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An engine or motor is a machine
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 designed to convert energy into useful mechanical motion
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...

. Heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

s, including internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s and external combustion engine
External combustion engine
An external combustion engine is a heat engine where an working fluid 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...

s (such as steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s) burn a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 to create heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 which is then used to create motion. Electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s convert electrical energy in mechanical
Mechanical
Mechanical may refer to:* Mechanical engineering, a branch of engineering concerned with the application of physical mechanics* HVAC , the mechanical systems of a building...

 motion, pneumatic motor
Pneumatic motor
A pneumatic motor or compressed air engine is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air to mechanical work through either linear or rotary motion...

s use compressed air
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....

 and others, such as wind-up toy
Wind-up toy
A wind-up toy is a toy powered by a clockwork motor.-History:Wind-up toys date far back into history, into the 15th century. Karel Grod, a German inventor, created some of the first wind-up toys, including a metal fly and a mechanical eagle. Also, in 1509, Leonardo da Vinci created a wind-up lion...

s use elastic energy
Elastic energy
Elastic energy is the potential mechanical energy stored in the configuration of a material or physical system as work is performed to distort its volume or shape....

. In biological systems molecular motors like myosin
Myosin
Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...

s in muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s use chemical energy
Chemical energy
Chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction or, to transform other chemical substances...

 to create motion.

Terminology


Originally an engine was a mechanical device that converted force into motion. Military devices such as catapult
Catapult
A catapult is a device used to throw or hurl a projectile a great distance without the aid of explosive devices—particularly various types of ancient and medieval siege engines. Although the catapult has been used since ancient times, it has proven to be one of the most effective mechanisms during...

s, trebuchet
Trebuchet
A trebuchet is a siege engine that was employed in the Middle Ages. It is sometimes called a "counterweight trebuchet" or "counterpoise trebuchet" in order to distinguish it from an earlier weapon that has come to be called the "traction trebuchet", the original version with pulling men instead of...

s and battering ram
Battering ram
A battering ram is a siege engine originating in ancient times and designed to break open the masonry walls of fortifications or splinter their wooden gates...

s are referred to as siege engine
Siege engine
A siege engine is a device that is designed to break or circumvent city walls and other fortifications in siege warfare. Some have been operated close to the fortifications, while others have been used to attack from a distance. From antiquity, siege engines were constructed largely of wood and...

s
. The term "gin" as in cotton gin
Cotton gin
A cotton gin is a machine that quickly and easily separates cotton fibers from their seeds, a job formerly performed painstakingly by hand...

 is recognised as a short form of the Old French
Old French
Old French was the Romance dialect continuum spoken in territories that span roughly the northern half of modern France and parts of modern Belgium and Switzerland from the 9th century to the 14th century...

 word engin, in turn from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 ingenium, related to ingenious. Most devices used in the industrial revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

 were referred to as engines, and this is where the steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 gained its name.

In modern usage, the term is used to describe devices capable of performing mechanical work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

, as in the original steam engine. In most cases the work is produced by exerting a torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 or linear force, which is used to operate other machinery which can generate electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

, pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

 water, or compress gas
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...

. In the context of propulsion systems, an air-breathing engine is one that uses atmospheric air to oxidise the fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 carried rather than supplying an independent oxidizer, as in a rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

.

In common usage, an engine burns
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 or otherwise consumes fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, and is differentiated from an electric machine (i.e., electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

) that derives power without changing the composition of matter. A heat engine may also serve as a prime mover, a component that transforms the flow or changes in pressure of a fluid
Fluid mechanics
Fluid mechanics is the study of fluids and the forces on them. Fluid mechanics can be divided into fluid statics, the study of fluids at rest; fluid kinematics, the study of fluids in motion; and fluid dynamics, the study of the effect of forces on fluid motion...

 into mechanical energy
Mechanical energy
In physics, mechanical energy is the sum of potential energy and kinetic energy present in the components of a mechanical system. It is the energy associated with the motion and position of an object. The law of conservation of energy states that in an isolated system that is only subject to...

