long would be required to connect the center of each engine to the side of the fuselage. If the propfans are mounted to

11526-498: The wells to force oil up via another bore, or to compress the gas for transportation. They are also often used to provide power for the platform. These platforms do not need to use the engine in collaboration with a CHP system due to getting the gas at an extremely reduced cost (often free from burn off gas). The same companies use pump sets to drive the fluids to land and across pipelines in various intervals. One modern development seeks to improve efficiency in another way, by separating

11639-468: The wings, the wings would be attached to the aircraft in a high wing configuration , which allows for ground clearance without requiring excessively long landing gear . For the same amount of power or thrust produced, an unducted fan requires shorter blades than a geared propfan, although the overall installation issues still apply. Turboprops and most propfans are rated by the amount of shaft horsepower (shp) that they produce, as opposed to turbofans and

11752-578: Was a 10,100 hp (7,500 kW) propfan mounted to an Ilyushin Il-76 and flown to the Hannover ILA 90 airshow, which was intended for an unidentified four-propfan aircraft. The D-236 flew 36 times for a total of 70 flight test hours on the Il-76. The other testbed was a 10,990 hp (8,195 kW), 14 ft unit (4.2 m; 170 in; 420 cm) mounted to a Yakovlev Yak-42 E-LL and flown to

11865-401: Was a pair of contra-rotating rows. Airframers, who had been wary of issue-prone gearboxes since the 1950s, liked GE's gearless version of the propfan: Boeing intended to offer GE's pusher UDF engine on the 7J7 platform (which would have had a cruise speed of Mach 0.83), and McDonnell Douglas planned to do likewise on their MD-94X airliner . The GE36 was first flight tested mounted on

11978-451: Was a variation on the original propfan concept and resembled a pusher configuration piston engine. GE's UDF had a novel direct-drive arrangement, where the reduction gearbox was replaced by a low-speed seven-stage free turbine. One set of turbine rotors drove the forward set of propellers, while the rear set was driven by the other set of rotors which rotated in the opposite direction. The turbine had 14 blade rows with seven stages. Each stage

12091-619: Was assembled in 2015, and ground tested in May 2017 on its open-air test rig in Istres , aiming to reduce fuel consumption and associated CO 2 emissions by 30% compared with current CFM56 turbofans. After the completion of ground testing at the end of 2017, Safran's geared open rotor engine had reached technology readiness level 5. The demonstrator's twelve-blade front propeller and ten-blade back propeller had diameters of 13.1 and 12.5 ft (4.0 and 3.8 m; 160 and 150 in; 400 and 380 cm), respectively. The demonstrator, based on

12204-477: Was expected to produce 20,000–35,000 lbf (9,100–15,900 kgf; 89–156 kN) of thrust, with a 20% increase in fuel efficiency. The company claimed its motivation was the global emphasis on reducing emissions. The engine was planned to support both hydrogen and sustainable aviation fuels . The engine was expected to include a compact high-pressure core and a recuperating system to preheat combustion air with exhaust heat along with ceramic matrix composites in

12317-655: Was jointly developed between Allison and another division of United Technologies, the engine maker Pratt & Whitney . Unlike the competing GE36 UDF, the 578-DX was fairly conventional, having a reduction gearbox between the LP turbine and the propfan blades. Due to jet fuel price drops and shifting marketing priorities, Douglas shelved the propfan program later that year. Other announcements of future propfan-powered airliners included: None of these projects came to fruition, however, mainly because of excessive cabin noise (compared to turbofans) and low fuel prices. For General Electric,

12430-431: Was outlined by Carl Rohrbach and Bruce Metzger of the Hamilton Standard division of United Technologies in 1975 and was patented by Rohrbach and Robert Cornell of Hamilton Standard in 1979. Later work by General Electric on similar propulsors adopted the name unducted fan, which was a modified turbofan engine, with the fan placed outside the engine nacelle on the same axis as the compressor blades. During this era,

12543-399: Was planned for 2017–2018, with market entry with airlines planned by 2020. Comparable engines Related lists Propfan In the 1970s, Hamilton Standard described its propfan as "a small diameter, highly loaded multiple bladed variable pitch propulsor having swept blades with thin advanced airfoil sections, integrated with a nacelle contoured to retard the airflow through

12656-476: Was stymied by the Russo-Ukrainian War . Antonov began working instead with Turkey in 2018 to redevelop the An-70 as a rebranded An-77 , so that the aircraft can comply with modern-day requirements without Russian supplier participation. In the first decade of the 21st century, rising jet fuel prices increased emphasis on engine/airframe efficiency to reduce emissions, which renewed interest in

12769-485: Was tested on the Boeing 727 had front and back blades that weighed 22.5 and 21.5 lb (10.2 and 9.8 kg) each.) One of the major problems with the propfan is noise. The propfan research in the 1980s discovered ways to reduce noise, but at the cost of reduced fuel efficiency, mitigating some of the advantages of a propfan. General methods for reducing noise include lowering tip speeds and decreasing blade loading, or

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