| Atkinson Cycle |
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| CATEGORIES ABOUT ATKINSON CYCLE | |
| thermodynamic cycles | |
| hybrid vehicles | |
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The Atkinson cycle allows the intake, compression, power, and exhaust strokes of the Four-stroke Cycle to occur in a single turn of the Crankshaft . Owing to the linkage, the expansion ratio is greater than the compression ratio, leading to greater efficiency than with engines using the alternative Otto Cycle . The ''Atkinson cycle'' may also refer to a Four Stroke Engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. This reduces the effective compression ratio and, when combined with an increased stroke and/or reduced combustion chamber volume, allows the expansion ratio to exceed the compression ratio while retaining a normal compression pressure. This is desirable for improved fuel economy because the compression ratio in a spark ignition engine is limited by the octane rating of the fuel used. A high expansion ratio delivers a longer power stroke, allowing more expansion of the combustion gases and reducing the amount of heat wasted in the exhaust. This makes for a more efficient engine. The disadvantage of the four-stroke Atkinson cycle engine versus the more common Otto Cycle engine is reduced power density. Because a smaller portion of the intake stroke is devoted to compressing the intake air, an Atkinson cycle engine does not intake as much air as would a similarly-designed and sized Otto Cycle engine. Four stroke engines of this type with this same type of intake valve motion but with forced induction ( Supercharging ) are known as Miller Cycle engines. Multiple production vehicles use Atkinson cycle engines: : Toyota Prius Hybrid Electric (front-wheel-drive) : Ford Escape Hybrid Electric (front- and four-wheel drive) In all of these vehicles, the lower power level of the Atkinson cycle engine is compensated for through the use of Electric Motor s in a Hybrid Electric drive train. These electric motors can be used independent of, or in combination with, the Atkinson cycle engine. EXTERNAL LINKS
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