Stroke (engine)
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2008-05-23T10:41:51Z
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A '''stroke''' is a single action of certain [[engine]]s.
In a [[Steam engine|steam]], [[Otto cycle|Otto]] or [[Diesel engine|Diesel]] [[piston]] [[engine]], a stroke is the action of a [[piston]] travelling the full length of its [[Cylinder (engine)|cylinder]] in one direction.
The stroke length is determined by the [[crank (mechanism)|cranks]] on the [[crankshaft]]. Stroke can also refer to the distance the piston travels; for example, the phrase "''This engine has a four inch stroke''" means that on each stroke, the piston travels four [[inch]]es. Bore is the diameter of the cylinder, which means that [[engine displacement]] is dependent on both the [[bore (engines)|bore]] and the stroke of the cylinder.
In a [[pistonless rotary engine]], the term is applied to the corresponding rotor movement, see ''[[top dead centre]]''.
===Intake stroke===
The '''intake stroke''', or '''induction stroke''', is the first stroke in a four-stroke internal combustion engine cycle. It involves the downward movement of the [[piston]], creating a partial vacuum that draws a fuel/air mixture into the combustion chamber.
===Compression stroke===
The '''compression stroke''' is the second of four stages in an [[otto cycle]] or [[diesel cycle]] [[internal combustion engine]].
In this stage, the mixture (in the case of an Otto engine) or air (in the case of a Diesel engine) is [[Gas_compressor|compressed]] to the top of the [[Cylinder (engine)|cylinder]] by the [[piston]] until it is either ignited by a [[spark plug]] in an Otto engine or, in the case of a [[Diesel engine]], reaches the point at which the fuel which has been injected spontaneously combusts, forcing the piston back down.
Compression serves to increase the proportion of energy which can be extracted from the hot gas and should be optimised for a given application. Too high a compression can cause detonation which is undesirable compared with a smooth, controlled burn. Too low a compression may result in the fuel/air mixture still burning when the piston reaches the bottom of the stroke and the exhaust valve opens.
===Power stroke===
A '''power stroke''' is, in general, the stroke of a cyclic motor which generates [[force (physics)|force]]. It is used in describing mechanical engines.
In 5events 4 stroke engine a power stroke happens once in two rotation of crank shaft while in 2stroke it happens two in similar case.
===Exhaust stroke===
The '''exhaust stroke''' is the fourth of four stages in an [[internal combustion engine]] cycle. In this stage gases remaining in the cylinder from the [[fuel]] ignited during the compression step are removed from the [[cylinder (engine)|cylinder]] through an exhaust [[valve]] at the top of the cylinder. The gases are forced up to the top of the cylinder as the piston rises and are pushed through the opening which then closes to allow fresh air/fuel mixture into the cylinder so the process can repeat itself.
==See also==
* [[Compression ratio]]
* [[Cylinder head porting]]
* [[Four-stroke cycle]]
* [[Reciprocating engine]]
* [[Two-stroke cycle]]
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[[Category:Engine technology]]
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