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Topic: Bypass ratio

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	Bypass ratio - Wikipedia, the free encyclopedia
		Higher bypass ratios generally infer better specific fuel consumption as an increasing amount of thrust is being generated without burning more fuel.
		The Conway had a very small bypass ratio of only 0.3, but the fuel economy was nevertheless improved enough that it, and its derivatives like the Spey became some of the most popular jet engines in the world.
		Through the 1960s the bypass ratios grew, making jetliners competitive in fuel terms with piston-powered planes for the first time.
	en.wikipedia.org /wiki/bypass_ratio (604 words)

	Encyclopedia: Turbofan (Site not responding. Last check: 2007-11-06)
		Bypass ratio (the ratio of bypassed air mass to combustor air mass) is a parameter often used for classifying turbofans, although specific thrust is a better parameter.
		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.
		This is not so much due to the higher bypass ratio, but as to the use of low pressure ratio, single stage, fans, which significantly reduce specific thrust and, thereby, jet velocity.
	www.nationmaster.com /encyclopedia/Turbofan (3967 words)

	Bypass Ratio (Site not responding. Last check: 2007-11-06)
		For instance, an engine that blows 2 kg of air around the engine for every kg that passes through it is said to have a bypass ratio of 2.
		Through the 1960s the bypass ratios grew, leading to jet airliners becoming competitive in fuel terms with the piston powered planes for the first time.
		For "low speed" operations like airliners modern engines use bypass ratios up to 6, while for "high speed" operations like fighter aircraft the ratios are much lower, around 0.7.
	www.wikiverse.org /bypass-ratio (615 words)

	Turbofan - Wikipedia
		De bypass ratio (de verhouding tussen de hoeveelheid lucht die door de "bypass" stroomt ten opzichte van de hoeveelheid lucht die door de verbrandingskamer stroomt) is een belangrijke parameter voor turbofans.
		Gevechtsvliegtuigen hebben vaak motoren met een bypass ratio van minder dan 1 maar de motoren van de meeste verkeersvliegtuigen hebben bypass ratio's van 3 of meer.
		In een turbofan wordt die hete lucht gemengd met een koude lucht uit de bypass en het resultaat is een veel lager geluidsniveau.
	nl.wikipedia.org /wiki/Turbofan (289 words)

	Turbofan - Open Encyclopedia (Site not responding. Last check: 2007-11-06)
		The bypass ratio (the ratio of bypassed air mass to combustor air mass) is an important parameter for turbofans.
		The Rolls-Royce Conway, the first turbofan, had a bypass ratio of 0.3, similar to the modern General Electric F404 fighter engine.
		In the turbofan this hot air is mixed with the cold air bypassing the engine, so the result is a much lower temperature.
	www.open-encyclopedia.com /Turbofan (266 words)

	Coronary Artery Bypass Surgery in New York State - New York State Department of Health
		In particular, coronary artery bypass surgery during the same hospital admission as the angioplasty, and myocardial infarction (heart attack) during or after the angioplasty in the same hospital admission will be reported as soon as possible, probably in 1999 (using 1997 data).
		Also, coronary artery bypass graft surgery may be related to myocardial infarctions in that the tendency not to perform bypass surgery when it is necessary could lead to a myocardial infarction.
		Roughly speaking, the odds ratio for a risk factor represents the number of times more likely a patient with that risk factor is of dying in the hospital during or after angioplasty than a patient without the risk factor, all other risk factors being the same.
	www.health.state.ny.us /nysdoh/reports/report.htm (3130 words)

	Mechanical Engineering "100 Years of Flight," Dec. 2003 -- "Jets Fans," Feature Article
		Early arguments against the high bypass turbofan said that the external losses and drag of the nacelle were proportionately greater due to large flow of relatively low-velocity air from the fan.
		The GE TF39, with its 8:1 bypass ratio, won the competition to power the large military transport, the C-5A, in August 1965.
		Thus, by the late 1960s, the high bypass ratio engine was the engine of choice for aircraft flying long distances at high subsonic speeds (0.7 to 0.9 Mach).
	www.memagazine.org /supparch/flight03/jetsfans/jetsfans.html (1917 words)

