Engine

An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.[1][2]

Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power generation), heat energy (e.g. geothermal), chemical energy, electric potential and nuclear energy (from nuclear fission or nuclear fusion). Many of these processes generate heat as an intermediate energy form; thus heat engines have special importance. Some natural processes, such as atmospheric convection cells convert environmental heat into motion (e.g. in the form of rising air currents). Mechanical energy is of particular importance in transportation, but also plays a role in many industrial processes such as cutting, grinding, crushing, and mixing.

Mechanical heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a mechanical heat engine in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft. Unlike internal combustion engines, a reaction engine (such as a jet engine) produces thrust by expelling reaction mass, in accordance with Newton's third law of motion.

Apart from heat engines, electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion (a chemical engine, but not a heat engine).

Chemical heat engines which employ air (ambient atmospheric gas) as a part of the fuel reaction are regarded as airbreathing engines. Chemical heat engines designed to operate outside of Earth's atmosphere (e.g. rockets, deeply submerged submarines) need to carry an additional fuel component called the oxidizer (although there exist super-oxidizers suitable for use in rockets, such as fluorine, a more powerful oxidant than oxygen itself); or the application needs to obtain heat by non-chemical means, such as by means of nuclear reactions.

## Contents

* 1 Emission and byproducts
* 2 Terminology
* 3 History
* 3.1 Antiquity
* 3.2 Medieval
* 3.3 Industrial Revolution
* 3.4 Automobiles
* 3.4.1 Horizontally-opposed pistons
* 3.4.2 Advancement
* 3.4.3 Increasing power
* 3.4.4 Combustion efficiency
* 3.4.5 Engine configuration
* 4 Types
* 4.1 Heat engine
* 4.1.1 Combustion engine
* 4.1.2 Internal combustion engine
* 4.1.3 External combustion engine
* 4.1.4 Air-breathing combustion engines
* 4.1.5 Environmental effects
* 4.1.6 Air quality
* 4.1.7 Non-combusting heat engines
* 4.2 Non-thermal chemically powered motor
* 4.3 Electric motor
* 4.4 Physically powered motor
* 4.4.1 Pneumatic motor
* 4.4.2 Hydraulic motor
* 4.4.3 Hybrid
* 5 Performance
* 5.1 Speed
* 5.2 Thrust
* 5.3 Torque
* 5.4 Power
* 5.5 Efficiency
* 5.6 Sound levels
* 6 Engines by use
* 7 See also
* 8 References
* 8.1 Citations
* 8.2 Sources
* 9 External links

## Emission and byproducts

All chemically fueled heat engines emit exhaust gases. The cleanest engines emit only water. Strict zero-emissions generally means zero emissions other than water and water vapour. Only heat engines which combust pure hydrogen (fuel) and pure oxygen (oxidizer) achieve zero-emission by a strict definition (in practice, some rocket engines). If hydrogen is burnt in combination with air (all airbreathing engines), a side reaction between atmospheric oxygen and atmospheric nitrogen produces small amounts of NO
x . If a hydrocarbon (such as alcohol or gasoline) is burnt as fuel, CO
2, a greenhouse gas, is emitted. Hydrogen and oxygen can also be made to react and form water in a fuel cell without producing NO
x , but a fuel cell is a type of electrochemical device, not a heat engine.[3]

## Terminology

The word engine derives from Old French Lua error in Module:Language at line 197: Name for the language code "fro" could not be retrieved with mw.language.fetchLanguageName, so it should be added to Module:Language/data., from the Latin ingenium–the root of the word ingenious. Pre-industrial weapons of war, such as catapults, trebuchets and battering rams, were called siege engines, and knowledge of how to construct them was often treated as a military secret. The word gin, as in cotton gin, is short for engine. Most mechanical devices invented during the Industrial Revolution were described as engines—the steam engine being a notable example. However, the original steam engines, such as those by Thomas Savery, were not mechanical engines but pumps. In this manner, a fire engine in its original form was merely a water pump, with the engine being transported to the fire by horses.[4]

In modern usage, the term engine typically describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform mechanical work by exerting a torque or linear force (usually in the form of thrust). Devices converting heat energy into motion are commonly referred to simply as engines.[5] Examples of engines which exert a torque include the familiar automobile gasoline and diesel engines, as well as turboshafts. Examples of engines which produce thrust include turbofans and rockets.

