How is Petrol Used in a Car Engine?

The Basics of Petrol

Petrol, also known as gasoline, is the most common type of fuel used in cars. It is a highly flammable liquid that is derived from crude oil. When petrol is burned, it releases energy that is used to power the car’s engine.

Petrol is made up of a mixture of hydrocarbons, which are molecules that contain hydrogen and carbon atoms. The most common hydrocarbon in petrol is octane, which has eight carbon atoms and 18 hydrogen atoms. The octane number of petrol is a measure of its resistance to knocking, which is a harmful condition that can occur when the petrol is ignited too early in the engine’s combustion cycle.

The Carburetor

The carburetor is a device that mixes petrol with air to create a combustible mixture. The mixture is then drawn into the engine’s cylinders, where it is ignited by the spark plugs.

The carburetor has a float bowl that contains a float that rises and falls with the level of petrol in the bowl. The float is connected to a needle valve that controls the flow of petrol into the bowl. When the float is low, the needle valve opens to allow more petrol to flow into the bowl. When the float is high, the needle valve closes to stop the flow of petrol.

The carburetor also has a venturi, which is a narrow section of the carburetor that increases the speed of the air flowing through it. The increased air speed creates a lower pressure in the venturi, which draws petrol from the float bowl and mixes it with the air.

The Fuel Injector

Fuel injectors are devices that spray petrol directly into the engine’s cylinders. They are more efficient than carburetors, as they allow for a more precise control of the fuel mixture.

Fuel injectors are controlled by the engine’s computer. The computer opens and closes the injectors at the appropriate times to ensure that the correct amount of petrol is injected into each cylinder.

The Combustion Cycle

The combustion cycle is the process by which petrol is burned in the engine’s cylinders to create power. The combustion cycle consists of four strokes:

1. Intake stroke: The intake valve opens and the piston moves down, drawing the air-fuel mixture into the cylinder.
2. Compression stroke: The intake valve closes and the piston moves up, compressing the air-fuel mixture.
3. Power stroke: The spark plug ignites the air-fuel mixture, causing it to burn and expand. The expanding gases push the piston down, creating power.
4. Exhaust stroke: The exhaust valve opens and the piston moves up, pushing the exhaust gases out of the cylinder.

The combustion cycle repeats itself continuously as the engine runs.

Conclusion

Petrol is an essential fuel for cars. It provides the energy that is needed to power the engine and drive the car. The carburetor and fuel injector are two important devices that are used to deliver petrol to the engine’s cylinders. The combustion cycle is the process by which petrol is burned in the cylinders to create power.