How do Diesel Engines Work?

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Today, diesel engines are used in both heavy-duty vehicles and family cars. Why do many prefer this fuel over benzine? How does a diesel engine work?

In general terms, it can be said that a diesel engine works differently from a gasoline engine, despite sharing main components and both running on a four-stroke cycle. The main differences are the ignition of the fuel and the regulation of the output power.

To begin, we will locate the origin of diesel engines. These were developed by the engineer Rudolf Diesel in the year 1893. Diesel worked for MAN, a company that already manufactured high-powered engines to move large vehicles. And from that idea arose the need to create a motor with higher thermal performance. Finally, the explosion of one of its experimental engines caused severe injuries to the engineer and his assistants. Luckily, the work continued and paid off.

The experiments were not easy and were even close to cost him his life, but in 1897 MAN produced the first diesel engine powered by fuel oil, a low-volatile fuel commonly used in street lamps and heating.

Already in 1927, Bosch created the injection pump for diesel engines, thereby allowing the manufacture of internal combustion engines with lower consumption and cheaper fuel, which also had a compression ratio higher than that of those of gasoline and with the capacity to work at temperatures close to 900 ºC.

Diesel engines are also considered to be more durable when working at a lower speed, being, therefore, indicated to cover large amounts of kilometers.

Diesel Engine Operation – Diesel Cycle

The diesel engine shares most of the mechanics with those of gasoline, although it works differently. It works in four stages, just like those, but the way to produce diesel combustion is different, and in this lies its difference.

This is how the Diesel cycle works:

  • Intake: In this first time the intake valve opens, allowing air to pass and moving the piston down. The piston travel takes it to the lowest part, allowing the entire space to fill with air.
  • Compression: In the second time, the piston rises again, and its action causes the air to compress. Its temperature increases, preparing the arrival of the fuel, which is responsible for operating the engine.
  • Combustion: As the air is compressed, and at a specific moment, the injection of the pulverized fuel takes place, which, when it comes into contact with the compressed air, increases its temperature until reaching between 700 and 900 degrees Celsius, ignites and makes that the piston goes down.
  • Exhaust: The combustion of the fuel causes the residual gases to appear, which are evacuated from the engine through the exhaust valve. The re-entering air pushes them through it, leaving the space clean and ready to start the cycle again. The gases pass into the exhaust, where the filters treat that the diesel vehicle equips to prevent polluting gases from reaching the atmosphere.

This type of engine has no spark since combustion occurs by contacting the pulverized fuel with the compressed air, making it a much more efficient engine than the way to produce that explosion in a gasoline engine. Of course, it requires that the walls of the motor be thicker and stronger, but it also has to have several elements to produce adequate pressure for its operation.

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Lubricating oil for diesel engines

Because the diesel engine works this way, the lubricating oil required to maintain ideal operating temperatures is different. When injected, the fuel cools the walls of the cylinders, so we cannot allow it to fall below the engine’s ideal operating temperature. Otherwise, combustion would be complicated by compression.

The effort required by a diesel engine is more focused on torque, drag, and load. At more significant effort, it requires a lubricating oil that protects the engine components from the effort they make while allowing combustion in the engine.

Therefore, the oil in a diesel engine is thick and requires a higher starting warm-up than a gasoline engine. To cool the engine, we must rely more on the truck’s engine cooling system, rather than on the lubricating oil.

More thermal efficiency, but more air pollution

Fuel is cheaper, and its efficiency is better than that of gasoline. The diesel engine works at lower revs and therefore, can have a longer life. It requires less maintenance, although breakdowns are more expensive to repair.

Plus, we all know what’s going on with diesel engines. Pollution is higher and is causing many cities to consider banning diesel-powered cars. Unless, you get specific types of high performance diesel like Sinister Diesel to cut down on fuel.

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Gasoline engine vs. diesel engine

The main difference between a gasoline and a diesel engine is fuel. Diesel engines were originally built to be used with the same fuel used for street lighting, a heavier and more economical fuel than gasoline. This was confirmed as a more efficient fuel for heavy transport and soon for smaller, more popular cars. It is less refined than gas and emits more impurities after combustion.

Diesel has always been considered a cheaper fuel with a more effective performance per liter than gasoline. Although, when talking about prices, we must not forget that diesel vehicles are more expensive when purchased on the market and more costly to maintain.

Even though pollution levels are always higher in a diesel engine, (even with EGR, particle filters, catalysts), more technologies are developed around these than gasoline ones gives them more output and reputation, so that their sales have been increasing until exceeding them.

In particular, the acquisition of a diesel motor vehicle is recommended compared to a gasoline one when we plan to travel many kilometers. The difference in fuel consumption compensates and because they tend to be more durable engines since they suffer less wear and tear when driving at low revolutions.

Most common applications of diesel engines

  • Four-stroke heavy or agricultural machinery, cargo trucks, short and long-distance buses
  • Tourism and competition cars, commercial and industrial vehicles
  • Railway propulsion
  • Crawler Powered Vehicles
  • Electric power generating groups (power and emergency plants)
  • Industrial drive (motor pumps, compressors, stationary motors, etc.)

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