Internal combustion engine

An internal combustion engine is an engine that is powered by the expansion of hot combustion products of fuel directly acting within an engine. A piston internal combustion engine works by burning hydrocarbon or hydrogen fuel that presses on a piston; and a jet engine works as the hot combustion products press on the interior parts of the nozzle and combustion chamber, directly accelerating the engine forwards. The rotary combustion engine uses a rotor instead of reciprocating pistons.

Classification

There is a wide range of internal combustion engines corresponding to their many varied applications. Likewise there is a wide range of ways to classify internal-combustion engines, some of which are listed below.

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Although the terms sometimes cause confusion, there is no real difference between an "engine" and a "motor." At one time, the word "engine" (from Latin, via Old French, ingenium, "ability") meant any piece of machinery. A "motor" (from Latin motor, "mover") is any machine that produces mechanical power. Traditionally, electric motors are not referred to as "engines," but combusion engines are often referred to as "motors."

Related Topics:
Latin - Old French - Machinery - Power - Electric motor

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Principles of operation

Reciprocating:

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• Two-stroke engine
• Four-stroke engine
• Bourke engine

Rotary:

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• Wankel engine
• quasiturbine

Continuous combustion:

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• gas turbine
• jet engine
• rocket engine

Engine cycle

Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke, relying on the action of the bottom of the piston within the crankcase to help move the fuel-air mixture, and are used where small size and weight are important, such as snowmobiles, lawnmowers, mopeds, outboard motors and some motorcycles. Gasoline two-stroke engines are generally louder, less efficient, more polluting, and smaller than their four-stroke counterparts, although large two-stroke diesel engines are not subject to these complaints and are used in many applications, for instance some locomotives built by EMD.

Related Topics:
Two-stroke cycle - Snowmobile - Lawnmower - Moped - Outboard motor - Motorcycle - EMD

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Engines based on the four-stroke cycle or Otto cycle have one power stroke for every four strokes (up-down-up-down) and are used in cars, larger boats and many light aircraft. They are generally quieter, more efficient and larger than their two-stroke counterparts. There are a number of variations of these cycles, most notably the Atkinson and Miller cycles. Most truck and automotive Diesel engines use a four-stroke cycle, but with a compression heating ignition system it is possible to talk separately about a diesel cycle. The Wankel engine operates with the same separation of phases as the four-stroke engine (but with no piston strokes, would more properly be called a four-phase engine), since the phases occur in separate locations in the engine; however like a two-stroke piston engine, it provides one power 'stroke' per revolution per rotor, giving it similar space and weight efficiency. The Bourke cycle's combustion phase more closely approximates constant volume combustion than either four stroke or two stroke cycles do. It also uses less moving parts, hence needs to overcome less friction than the other two reciprocating types have to. In addition, its greater expansion ratio also means more of the heat from its combustion phase is utilized than is used by either four stroke or two stroke cycles.

Related Topics:
Four-stroke cycle - Boat - Aircraft - Atkinson - Miller - Diesel cycle - Wankel engine - Bourke cycle - Constant volume combustion - Friction - Expansion ratio

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Fuel type

Diesel engines are generally heavier, noisier and more powerful at lower speeds than gasoline engines. They are also more fuel-efficient in some circumstances and are used in heavy road-vehicles, some automobiles, ships and some locomotives and light aircraft. Gasoline engines are used in most other road-vehicles including most cars, motorcycles and mopeds. Note that in Europe, sophisticated diesel-engined cars are far more prevalent, representing around 40% of the market. Both gasoline and diesel engines produce significant emissions. There are also engines that run on hydrogen, methanol, ethanol, liquefied petroleum gas (LPG) and biodiesel. Paraffin and Tractor vaporising oil (TVO) engines are no longer seen.

Related Topics:
Diesel engines - Gasoline engine - Locomotive - Aircraft - Motorcycle - Moped - Europe - Hydrogen - Methanol - Ethanol - Liquefied petroleum gas - Biodiesel - Paraffin - Tractor vaporising oil

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Cylinders

Internal combustion engines can contain any number of cylinders with numbers between one and twelve being common, though as many as 28 have been used. Having more cylinders in a engine yields two potential benefits: First. the engine can have a larger displacement with smaller individual reciprocating masses (that is, the mass of each piston can be less) thus making a smoother running engine (since the engine tends to vibrate as a result of the pistons moving up and down). Second, with a greater displacement and more pistons, more fuel can be combusted and there can be more combustion events (that is, more power strokes) in a given period of time, meaning that such an engine can generate more torque than a similar engine with fewer cylinders. The down side to having more pistons is that, over all, the engine will tend to weigh more and tend to generate more internal friction as the greater number of pistons rub against the inside of their cylinders. This tends to decrease fuel efficiency and rob the engine of some of its power. For high performance gasoline engines using current materials and technology (such as the engines found in modern automobiles), there seems to be a break point around 10 or 12 cylinders, after which addition of cylinders becomes an overall detriment to performance and efficiency, although exceptions such as the W-16 engine from Volkswagen exist.