. An automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 powered by an internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 may make use of various motors and pumps, but ultimately all such devices derive their power from the engine.

The term motor was originally used to distinguish the new internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

-powered vehicles from earlier vehicles powered by steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s, such as the steam roller
Steamroller
A steamroller is a form of road roller – a type of heavy construction machinery used for levelling surfaces, such as roads or airfields – that is powered by a steam engine...

 and motor roller
Road roller
A road roller is a compactor type engineering vehicle used to compact soil, gravel, concrete, or asphalt in the construction of roads and foundations, similar rollers are used also at landfills or in agriculture.In some parts of the world, road rollers are still known colloquially as steam...

, but may be used to refer to any engine.

Devices converting heat energy into motion are referred to as engines,.

Antiquity


Simple machine
Simple machine
A simple machine is a mechanical device that changes the direction or magnitude of a force.In general, they can be defined as the simplest mechanisms that use mechanical advantage to multiply force. A simple machine uses a single applied force to do work against a single load force...

s, such as the club and oar
Oar
An oar is an implement used for water-borne propulsion. Oars have a flat blade at one end. Oarsmen grasp the oar at the other end. The difference between oars and paddles are that paddles are held by the paddler, and are not connected with the vessel. Oars generally are connected to the vessel by...

 (examples of the lever
Lever
In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...

), are prehistoric
Prehistory
Prehistory is the span of time before recorded history. Prehistory can refer to the period of human existence before the availability of those written records with which recorded history begins. More broadly, it refers to all the time preceding human existence and the invention of writing...

. More complex engines using human power
Manual labour
Manual labour , manual or manual work is physical work done by people, most especially in contrast to that done by machines, and also to that done by working animals...

, animal power, water power
Water wheel
A water wheel is a machine for converting the energy of free-flowing or falling water into useful forms of power. A water wheel consists of a large wooden or metal wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface...

, wind power
Windmill
A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades. Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses. An important...

 and even steam power
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 date back to antiquity. Human power was focused by the use of simple engines, such as the capstan
Capstan (nautical)
A capstan is a vertical-axled rotating machine developed for use on sailing ships to apply force to ropes, cables, and hawsers. The principle is similar to that of the windlass, which has a horizontal axle.- History :...

, windlass
Windlass
The windlass is an apparatus for moving heavy weights. Typically, a windlass consists of a horizontal cylinder , which is rotated by the turn of a crank or belt...

 or treadmill
Treadwheel
A treadwheel is a form of animal engine typically powered by humans. It may resemble a water wheel in appearance, and can be worked either by a human treading paddles set into its circumference , or by a human or animal standing inside it .Uses of treadwheels included raising water, to power...

, and with rope
Rope
A rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...

s, pulley
Pulley
A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...

s, and block and tackle
Block and tackle
A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads.The pulleys are assembled together to form blocks so that one is fixed and one moves with the load...

 arrangements; this power was transmitted usually with the forces multiplied
Mechanical advantage
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...

 and the speed reduced. These were used in cranes
Crane (machine)
A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of...

 and aboard ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

s in Ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, as well as in mine
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...

s, water pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

s and siege engines in Ancient Rome
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

. The writers of those times, including Vitruvius
Vitruvius
Marcus Vitruvius Pollio was a Roman writer, architect and engineer, active in the 1st century BC. He is best known as the author of the multi-volume work De Architectura ....

, Frontinus and Pliny the Elder
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

, treat these engines as commonplace, so their invention may be more ancient. By the 1st century AD, cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

 and horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

s were used in mill
Mill (grinding)
A grinding mill is a unit operation designed to break a solid material into smaller pieces. There are many different types of grinding mills and many types of materials processed in them. Historically mills were powered by hand , working animal , wind or water...

s, driving machines similar to those powered by humans in earlier times.

