Airlocks - Revision history

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2014-04-04T16:11:17Z

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	* Only edit this page if you can improve the content.		An '''Airlock''' is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rotary valve.
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	[[File:~~Airlocks~~.jpg\|thumb\|right\|~~Airlocks~~]]
	[[File:~~Airlocks1~~.~~JPG~~\|thumb\|right\|~~Airlocks~~]]
	'''Airlock''' is a ~~device which permits the passage~~ of ~~people and objects between a pressure vessel and its surroundings while minimizing the change of pressure~~ in the ~~vessel and loss of air from it. The lock consists~~ of a ~~small chamber with two airtight doors in series which do not open simultaneously.~~
	~~An airlock may be used for~~ passage ~~between environments of different gases rather than different pressures, to minimize~~ or ~~prevent the gases from mixing.~~
	~~An airlock may also be used underwater to allow passage between an air environment~~ in a ~~pressure vessel and a water environment outside, in which case~~ the ~~airlock can contain air~~ or ~~water~~. ~~This~~ is ~~called a floodable airlock or an underwater airlock, and is used to prevent water from entering a submersible vessel or an underwater habitat~~.
	~~==Use==~~
	Before opening either door, the air pressure of the airlock the space between the doors is equalized with that of the environment beyond the next door to open. This is analogous to a water way lock: a section of waterway with two watertight gates, in which the water level is varied to match the water level on either side.

	A gradual pressure transition minimizes air temperature fluctuations , which helps reduce fogging and condensation, decreases stresses on air seals and allows safe verification of pressure suit and space suit operation.
	Where a person who is not in a pressure suit moves between environments of greatly different pressures, an airlock changes the pressure slowly to help with internal air cavity equalization and to prevent decompression sickness. This is critical in scuba diving, and a diver may have to wait in an airlock for some hours in line with decompression tables.
	==Applications==		==Applications==
	* ~~airlocks are used inaviation, certain airplanes are equipped with airlocks for skydiving, and/or emergency exits~~.		Rotary valves have been applied in numerous applications, including:
	* ~~spacecraft~~ and ~~space stations~~, ~~to maintain the habitable environment when persons are exiting or entering~~ the ~~craft~~.		* Changing the pitch of brass instruments.
	* ~~hyperbaric chambers, to allow entry~~ and ~~exit while maintaining~~ the ~~pressure difference with the surroundings~~.		* Controlling the steam and exhaust ports of steam engines, most notably in the Corliss steam engine.
	* ~~submarines, diving chambers, and underwater habitats to permit divers to exit and enter~~.		* Periodically reversing the flow of air and fuel across the open hearth furnace.
	* ~~torpedo tubes and escape trunks in submarines are airlocks~~.		* Loading sample on chromatography columns.
	* ~~cleanrooms~~, ~~protected environments in which dust~~, ~~dirt particles~~, and ~~other contaminants~~ are ~~excluded partially by maintaining~~ the ~~room at a higher pressure than the surroundings.~~		* Certain types of two-stroke engines.
	* hazardous environments, such as ~~nuclear reactors~~ and ~~some biochemical laboratories , in which dust and particles are prevented from leaking out by maintaining the room at a lower pressure than the surroundings~~.		* Most hydraulic automotive power steering control valves.
	* electron microscopes, where the interior is ~~near vacuum so air does not affect~~ the ~~electron path~~.
	* parachute airlocks, ~~where airfoil collapse due~~ to ~~depressurization can result in dangerous loss of altitude.~~
	* On oil rigs or ~~platforms in rooms~~ with ~~over~~ pressure ~~to avoid pressure alarm from going off~~.
	* brewer's airlock allows fermentation gases to escape while keeping air out of the ~~fermentation vessel~~.
	==~~Similar mechanisms~~==		==Use in brass instruments==
	* In cold climates, ~~two doors arranged in an airlock configuration~~ are ~~common~~ in ~~building entrances~~. ~~While not airtight~~, the ~~double doors minimize~~ the ~~loss of heated air from~~ the ~~building~~. ~~A similar arrangement is common~~ in ~~hot climates~~, where ~~it is~~ used to ~~keep interior spaces cool~~. ~~Revolving doors may be used~~ for the ~~same purpose~~.		In the context of brass instruments, rotary valves are found on horns, trumpets, trombones, flugelhorns, and tubas. Many European trumpet players tend to favor rotary valves.
	* Some jewelry stores and banks have airlock-~~like doors to slow~~ the ~~escape~~ of ~~thieves~~.		Trombone F-attachment valves are usually rotary, with several variations on the basic design also in use, such as the Thayer axial-flow valve and Hagmann valve.
	* Butterfly farms and ~~aviaries usually have an airlock~~-~~like entrance~~ to ~~prevent~~ the ~~exit of inhabitants~~ and ~~entrance~~ of ~~predatory species~~.		Joseph Riedlin is credited with the first use of rotary valves on brass instruments in 1832.
	~~==Fictional airlocks==~~
	~~A four-door airlock was proposed by science fiction writer H~~. ~~Beam Piper in his novel Uller Uprising~~. The ~~atmosphere inside~~ the ~~fictional structure was human~~-~~breathable, while~~ the ~~outside atmosphere~~ was ~~highly toxic. Only~~ one ~~door~~ of the ~~airlock opened~~ at ~~a time~~, and ~~the middle chamber of the three would always contain a vacuum~~ to ~~minimize traces of~~ the ~~exterior atmosphere reaching the habitat~~.
	~~Airlocks~~ are ~~also~~ used ~~in the Bioshock game series~~ for ~~entrance and exit into water environments~~.
	~~Airlocks~~ are ~~a common feature in the reimagined Battlestar Galactica~~, ~~as a common method of execution used by the Colonial Humans~~.
			==Use in industry==
			In industry, a rotary valve which can also be called [[Airlocks]] are often used to enter or extract material from two chambers with different pressure level.As part of the material exchange process, the valve is often used as a measuring or metering device.




