Automobile diesel engine

Understanding diesel engine

The diesel engine is one of the most effective and powerful engines when compared to that of a gasoline engine. Though it is the continuation of a gasoline engine. So, what are the things to know about the diesel engine?

diesel engine

The diesel engine is an internal combustion engine in which the ignition of fuel is caused by the rising temperature of the air in the cylinder due to the mechanical compression called “adiabatic compression”. Let’s get into details…

Unlike spark-ignition engines such as gasoline engines (petrol engines) that use a spark plug to ignite the air-fuel mixture. It totally differs from diesel engines. Diesel engines work by compressing only air in the cylinder, which increases to an elevated temperature (hot air), and atomizes the diesel fuel injected into the combustion chamber, causing the ignition spontaneously. These engines work with a heterogeneous air-fuel mixture. That is, the injected fuel into the air before combustion dispersed unevenly. The torque a diesel engine produces is controlled by manipulating the air-fuel ratio (λ); instead of throttling the intake air, the diesel engine relies on altering the amount of fuel that is injected, and the air-fuel ratio is usually high.

The diesel engine is also known as a compression-ignition or CI engine, named after the founder Rudolf Diesel. Rudolf Diesel was a student of Polytctechnikum in Munich, where he attended the lectures of Carl von Linden. Carl examined a steam engine and said steam engines are capable of converting just 6-10% of the heat energy into work, but the Carnot cycle has the ability to convert much more heat energy into work by means of isothermal change in condition.

These ideas built momentum on Diesel for creating a highly efficient engine that could work on the Carnot cycle. He was also exposed to a fire piston, a traditional fire starter using rapid adiabatic compression principles which Linde had acquired from Southeast Asia. After several years of working on his ideas, Diesel published them in 1893 in the essay Theory and Construction of a Rational Heat Motor.

The diesel engine exists as the engine with the highest thermal efficiency either with the internal or external combustion engine. This occurs due to the very high expansion ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared with non-direct-injection gasoline engines since unburned fuel is not present during valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Diesel engines have been applicable since the 1910s in ships and Submarines, locomotives, trucks, heavy equipment, electricity generation plants, etc.


Parts of a diesel engine


The block is where all the parts for the basic internal combustion process are contained. The block has an open space for each cylinder, where the combustion happens.


The pistons create the bottom of the combustion chamber, they move up and down in the cylinder while the engine is working. The movement creates the compression of the air which leads to combustion.

Cylinder head

The cylinder head closes the top of the open space in the block to reach the chamber where combustion happens.

Fuel Injector

The fuel injector gets fuel inside the cylinder in order to combust. It sprays fuel in very precise patterns with highly controlled timing.


The valves help in allowing fresh air in and the leftover gasses out. There are usually two valves for taking in air and two for the exhaust for each cylinder.


The crankshaft transfers the up-and-down part of the combustion process into a rotational motion.

Connecting rod

These connects to a piston at the bottom arm and carry the force of the combustion to the crankshaft.


The camshaft’s revolutions control the timing of opening valves and fuel injection by lobes on the shaft that set them into motion.

Diagram of the diesel engine:

diesel engine parts

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That is all for this article, that’s all for this article where we discussed about the diesel engines. Hope it was helpful. If so, kindly share. Thanks for reading.


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