Work of engine could be grouped under four parts: inlet of Air-Fuel Mixture, Compression, Ignition of Fuel, Exhaust. These four parts are operating cycles.
What is Operating cycle?
Operating cycle of engine is assembly of processes, it repeats in timely manner in certainly sequence. The result of this processes are work of engine. If operating cycle makes for 2 crankshaft rotation is four-stroke engine. If operating cycle makes for one crankshaft rotation is two-stroke engine.
- Inlet of Air-Fuel Mixture: the mixture enters through Intake valve. This is called as Inlet Stroke. In this stroke, the piston travels from top to bottom or generally written as from TDC (Top Dead Center) to BDC (Bottom Dead Center).
2. Compression Stroke: Now, when the chamber is filled with mixture, the intake valve gets closed and the piston starts traveling from BDC-TDC. This Stroke is called as Compression Stroke. Here in this stroke the mixture is compressed inside the chamber and hence is pressurized leading to increase in temperature. Both the valves are kept closed (as adjusted during valve timing).
3. Ignition/Burning of Fuel: Then it comes to take power out of the mixture, now the mixture just before the end of compression stroke is ignited with the help of a spark plug (only in case of Petrol Engines) provided at the top of chamber which gives spark to the mixture and hence power is taken from the source. This stroke is known as Power Stroke.
4. Exhaust: The burned mixture produces flue gasses inside the chamber and are needed to be removed. This is called Exhaust stroke and at this time the exhaust valve is opened to allow the high pressure flue gasses to move out of chamber.