			==Use in engine design==
			The rotary valve combustion engine possesses several significant advantages over the conventional assemblies, including significantly higher compression ratios and rpm, meaning more power, a much more compact and light-weight cylinder head, and reduced complexity, meaning higher reliability and lower cost. As inlet and exhaust are usually combined special attention should be given to valve cooling to avoid engine knocking.

			Rotary valves have been used in several different engine designs. In Britain, the National Engine Company Ltd advertised its rotary valve engine for use in early aircraft, at a time when poppet valves were prone to failure by sticking or burning.From the 1930s, Frank Aspin developed a design with a rotary valve that rotated on the same axis as the cylinder bore, but with limited success.Kawasaki and others have also used rotary valves in two-stroke motorcycle engines, where the arrangement helps to prevent reverse flow back into the intake port during the compression stroke.

			Austrian engine manufacturer Rotax used rotary intake valves in their now out-of-production 64 hp (48 kW) Rotax 532 two-stroke engine design and continues to use rotary intake valves in the 532's successor, the current-production 64 hp (48 kW) Rotax 582.US company Coates International Ltd has developed a spherical rotary valve for internal combustion engines which replaces the poppet valve system. This particular design is four-stroke, with the rotary valves operated by overhead shafts in lieu of overhead camshafts . The first sale of such an engine was part of a natural gas engine-generator.UK company RCV Engines Ltd uses rotating cylinder liner technology as a specialized form of rotary valve in their model engine and small-engine line-up.Rotary valves are highly suitable for high reving engines, such as those used in sportscars and F1 racing cars, on which traditional [[Poppet Valves]] with springs can fail due to spring resonance and where the desmodromic valve gear is too heavy, large in size and too complex to time and design properly. Rotary valves allow for a more compact and lightweight cylinder head design. They rotate at half engine speed and lack the inertia forces of reciprocating valve mechanisms. This allows for higher engines speeds offering appr. 10% more power. The 1980s MGN W12 F1 engine used rotary valves but never raced. Between 2002 and 2004 the Australian developer Bishop Innovation and Mercedes-Ilmor tested rotary valves for a F1 V10 engine.

			Bishop Innovations patent for the rotary valve engine was bought out by BRV Pty Ltd, owned by Tony Wallis, one of the valves original designers. BRV has constructed several functional motors using the rotary valve technology, such as a Honda CRF 450, which had greater torque at both low(17% increase) and high (9% increase) engine speeds, and also produced more brake horsepower up to around 30% more at functional engine speeds.The engine was also considerably smaller and lighter, as the cylinder head assembly was not as large.


			==Use in chromatography==
			Rotary valves are used for loading samples on columns used for liquid or gas chromatography. The valves used in these methods are usually 6-port, 2-position rotary valves.




	==Sources==		==Sources==
	[http://en.wikipedia.org/wiki/~~Airlock~~ Wikipedia ~~Airlock~~]		[http://en.wikipedia.org/wiki/Rotary_valve Wikipedia Rotary valves]

Kodiyath at 06:08, 30 December 2012

2012-12-30T06:08:21Z

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