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How Does a Diesel Engine Work

Luc Viator model diesel (Wikimedia)

For many, the operation of a diesel engine appears exactly the same as that of a gasoline engine. The two are similar in that they are both combustion engines, so they have many parts in common. The major difference between a diesel and gasoline engine is in the way the fuel is burned in the cylinder.

This seemingly small difference is what makes the two engines very different in operation, however, and is the reason that a diesel-burning engine is generally more robust and longer-lived than is its gasoline counterpart.

How Diesel Engines Work

Diesel engines burn fuel through heat whereas a gasoline engine does so with spark. Air is sent into the cylinder and compressed by the piston. When it is at its apex of compression (and thus heat), diesel fuel is injected into the chamber and ignites under the heat.

The ignition pushes the piston back down, continuing the turn of the crankshaft and compressing the next chamber in line.

Because of the heavy pressures in the cylinders, components in and around them are built to be more robust than their gasoline counterparts. This makes diesel engines heavier than gasoline engines in most applications. It also means the engines are generally longer-lived and have fewer maintenance needs by comparison, so while up-front costs are higher, lifetime costs are usually lower.

Another great advantage of diesel is volatility. Diesel is not easily combusted - a puddle of it can have a burning match thrown in and not ignite. This makes it safer to deliver and store compared to gasoline.

History of Diesel Engines

In the early days of combustion engine technology, diesel engines were very simple and inefficient by today's standards. The first engines were produced to run on vegetable oil as a replacement for steam engines, which were horribly inefficient and often dangerous.

Petroleum was not yet in use as a fuel source for most things, so alternatives to steam were limited. Because vegetable oils (and waste) were so common, the idea of using them as a fuel source had potential.

As time went on, despite being largely displaced by gasoline before it had even taken hold in automotive, diesel remained an engine option of choice for many applications requiring high torque outputs at steady RPM.

Eventually, diesel was combined with other technologies (notably electricity in hybrid configurations) and became the commercial transportation fuel of choice worldwide. Because the distillery process is simpler and the source for the fuel (outside of petroleum) is universally common, diesel engine development continued through to today.

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