According to Strabo
Strabo
Strabo, also written Strabon was a Greek historian, geographer and philosopher.-Life:Strabo was born to an affluent family from Amaseia in Pontus , a city which he said was situated the approximate equivalent of 75 km from the Black Sea...

, a water powered mill was built in Kaberia of the kingdom of Mithridates
Parthian Empire
The Parthian Empire , also known as the Arsacid Empire , was a major Iranian political and cultural power in ancient Persia...

 during the 1st century BC. Use of water wheel
Water wheel
A water wheel is a machine for converting the energy of free-flowing or falling water into useful forms of power. A water wheel consists of a large wooden or metal wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface...

s in mills spread throughout the Roman Empire
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

 over the next few centuries. Some were quite complex, with aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

s, dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

s, and sluice
Sluice
A sluice is a water channel that is controlled at its head by a gate . For example, a millrace is a sluice that channels water toward a water mill...

s to maintain and channel the water, along with systems of gears, or toothed-wheels made of wood and metal to regulate the speed of rotation. In a poem by Ausonius
Ausonius
Decimius Magnus Ausonius was a Latin poet and rhetorician, born at Burdigala .-Biography:Decimius Magnus Ausonius was born in Bordeaux in ca. 310. His father was a noted physician of Greek ancestry and his mother was descended on both sides from long-established aristocratic Gallo-Roman families...

 in the 4th century AD, he mentions a stone-cutting saw powered by water. Hero of Alexandria
Hero of Alexandria
Hero of Alexandria was an ancient Greek mathematician and engineerEnc. Britannica 2007, "Heron of Alexandria" who was active in his native city of Alexandria, Roman Egypt...

 is credited with many such wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

 and steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 powered machines in the 1st century AD, including the Aeolipile
Aeolipile
An aeolipile , also known as a Hero engine, is a rocket style jet engine which spins when heated. In the 1st century AD, Hero of Alexandria described the device, and many sources give him the credit for its invention.The aeolipile Hero described is considered to be the first recorded steam engine...

, but it is not known if any of these were put to practical use.

Medieval


Medieval Muslim engineers employed gear
Gear
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

s in mills and water-raising machine
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

s, and used dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

s as a source of water power to provide additional power to watermills and water-raising machines. Such advances made it possible for many industrial tasks that were previously driven by manual labour
Manual labour
Manual labour , manual or manual work is physical work done by people, most especially in contrast to that done by machines, and also to that done by working animals...

 to be mechanized
Mechanization
Mechanization or mechanisation is providing human operators with machinery that assists them with the muscular requirements of work or displaces muscular work. In some fields, mechanization includes the use of hand tools...

 and driven by machine
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

ry to some extent in the medieval Islamic world
Islamic Golden Age
During the Islamic Golden Age philosophers, scientists and engineers of the Islamic world contributed enormously to technology and culture, both by preserving earlier traditions and by adding their own inventions and innovations...

.

In 1206, al-Jazari
Al-Jazari
Abū al-'Iz Ibn Ismā'īl ibn al-Razāz al-Jazarī was a Muslim polymath: a scholar, inventor, mechanical engineer, craftsman, artist, mathematician and astronomer from Al-Jazira, Mesopotamia, who lived during the Islamic Golden Age...

 employed a crank
Crank (mechanism)
A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to change circular into reciprocating motion, or reciprocating into circular motion. The arm may be a bent portion of the shaft, or a separate arm...

-conrod system for two of his water-raising machines. A rudimentary steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

 device was described by Taqi al-Din in 1551 and by Giovanni Branca
Giovanni Branca
Giovanni Branca was an Italian engineer and architect, chiefly remembered today for what some commentators have taken to be an early steam engine.-Life:...

 in 1629.

Industrial Revolution


The Watt steam engine was the first type of steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 to make use of steam at a pressure just above atmospheric
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

 to drive the piston helped by a partial vacuum. Improving on the design of the 1712 Newcomen steam engine
Newcomen steam engine
The atmospheric engine invented by Thomas Newcomen in 1712, today referred to as a Newcomen steam engine , was the first practical device to harness the power of steam to produce mechanical work. Newcomen engines were used throughout Britain and Europe, principally to pump water out of mines,...

