Engine Structure & Operating Principle

The internal combustion engine acts as the power unit and is widely used in vehicle & construction machinery. Because fuel is burned inside the engine cylinder, the engine is called an IC engine. There are two types of engines: a gasoline engine ( also called a SI engine) & diesel engine(also called a CI engine). 

Both engines are called heat engines. The burning fuel generates heat which causes the gas inside the cylinder to increase its pressure & supply power to rotate the crankshaft connected to the power train by the pistons attached to the crankshafts.

The most common engine is the four-stroke engine. “Stroke” refers to piston movement --- a stroke occurs when the piston moves from one limiting position to the other. The upper limit of piston movement is called TDC( Top Dead Center). The lower limit of piston movement is called BDC( Bottom Dead Center). A stroke is piston movement from TDC to BDC or from BDC to TDC. In other words, the piston completes a stroke each time it changes its direction of motion. Where the entire cycle of events in the cylinder requires four strokes (or two crankshaft revolutions), the engine is called a four-stroke-cycle engine. These four piston strokes are intake stroke, compression stroke, power stroke & exhaust stroke. The four strokes are continuously repeated in every cylinder as long the engine remains running.

Structure Of An Engine

The engine has hundreds of other parts. The major parts of the engine are the engine block, cylinder, engine heads(cylinder heads), pistons, connecting rods, crankshaft, camshaft, valves, fuel pump & fuel nozzle. The other parts are joined to make systems. These systems are the fuel system and ignition system. (gasoline engine only), lubricating system, cooling system & starting system. Each of these systems has a definite function.

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