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The Four-Stroke Five-Event-Cycle Principle. During the intake or admission stroke, the piston moves downward as a charge of combustible fuel and air is admitted into the cylinder through the open intake valve. At the completion of this stroke the intake valve closes. This is event No. 1.
- Intake Or Induction
- Compression
- Power
- Exhaust
- Valve Operation
- Otto Cycle
- Cylinder Numbering and Firing Order
- Pre-Ignition and Detonation
The purpose of the intake or induction stroke is to draw a mixture of air and fuel into the cylinder. This stroke takes place with the piston moving down from TDC to BDC. The inlet valve must be open to allow the air-fuel mixture into the cylinder while the exhaust valve remains closed. The downward motion of the piston causes the pressure in the c...
As the name suggests, the purpose of the compression stroke is to compress the air-fuel mixture that has been sucked into the cylinder head before ignition takes place. This is accomplished by the piston moving upward from BDC towards TDC. The motion of the piston reduces the volume occupied by the mixture, causing the pressure and temperature to i...
The rapidly expanding gas ignited by the spark plug causes the pressure inside the cylinder to spike, forcing the piston back down from TDC to BDC. As the piston moves downward the increasing volume causes a reduction in pressure and temperature in the cylinder. It is this power stroke that forces the crankshaft to rotate, which ultimately drives t...
The exhaust valve opens just before the power stroke completes and remains open during the piston’s movement from BDC to TDC. The piston motion forces the exhaust gasses out through the open exhaust valve, clearing the cylinder before the intake stroke begins. This completes the cycle and the piston will start to move downward again as the inductio...
One fundamental property of all matter is that it possesses mass and therefore inertia. This means that just like a solid, the fuel-air mixture is subjected to Newton’s laws and requires a force to overcome its inertia and accelerate into the cylinder. This force comes from the pressure drop in the cylinder as the piston moves downward, but the mov...
The four-stroke cycle described above results in pressure and volume changes to the gas inside the cylinder as the piston moves up and down through the various strokes of the cycle. The thermodynamic representation of this cycle is referred to as the Otto Cycle named after German engineer Nikolaus Otto; the first person to build a working four-stro...
It is important to understand that the cylinders in any engine do not all complete the same part of cycle at the same time; rather they each fire in a particular sequence designed to keep the engine running smoothly and delivering continuous power to the propeller. Aircraft engine manufacturers will always label each cylinder on an engine and publi...
Pre-ignition and detonation are two separate but similar phenomena that result in the fuel-air charge igniting prematurely causing damage to the pistons and a loss in power. Pre-ignition:this refers to ignition of the fuel-air mixture before the spark plug fires and is caused by any source in the cylinder sufficiently hot to incite ignition. Common...
- Cycles of Operation. Before explaining about engine operating cycles, it is necessary to first define a few terms we will be using. ‘CYCLE’ refers to one complete sequence of operations required to produce power in an engine.
- The Four Stroke Cycle. As the name implies, this cycle of operation is completed once every four strokes of a piston, or once every two revolutions of the crankshaft.
- Induction: The cycle begins with the piston at Top Dead Centre in the cylinder. The inlet valve is open as the piston moves down within the cylinder. This downwards movement causes air to be drawn in through the open inlet valve.
- Compression: As the piston reaches the bottom of its stroke (bottom dead centre) the inlet valve is closed. As the exhaust valve is also closed, the volume of air above the piston is now trapped between the piston crown, the cylinder wall and the cylinder head.
The four-stroke cycle is a thermodynamic process used in internal combustion engines, which completes a power cycle in four distinct strokes: intake, compression, power, and exhaust. Each stroke corresponds to a specific movement of the piston within the cylinder, converting fuel into mechanical energy efficiently. This process is crucial for the functioning of piston engines, facilitating the ...
Four-Stroke Cycle. The vast majority of certified aircraft reciprocating engines operate on the four-stroke cycle, sometimes called the Otto cycle after its originator, a German physicist. The four-stroke cycle engine has many advantages for use in aircraft. One advantage is that it lends itself readily to high performance through supercharging ...
Apr 27, 2017 · The term, “four-stroke cycle” means that the engine needs to move the piston up or down the bore 4 times to complete all the functions that go into producing power from gasoline. Because the piston is connected to the crank via the connecting rod, each “stroke” takes a half revolution of the crank, or two full revolutions for the four necessary strokes.
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Sep 11, 2019 · The duration of the stroke is simply the time the piston takes to run from the bottom to the top of the cylinder or vice versa, half a rotation. So if the engine is running 2000 rpm, or 33.33 revolutions per second, or 16.66 strokes per second, the stroke duration is .06 seconds, half of one full revolution. That's the physical mechanical stroke.
