Basic Working Principle 4-Stroke Marine Diesel Engine

ENGINE, Marine 4-Stroke Engine

In 1912 World First Ocean going Vessel name Selandia is Diesel 8 Cylinder Four Stroke Engine.

As the name suggest the four stroke Engine works on the four stroke means it requires the four stroke to complete one cycle.Because the engine is reciprocating, this means that the piston must move up and down the cylinder twice, and therefore the crankshaft must revolve twice.

The four strokes of the piston are known as the induction stroke, the compression stroke, the power stroke, and the exhaust stroke. Students sometimes remember this as “suck, squeeze, bang, blow.”

1. INDUCTION: The crankshaft is rotating clockwise and the piston is moving down the cylinder. The inlet valve is open and a fresh charge of air is being drawn or pushed into the cylinder by the turbocharger

2. COMPRESSION: The inlet valve has closed and the charge of air is being compressed by the piston as it moves up the cylinder. Because energy is being transferred into the air, its pressure and temperature increase. By the time the piston is approaching the top of the cylinder (known as Top Dead Centre or TDC) the pressure is over 100 bar and the temperature over 500°C

3. POWER: Just before TDC fuel is injected into the cylinder by the fuel injector. The  fuel is “atomised” into tiny droplets. Because they are very small these droplets heat up very quickly and start to burn as the piston passes over TDC. The expanding gas from the fuel burning in the oxygen forces the piston down the cylinder, turning the crankshaft. It is during this stroke that work energy is being put into the engine; during the other 3 strokes of the piston, the engine is having to do the work.

4. EXHAUST: As the piston approaches the bottom of the cylinder (known as Bottom Dead Centre or BDC) the exhaust valve starts to open. As the piston now moves up the cylinder, the hot gases (consisting mostly of nitrogen, carbon dioxide, water vapour and unused oxygen)  are expelled  from the cylinder.

As the Piston approaches TDC again the inlet valve starts to open and the cycle repeats itself

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