, the Watt steam engine, developed sporadically from 1763 to 1775, was a great step in the development of the steam engine. Offering a dramatic increase in fuel efficiency
Fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...

, the James Watt
James Watt
James Watt, FRS, FRSE was a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine were fundamental to the changes brought by the Industrial Revolution in both his native Great Britain and the rest of the world.While working as an instrument maker at the...

's design became synonymous with steam engines, due in no small part to his business partner, Matthew Boulton
Matthew Boulton
Matthew Boulton, FRS was an English manufacturer and business partner of Scottish engineer James Watt. In the final quarter of the 18th century the partnership installed hundreds of Boulton & Watt steam engines, which were a great advance on the state of the art, making possible the...

. It enabled rapid development of efficient semi-automated factories on a previously unimaginable scale in places where waterpower was not available. Later development led to steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

s and great expansion of railway transportation
Railway Transportation
Railway Transportation was an Australian magazine published by Shennan Publications between 1951 and 1972. It came out monthly....

.

As for internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s, these were tested in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 in 1807 by de Rivaz and independently, by the Niépce brothers
Nicéphore Niépce
Nicéphore Niépce March 7, 1765 – July 5, 1833) was a French inventor, most noted as one of the inventors of photography and a pioneer in the field.He is most noted for producing the world's first known photograph in 1825...

 . They were theoretically advanced by Carnot
Nicolas Léonard Sadi Carnot
Nicolas Léonard Sadi Carnot was a French military engineer who, in his 1824 Reflections on the Motive Power of Fire, gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the foundations of the second law of thermodynamics...

 in 1824. The breakthrough was the invention of the Otto cycle
Otto cycle
An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....

 in 1877, which has practically shown that this type of engines have more potential than steam engines.

Automobiles


The first commercially successful automobile, created by Karl Benz
Karl Benz
Karl Friedrich Benz, was a German engine designer and car engineer, generally regarded as the inventor of the gasoline-powered car, and together with Bertha Benz pioneering founder of the automobile manufacturer Mercedes-Benz...

, added to the interest in light and powerful engines. The lightweight petrol internal combustion engine, operating on a four-stroke Otto cycle, has been the most successful for light automobiles, while the more efficient Diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 is used for trucks and buses.

Horizontally opposed pistons


In 1896, 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. Engines of this design are often referred to as flat engines because of their shape and lower profile. They are or were used in: the Volkswagen Beetle
Volkswagen Beetle
The Volkswagen Type 1, widely known as the Volkswagen Beetle or Volkswagen Bug, is an economy car produced by the German auto maker Volkswagen from 1938 until 2003...

, some Porsche and Subaru cars, many BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

 motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s, and aircraft engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...

s (for propeller driven aircraft), etc.

Advancement





Continuance of the use of the internal combustion engine for automobiles is partly due to the improvement of engine control systems (onboard computers providing engine management processes, and electronically controlled fuel injection). Forced air induction by turbocharging and supercharging have increased power outputs and engine efficiencies. Similar changes have been applied to smaller diesel engines giving them almost the same power characteristics as petrol engines. This is especially evident with the popularity of smaller diesel engine propelled cars in Europe. Larger diesel engines are still often used in trucks and heavy machinery, although they require special machining not avaialble in most factories. They do not burn as clean as gasoline engines, however they have far more torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

. The internal combustion engine was originally selected for the automobile due to its flexibility over a wide range of speeds. Also, the power developed for a given weight engine was reasonable; it could be produced by economical mass-production methods; and it used a readily available, moderately priced fuel - petrol.

