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Topic: Unducted fan

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	AMT 223 - Gas Turbine Powerplants I
		Discuss the inspection procedures for unducted fan systems and components.
		Describe the method of thrust generation in unducted fan systems.
		Discuss the operating principles involved in the unducted fan systems and components.
	www.dtae.org /TECHED/standards/courses/AMT223.html (262 words)

	Fan (implement) at AllExperts
		The folding fan was invented in Japan in the 8th century and taken to China in the 9th century.
		Fans are useful for moving large quantities of air, which is suited for applications such as winnowing grain or blowing a fire, cooling and ventilation purposes, and in conjunction with a heat source for heating and drying.
		An impeller rotates, causing air to enter the fan near the shaft and move perpendicularly from the shaft to the opening in the scroll-shaped fan casing.
	en.allexperts.com /e/f/fa/fan_(implement).htm (3950 words)

	Fan (implement) Summary
		Fans have had several purposes, the most common being to move air for creature comfort or for ventilation and to move air or gas from one location to another for industrial purposes.
		In automobiles, a mechanical fan, driven with a belt and pulley off the engine's crankshaft, or an electric fan switched on/off by a thermo switch is used to blow or suck air through a coolant filled radiator, to prevent the engine from overheating.
		A fan is also a small vane or sail that is used to keep the large sail of a smock windmill always in the direction of the wind.
	www.bookrags.com /Fan_(implement) (4514 words)

	Mailgate: sci.aeronautics: Aircraft engine propulsion and a little thermodynamics
		GE's unducted fan was something like 9 bladed, whereas the most you usually see on a propellor is ~6 (typically 3-5).
		Fan baldes can be down around 4 or 5 where propellors are up over 10.
		The biggest current divider is that a propellor is geared to spin slower than the turbine it's attached to while a fan is directly coupled to one of the engine spools.
	mailgate.supereva.it /sci/sci.aeronautics/msg02642.html (215 words)

	Fan (implement) information - Search.com (Site not responding. Last check: 2007-09-22)
		A fan has two purposes – to move air for creature comfort or for ventilation and to move air or gas from one location to another for industrial purposes.
		The folding fan was invented in Japan and taken to China in the 9th century.
		In the 17th century and 18th century, fans reached a high degree of artistry and were being made throughout Europe.
	c10-ss-1-lb.cnet.com /reference/Fan_(implement)?redir=1 (3500 words)

	Unducted Fan (Site not responding. Last check: 2007-09-22)
		unducted fan supreme convulsion he seized his comrade about the body, and unducted fan they lay, locked in each other's arms in a last embrace, "married" even in death.
		It was a great discouragement to all that their projectiles ranged short and burst almost without exception in unducted fan air, inflicting no injury on the powerful batteries of the foe, the fire of which was so efficient.
		The sight unducted fan tears to his eyes, he laid his trembling hand upon the breech, as if the ardor of his love might avail to warm his dear mistress back to life.
	www.appliancesmall.com /unducted_fan.htm (637 words)

	NationMaster - Encyclopedia: Propfan
		A propfan is a modified turbofan engine, with the fan placed outside of the engine nacelle on the same axis as the compressor blades.
		The General Electric GE-36 engine was an experimental turbojet engine that was a hybrid between turbojet and turboprop aircraft engines, known as an Unducted Fan or Propfan.
		General Electric's Unducted Fan (UDF) is a variation on NASA's original propfan concept, and appears similar to a pusher configuration piston engine.
	www.nationmaster.com /encyclopedia/Propfan (1953 words)

	Power turbine ventilation system - Patent 5039278
		Because of the close proximity of the fan blades to the power turbine in such a configuration, the blade hub structures, under certain flight conditions, will be subjected to relatively high rates of heating (heat loads).
		It is a further object of the present invention to provide a ventilation system for an unducted fan engine which apportions the ventilation to different locations.
		Each fan blade has a pitch change axis 54 about which the blade may be turned to vary the pitch of the blade.
	www.freepatentsonline.com /5039278.html (5125 words)

	Aircraft Engines - Level 3
		The turbofan is a turbojet with a fan to generate a bypass flow along the core turbojet in order to increase the mass flow.
		The fan is driven by the gas turbine.
		The difference between the prop-fan and the turboprop is that in the prop-fan the exhaust jet is used for propulsion in combination with the propeller/fan.
	www.allstar.fiu.edu /aero/Propulsion1.htm (1544 words)

	Aircraft engineering - Ducted Fan
		A ducted fan will be quieter for a given power level; because sideline noise, which is the worst part of a fan's or propeller's noise signature, is largely captured by the shroud.
		Their fan blades were fewer in number and larger in diameter than the fan blades on an equivalent ducted fanjet engine.
		A low pressure ducted fan, usually called a shrouded propulsor, can be designed in the same way as a free propellor with the adition of the flow from a series of ring vortices to simulate the duct as well as the flow field from a fuselage or nacelle.
	www.eng-tips.com /viewthread.cfm?qid=58711&am (2919 words)

