Your guide to the Diesel Engine

In one of our first articles we went over 5 amazing facts about diesel fuel. In today’s article we will be continuing where we left off as we go into the specifications of the diesel engine. What makes them different from standard gasoline engines, and what role they play on the current economy. It’s not privileged information to know that there are a great many industrial vehicles and equipment that use diesel engines and fuel as a main source of functionality. Why is it that we use two different engines in our economy?

Diesel and gasoline engines are a lot more a lot more alike than you would think. Theoretically they function the same; they both combust chemical energy fro fuel. they both turn that energy into mechanical energy by moving pistons within a cylinder. This repetitive circular motion is what causes your wheels to move your vehicle forward. The difference in these engines is not their function exactly, but rather the way the fuel is combusted and how oxygen is involved.

Diesel Engine, Diesel fuel

For gasoline engines, air and fuel are injected into the combustion chamber together . Then they are both pressurized, finally  the fuels are ignited by the spark plug to cause the reaction. In diesel engines, the air is pressurized in the chamber before fuel is injected. As air temperature rises with pressure once the pressure threshold is reached a combustion is achieved and all the benefits that come with it.

The diesel engine differs in other ways as well, cylinders are larger to capture  more air to be combusted. Because the temperature of air must reach a critical level for combustions to take place sometimes in colder weather it gets difficult to reach an appropriate level. Combustion engines contain what is known as a “glow plug”. These heating wires keep the combustion chamber at an appropriate temperature during the cold seasons when starting a diesel engine would fail from a Cold Start.

In a standard gasoline engine, the combustion process is as follows.

  1. Intake stroke- Fuel is introduced to air
  2. Compression stroke- piston moves up, then air and fuel mixture are compressed
  3. Ignition Stroke- Fuel/air is ignited with a spark plug
  4. Exhaust stroke- piston goes up pushes exhaust through exit valve

In diesel engines the four strokes are still the same, however the introduction of fuel is delayed.

  1. Intake stroke- intake valve opens only air is entered in the chamber
  2. Compression stroke- Piston moves to compress air heats it more than 540°C
  3. Combustion stroke- fuel is injected into the chamber and introduced into the super-heated air causing a combustion of the materials
  4. Exhaust stroke. Exhaust is ejected through the exhaust valve as the piston goes up.
Diesel Engine, Diesel fuel
Image credit NCH Europe and Re: Solutions Link

These mechanical differences are not the only thing separating the 2 engine types. The fuel itself plays a large part into the differences between the two engines. Diesel fuel still has the bones of dinosaurs floating in it. Its simply that regular unleaded gasoline has a significantly lower combustible temperature than diesel. Fuel is added much later in the combustion cycle for diesel fuel, during the 2nd rotation fuel is introduced to produce a combustion that will complete the rotation and ensure energy is getting to your tires.

Created by Rudolf Diesel (where diesel gets its name from) the Diesel engine is a fascinating system of heat and moving parts that has revolutionized the landscape of the civilized modern world. Diesel accounted for about 21% of the petroleum fuels consumed by the United states and that number is expected to rise in 2018 and 2019. If you have enjoyed this, please consider subscribing for more about the fuel industry.



-The SC Fuels team

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