	High-bypass Turbofan Engine Encyclopedia Article, Definition, History, Biography (Site not responding. Last check: 2007-11-06)
		The difference between a ducted fan and a propeller is that the duct slows the air before it arrives at the fan.
		The first high-bypass turbofan engine was the General Electric TF39, built to power the Lockheed C-5 Galaxy military transport aircraft.
		Pratt and Whitney is behind GE and Rolls-Royce, the JT9D has the proud distinction of being chosen by Boeing to power the original 747 "Jumbo jet".
	www.alienartifacts.com /encyclopedia/High-bypass_turbofan_engine (2311 words)

	Robotic gastric bypass surgery shows promise
		CHICAGO — A system that allows surgeons to perform laparoscopic gastric bypass surgery from a remote console, controlling up to three robotic arms and a binocular camera, was successfully tested in 10 patients, according to a study in the August issue of Archives of Surgery, one of the JAMA/Archives journals.
		The laparoscopic gastric bypass surgery (a Roux-en-Y procedure) is often considered the most challenging minimally invasive procedure in general surgery, requiring a learning curve of 75 to100 cases for even experienced surgeons to achieve the highest level of proficiency, according to background information in the article.
		Although robotic surgical techniques have been developed to assist laparoscopic gastric bypass surgery, the complex geometry of the surgery has required repositioning of the robot, complicating its use.
	www.eurekalert.org /pub_releases/2005-08/jaaj-rgb081105.php (499 words)

	Cholesterol levels not necessarily indicative of cardiac health
		In a new study, cholesterol levels were found to be under so-called danger levels for 750 men and women who were diagnosed with serious blockage of coronary arteries and had bypass surgery after complaining of chest pains and undergoing cardiac catheterization.
		Thirty-two percent of the 244 women who had bypass surgery had levels above 240; 34 percent were below 200.
		To date, a 3-to-1 ratio of LDL (bad cholesterol) to HDL (good cholesterol) is a low heart-disease risk -- with a total cholesterol of less than 200 being the most desirable.
	www.eurekalert.org /pub_releases/2000-03/UoIa-Clnn-0203100.php (494 words)

	Turbofan Thrust
		The ratio of (m dot)f to (m dot)c is called the bypass ratio.
		In fact, high bypass ratio turbofans are nearly as fuel efficient as turboprops.
		Low bypass ratio turbofans are still more fuel efficient than basic turbojets.
	www.grc.nasa.gov /WWW/K-12/airplane/turbfan.html (733 words)

	BMW Turbo Discussion - BMW 745i and BMW Turbo Project Forums (© 2004) - AFM vs. bypass screw
		I know that clockwise at the bypass screw and counterclockwise at the AFM are both for richening and that CCW at bypass and CW at AFM are for leaning out.
		Bypass screw generally affects the calibrated vacuum leak at idle and afm spring will afect mixture accross the full range.
		The bypass going around the dam is still flowing water (air in the case of the AFM) even if the dam door is not open.
	bmwturbos.scottiesharpe.com /topics/814.htm (760 words)

	CRS Report: RL30547 - Aircraft Hushkits: Noise and International Trade - NLE
		By using the bypass ratio standard the EU seems to be creating a noise regime based on engine design standards rather then the performance standards detailed in ICAO regulations.
		Rather, the EU contends that bypass ratio data is an effective tool for distinguishing noisier hushkitted aircraft and that the data itself is scientifically sound.
		Finally, the EU argues that while bypass ratios may not be specifically mentioned in the ICAO regulations, they have been used elsewhere to identify noisier aircraft.
	www.ncseonline.org /NLE/CRSreports/air/air-41.cfm (5671 words)

	TURBOFAN (Site not responding. Last check: 2007-11-06)
		In de praktijk blijkt dit motortype het beste te zijn voor snelheden die variëren van 400 tot 1000 kilometer per uur wat ervoor gezorgd heeft dat dit motortype verreweg de meest populaire vliegtuigmotor is.
		De "bypass ratio" (de verhouding tussen de hoeveelheid lucht die door de "bypass" stroomt t.o.v.
		Turbofans (vooral als ze een hoge bypass ratio hebben) hebben nog een leuke eigenschap, ze zijn redelijk stil.
	www.thumpershollow.com /encyclopedia/T/Turbofan (288 words)