When the internal combustion engine was invented, the term motor was initially used to distinguish it from the steam engine—which was in wide use at the time, powering locomotives and other vehicles such as steam rollers. The term motor derives from the Latin noun mōtor which means 'that which moves something'. Thus a motor is a device that imparts motion.[6]

Motor and engine are interchangeable in standard English.[7] In some engineering jargons, the two words have different meanings, in which engine is a device that burns or otherwise consumes fuel, changing its chemical composition, and a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source.[8][9] However, rocketry uses the term rocket motor, even though they consume fuel.

A heat engine may also serve as a prime mover—a component that transforms the flow or changes in pressure of a fluid into mechanical energy.[10] An automobile powered by an internal combustion engine may make use of various motors and pumps, but ultimately all such devices derive their power from the engine. Another way of looking at it is that a motor receives power from an external source, and then converts it into mechanical energy, while an engine creates power from pressure (derived directly from the explosive force of combustion or other chemical reaction, or secondarily from the action of some such force on other substances such as air, water, or steam).[11]

## History

### Antiquity

### Medieval

Medieval Muslim engineers employed gears in mills and water-raising machines, and used dams as a source of water power to provide additional power to watermills and water-raising machines.[12] In the medieval Islamic world, such advances made it possible to mechanize many industrial tasks previously carried out by manual labour.

In 1206, al-Jazari employed a crank-conrod system for two of his water-raising machines. A rudimentary steam turbine device was described by Taqi al-Din[13] in 1551 and by Giovanni Branca[14] in 1629.[15]

In the 13th century, the solid rocket motor was invented in China. Driven by gunpowder, this simplest form of internal combustion engine was unable to deliver sustained power, but was useful for propelling weaponry at high speeds towards enemies in battle and for fireworks. After invention, this innovation spread throughout Europe.[16]

### Industrial Revolution

Boulton & Watt engine of 1788

As for internal combustion piston engines, these were tested in France in 1807 by de Rivaz and independently, by the Niépce brothers. They were theoretically advanced by Carnot in 1824. In 1853–57 Eugenio Barsanti and Felice Matteucci invented and patented an engine using the free-piston principle that was possibly the first 4-cycle engine.[17]

The invention of an internal combustion engine which was later commercially successful was made during 1860 by Etienne Lenoir.[18]

A V6 internal combustion engine from a Mercedes-Benz

### Automobiles

#### Horizontally-opposed pistons

In 1897, Karl Benz was granted a patent for his design of the first engine with horizontally opposed pistons. His design created an engine in which the corresponding pistons move in horizontal cylinders and reach top dead center simultaneously, thus automatically balancing each other with respect to their individual momentum.[19][20] Engines of this design are often referred to as “flat” or “boxer” engines due to their shape and low profile. They were used in the Volkswagen Beetle,[21] the Citroën 2CV,{{Citation needed|date=April 2026} y BMW and Honda motorcycles. Opposed four- and six-cylinder engines continue to be used as a power source in small, propeller-driven aircraft.[22]

#### Advancement

The continued use of internal combustion engines in automobiles is partly due to the improvement of engine control systems, such as on-board computers providing engine management processes, and electronically controlled fuel injection. Forced air induction by turbocharging and supercharging have increased the power output of smaller displacement engines that are lighter in weight and more fuel-efficient at normal cruise power. Similar changes have been applied to smaller Diesel engines, giving them almost the same performance characteristics as gasoline engines. This is especially evident with the popularity of smaller diesel engine-propelled cars in Europe. Diesel engines produce lower hydrocarbon and CO
2 emissions, but greater particulate and NO
x pollution, than gasoline engines.[23] Diesel engines are also 40% more fuel efficient than comparable gasoline engines.[23]

#### Increasing power

In the first half of the 20th century, a trend of increasing engine power occurred, particularly in the U.S. models.[clarification needed] Design changes incorporated all known methods of increasing engine capacity, including increasing the pressure in the cylinders to improve efficiency, increasing the size of the engine, and increasing the rate at which the engine produces work. The higher forces and pressures created by these changes created engine vibration and size problems that led to stiffer, more compact engines with V and opposed cylinder layouts replacing longer straight-line arrangements.