Increasing power


The first half of the 20th century saw a trend to increasing engine power, particularly in the American models. Design changes incorporated all known methods of raising engine capacity, including increasing the pressure in the cylinders to improve efficiency, increasing the size of the engine, and increasing the speed at which power is generated. 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


The design principles favoured in Europe, because of economic and other restraints such as smaller and twistier roads, leant toward smaller cars and corresponding to the design principles that concentrated on increasing the combustion efficiency of smaller engines. This produced more economical engines with earlier four-cylinder designs rated at 40 horsepower (30 kW) and six-cylinder designs rated as low as 80 horsepower (60 kW), compared with the large volume V-8 American engines with power ratings in the range from 250 to
350 hp (190 to 260 kW).

Engine configuration


Earlier automobile engine development produced a much larger range of engines than is in common use today. Engines have ranged from 1- to 16-cylinder designs with corresponding differences in overall size, weight, piston displacement, and cylinder bores. Four cylinders and power ratings from 19 to 120 hp (14 to 90 kW) were followed in a majority of the models. Several three-cylinder, two-stroke-cycle models were built while most engines had straight or in-line cylinders. There were several V-type models and horizontally opposed two- and four-cylinder makes too. Overhead camshafts were frequently employed. The smaller engines were commonly air-cooled and located at the rear of the vehicle; compression ratios were relatively low. The 1970s and '80s saw an increased interest in improved fuel economy which brought in a return to smaller V-6 and four-cylinder layouts, with as many as five valves per cylinder to improve efficiency. The Bugatti Veyron
Bugatti Veyron
The Bugatti Veyron EB 16.4 is a mid-engined grand touring car. The Super Sport version is the fastest road-legal production car in the world, with a top speed of . The original version has a top speed of...

 16.4 operates with a W16 engine
W16 engine
A W16 engine is a sixteen cylinder piston internal combustion engine in a four-bank W configuration. All W16 engines consist of two 'offset double-row' banks of eight cylinders, coupled to a single crankshaft....

 meaning that two V8
V8 engine
A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....

 cylinder layouts are positioned next to each other to create the W shape sharing the same crankshaft.

The largest internal combustion engine ever built is the Wärtsilä-Sulzer RTA96-C
Wärtsilä-Sulzer RTA96-C
The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is currently considered the largest reciprocating engine in the world, designed for large container ships, running on heavy fuel oil...

, a 14-cylinder, 2-stroke turbocharged diesel engine that was designed to power the Emma Maersk, the largest container ship in the world. This engine weighs 2300 tons, and when running at 102 RPM produces 109,000 bhp (80,080 kW) consuming some 13.7 tons of fuel each hour.

Combustion engine


Combustion engines are heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

s driven by the heat of a combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 process.

Internal combustion engine


The internal combustion engine is an engine in which the combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 of a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 (generally, fossil fuel
Fossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

) occurs with an oxidizer (usually air) in a combustion chamber
Combustion chamber
A combustion chamber is the part of an engine in which fuel is burned.-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber...

. In an internal combustion engine the expansion of the high temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 and high pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 gases, which are produced by the combustion, directly applies force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...

 to components of the engine, such as the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

s or turbine blade
Turbine blade
A turbine blade is the individual component which makes up the turbine section of a gas turbine. The blades are responsible for extracting energy from the high temperature, high pressure gas produced by the combustor. The turbine blades are often the limiting component of gas turbines...

s or a nozzle, and by moving it over a distance, generates useful mechanical energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

.

External combustion engine



An external combustion engine (EC engine) is a heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

 where an internal working fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

 is heated by combustion of an external source, through the engine wall or a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

. The fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

 then, by expanding and acting on the mechanism
Mechanism (engineering)
A mechanism is a device designed to transform input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components such as gears and gear trains, belt and chain drives, cam and follower mechanisms, and linkages as well as friction devices...

 of the engine produces motion and usable work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

. The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine).

"Combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

" refers to burning fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 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; but are not then strictly classed as external combustion engines, but as external thermal engines.

The working fluid can be a gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 as in a Stirling engine
Stirling engine
A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....

