Six Stroke Engine b

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SIX STROKE ENGINE

The six-stroke engine is a type of internal combustion engine based on the four-

stroke engine, but with additional complexity to make it more efficient and reduce emissions.Two different types of six-stroke engine have been developed since the 1990s:

1. In the first approach, the engine captures the heat lost from the four-stroke Otto cycle orDiesel cycle and uses it to power an additional power and exhaust stroke of the piston in thesame cylinder. Designs use either steam or air as the working fluid for the additional powerstroke. The pistons in this type of six-stroke engine go up and down three times for eachinjection of fuel. There are two power strokes: one with fuel, the other with steam or air. Thecurrently notable designs in this class are the Crower six-stroke engine, invented by BruceCrower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of Switzerland; and the

Velozeta Six-stroke engine built by the College of Engineering, at Trivandrum in India.

2. The second approach to the six-stroke engine uses a second opposed piston in each cylinderthat moves at half the cyclical rate of the main piston, thus giving six piston movements percycle. Functionally, the second piston replaces the valve mechanism of a conventional engine butalso increases the compression ratio. The currently notable designs in this class include twodesigns developed independently: the Beare Head engine, invented by Australian MalcolmBeare, and the German Charge pump, invented by Helmut KottmannGriffin six-stroke engine

In 1883, the Bath-based engineer Samuel Griffin was an established maker ofsteam and gas engines. He wished to produce an internal combustion engine, but without payingthe licensing costs of the Otto patents. His solution was to develop a 'Patent slide valve' and asingle-acting six-stroke engine using it.

By 1886, Scottish steam locomotive maker Dick, Kerr & Co. saw a future in largeoil engines and licensed the Griffin patents. These were double acting, tandem engines and soldunder the name "Kilmarnock". A major market for the Griffin engine was in electricitygeneration, where they developed a reputation for happily running light for long periods, thensuddenly being able to take up a large demand for power. Their large heavy construction didn't

suit them to mobile use, but they were capable of burning heavier and cheaper grades of oil.


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The key principle of the "Griffin Simplex" was a heated exhaust-jacketed external

vapouriser, into which the fuel was sprayed. The temperature was held around 550 F (288C), sufficient to physically vapourise the oil but not to break it down chemically. Thisfractional distillation supported the use of heavy oil fuels, the unusable tars and asphaltsseparating out in the vapouriser.

Hot bulb ignition was used, which Griffin termed the 'Catathermic Igniter' , asmall isolated cavity connected to the combustion chamber. The spray injector had an adjustableinner nozzle for the air supply, surrounded by an annular casing for the oil, both oil and airentering at 20 lbs sq in. pressure, and being regulated by a governor The Bajulaz six-stroke

engine is similar to a regular combustion engine in design. There are however modifications tothe cylinder head, with two supplementary fixed capacity chambers: a combustion chamber andan air preheating chamber above each cylinder. The combustion chamber receives a charge ofheated air from the cylinder; the injection of fuel begins an isochoric burn which increases thethermal efficiency compared to a burn in the cylinder. The high pressure achieved is thenreleased into the cylinder to work the power or expansion stroke. Meanwhile a second chamberwhich blankets the combustion chamber, has its air content heated to a high degree by heat passing through the cylinder wall. This heated and pressurized air is then used to power anadditional stroke of the piston.

The advantages of the engine include reduction in fuel consumption by at least 40%, twoexpansion strokes in six strokes, multi-fuel usage capability, and a dramatic reduction inpollution


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VELOZETA SIX-STROKE ENGINE:

In a Velozeta engine, during the exhaust stroke, fresh air is injected into thecylinder, which expands by heat and therefore forces the piston down for an additional stroke.The valve overlaps have been removed and the two additional strokes using air injection providefor better gas scavenging. The engine seems to show 40% reduction in fuel consumption anddramatic reduction in air pollution.[7] Its specific power is not much less than that of a four-

stroke petrol engine.[7] The engine can run on a variety of fuels, ranging from petrol and dieselto LPG. An altered engine shows a 65% reduction in carbon monoxide pollution when comparedwith the four stroke engine from which it was developed.

The Velozeta engine features are:

* Reduction in fuel consumption.

* Dramatic reduction in pollution

* Better scavenging and more extraction of work per cycle* Lower working temperature makes it easy to maintain optimum engine temperature level forbetter performance

* The six-stroke engine does not require significant modification to existing engines.* Better cooling due to additional air strokes, which mostly removes the need for a coolingsystem* Lighter engine


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CROWER SIX-STROKE ENGINE:

In a six-stroke engine developed in the U.S. by Bruce Crower, fresh water isinjected into the cylinder after the exhaust stroke, and is quickly turned to superheated steam,which causes the water to expand to 1600 times its volume and forces the piston down for anadditional stroke. This design also claims to reduce fuel consumption by 40%. Maximumefficiency would theoretically be obtained by applying the design to a non-turbocharged dieselengine, where the high compression ratio would allow greater expansion of the steam.

The Crower six-stroke engine was invented in 2004 by 75 year old Americaninventor Bruce Crower who has applied for a patent on a design involving fresh water injectioninto the cylinders. As of May 2008, no patent has been awarded. Leonard Dyer invented the firstsix-stroke internal combustion water injection engine in 1915, which is very similar to Crower'sdesign. [11]

Crower's six-stroke engine features:

* No cooling system required.

* Improves a typical engines fuel consumption

* Requires a supply of distilled water to act as the medium for the second power stroke.

BEARE HEAD:

The term "Six Stroke" was coined by the inventor of the Beare Head, MalcolmBeare. The technology combines a four stroke engine bottom end with an opposed piston in thecylinder head working at half the cyclical rate of the bottom piston. Functionally, the secondpiston replaces the valve mechanism of a conventional engine.


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PISTON CHARGER ENGINE:

In this engine, similar in design to the Beare head, a "piston charger" replaces the

valve system. The piston charger charges the main cylinder and simultaneously regulates theinlet and the outlet aperture leading to no loss of air and fuel in the exhaust.In the main cylinder, combustion takes place every turn as in a two-stroke engine and lubricationas in a four-stroke engine. Fuel injection can take place in the piston charger, in the gas transferchannel or in the combustion chamber. It is also possible to charge two working cylinders withone piston charger. The combination of compact design for the combustion chamber togetherwith no loss of air and fuel is claimed to give the engine more torque, more power and better fuelconsumption. The benefit of less moving parts and design is claimed to lead to lowermanufacturing costs. Good for hybrid technology and stationary engines. The engine is claimedto be suited to alternative fuels since there is no corrosion or deposits left on valves. The six

strokes are: aspiration, precompression, gas transfer, compression, ignition and ejection. This isan invention of Helmut Kottmann from Germany, working 25 years at MAHLE GmbH pistonand cylinder construction.

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Six Stroke Engine b