Internal combustion engine

From New World Encyclopedia
Jump to: navigation, search
Four-stroke cycle (or Otto cycle)
1. intake
2. compression
3. power
4. exhaust


This contrasts with external combustion engines, such as steam engines, which use the combustion process to heat a separate working fluid, typically water or steam, which then in turn does work, for example by pressing on a steam actuated piston.


Internal combustion engines are seen mostly in transportation. Several other uses are for any portable situation where you need an non-electric motor. The largest application in this situation would be an Internal combustion engine driving an electric generator. That way, you can use standard electric tools driven by an internal combustion engine.


The advantages of these is the portability. It is more convenient using this type of engine in vehicles over electricity. Even in cases of hybrid vehicles, they still use an internal combustion engine to charge the battery. The disadvantage is the pollution that they put out. Not only the obvious, air pollution, but also pollution of broken or obsolete engines and waste parts, such as oil or rubber items that have to be discarded. Noise pollution is another factor, many internal combustion engines are very loud. Some are so loud, people need hearing protection to prevent damage their ears. Another disadvantage is size. It is very impractical to have small motors that can have any power. Electric motors are much more practical for this. That is why it is more likely to see an gas powered electric generator in an area that has no electricity to power smaller items.


A colorized automobile engine
Demonstration of the internal combustion indirect or suction principle. This may not meet the definition of an engine, because the process does not repeat.


  • 1673: Christiaan Huygens described a compression-less engine.[1]
  • 1780's: Alessandro Volta built a toy electric pistol in which an electric spark exploded a mixture of air and hydrogen, firing a cork from the end of the gun.
  • Seventeenth century: English inventor Sir Samuel Morland used gunpowder to drive water pumps.
  • 1870: In Vienna, Siegfried Marcus, put the first mobile gasoline engine on a handcart.
Karl Benz
  • 1891: Herbert Akroyd Stuart builds his oil engine leasing rights to Hornsby of England to build engines. They build the first cold start, compression ignition engines. In 1892, they install the first ones in a water pumping station. An experimental higher-pressure version produces self-sustaining ignition through compression alone in the same year.
  • 1892: Rudolf Diesel develops his Carnot heat engine type motor burning powdered coal dust.
  • 1896: Karl Benz invented the boxer engine, also known as the horizontally opposed engine, in which the corresponding pistons reach top dead center at the same time, thus balancing each other in momentum.
  • 1900: Rudolf Diesel demonstrated the diesel engine in the 1900 Exposition Universelle (World's Fair) using peanut oil (biodiesel).
  • 1900: Wilhelm Maybach designed an engine built at Daimler Motoren Gesellschaft—following the specifications of Emil Jellinek—who required the engine to be named Daimler-Mercedes after his daughter. In 1902, automobiles with that engine were put into production by DMG.


Internal combustion engines are most commonly used for mobile propulsion in automobiles, equipment, and other portable machinery. In mobile scenarios internal combustion is advantageous, since it can provide high power to weight ratios together with excellent fuel energy-density. These engines have appeared in almost all automobiles, motorcycles, boats, and in a wide variety of aircraft and locomotives. Where very high power is required, such as jet aircraft, helicopters, and large ships, they appear mostly in the form of turbines. They are also used for electric generators and by industry.


All internal combustion engines depend on the exothermic chemical process of combustion: The reaction of a fuel, typically with air, although other oxidizers such as nitrous oxide may be employed.

The most common fuel in use today are made up of hydrocarbons and are derived from mostly petroleum. These include the fuels known as diesel fuel, gasoline, and petroleum gas, and rare use of propane gas. Most internal combustion engines designed for gasoline can run on natural gas or liquified petroleum gases without major modifications except for the fuel delivery components. Liquid and gaseous biofuels, such as Ethanol and biodiesel, a form of diesel fuel that is produced from crops that yield triglycerides such as soy bean oil, can also be used. Some can also run on Hydrogen gas.

All internal combustion engines must have a method for achieving ignition in their cylinders to create combustion. Engines use either a electrical method or a compression ignition system.