, or steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 as in a steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 or an organic liquid such as n-pentane in an Organic Rankine Cycle
Organic Rankine Cycle
The Organic Rankine cycle is named for its use of an organic, high molecular mass fluid with a liquid-vapor phase change, or boiling point, occurring at a lower temperature than the water-steam phase change. The fluid allows Rankine cycle heat recovery from lower temperature sources such as...

. The fluid can be of any composition; gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 is by far the most common, although even single-phase liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 is sometimes used. In the case of the steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

, the fluid changes phase
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...

s between liquid and gas...

Gas turbine


A gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

 is internal combustion in the sense that the combustion takes place in the working fluid, but external combustion in the sense that the combustion is not fully closed in and is outside the actual moving turbine section. Traditionally, "internal combustion" usually includes gas turbines, jets and rockets.

Air-breathing combustion engines


Air-breathing engines are combustion engines that use the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 in atmospheric air to oxidise ('burn') the fuel carried, rather than carrying an oxidiser, as in a rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

. Theoretically, this should result in a better specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...

 than for rocket engines.

A continuous stream of air flows through the Air-breathing engine. This air is compressed, mixed with fuel, ignited and expelled as the exhaust gas.

Examples
Typical air-breathing engines include:
  • Reciprocating engine
    Reciprocating engine
    A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...

  • Steam engine
    Steam engine
    A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

  • Gas turbine
    Gas turbine
    A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

duct jet engine
Turbo-propeller engine
Turboprop
A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear.The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller...

  • Pulse detonation engine
    Pulse detonation engine
    A pulse detonation engine, or "PDE", is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave initiated by an ignition source. Theoretically, a...

  • Pulse jet
  • Ramjet
    Ramjet
    A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...

  • Scramjet
    Scramjet
    A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...

  • Liquid air cycle engine
    Liquid air cycle engine
    A Liquid Air Cycle Engine is a type of spacecraft propulsion engine that attempts to increase its efficiency by gathering part of its oxidizer from the atmosphere...

    /Reaction Engines SABRE

Environmental effects


Operation of engines typically has a negative impact upon air quality and ambient sound levels
Noise pollution
Noise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...

. 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. Although a few limited-production battery-powered electric vehicles have appeared, they have not proved to be 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, with its new emission-control devices to improve emission performance, has not yet been significantly challenged.

Air quality


Exhaust from a spark ignition engine consists of the following: nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 70 to 75% (by volume), water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...

 10 to 12%, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 10 to 13.5%, hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 0.5 to 2%, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 0.2 to 2%, carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

: 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
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

 <100 ppm, sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

 15 to 60 ppm, traces of other compounds such as fuel additives and lubricants, also halogen and metallic compounds, and other particles. Carbon monoxide is highly toxic, and can cause carbon monoxide poisoning
Carbon monoxide poisoning
Carbon monoxide poisoning occurs after enough inhalation of carbon monoxide . Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect...

, so it is important to avoid any build-up of the gas in a confined space. Catalytic converter
Catalytic converter
A catalytic converter is a device used to convert toxic exhaust emissions from an internal combustion engine into non-toxic substances. Inside a catalytic converter, a catalyst stimulates a chemical reaction in which noxious byproducts of combustion are converted to less toxic substances by dint...

s can reduce toxic emissions, but not completely eliminate them. Also, resulting greenhouse gas emissions, chiefly carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, from the widespread use of engines in the modern industrialized world is contributing to the global greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...

 – a primary concern regarding global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

.

Noncombustive heat engines



Some engines convert heat from noncombustive processes into mechanical work, for example a nuclear power plant uses the heat from the nuclear reaction to produce steam and drive a steam engine, or a gas turbine in a rocket engine may be driven by decomposing hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

. Apart from the different energy source, the engine is often engineered much the same as an internal or external combustion engine.