	AIN Online January 2002: Startup to offer 560-lb-thrust turbofan (Site not responding. Last check: 2007-11-06)
		Bypass ratio is 8:1 and total dry weight should be around 90 lb.
		“This relatively higher weight is due to the higher bypass ratio, which increases the size of the engine,” Etcheparre answered.
		Specific fuel consumption for the DGEN engine would be 0.49 lb of fuel per pound of thrust per hour, whereas it would be about 0.75 lb of fuel per pound of thrust per hour at Mach 0.30 and 10,000 ft, according to Etcheparre.
	www.ainonline.com /issues/01_02/01_02_560lbthrustturbopg10.html (707 words)

	Engines (Site not responding. Last check: 2007-11-06)
		The three main Rolls Royce Spey 512 engines are of twin spool low bypass ratio design, using axial compressors and turbines.
		The combustion chambers are of the interlinked can-annular design and the engine features a complex shaped nozzle to integrate the hot and cold exhaust flows in an effort to reduce noise.
		Two engines are located in nacelles either side of the rear fuselage, while the third is located inside the rear fuselage, with an intake at the front of the vertical tail and an "s" duct leading to the first impeller stage.
	www.shockcone.co.uk /trident/engines.htm (192 words)

	[No title]
		The basic philosophy of high thrust/weight ratio and sus- tained turning performance in transonic dogfights shaped these aircraft aerodynamically and hence imposed fundamental constraints to the other performance characteristics of this family of aircraft.
		The ATF flight profiles are suf- ficiently unconventional to create major difficulties for a fixed bypass ratio engine designer attempting to reconcile the diverse demands of lower speed operation and supersonic cruise.
		The variable bypass ratio allows the engine to optim- ise itself for the flight regime, allowing thus efficient dry cruise at speeds between 1.4 and 1.58 Mach.
	www.paranetinfo.com /UFO_Files/ufo/atf.txt (9724 words)

	Active Core Exhaust Control
		The ground test with the low-bypass ratio engine also provided experimental data, which has been used to develop and validate a Computational Fluid Dynamics (CFD) model for use in trade studies of the high-bypass ratio design.
		In a concurrent effort to redesign the nozzle and optimize injection parameters, a trade study evaluating six flight conditions was performed.
		Based on the analysis of take-off, cruise, penetration, maximum reverse, idle reverse, and airdrop scenarios, a reasonably mature configuration for the nozzle and the ACE control system was established, as illustrated in Figure 3.
	www.afrlhorizons.com /Briefs/0001/VA9905.html (799 words)

	P-9 LRAACA [Long-Range Air ASW Capable Aircraft]
		Turbofans in civil aircraft are generally divided intro three classifications, bases on by-pass ratio: low bypass (1:1), medium bypass (2 or 3:1), and high bypass (4:1 or greater).
		During the 1980s, GE developed the Unducted Fan UDF® unducted ultrahigh bypass ratio turbofan, which eliminated the need for a gearbox to drive a large fan.
		The propfan´s required high by-pass ratio of 30:1 came from dual 12- to 15-foot diameter propellers with a higher tip speed than propellers.
	www.globalsecurity.org /military/systems/aircraft/p-9.htm (783 words)

	Airliners.net Tech Ops: Jet Engine Thrust Percentage
		The short answer is that in a modern high bypass engine, at takeoff thrust, about 75% of overall thrust comes from the fan; in cruise about 60% of the overall thrust comes from the fan.
		A mixed-flow turbofan is one where the bypass flow and the core flow are mixed prior to being exhausted through a nozzle.
		Most Low bypass TFs are mixed flow (JT8D, F404, F100, F101, F110, etc.), also the CFM56s on the A340's, The MD-90 motors, and the RB211s on the 757 are mixed-flow installations.
	www.airliners.net /discussions/tech_ops/read.main/95616 (1570 words)