Gasoline ignition Process


Diesel engine ignition process

Compression ignition systems, such as the diesel engine and HCCI (Homogeneous Charge Compression Ignition) engines, rely solely on heat and pressure created by the engine in its compression process for ignition. Compression that occurs is usually more than three times higher than a gasoline engine. Diesel engines will take in air only, and shortly before peak compression, a small quantity of diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines will take in both air and fuel but will continue to rely on an unaided auto-combustion process due to higher pressures and heat. This is also why diesel and HCCI engines are also more susceptible to cold starting issues though they will run just as well in cold weather once started. Most diesels also have battery and charging systems however this system is secondary and is added by manufacturers as luxury for ease of starting, turning fuel on and off which can also be done via a switch or mechanical apparatus, and for running auxiliary electrical components and accessories. Most modern diesels, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions.





An illustration of several key components in a typical four-stroke engine.







With that said, one must understand that common usage does often dictate definitions. Many individuals consider engines as those things which generate their power from within, and motors as requiring an outside source of energy to perform their work. Evidently, the roots of the words seem to actually indicate a real difference. Further, as in many definitions, the root word only explains the beginnings of the word, rather than the current usage. It can certainly be argued that such is the case with the words motor and engine.

Principles of operation

A 1906 gasoline engine.


  • Crude oil engine
  • Two-stroke cycle
  • Four-stroke cycle
  • Hot bulb engine
  • Poppet valves
  • Sleeve valve
  • Atkinson cycle
  • Proposed
    • Bourke engine
  • Improvements
  • Controlled Combustion Engine


  • Demonstrated:
    • Wankel engine
  • Proposed:
    • Orbital engine
    • Quasiturbine
    • Rotary Atkinson cycle engine
    • Toroidal engine

Continuous combustion:

  • 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. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to scavenge the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh charge in the crankcase, which is then blown through the cylinder through ports in the cylinder walls. Spark-ignition two-strokes are small and light (for their power output), and mechanically very simple. Common applications include snowmobiles, lawnmowers, weed-whackers, chain saws, jet skis, mopeds, outboard motors, and some motorcycles. Unfortunately, they are also generally louder, less efficient, and far more polluting than their four-stroke counterparts, and they do not scale well to larger sizes. Interestingly, the largest compression-ignition engines are two-strokes, and are used in some locomotives and large ships. These engines use forced induction to scavenge the cylinders. two stroke engines are less fuel efficient than other types of engines because unspent fuel being sprayed into the combustion chamber can some times escape out of the exhaust duct with the previously spent fuel. Without special exhaust processing, this will also produce very high pollution levels, requiring many small engine applications such as lawnmowers to employ four stroke engines, and smaller two-strokes to be outfitted with catalytic converters in some jurisdictions.




Engines based on the five-stroke cycle are a variant of the four stroke cycle. Normally the four cycles are intake, compression, combustion and exhaust. The fifth cycle added by Delautour[2] is refrigeration. Engines running on a five-stroke cycle are up to 30 percent more efficient than an equivalent four stroke engine.

Bourke engine


Controlled combustion engine



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. This engine provides three power "strokes" per revolution per rotor, giving it a greater power-to-weight ratio, on average, than piston engines. This type of engine is used in the Mazda current RX8 and earlier RX7 as well as other models.

Gas turbine

With gas turbine cycles (notably Jet engines), rather than use the same piston to compress and then expand the gases, instead separate compressors and gas turbines are employed; giving continuous power. Essentially, the intake gas (air normally) is compressed, and then combusted with a fuel, which greatly raises the temperature and volume. The larger volume of hot gas from the combustion chamber is then fed through the gas turbine which is then easily able to power the compressor.

Disused methods


Fuel and oxidizer types

Fuels used include petroleum spirit (North American term: Gasoline, British term: Petrol), autogas (liquified petroleum gas), compressed natural gas, hydrogen, diesel fuel, jet fuel, landfill gas, biodiesel, biobutanol, peanut oil and other vegoils, bioethanol, biomethanol (methyl or wood alcohol), and other biofuels. Even fluidized metal powders and explosives have seen some use. Engines that use gases for fuel are called gas engines and those that use liquid hydrocarbons are called oil engines. However, gasoline engines are unfortunately also often colloquially referred to as "gas engines."


