Stroke (engines)
Encyclopedia
Reciprocating
motion, used in reciprocating engine
s and other mechanisms, is back-and-forth motion. Each cycle of reciprocation consists of two opposite motions: there is a motion in one direction, and then a motion back in the opposite direction. Each of these is called a stroke. The term is also used to mean the length of the stroke.
In a steam locomotive
, steam
, Otto
or Diesel
piston
engine
, a stroke is the action of a piston
travelling the full length of its locomotive cylinder or engine cylinder
in one direction.
The stroke length is determined by the cranks
on the crankshaft
. Stroke can also refer to the distance the piston travels. Bore is the diameter of the cylinder, which means that engine displacement
is dependent on both the bore and the stroke of the cylinder.
In a pistonless rotary engine
, the term is applied to the corresponding rotor movement, see dead centre
.
, creating a partial vacuum that draws (allows atmospheric pressure to push) a fuel/air mixture into the combustion chamber.
In a reciprocating engine, that portion of the cycle when the pistons move from TDC (top dead center) to BDC (bottom dead center) and the fuel-air mixture is drawn into the cylinders.
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 compressed
to the top of the 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.
Solve for variable
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
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.
Reciprocation
Reciprocation may refer to:* Reciprocating motion, a type of oscillatory motion, as in the action of a reciprocating saw* Reciprocation in geometry, an operation with circles that involves transforming each point in plane into its polar line and each line in the plane into its pole...
motion, used in reciprocating engine
Reciprocating engine
A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...
s and other mechanisms, is back-and-forth motion. Each cycle of reciprocation consists of two opposite motions: there is a motion in one direction, and then a motion back in the opposite direction. Each of these is called a stroke. The term is also used to mean the length of the stroke.
In a steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
, steam
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
, Otto
Otto cycle
An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....
or Diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
engine
Engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
, a stroke is the action of a piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
travelling the full length of its locomotive cylinder or engine cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
in one direction.
The stroke length is determined by the cranks
Crank (mechanism)
A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to change circular into reciprocating motion, or reciprocating into circular motion. The arm may be a bent portion of the shaft, or a separate arm...
on the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
. Stroke can also refer to the distance the piston travels. Bore is the diameter of the cylinder, which means that engine displacement
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...
is dependent on both the bore and the stroke of the cylinder.
In a pistonless rotary engine
Pistonless rotary engine
A pistonless rotary engine is an internal combustion engine that does not use pistons in the way a reciprocating engine does, but instead uses one or more rotors, sometimes called rotary pistons...
, the term is applied to the corresponding rotor movement, see dead centre
Dead centre
In a reciprocating engine, the dead centre is the position of a piston in which it is farthest from, or nearest to, the crankshaft. The former is known as top dead centre while the latter is known as bottom dead centre ....
.
Four-stroke internal combustion engine
Most modern internal combustion engines work on a four-stroke cycle; that is, a complete cylinder cycle consists of four discrete strokes, as described below. Other types of engines can have very different stroke cycles.Induction stroke
The induction stroke is the first stroke in a four-stroke internal combustion engine cycle. It involves the downward movement of the pistonPiston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
, creating a partial vacuum that draws (allows atmospheric pressure to push) a fuel/air mixture into the combustion chamber.
In a reciprocating engine, that portion of the cycle when the pistons move from TDC (top dead center) to BDC (bottom dead center) and the fuel-air mixture is drawn into the cylinders.
Compression stroke
The compression stroke is the second of four stagesFour-stroke cycle
A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine's crankshaft, and one single thermodynamic cycle.There are two...
in an otto cycle
Otto cycle
An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....
or diesel cycle
Diesel cycle
The Diesel cycle is the thermodynamic cycle which approximates the pressure and volume of the combustion chamber of the Diesel engine, invented by Rudolph Diesel in 1897. It is assumed to have constant pressure during the first part of the "combustion" phase...
internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
.
In this stage, the mixture (in the case of an Otto engine) or air (in the case of a Diesel engine) is compressed
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
to the top of the cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
by the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
until it is either ignited by a spark plug
Spark plug
A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.Spark plugs have an insulated central electrode which is connected by...
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.
Solve for variable
Power stroke
A power stroke is, in general, the stroke of a cyclic motor which generates force. It is used in describing mechanical engines. This force is the result of the spark plug igniting the compressed fuel-air mixture.Exhaust stroke
The exhaust stroke is the fourth of four stages in a four strokeFour-stroke cycle
A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine's crankshaft, and one single thermodynamic cycle.There are two...
internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
cycle. In this stage gases remaining in the cylinder from the fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
ignited during the compression step are removed from the cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
through an exhaust valve
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
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
- Bore (engine)
- Compression ratioCompression ratioThe 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...
- Cylinder head portingCylinder head portingCylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve the quality and quantity of the air flow. Cylinder heads, as manufactured, are usually suboptimal due to design and manufacturing constraints...
- Reciprocating engineReciprocating engineA reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...
- Two-stroke cycleTwo-stroke cycleA two-stroke engine is an internal combustion engine that completes the process cycle in one revolution of the crankshaft...