A four-stroke engine operates through a series of four distinct strokes, each driven by the movement of the piston within a cylinder. These strokes are:
1. Intake Stroke:
* What happens: The piston moves downwards, creating a vacuum in the cylinder.
* Purpose: This draws in a mixture of air and fuel (in gasoline engines) or just air (in diesel engines) through the intake valve.
2. Compression Stroke:
* What happens: The piston moves upwards, compressing the air-fuel mixture (or air in diesel engines).
* Purpose: This increases the temperature and pressure of the mixture, preparing it for combustion.
3. Power Stroke:
* What happens: The spark plug ignites the compressed air-fuel mixture (or the fuel is injected and ignited by high temperature and pressure in diesel engines). This rapid expansion of hot gases drives the piston downwards, creating the engine's power.
* Purpose: This is the stroke that produces the force that drives the crankshaft and ultimately powers the vehicle.
4. Exhaust Stroke:
* What happens: The piston moves upwards, pushing the burnt gases out of the cylinder through the exhaust valve.
* Purpose: This clears the cylinder for the next intake stroke.
The Cycle Repeats:
These four strokes form a continuous cycle, repeating over and over again as long as the engine is running. Each complete cycle generates one power stroke, creating the engine's power output.
Key Components:
* Piston: A cylindrical component that moves up and down within the cylinder, driven by the combustion process.
* Cylinder: A cylindrical chamber that houses the piston and where the combustion process occurs.
* Crankshaft: A rotating shaft that converts the linear motion of the piston into rotational motion.
* Connecting Rod: Connects the piston to the crankshaft, transmitting the force from the piston to the crankshaft.
* Intake Valve: Opens during the intake stroke to allow air and fuel (or air in diesel engines) into the cylinder.
* Exhaust Valve: Opens during the exhaust stroke to allow the burnt gases to exit the cylinder.
* Spark Plug: Ignites the air-fuel mixture in gasoline engines.
* Fuel Injector: Injects fuel into the cylinder in diesel engines.
Variations:
While this is a general explanation of the 4-stroke cycle, there are various design variations and technologies applied to different types of engines. For example, different fuel delivery systems, valve timing mechanisms, and combustion chamber shapes contribute to varying engine performance and efficiency.
In Summary: The 4-stroke cycle is a fundamental principle of internal combustion engines, converting fuel energy into mechanical power through a series of precise piston movements and controlled combustion. It is a complex yet efficient process that powers numerous vehicles and machinery around the world.
