Working Of Four Stroke Diesel Engine.

Four stroke petrol engines simple means anengine which works on petrol fuel and produces power in two strokes. The figureshows the four strokes involved in it.

Main components of a four stroke engine:

1.   Cylinder
2.  Piston
3. Spark plug
4. Connecting rod
5. Crank shaft
6. Flywheel
7. FIP

Four strokes mentioned in the drawing

 Cylinder: It is marked in the figure; this is the space where the piston is reciprocating.

Piston: this is like a ram which is moving inside the cylinder as shown in the video.

Spark plug: this unit produces the spark for facilitating ignition or combustion.

Connecting rod: this is the part connecting piston with the crank shaft as shown in the video, the reciprocation of the piston inside the cylinder is converted to rotary motion of the crank shaft.

Crank shaft: this is the part which is linked to the flywheel; one of the most vital parts of an engine, crank shaft is responsible for carrying engine torque as rotational motion to the flywheel.

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FIP: fuel injection pump, this unit is supplying the correct amount of fuel to each cylinder.

Injector: this unit is injects the fuel pressured to the engine cylinder.

Working of four stroke petrol enginesexplained:

The cycle of events happening in a four stroke petrol engine is shown in the figure and also explained in the video.

So the various cycles of events are:

1. Suction
2. Compression
3. Ignition
4. Exhaust

As you all know the crank shaft rotation of 720 degrees is resulting in all the four strokes as shown above. That means 720 divided by 4 is 180 degrees, is one stroke. So in each stroke, the crank shaft rotates 180 degree.

Suction stroke: this is the first stroke in the series, as shown in the figure, this stroke the piston moves from TDC (top dead centre) to BDC (bottom dear centre). This involves the crank shaft rotation of 180 degrees. This creates suction due to the depression below the atmospheric pressure, as the piston drops (so it is also called naturally aspirated system). At this stroke the inlet valves will be in open and exhaust in closed condition.

Compression stroke: after the suction stroke the piston reaches 180 degree of complete rotation and this reaches the BDC. Now in the compression stroke the piston moves from 180 to 360 degree of full rotation and the piston moves form BDC to TDC resulting in the compression of the air fuel mixture. In this stroke the both valve will be in closed condition.

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Ignition stroke: at the end of the suction stroke the ignition takes place (it also called the combustion). The spark plug sparks and as the air fuel mixture is compressed it ignites and busts, releasing immense amount of pressure which pushed the piston down. In this stroke the piston moves from TDC to BDC, ie 360 to 540 degree of crank shaft rotation. This stroke, both the valve will be in closed condition.

Exhaust stroke: this is the fourth stroke. In this stroke the piston moves from BDC to TDC, which means from 540 – 720 degrees. At this stage the inlet valve will be in closed condition and exhaust will be in open condition.