Internal Combustion: Engines 101
By Rafael Perez Vicente
August 29, 2022
For years internal combustion engines have been the only available option when it comes to private transportation means in society. In fact, in the United States alone, more than 250 million highway transportation vehicles use this mechanism. Their popularity mostly relies upon their durability and reliability as efficient transportation devices. Even other sectors of transportation use this method for buses, airplanes, or heavy machinery. Nevertheless, the vast majority of people owning an internal combustion automobile don´t understand the process behind the movement of their wheels.
As the name implies, internal combustion engines rely primarily on the chemical reaction of combustion to perform their practical functions. An engine will always be comprised of a set of sealed cylinders with a piston and at least a pair of valves to control the flow of gases. With combustion at these cylinder chambers, the engine transforms chemical energy into mechanical energy with the help of a crankshaft connected to the pistons, which rotates with energy generated by the combustion of gasoline.
The cylinder cycle and the piston's movement inside it may be divided into 4 strokes: intake, compression, combustion, and exhaust. In each of these, the piston moves upwards or downwards causing the rotation of the crankshaft.
During the intake stroke, one of the valves connected to the cylinder, known as the intake valve, opens; allowing the flow of a mixture of air and gasoline into the cylinder and pushing the piston down. In some old vehicles, this air/gasoline mixture was prepared in the carburetor. However, nowadays, fuel injection systems do this process without the need for a carburetor.
After the piston has been displaced downwards, the compression stroke begins by moving the piston back up and increasing the pressure of the air/gasoline mixture inside the cylinder. It is worth mentioning that at this point a difference may be noted between the engines, depending on the type of fuel that they use; since while gasoline engines rely on a spark that ignites the mixture and pushes the piston back down; diesel engines use pressure from the piston alone to ignite diesel and cause the combustion stroke.
Hence, after compression has been achieved, the combustion stage consumes gasoline and pushes the piston heavily back down. Finally, during exhaust, the second valve opens allowing the already fired mixture of gases to escape through the exhaust pipe into the air.
After knowing the basic principles behind their practical applications, it is worth noting that the basic unit known as a cylinder may be arranged in many different configurations in order to achieve different objectives. Cylinders may be arranged in-line, in a V shape, horizontally, radially, or even in a W shape. This gives engineers the possibility of building engines for compact cars, heavy machinery, race cars, or even motorcycles.
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