	Blade pitch varying mechanism - Patent 4738591
		In the unducted fan engine, the power turbine includes counterrotating rotors and turbine blades which drive counterrotating unducted fan blades radially located with respect to the power turbines.
		The fan blades of the unducted fan engine are variable pitched blades to achieve optimum performance.
		To further optimize the performance of the unducted fan engine 20 it is desirable to vary the pitch of the forward propulsor blades 22 and aft propulsor blades 24.
	www.freepatentsonline.com /4738591.html (4812 words)

	Aerospaceweb.org \| Ask Us - Propfan Engines
		Like the turbofan, the small jet core rotates at least one set of fan blades (often two or three), and these fans produce the majority of the thrust.
		However, the fans on a turbofan engine are contained within the engine nacelle ducting while those on a propfan are external like the propeller of a turboprop.
		It is for this reason that propfans are sometimes called unducted fans.
	www.aerospaceweb.org /question/propulsion/q0067.shtml (686 words)

	Aviation and the Global Atmosphere
		Unducted propulsors resembling large, swept propellers, with bypass ratios of more than 30, have been flight tested and offer gains in propulsive efficiency of about 0.15 (i.e., a gain of about 25%) compared to modern transport engines.
		These engines are labeled as "UDF" (unducted fan) in Figure 7-12.
		Thus, the application of large unducted propulsors is restricted to new aircraft designs for which special accommodation for the propulsion unit can be made.
	www.grida.no /climate/ipcc/aviation/098.htm (949 words)

	DAYS OF AIR AND SPACE CALENDAR
		Therefore, the new "fan" would little resemble its ancestor, the propeller; it would have to be much thinner, yet stronger, and shaped differently to allow faster rotation.
		In flight tests on a Boeing 727 (left), the General Electric Unducted Fan was flown as the starboard engine in place of one of the regular three turbofans first flown in August 1986, the UDF is a pusher-type propfan with two counter-rotating rotors of eight blades each.
		Unlike the NASA PTA system, it has no gearbox; the fans are driven directly by the turbine, a weight-saving measure that eliminates the weight of the gearbox and its oil cooling system.
	www1.jsc.nasa.gov /er/seh/profan.html (1485 words)

	The Ultra High Bypass Engine (Site not responding. Last check: 2007-09-22)
		During the 1980s, GE developed the Unducted Fan UDF® engine which eliminated the need for a gearbox to drive a large fan.
		The jet exhaust drives two counter-rotating turbines that are directly coupled to the fan blades.
		These large span fan blades, made of composite materials, have variable pitch to provide the proper blade angle of attack to meet varying aircraft speed and power requirements.
	www.aviation-history.com /engines/bypass.htm (97 words)

	DAYS OF AIR AND SPACE CALENDAR
		Therefore, the new "fan" would little resemble its ancestor, the propeller; it would have to be much thinner, yet stronger, and shaped differently to allow faster rotation.
		In flight tests on a Boeing 727 (left), the General Electric Unducted Fan was flown as the starboard engine in place of one of the regular three turbofans first flown in August 1986, the UDF is a pusher-type propfan with two counter-rotating rotors of eight blades each.
		Unlike the NASA PTA system, it has no gearbox; the fans are driven directly by the turbine, a weight-saving measure that eliminates the weight of the gearbox and its oil cooling system.
	www.space-explorers.com /internal/chronos/more/propfan.html (1495 words)

	TCC 402 - Thesis Technical Report Outline
		A smaller diameter fan effectively decreases the engine's bypass ratio and means that a ducted configuration is not able to achieve the fuel efficiency of an unducted version for the same level of thrust.
		The results showed that "both fan blade stresses and performance behind the pylon were within acceptable levels at conditions expected during the flight tests" (GE Design report, 1987).
		The design and manufacture of the composite fan blades used in the GE90 are a direct carry-over of those techniques pioneered during the GE36 program for propfan blades.
	members.aol.com /sciszek/propfan.htm (10853 words)

	Review: SilverStone TJ06 PC case
		Most PCs were, therefore, perfectly adequately cooled by the single fan in the power supply; one more intake fan was overkill, unless you had a great big drive array or something.
		The usual way to make an ATX case that runs cool is to infest it with regular fans, or use a single huge one.
		The 120mm fans have a 0.2 amp nominal current rating, which adds up to 2.4 watts; that's medium power, but should deliver more than adequate air flow from a 120mm impeller - all things being equal, bigger fans work better.
	www.dansdata.com /tj06.htm (2232 words)

	unducted fan - Article and Reference from OnPedia.com
		unducted fan - Article and Reference from OnPedia.com
		An unducted fan, (abbreviated as UDF), or propfan, is a modified turbofan engine with the fan placed outside of the engine nacelle on the same axis as the compressor blades.
		Russian air forces ordered 164 aircraft in 2003.
	www.onpedia.com /encyclopedia/unducted-fan (430 words)