#### Combustion efficiency

Optimal combustion efficiency in passenger vehicles is reached with a coolant temperature of around 110 °C (230 °F).[24]

#### Engine configuration

The largest internal combustion engine ever built is the Wärtsilä-Sulzer RTA96-C, a 14-cylinder, 2-stroke turbocharged diesel engine that was designed to power the Emma Mærsk, the largest container ship in the world when launched in 2006. This engine has a mass of 2,300 tonnes, and when running at 102 rpm (1.7 Hz) produces over 80 MW, and can use up to 250 tonnes of fuel per day.[25]

## Types

### Heat engine

Main article: Physics:Heat engine

#### Combustion engine

#### Internal combustion engine

A three-horsepower internal combustion engine that ran on coal gas

Main article: Earth:Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel (generally, fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and high pressure gases, which are produced by the combustion, directly applies force to components of the engine, such as the pistons or turbine blades or a nozzle, and by moving it over a distance, generates mechanical work.[26][27][28][29]

#### External combustion engine

Main article: Engineering:External combustion engine

An external combustion engine (EC engine) is a heat engine where an internal working fluid is heated by combustion of 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.[30] The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine).

#### Air-breathing combustion engines

Examples

Typical air-breathing engines include:

* Reciprocating engine
* Steam engine
* Gas turbine
* Airbreathing jet engine
* Turbo-propeller engine
* Pulse detonation engine
* Pulse jet
* Ramjet
* Scramjet
* Liquid air cycle engine/Reaction Engines SABRE.

#### Environmental effects

The operation of engines typically has a negative impact upon air quality and ambient sound levels. There has been a growing emphasis on the pollution producing features of automotive power systems. This has created new interest in alternate power sources and internal-combustion engine refinements. Though a few limited-production battery-powered electric vehicles have appeared, they have not proved competitive owing to costs and operating characteristics. In the 21st century the diesel engine has been increasing in popularity with automobile owners. However, the gasoline engine and the Diesel engine, with their new emission-control devices to improve emission performance, have not yet been significantly challenged.{{Citation needed|date=November 2012} duced hybrid engines, mainly involving a small gasoline engine coupled with an electric motor and with a large battery bank, these are starting to become a popular option because of their environment awareness.

#### Air quality

Exhaust gas from a spark ignition engine consists of the following: nitrogen 70 to 75% (by volume), water vapor 10 to 12%, carbon dioxide 10 to 13.5%, hydrogen 0.5 to 2%, oxygen 0.2 to 2%, carbon monoxide: 0.1 to 6%, unburnt hydrocarbons and partial oxidation products (e.g. aldehydes) 0.5 to 1%, nitrogen monoxide 0.01 to 0.4%, nitrous oxide <100 ppm, sulfur dioxide 15 to 60 ppm, traces of other compounds such as fuel additives and lubricants, also halogen and metallic compounds, and other particles.[31] Carbon monoxide is highly toxic, and can cause carbon monoxide poisoning, so it is important to avoid any build-up of the gas in a confined space. Catalytic converters can reduce toxic emissions, but not eliminate them. Also, resulting greenhouse gas emissions, chiefly carbon dioxide, from the widespread use of engines in the modern industrialized world is contributing to the global greenhouse effect – a primary concern regarding global warming.

#### Non-combusting heat engines

Another group of noncombustive engines includes thermoacoustic heat engines (sometimes called "TA engines") which are thermoacoustic devices that use high-amplitude sound waves to pump heat from one place to another, or conversely use a heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices.[32]

Stirling engines can be another form of non-combustive heat engine. They use the Stirling thermodynamic cycle to convert heat into work. An example is the alpha type Stirling engine, whereby gas flows, via a recuperator, between a hot cylinder and a cold cylinder, which are attached to reciprocating pistons 90° out of phase. The gas receives heat at the hot cylinder and expands, driving the piston that turns the crankshaft. After expanding and flowing through the recuperator, the gas rejects heat at the cold cylinder and the ensuing pressure drop leads to its compression by the other (displacement) piston, which forces it back to the hot cylinder.[33]

### Non-thermal chemically powered motor

* Molecular motor – motors found in living things
* Synthetic molecular motor.

### Electric motor

Main articles: Physics:Electric motor and Electric vehicle

An electric motor uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo. Traction motors used on vehicles often perform both tasks. Electric motors can be run as generators and vice versa, although this is not always practical.