	News - Brain Damage After Coronary Artery Bypass Grafting
		However, although focal ischemic lesions after coronary artery bypass grafting (CABG) are more frequent than is the apparent neurological complication rate, the lesions are not related to the diffuse postoperative encephalopathy, suggests a study in Germany.
		After surgery, MRS revealed a significant decrease in the metabolite ratio of N-acetylaspartate-creatine.
		A normalization of the N-acetylaspartate-creatine ratio revealed on follow-up MRS scan accompanied the recovery in psychological test performance.
	www.docguide.com /news/content.nsf/news/8525697700573E1885256BFA00666733 (404 words)

	Bypass ratio - Definition up Erdmond.Com
		Higher bypass ratios generally infer better specific_fuel_consumption as an increasing amount of thrust is being generated without burning more fuel.
		Most of the very-large engines in this class were pioneered in the United_States by Pratt_&_Whitney and General_Electric, which for the first time was outcompeting England in engine design.
		For "low speed" operations like airliners modern engines use bypass ratios up to 6, while for "high speed" operations like fighter_aircraft the ratios are much lower, around 0.7.
	www.erdmond.com /Bypass_ratio.html (513 words)

	Article #2455, Risk Factors for Prolonged ICU Stay in Patients Following Coronary Artery Bypass Grafting With a Long ...
		Therefore we examined immediate postoperative risk factors for prolonged ICU stay after CABG with a long duration of cardiopulmonary bypass (CPB).
		Perioperative variables were compared among the three groups and we demonstrated risk factors for prolonged (more than 3 days) ICU stay.
		Conclusion: Advanced age, increased MPAP, and decreased PF ratio on admission to the ICU were significant risk factors for a prolonged ICU stay of more than 3 days.
	www.perfusion.com /cgi-bin/absolutenm/templates/mobilearticledisplay.asp?articleid=2455 (264 words)

	Cessna Citation X
		One attribute that is often first noticed is the large diameter of the engine intakes.
		This feature, related to the high bypass ratio turbofan, reduces the noise from the engines and improves fuel efficiency.
		The engine's fan has a 5 to 1 bypass ratio for improved fuel efficiency and low acoustic signature.
	www.theinfrequentflyer.com /cessna-citation-x.php (321 words)

	GE - Aviation: CF6
		For more than 30 years, the GE CF6 family of engines has been the cornerstone of the widebody, high bypass ratio turbofan engine market.
		The GE CF6 family is the cornerstone of the widebody, high bypass ratio turbofan engine business at GE.
		In 1965, GE was awarded the contract to develop the engines for the USAF's Lockheed C-5A "Galaxy" transport.
	www.geae.com /engines/commercial/cf6/index.html (299 words)

	ATF (www.combatsim.com)
		The unique and new supersonic cruise mission profile of the ATF has had a major impact upon the powerplants to be used for the aircraft.
		The engine is known to be a two shaft design with a minimum number of rotating stages, a fan which has been speculated to be a single stage design and a compressor using integrated bladed rotors.
		The ATF flight profiles are sufficiently unconventional to create major difficulties for a fixed bypass ratio engine designer attempting to reconcile the diverse demands of lower speed operation and supersonic cruise.
	www.combatsim.com /archive/htm/htm_arc1/atfighter-2.htm (6117 words)

	JET NOISE REDUCTION (Site not responding. Last check: 2007-11-06)
		The fundamental principle is reduction of the convective Mach number of turbulent eddies that cause intense noise.
		In a turbofan engine, a very effective way to achieve this is by tilting sligtly downward the bypass plume relative to the core plume.
		The downward tilt of the bypass stream results in a thick layer of low-speed flow under the end of the primary potential core (end of dark brown region).
	supersonic.eng.uci.edu /jnr.htm (276 words)

	Variable-Area Fan Nozzles Actuated by a Shape Memory Alloy
		As the design fan pressure ratio is reduced below about 1.4, an operational disparity is set up in the fan between high and low flight speeds.
		The NASA analytical model of a performance-optimized VAFN turbofan with a fan pressure ratio of 1.28 is shown in the preceding figure.
		The mission fuel reduction benefit of very high bypass shape-memory-alloy VAFN aircraft was calculated to be 8.3 percent lower than a moderate bypass cycle using a conventional fixed nozzle.
	www-psao.grc.nasa.gov /Library/Abstracts/berton12.html (559 words)

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