diesel engine

Introduction
Diesel combustion
Major types of diesel engines
- Three basic size groups
- Two-stroke and four-stroke engines
Fuel for diesels
Development of diesel engines
- Early work
- Fuel-injection technology
- Price’s engine
- Subsequent developments and applications

References & Edit History Quick Facts & Related Topics

Images

Diagram showing the four-stroke cycle of a typical diesel engine, with labeled stages: intake (air enters), compression (air is compressed), power (fuel ignites and pushes piston down), and exhaust (gases exit).

At a Glance

diesel engine summary

Related Questions

How did Adolphus Busch help introduce diesel engines in the United States and Canada?
How did Rudolf Diesel’s 1897 engine demonstration contribute to the engine’s commercial success?
How did diesel locomotives improve operating efficiency compared with steam locomotives?
How did the common-rail fuel-injection method work in early diesel engines?
How do aftercoolers improve diesel engine performance?
How do air swirl and squish improve combustion in a diesel engine?
How do intake and exhaust ports simplify the design of a two-stroke diesel engine?
How do turbochargers increase the power and efficiency of diesel engines?
How does a catalytic converter reduce harmful engine exhaust emissions?
How does a diesel-electric locomotive turn diesel engine power into motion?
How does a diesel engine ignite fuel without spark plugs?
How does air compression heat the air enough to ignite diesel fuel?
How does an electric starter motor start a diesel engine?
How does fuel injection timing affect diesel engine performance?
How does hydraulic transmission transfer power in a diesel locomotive?
How does the diesel cycle differ from the Otto cycle?
How was a diesel engine demonstrated using peanut oil at the 1900 Paris World’s Fair?
What compression ratios are typical in diesel engines?
What fuels did Rudolf Diesel first consider for his engine?
What is the difference between direct injection and precombustion-chamber injection in diesel engines?
What jobs are medium-size diesel engines mainly used for?
What types of vehicles and machines commonly use small diesel engines?
When is fuel injected into a diesel engine cylinder?
Where is mechanical transmission mainly used in diesel locomotives and railcars?
Where was the first commercial engine built using Rudolf Diesel’s patents installed?
Who invented the diesel engine?
Why are diesel engines generally heavier and more expensive than gasoline engines of the same horsepower?
Why are diesel engines often more fuel-efficient at idle and reduced power than gasoline engines?
Why are large diesel engines used in ships and locomotives?
Why are nitrogen oxides produced by diesel engines a pollution concern?
Why can diesel engines achieve higher compression ratios than gasoline engines?
Why can diesel engines be difficult to start in cold conditions?
Why did common-rail direct-injection technology increase interest in diesel passenger cars in Europe during the late 1990s?
Why did diesel engines become important for submarines during World War I?
Why did diesel engines become widely used in heavy trucks buses tractors and construction machinery?
Why did diesel-powered cars become popular in Europe after World War II?
Why do diesel engines produce particulate matter called soot?
Why is rapid mixing of fuel and air important in diesel combustion?
Why must diesel fuel be injected at high pressure?
Why was diesel fuel safer to store and handle on submarines than gasoline?
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What is a supercritical carbon dioxide turbine?
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How does a supercritical carbon dioxide turbine compare to a steam turbine?
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How was the aeolipile adapted in later centuries?
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Are Wankel engines still in use?

Technology Engineering Mechanical Engineering

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External Websites

BBC News - How Rudolf Diesel's engine changed the world
National Center for Biotechnology Information - PubMed Central - Diesel exhaust: current knowledge of adverse effects and underlying cellular mechanisms
IOPscience - Journal of Physics: Conference Series - Numerical Study of Diesel Engine with Different Injection Strategies
Indian Academy of Sciences - The Evolution of Diesel Engines

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Articles from Britannica Encyclopedias for elementary and high school students.

diesel engine - Student Encyclopedia (Ages 11 and up)

diesel engine

technology

Also known as: compression-ignition engine

Written by

Charles Lafayette Proctor

Engineer-of-Record, Proctor Engineering Research & Consulting, Inc., Alachua, Florida.

Charles Lafayette ProctorAll

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Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

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Last updated

Oct. 14, 2026 •History

diesel engine, any internal-combustion engine in which air is compressed to a sufficiently high temperature to ignite diesel fuel injected into the cylinder, where combustion and expansion actuate a piston. It converts the chemical energy stored in the fuel into mechanical energy, which can be used to power freight trucks, large tractors, locomotives, and marine vessels. A limited number of automobiles also are diesel-powered, as are some electric-power generator sets. The diesel engine is an...

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