Nonthermal chemically powered motor


Nonthermal motors usually are powered by a chemical reaction, but are not heat engines. Examples include:
  • Molecular motor - motors found in living things
  • Synthetic molecular motor

Electric motor



An electric motor uses electrical energy to produce mechanical energy
Mechanical energy
In physics, mechanical energy is the sum of potential energy and kinetic energy present in the components of a mechanical system. It is the energy associated with the motion and position of an object. The law of conservation of energy states that in an isolated system that is only subject to...

, usually through the interaction of magnetic fields and current-carrying conductors
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...

. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

 or dynamo
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...

. Traction motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

s used on vehicles often perform both tasks. Electric motors can be run as generators and vice versa, although this is not always practical.
Electric motors are ubiquitous, being found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. They may be powered by direct current (for example a battery powered portable device or motor vehicle), or by alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 from a central electrical distribution grid. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of large ships, and for such purposes as pipeline compressors, with ratings in the thousands of kilowatts. Electric motors may be classified by the source of electric power, by their internal construction, and by their application.

The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution networks.

By convention, electric engine refers to a railroad electric locomotive
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

, rather than an electric motor.

Physically powered motor


Some motors are powered by potential energy, for example some funicular
Funicular
A funicular, also known as an inclined plane or cliff railway, is a cable railway in which a cable attached to a pair of tram-like vehicles on rails moves them up and down a steep slope; the ascending and descending vehicles counterbalance each other.-Operation:The basic principle of funicular...

s, gravity plane and ropeway conveyor
Ropeway conveyor
A ropeway conveyor or material ropeway is essentially a subtype of gondola lift, from which containers for goods rather than passenger cars are suspended....

s have used potential energy of water or rocks, and some clocks have a weight that falls under gravity. Other forms of potential energy include compressed gases (such as pneumatic motor
Pneumatic motor
A pneumatic motor or compressed air engine is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air to mechanical work through either linear or rotary motion...

s), springs (clockwork motors) and elastic bands.

Historic military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

 siege engines included large catapult
Catapult
A catapult is a device used to throw or hurl a projectile a great distance without the aid of explosive devices—particularly various types of ancient and medieval siege engines. Although the catapult has been used since ancient times, it has proven to be one of the most effective mechanisms during...

s, trebuchet
Trebuchet
A trebuchet is a siege engine that was employed in the Middle Ages. It is sometimes called a "counterweight trebuchet" or "counterpoise trebuchet" in order to distinguish it from an earlier weapon that has come to be called the "traction trebuchet", the original version with pulling men instead of...

s, and (to some extent) battering ram
Battering ram
A battering ram is a siege engine originating in ancient times and designed to break open the masonry walls of fortifications or splinter their wooden gates...

s were powered by potential energy.

Pneumatic motor



A pneumatic motor is a machine which converts potential energy in the form of compressed air
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....

 into mechanical work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

. Pneumatic motors generally convert the compressed air to mechanical work though either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor. Pneumatic motors have found widespread success in the hand-held tool industry and continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome efficiency deficiencies before being seen as a viable option in the transportation industry.

Hydraulic engine



A hydraulic engine one that derives its power from a pressurized
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

. This type of engine can be used to move heavy loads or produce motion.

Sound levels


In the case of sound levels, engine operation is of greatest impact with respect to mobile sources such as automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

s and trucks. Engine noise is a particularly large component of mobile source noise for vehicles operating at lower speeds, where aerodynamic and tyre noise is less significant. Petrol and diesel engines are fitted with muffler
Muffler
A muffler is a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine. A US Patent for an Exhaust muffler for engines was granted to Milton and Marshall Reeves in 1897....

s (silencers) to reduce noise.

Engine efficiency



Depending on the type of engine employed, different rates of efficiency are attained.

Engines by use


Particularly notable kinds of engines include:
  • Aircraft engine
    Aircraft engine
    An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...

  • Automobile engine
  • model engine
    Model engine
    In radio-controlled modeling, a model engine is an internal combustion engine used to power a radio-controlled aircraft, radio-controlled car, radio-controlled boat, free flight and control line aircraft, and tether car models also use these engines....

