Diesel Engine

Diesel engine inventor

Rudolf Diesel                                                                           

Occupation: Engineer

Known For: Inventor of the Diesel engine

Born: March 18, 1858, in Paris, France

Parents: Theodor Diesel and Elise Strobel

Died: September 29 or 30, 1913, in the English Channel

Education: Technische Hochschule (Technical High School), Munich, Germany; Industrial School of Augsburg, Royal Bavarian Polytechnic of Munich (Polytechnic Institute)

Published Works: “Theorie und Konstruktion eines rationellen Wäremotors” (“Theory and Construction of a Rational Heat Motor”), 1893

Spouse: Martha Flasche (m. 1883)

Children: Rudolf, Jr. (b. 1883), Heddy (b. 1885), and Eugen (b. 1889)

Diesel engine

“Diesel saw his engine as a tool that was adaptable in size and cost, but also able to use available fuels,” Stein wrote. “It would allow independent craftsmen to avoid having to use expensive, fuel-wasting steam engines. It would help the small businessman try to beat out the big companies.”

Internal combustion engine

The diesel engine (also known as a compression-ignition or CI engine), named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel, which is injected into the combustion chamber, is caused by the elevated temperature of the air in the cylinder due to the mechanical compression (adiabatic compression). Diesel engines work by compressing only the air. This increases the air temperature inside the cylinder to such a high degree that atomised diesel fuel injected into the combustion chamber ignites spontaneously. This contrasts with spark-ignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to petrol), which use a spark plug to ignite an air-fuel mixture. In diesel engines, glow plugs (combustion chamber pre-warmers) may be used to aid starting in cold weather, or when the engine uses a lower compression-ratio, or both. The original diesel engine operates on the “constant pressure” cycle of gradual combustion and produces no audible knock.  

External combustion engine

An external combustion engine (EC engine) is a heat engine where a working fluid, contained internally, is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work.The fluid is then cooled, compressed and reused (closed cycle), or dumped (open cycle). In these types of engine, the combustion is primarily used as a heat source, and the engine can work equally well with other types of heat source.


“Combustion” refers to burning fuel with an oxidizer, to supply the heat. Engines of similar (or even identical) configuration and operation may use a supply of heat from other sources such as nuclear, solar, geothermal or exothermic reactions not involving combustion; they are not then strictly classed as external combustion engines, but as external thermal engines.

Working fluid

The working fluid can be of any composition and the system may be single phase (liquid only or gas only) or dual phase (liquid/gas).

Single phase

Gas is used in a Stirling engine. Single-phase liquid may sometimes be used.

Dual phase

Dual-phase external combustion engines use a phase transition to convert temperature to usable work, for example from liquid to (generally much larger) gas. This type of engine follows variants of the Rankine cycle. Steam engines are a common example of dual-phase engines. Another example is engines that use the Organic Rankine cycle.

Diesel engine efficiency

The diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high expansion ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared to two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) can have a thermal efficiency that exceeds 50%; it can reach up to as high as 55%.

Diesel engines may be designed as either two-stroke or four-stroke cycles. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, trucks, heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s, the use of diesel engines in larger on-road and off-road vehicles in the US increased. According to the British Society of Motor Manufacturing and Traders, the EU average for diesel cars accounts for 50% of the total sold, including 70% in France and 38% in the UK.

diesel engine parts

Let’s look at some key engine parts in more detail.

Spark plug

The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.


The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.


A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston Rings

Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

  • They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.
  • They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Most cars that “burn oil” and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly. Many modern vehicles use more advance materials for piston rings. That’s one of the reasons why engines last longer and can go longer between oil changes.

Connecting rod

The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.


The crankshaft turns the piston’s up-and-down motion into circular motion just like a crank on a jack-in-the-box does.

Oil pump

The oil pump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the pump (the oil pan).

Types of diesel engine




A four stroke cycle diesel engine produces power in 4 piston stroke and in two crankshaft revolution.


A 2 stroke cycle diesel engine produces power in two piston stroke and in one crankshaft revolution. engineering.

Diesel cycle

The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected. This is in contrast to igniting the fuel-air mixture with a spark plug as in the Otto cycle (four-stroke/petrol) engine. Diesel engines are used in aircraft, automobiles, power generation, diesel-electric locomotives, and both surface ships and submarines.

Otto cycle

The Diesel cycle is assumed to have constant pressure during the initial part of the combustion phase display style V2 to display style V3 in the diagram, below. This is an idealized mathematical model: real physical diesels do have an increase in pressure during this period, but it is less pronounced than in the Otto cycle. In contrast, the idealized Otto cycle of a gasoline engine approximates a constant volume process during that phase.

Brayton cycle

The Brayton cycle is a thermodynamic cycle named after George Brayton that describes the workings of a constant-pressure heat engine. The original Brayton cycle engines used a piston compressor and piston expander, but more modern gas turbine engines and airbreathing jet engines also follow the Brayton cycle.

Rankine cycle

DescriptionThe Rankine cycle is a model used to predict the performance of steam turbine systems. It was also used to study the performance of reciprocating steam engines. The Rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into mechanical work while undergoing phase change.

About Zaighum Shah 90 Articles
Zaighum Shah is a mechanical engineer having more than 20 years of experience. Zaighum is specializing in product development in Sugar Mill industries. Zaighum has gone through all phases of mechanical engineering and it’s practical implementation. Zaighum has been solving most complex problems, designing new systems and improving existing models and systems.