Electric motor

To reduce the electric energy consumption from motors and their associated carbon footprints, various regulatory authorities in many countries have introduced and implemented legislation to encourage the manufacture and use of higher efficiency electric motors. A well-designed motor can convert over 90% of its input energy into useful power for decades.[34] When the efficiency of a motor is raised by even a few percentage points, the savings, in kilowatt hours (and therefore in cost), are enormous. The electrical energy efficiency of a typical industrial induction motor can be improved by: 1) reducing the electrical losses in the stator windings (e.g., by increasing the cross-sectional area of the conductor, improving the winding technique, and using materials with higher electrical conductivities, such as copper), 2) reducing the electrical losses in the rotor coil or casting (e.g., by using materials with higher electrical conductivities, such as copper), 3) reducing magnetic losses by using better quality magnetic steel, 4) improving the aerodynamics of motors to reduce mechanical windage losses, 5) improving bearings to reduce friction losses, and 6) minimizing manufacturing tolerances. For further discussion on this subject, see Premium efficiency).

### Physically powered motor

Some motors are powered by potential or kinetic energy, for example some funiculars, gravity plane and ropeway conveyors have used the energy from moving water or rocks, and some clocks have a weight that falls under gravity. Other forms of potential energy include compressed gases (such as pneumatic motors), springs (clockwork motors) and elastic bands.[35]

Historic military siege engines included large catapults, trebuchets, and (to some extent) battering rams were powered by potential energy.[36]

#### Pneumatic motor

Main article: Physics:Pneumatic motor

#### Hydraulic motor

A hydraulic motor derives its power from a pressurized liquid. This type of engine is used to move heavy loads and drive machinery.[37]

#### Hybrid

Some motor units can have multiple sources of energy. For example, a plug-in hybrid electric vehicle's electric motor could source electricity from either a battery or from fossil fuels inputs via an internal combustion engine and a generator.[38]

## Performance

### Speed

### Thrust

### Torque

Torque is a turning moment on a shaft and is calculated by multiplying the force causing the moment by its distance from the shaft.

### Power

Power is the measure of how fast work is done.

### Efficiency

Main article: Engineering:Engine efficiency

### Sound levels

Vehicle noise is predominantly from the engine at low vehicle speeds and from tires and the air flowing past the vehicle at higher speeds.[39] Electric motors are quieter than internal combustion engines. Thrust-producing engines, such as turbofans, turbojets and rockets emit the greatest amount of noise due to the way their thrust-producing, high-velocity exhaust streams interact with the surrounding stationary air. Noise reduction technology includes intake and exhaust system mufflers (silencers) on gasoline and diesel engines and noise attenuation liners in turbofan inlets.

## Engines by use

Particularly notable kinds of engines include:

* Aircraft engine
* Automobile engine
* Model engine
* Motorcycle engine
* Marine propulsion engines such as Outboard motor
* Non-road engine is the term used to define engines that are not used by vehicles on roadways.
* Railway locomotive engine
* Spacecraft propulsion engines such as Rocket engine
* Traction engine

## See also

* Aircraft engine
* Automobile engine replacement
* Electric motor
* Engine cooling
* Engine swap
* Gasoline engine
* HCCI engine
* Hesselman engine
* Hot bulb engine
* IRIS engine
* Micromotor
* Flagella – biological motor used by some microorganisms
* Nanomotor
* Molecular motor
* Synthetic molecular motor
* Adiabatic quantum motor
* Multifuel
* Reaction engine
* Solid-state engine
* Timeline of heat engine technology
* Timeline of motor and engine technology