	Aircraft engine propulsion and a little thermodynamics (Site not responding. Last check: 2007-09-22)
		Even worse, as I recall, (it's been 10 years > since I last taught this stuff), the compressor on an axial flow engine > is but a series of little propeller blades, and thus its power > requirement rises as the cube of the rpm.
		So if we use a big slow > turning fan(s) to push a LOT of air out the back end we get more fuel > efficiency than if we sent less out faster to attain equal thrust.
		Your comment on compressor blades and propellers reminds me of GE's "unducted fan" engines.
	www.talkaboutaviation.com /group/sci.aeronautics/messages/15034.html (197 words)

	Propfan - Definition, explanation
		UDF Unducted Fan engine on a McDonnell Douglas MD-81 testbed
		General Electric's Unducted Fan (UDF) is a variation on NASA's original propfan concept, and appears similar to a pusher propeller-driven piston engine.
		The reason propeller engines lose efficiency at high speed is the same reason that airplanes find it difficult to fly at supersonic speeds: an effect known as wave drag significantly increases drag just below the speed of sound, and led to the concept of the sound barrier.
	www.calsky.com /lexikon/en/txt/p/pr/propfan.php (508 words)

	11.3 Implications of propulsive efficiency for engine design
		The large inlets of a Boeing 777-200's engines are shown in Figure 11.4.
		At low flight velocities, the highest propulsive efficiency is typically obtained with a propeller or an unducted fan.
		Figure 11.5 shows a propeller craft, and Figure 11.6 shows a sketch of a jet engine with an unducted fan.
	web.mit.edu /course/16/16.unified/www/FALL/thermodynamics/notes/node82.html (276 words)

	[No title]
		One of several terms used to describe new generations of jet engines which typically turn very large, multi-bladed propeller-like fans in order to produce the thrust needed for flight.
		A kind of engine that uses the basic core of a jet engine to drive large, fan-like blades which produce the major thrust component of the engine.
		A profan is one kind of unducted fan.
	www.speednews.com /glossary (2148 words)

	The Advanced Turboprop Project
		The passenger had to choose which one he or she would "prefer to travel in." Despite all the planes being in-flight, the sketches depicted the propellers as simple circles (no blades present), while the individual blades of the turbofan were visible.
		In 1983, the aircraft engine division of General Electric released the unducted fan design to NASA shortly before flight tests of the NASA industry design were scheduled.
		NASA Headquarters endorsed the "novel" unducted fan proposal and told NASA Lewis to cooperate with General Electric on the unducted fan development and testing.
	history.nasa.gov /SP-4219/Chapter14.html (9465 words)

	Unducted fan Details, Meaning Unducted fan Article and Explanation Guide
		Unducted fan Details, Meaning Unducted fan Article and Explanation Guide
		Unducted fan Guide, Meaning, Facts, Information and Description
		Both airliners were to use rear-fuselage mounted General Electric GE-36 engines.
	www.e-paranoids.com /u/un/unducted_fan.html (442 words)

	Unducted Fan Engines
		The new engines are designated ultra high bypass (UHB) propfan and unducted fan engine (UDF).
		These new designs utilize titanium, lightweight stainless steel, and composite materials to surpass the fuel economy of several high bypass turbofan engines by more than 15 percent.
		Unducted fan engines may eventually power transport aircraft at high speeds with substantial fuel savings.
	home.cinci.rr.com /millardturbine/unducted_fan_engines.htm (134 words)

	Airliners.net Photos: McDonnell Douglas McDonnell Douglas MD-81(UHB) (DC-9-81(UHB))
		The double row of fans in the back were counter rotating for balance.
		It was in-fact louder but not so loud that it couldn't be made to pass noise tests in sensitive areas with some management of the approaches and timing.
		It's an unducted fan (UDF), a type of propfan.
	www.airliners.net /open.file/947367/L (681 words)

	Jet turbine engines (Site not responding. Last check: 2007-09-22)
		Of course, this brings up the problem of what is the difference between a prop and an axial compressor or fan.
		To me the term 'unducted fan' is an oxymoron :-) I guess it is a moot point, since the engine/propulsion system did not succeed in market place.
		And no way an unducted fan is a compressor or fan, it is a PROP!
	www.science-one.com /new-3544165-4242.html (238 words)

	Flightlevel350.com Forums > Propeller Winglets
		Airline interest in the brand-new propfan technology was weak despite claims of up to a 60% reduction in fuel use, and both aircraft were cancelled.
		I think the unducted fan concept might be great for today's world of aviation!
		I don’t know the cost of an unducted fan engine in comparison with a modern turbo-jet/high by-pass engine but I do know that when adjusted for inflation, gasoline prices today are only 37% of what they were in 1955, 70% of what they were in 1972, and 45% of what they were in 1981.
	www.flightlevel350.com /forum/lofiversion/index.php/t5134.html (1629 words)

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