  • Motorcycle engine
    Motorcycle engine
    A motorcycle engine is an engine that powers a motorcycle.Motorcycle engines may be two-stroke or four-stroke, reciprocating or Wankel, single-cylinder or multicylinder , or single-rotor or twin-rotor . The engine typically drives the rear wheel, but some small bikes such as the Velosolex have a...

  • Marine propulsion
    Marine propulsion
    Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting a motor or engine turning a propeller, or less frequently, in jet...

     engines such as Outboard motor
    Outboard motor
    An outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox and propeller or jet drive, designed to be affixed to the outside of the transom and are the most common motorized method of propelling small watercraft...

  • Railway locomotive engine
  • Spacecraft propulsion
    Spacecraft propulsion
    Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...

     engines such as Rocket engine
    Rocket engine
    A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...

  • Traction engine
    Traction engine
    A traction engine is a self-propelled steam engine used to move heavy loads on roads, plough ground or to provide power at a chosen location. The name derives from the Latin tractus, meaning 'drawn', since the prime function of any traction engine is to draw a load behind it...


See also


  • Machine
    Machine
    A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

  • Timeline of motor and engine technology
    Timeline of motor and engine technology
    Timeline of motor and engine technology* – Hero of Alexandria describes the first documented steam-powered device, the aeolipile.* 1698 – Thomas Savery builds a steam-powered water pump for pumping water out of mines....

  • Timeline of heat engine technology
    Timeline of heat engine technology
    This Timeline of heat engine technology describes how heat engines have been known since antiquity but have been made into increasingly useful devices since the seventeenth century as a better understanding of the processes involved was gained...

  • Motor
    Electric motor
    An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

  • Multifuel
    Multifuel
    Multifuel, sometimes spelled multi-fuel, is a term applied to any type of engine, boiler, or heater or other fuel-burning device which is designed to burn multiple types of fuels in its operation...

  • Turbine
    Turbine
    A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

    • Gas turbine
      Gas turbine
      A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

    • Water turbine
      Water turbine
      A water turbine is a rotary engine that takes energy from moving water.Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy...

  • Air engine
  • Hydraulic engine
  • Engine test stand
    Engine test stand
    An engine test stand is a facility used to develop, characterize and test engines. The facility, often offered as a product to automotive OEMs, allows engine operation in different operating regimes and offers measurement of several physical variables associated with the engine operation.A...


  • Heat engine
    Heat engine
    In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

    • Reciprocating engine
      Reciprocating engine
      A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...

    • External combustion engine
      External combustion engine
      An external combustion engine is a heat engine where an working fluid 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...

      • Steam engine
        Steam engine
        A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

      • Steam turbine
        Steam turbine
        A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

      • Stirling engine
        Stirling engine
        A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....

    • Internal combustion engine
      Internal combustion engine
      The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

      • Diesel engine
        Diesel engine
        A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

      • Hot bulb engine
        Hot bulb engine
        The hot bulb engine, or hotbulb or heavy oil engine is a type of internal combustion engine. It is an engine in which fuel is ignited by being brought into contact with a red-hot metal surface inside a bulb....

      • Gasoline engine
      • Hesselman engine
        Hesselman engine
        The Hesselman engine is a hybrid between a petrol engine and a Diesel engine introduced by Swedish engineer Jonas Hesselman in 1925. It represented the first use of direct gasoline injection on a spark-ignition engine...

      • HCCI engine
        HCCI
        Homogeneous charge compression ignition is a form of internal combustion in which well-mixed fuel and oxidizer are compressed to the point of auto-ignition...

      • IRIS engine
        IRIS engine
        The IRIS Engine is a design for a new type of internal combustion engine. Its inventors say that engines constructed using this design can be smaller, lighter and significantly more efficient than traditional engines of comparable horsepower and displacement...

      • Engine cooling
        Engine cooling
        Internal combustion engine cooling refers to the cooling of an internal combustion engine, typically using either air or a liquid.- Overview :...



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