## References

### Citations

1. ↑ "Motor". Dictionary.reference.com. http://dictionary.reference.com/browse/motor. "a person or thing that imparts motion, esp. a contrivance, as a steam engine, that receives and modifies energy from some source in order to use it in driving machinery."
2. ↑ Dictionary.com: (World heritage) "3. any device that converts another form of energy into mechanical energy so as to produce motion"
3. ↑ "Fuel Cell Basics". US. 15 April 2026. https://www.energy.gov/cmei/fuels/fuel-cell-basics.
4. ↑ "World Wide Words: Engine and Motor" (in en-gb). http://www.worldwidewords.org/articles/engine.htm.
5. ↑ "Engine". Collins English Dictionary. http://www.collinsdictionary.com/dictionary/english/Engine.
6. ↑ Onions, Charles Talbut, ed (1966) (in en). The Oxford Dictionary of English Etymology. Oxford University Press (published 1966-12-31). pp. 592. ISBN 978-0198611127. http://archive.org/details/onions-ed.-the-oxford-dictionary-of-english-etymology-1966.
7. ↑ Dictionary definitions:
* motor (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=motor (Subscription or UK public library membership required.)
* engine (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=engine (Subscription or UK public library membership required.)
* "Motor". Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/motor.
* "Engine". Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/engine.
* "motor". Dictionary.com Unabridged. Random House. https://www.dictionary.com/browse/motor.
* "engine". Dictionary.com Unabridged. Random House. https://www.dictionary.com/browse/engine.
8. ↑ "Engine", McGraw-Hill Concise Encyclopedia of Science and Technology, Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 714.
9. ↑ Quinion, Michael. "World Wide Words: Engine and Motor". http://www.worldwidewords.org/articles/engine.htm.
10. ↑ "Prime mover", McGraw-Hill Concise Encyclopedia of Science and Technology, Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 1498.
11. ↑ Goldstein, Norm, ed (2007). The Associated Press Stylebook and Briefing on Media Law (42nd ed.). New York: Basic Books. p. 84. ISBN 978-0-465-00489-8.
12. ↑ Hassan, Ahmad Y.. "Transmission of Islamic Engineering". Transfer of Islamic Technology to the West, Part II. http://www.history-science-technology.com/Articles/articles 71.htm.
13. ↑ Hassan, Ahmad Y. (1976). Taqi al-Din and Arabic Mechanical Engineering, pp. 34–35. Institute for the History of Arabic Science, University of Aleppo.
14. ↑ "University of Rochester, NY, The growth of the steam engine online history resource, chapter one". History.rochester.edu. http://www.history.rochester.edu/steam/thurston/1878/Chapter1.html.
15. ↑ Nag, P.K. (2002). Power plant engineering. Tata McGraw-Hill. p. 432. ISBN 0-07-043599-5. https://books.google.com/books?id=Cv9LH4ckuEwC&pg=PA432.
16. ↑ "Rocket History – 13th Through 16th Centuries". US. https://www.grc.nasa.gov/WWW/K-12/rocket/BottleRocket/13thru16.htm.
17. ↑ "La documentazione essenziale per l'attribuzione della scoperta". http://www.barsantiematteucci.it/inglese/documentiStorici.html. "A later request was presented to the Patent Office of the Reign of Piedmont, under No. 700 of Volume VII of that Office. The text of this patent request is not available, only a photo of the table containing a drawing of the engine. This may have been either a new patent or an extension of a patent granted three days earlier, on 30 December 1857, at Turin."
18. ↑ Victor Albert Walter Hillier, Peter Coombes – Hillier's Fundamentals of Motor Vehicle Technology, Book 1 Nelson Thornes, 2004 ISBN 0-7487-8082-3 [Retrieved 2016-06-16]
19. ↑ Heventhal, Bryce (September 27, 2018). "The Boom of Motorization: How Karl and Bertha Benz Transformed the Automotive Industry Forever". US: AutoDesk. https://www.autodesk.com/products/fusion-360/blog/motorization-karl-benz-automotive-industry/.
20. ↑ "Benz Patent Motor Car: The First Automobile (1885–1886)". 2026-04-17. https://group.mercedes-benz.com/company/tradition/company-history/1885-1886.html.
21. ↑ "VW Beetle through the years" (Press release). Volkswagen. 2003-07-21. Retrieved 2026-04-17.
22. ↑ "Continental A-40, Horizontally-Opposed 4 Engine". US. https://airandspace.si.edu/collection-objects/continental-40-horizontally-opposed-4-engine/nasm_V20170186001.
23. ↑ 23.0 23.1 Harrison, Roy M. (2001), Pollution: Causes, Effects and Control (4th ed.), Royal Society of Chemistry, ISBN 978-0-85404-621-8
24. ↑ McKnight, Bill (August 2017). "The Electrically Assisted Thermostat" (in en-US). https://www.motor.com/magazine-summary/electrically-assisted-thermostat.
25. ↑ "The world's most powerful engine enters service". 2006-09-12. https://www.wartsila.com/media/news/12-09-2006-the-world's-most-powerful-engine-enters-service.
26. ↑ Proctor, Charles Lafayette II. "Internal Combustion engines". Encyclopædia Britannica Online. https://www.britannica.com/EBchecked/topic/290504/internal-combustion-engine. Retrieved 2011-05-09.
27. ↑ "Internal combustion engine". Answers.com. http://www.answers.com/topic/internal-combustion-engine?cat=technology.
28. ↑ "Columbia encyclopedia: Internal combustion engine". Inventors.about.com. http://inventors.about.com/gi/dynamic/offsite.htm?site=http://www.bartleby.com/65/in/intern-co.html.
29. ↑ "Internal-combustion engine". Infoplease.com. 2007. http://www.infoplease.com/ce6/sci/A0825332.html.
30. ↑ "External combustion". Merriam-Webster Online Dictionary. 2010-08-13. https://www.merriam-webster.com/dictionary/external combustion.
31. ↑ Paul Degobert, Society of Automotive Engineers (1995), Automobiles and Pollution
32. ↑ Emam, Mahmoud (2013). Experimental Investigations on a Standing-Wave Thermoacoustic Engine, M.Sc. Thesis. Egypt: Cairo University. https://www.scribd.com/doc/147785416/Experimental-Investigations-on-a-Standing-Wave-Thermoacoustic-Engine#fullscreen. Retrieved 2013-09-26.
33. ↑ Bataineh, Khaled M. (2018). "Numerical thermodynamic model of alpha-type Stirling engine". Case Studies in Thermal Engineering 12: 104–116. doi:10.1016/j.csite.2018.03.010. ISSN 2214-157X.
34. ↑ "Motors". American Council for an Energy-Efficient Economy. http://www.aceee.org/topics/motors.
35. ↑ "Forms of energy". US. https://www.eia.gov/energyexplained/what-is-energy/forms-of-energy.php.
36. ↑ Crawford, Jack (2021-01-22). "7 Powerful Medieval Weapons That Characterized Siege Warfare" (in en). https://www.thecollector.com/siege-warfare-powerful-medieval-weapons/.
37. ↑ "Howstuffworks "Engineering"". Reference.howstuffworks.com. 2006-01-29. http://reference.howstuffworks.com/hydraulic-engine-encyclopedia.htm.
38. ↑ "Alternative Fuels Data Center: How Do Plug-In Hybrid Electric Cars Work?". US: Department of Energy. https://afdc.energy.gov/vehicles/how-do-plug-in-hybrid-electric-cars-work.
39. ↑ Hogan, C. Michael (September 1973). "Analysis of Highway Noise". Journal of Water, Air, and Soil Pollution 2 (3): 387–92. doi:10.1007/BF00159677. ISSN 0049-6979. Bibcode: 1973WASP....2..387H.