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• Most car engines have four to eight cylinders, with some high performance cars having ten, twelve, or even sixteen, and some very small cars and trucks having two or three. In previous years some quite large cars, such as the DKW and Saab 92, had two cylinder, two stroke engines.
• Radial aircraft engines, now obsolete, had from five to 28 cylinders. A row contains an odd number of cylinders, so an even number indicates a two- or four-row engine.
• Motor cycles commonly have from one to four cylinders, with a few high performance models having six.
• Snowmobiles usually have two cylinders. Some larger (not necessarily high-performance, but also touring machines) have four.
• Small appliances such as chainsaws and domestic lawn mowers most commonly have one cylinder, although two-cylinder chainsaws exist.

Ignition system

Internal combustion engines can be classified by their ignition system. Today most engines use an electrical or compression heating system for ignition. However outside flame and hot-tube systems have been used historically. Nikola Tesla gained one of the first patents on the mechanical ignition system with {{US patent|609250}}, "Electrical Igniter for Gas Engines", on 16 August 1898.

Related Topics:
Ignition system - Electrical - Compression heating - Outside flame - Hot-tube - Nikola Tesla

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Fuel systems

Often for simpler reciprocating engines a carburetor is used to supply fuel into the cylinder. However, exact control of the correct amount of fuel supplied to the engine is difficult.

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Car engines have mostly moved to Fuel injection systems, and Diesel engines essentially always use this technique.

Related Topics:
Fuel injection - Diesel engines

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Other internal combustion engines like Jet engines use burners, and rocket engines use various different ideas including impinging jets, gas/liquid shear, preburners and many other ideas.

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Engine configuration

Internal combustion engines can be classified by their configuration which affects their physical size and smoothness (with smoother engines producing less vibration). Common configurations include the straight or inline configuration, the more compact V configuration and the wider but smoother flat or boxer configuration. Aircraft engines can also adopt a radial configuration which allows more effective cooling. More unusual configurations, such as "H", "U", "X", or "W" have also been used.

Related Topics:
Configuration - Vibration - Straight or inline configuration - V configuration - Flat or boxer configuration - Radial configuration - H - U - W

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Multiple-crankshaft configurations do not necessarily need a cylinder head at all, but can instead have a piston at each end of the cylinder, called an opposed piston design. This design was used in the Junkers Jumo 205 diesel aircraft engine, using two crankshafts, one at either end of a single bank of cylinders, and most remarkably in the Napier Deltic diesel engines, which used three crankshafts to serve three banks of double-ended cylinders arranged in an equilateral triangle with the crankshafts at the corners. It was also used in single-bank locomotive engines, and continues to be used for marine engines, both for propulsion and for auxiliary generators. The Gnome Rotary engine, used in several early aircraft, had a stationary crankshaft and a bank of radially arranged cylinders rotating around it. Technically this is a "rotary piston engine", to distinguish it from Wankel "rotary combustion engines".

Related Topics:
Opposed piston - Junkers Jumo 205 - Napier Deltic - Gnome Rotary - Rotary piston engine - Wankel - Rotary combustion engine

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Engine capacity

An engine's capacity is the displacement or swept volume by the pistons of the engine. It is generally measured in litres or cubic inches for larger engines and cubic centimetres (abbreviated to cc's) for smaller engines. Engines with greater capacities are usually more powerful and provide greater torque at lower rpms but also consume more fuel.

Related Topics:
Displacement - Swept volume - Litre - Cubic centimetre

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Apart from designing an engine with more cylinders, there are two ways to increase an engine's capacity. The first is to lengthen the stroke and the second is to increase the piston's diameter. In either case, it may be necessary to make further adjustments to the fuel intake of the engine to ensure optimal performance.

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An engine's quoted capacity can be more a matter of marketing than of engineering. The Morris Minor 1000, the Morris 1100, and the Austin-Healey Sprite Mark II all had engines of the same stroke and bore according to their specifications, and were from the same maker. However the engine capacities were quoted as 1000cc, 1100cc and 1098cc respectively in the sales literature and on the vehicle badges.

Related Topics:
Marketing - Morris Minor - Austin-Healey Sprite

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Engine pollution

Generally internal combustion engines, particularly reciprocating internal combustion engines produce moderately high pollution levels, due to incomplete combustion of carbonaceous fuel, leading to carbon monoxide and some soot along with oxides of nitrogen & sulphur and some unburnt hydrocarbons depending on the operating conditions and the fuel/air ratio.

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Diesel engines produce a wide range of pollutants including aerosols of many small particles that are believed to penetrate deeply into human lungs.

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• Many fuels contain sulphur leading to sulphur oxides in the exhaust, promoting acid rain.
• Net carbon dioxide production is not a necessary feature of engines, but since most engines are run from fossil fuels usually occurs. If engines are run from biomass, then no net carbon dioxide is produced as the growing plants absorb as much, or more carbon dioxide while growing.
• Hydrogen engines don't produce any carbon dioxide.