What Is a Piston?
Pistons are one of the key components inside an engine that converts the combustion energy of fuel into mechanical power.
There are two types of engines: reciprocating engines and rotary engines. Pistons move up and down inside a cylindrical part called a cylinder to produce the engine’s power, which is the driving force that makes the car run.
Pistons are also used not only in automobile engines but also in engines for motorcycles, ships, and aircraft.
Uses of Pistons
Pistons are mainly used in engines, compressors, air compressors, and other equipment. These devices use a mechanism in which the pistons move up and down to generate power through thermodynamic changes, such as compression and expansion.
In an engine, the combustion energy of fuel is converted into mechanical power by the movement of the Pistons, and this power is transmitted to the drive wheels of the car via a component called the crankshaft. Air compressors and compressors also use the movement of pistons to compress gas and use the energy to generate power.
The number of pistons varies depending on the application, but the four-cylinder engine, which consists of four pistons, is widely used in standard passenger cars. These Pistons move back and forth inside a cylinder, which is called a cylinder, at more than 1,000 revolutions per minute. It is also called the heart of the car because it is a necessary device for generating the car’s power.
Principle of Pistons
The principle of piston movement is that, in the case of an engine, the high pressure generated by the combustion of fuel causes the pistons to move up and down inside the cylinder. This movement is accomplished by repeating four motions (intake, compression, expansion, and exhaust).
1. Intake
This is the process of drawing air and fuel into the cylinder for compression. As the pistons descend, a negative pressure is created in the cylinder and the intake valves open, bringing in a mixture of air and fuel.
2. Compression
This is the process of the pistons rising and compressing the air-fuel mixture. With the intake and exhaust valves closed, the rising pistons compress the air-fuel mixture in the cylinder and raise its temperature.
3. Expansion (Combustion)
This is the process in which the spark plug sparks the compressed air mixture and causes it to burn. The hot, high-pressure gas generated by the combustion exerts a downward force on the Pistons, causing them to move downward. This movement generates power in the engine.
4. Exhaust
This is the process of exhausting the exhaust gases from the cylinder after combustion. The pistons rise again and the exhaust valves open to expel the post-combustion gases out of the cylinder.
The repetition of these processes causes the pistons to move up and down, producing power from the engine.
Structure of Pistons
Pistons are generally cylindrical metal parts, made primarily of materials such as aluminum alloys and cast iron. The main components of pistons are as follows:
Pistons are the heart of an engine, and their performance and durability greatly affect the performance and fuel economy of an automobile, so proper maintenance and replacement of parts is important.
1. Pistons Head
The piston head is the part of the cylinder where combustion takes place. It has a sturdy structure to withstand the pressure of the compressed air mixture and combustion gases.
2. Piston Rings
They fill the gap between the pistons and the cylinder, preventing gas leakage and ensuring proper distribution of lubricating oil. There are usually two types: compression rings and oil rings.
3. Piston Skirt
Located at the bottom of the pistons, it serves to support the steady movement of the pistons within the cylinder.
4. Piston Pins
The pistons are connected to the connecting rods (the parts that connect the crankshaft to the pistons) and transmit the movement of the pistons to the crankshaft.