### Sources

* Landels, J.G. (1978). Engineering in the Ancient World. Berkeley: University of California Press. ISBN 0-520-04127-5.

## External links

* U.S. Patent 194,047
* Detailed Engine Animations[Usurped!]
* Working 4-Stroke Engine – Animation
* Animated illustrations of various engines
* 5 Ways to Redesign the Internal Combustion Engine
* Article on Small SI Engines.
* Article on Compact Diesel Engines.
* Types Of Engines
* Motors (1915) by James Slough Zerbe

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Heat engines

* Carnot engine
* Fluidyne
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* Photo-Carnot engine
* Piston
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* Rijke tube
* Rocket
* Split-single
* Steam (reciprocating)
* Steam turbine
* Stirling
* Thermoacoustic

* Beale number
* West number

* Timeline of heat engine technology

Thermodynamic cycle

* v
* t
* e

Thermodynamic cycles

External
combustion|

Without phase change
(hot air engines)

* Bell Coleman
* Brayton / Joule
* Carnot
* Ericsson
* Stirling
* Stirling (pseudo / adiabatic)
* Stoddard

|

With phase change|

* Kalina
* Hygroscopic
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* Regenerative

Internal combustion|

* Atkinson
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* Diesel
* Expander
* Gas-generator
* Homogeneous charge compression ignition
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* Scuderi
* Staged combustion

Mixed|

* Combined
* HEHC
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Refrigeration|

* Hampson–Linde
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Uncategorized|

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Machines

Classical simple machines|

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Clocks|

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Compressors and pumps|

* Archimedes' screw
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External combustion engines|

* Steam engine
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Internal combustion engines|

* Reciprocating engine
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Linkages|

* Pantograph
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Turbine|

* Gas turbine
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Aerofoil|

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Electronics|

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Vehicles|

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Miscellaneous|

* Mecha
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