The oxidizer is typically air, and has the advantage of not being stored within the vehicle, increasing the power-to-weight ratio. Air can, however, be compressed and carried aboard a vehicle. Some submarines are designed to carry pure oxygen or hydrogen peroxide to make them air-independent. Some race cars carry nitrous oxide as oxidizer. Other chemicals, such as chlorine or fluorine, have seen experimental use; but most are impractical.



Some have theorized that in the future hydrogen might replace such fuels. Furthermore, with the introduction of hydrogen fuel cell technology, the use of internal combustion engines may be phased out. The advantage of hydrogen is that its combustion produces only water. This is unlike the combustion of fossil fuels, which produce carbon dioxide, a principle cause of global warming, carbon monoxide resulting from incomplete combustion, and other local and atmospheric pollutants such as sulfur dioxide and nitrogen oxides that lead to urban respiratory problems, acid rain, and ozone gas problems. However, free hydrogen for fuel does not occur naturally, burning it liberates less energy than it takes to produce hydrogen in the first place by the simplest and most widespread method, electrolysis. Although there are multiple ways of producing free hydrogen, those require converting currently combustible molecules into hydrogen, so hydrogen does not solve any energy crisis, moreover, it only addresses the issue of portability and some pollution issues. The big disadvantage of hydrogen in many situations is its storage. Liquid hydrogen has extremely low density- 14 times lower than water and requires extensive insulation, whilst gaseous hydrogen requires very heavy tankage. Although hydrogen has a higher specific energy, the volumetric energetic storage is still roughly five times lower than petrol, even when liquified. (The "Hydrogen on Demand" process, designed by Steven Amendola, creates hydrogen as it is needed, but this has other issues, such as the raw materials being relatively expensive.) Other fuels that are kinder on the environment include biofuels. These can give no net carbon dioxide gains.

One-cylinder gasoline engine (c. 1910).



  • 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 three to 28 cylinders, such as the Pratt & Whitney R-4360. A row contains an odd number of cylinders, so an even number indicates a two or four-row engine. The largest of these was the Lycoming R-7755 with 36 cylinders (four rows of nine cylinders) but never entered production.
  • Motorcycles commonly have from one to four cylinders, with a few high performance models having six (though some "novelties" exist with 8, 10, and 12).

Ignition system

Internal combustion engines can be classified by their ignition system. The point in the cycle at which the fuel/oxidizer mixture are ignited has a direct effect on the efficiency and output of the ICE. For a typical 4 stroke automobile engine, the burning mixture has to reach its maximum pressure when the crankshaft is 90 degrees after TDC (Top dead centre). The speed of the flame front is directly affected by compression ratio, fuel mixture temperature and octane or cetane rating of the fuel. Modern ignition systems are designed to ignite the mixture at the right time to ensure the flame front doesn't contact the descending piston crown. If the flame front contacts the piston, pinking or knocking results. Leaner mixtures and lower mixture pressures burn more slowly requiring more advanced ignition timing. 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 U.S. Patent 609250 (PDF), "Electrical Igniter for Gas Engines," on August 16, 1898.

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 impossible. Carburetors are the current most widespread fuel mixing device used in lawnmowers and other small engine applications. Prior to the mid-1980s, carburetors were also common in automobiles.

Larger gasoline engines such as those used in automobiles have mostly moved to fuel injection systems. Diesel engines always use fuel injection.


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.

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.


Engine capacity

An engine's capacity is the displacement or swept volume by the pistons of the engine. It is generally measured in liters (L) or cubic inches (c.i. or in³) for larger engines and cubic centimeters (abbreviated to cc) for smaller engines. Engines with greater capacities are usually more powerful and provide greater torque at lower rpm but also consume more fuel.

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.


Lubrication systems

There are several different types of lubrication systems used. Simple two-stroke engines are lubricated by oil mixed into the fuel or injected into the induction stream as a spray. Early slow speed stationary and marine engines were lubricated by gravity from small chambers, similar to those used on steam engines at the time, with an engine tender refilling these as needed. As engines were adapted for automotive and aircraft use, the need for a high power to weight ratio lead to increased speeds, higher temperatures, and greater pressure on bearings, which, in turn, required pressure lubrication for crank bearing and connecting rod journals, provided either by a direct lubrication from a pump, or indirectly by a jet of oil directed at pickup cups on the connecting rod ends, which had the advantage of providing higher pressures as engine speed increased.

Engine pollution


Diesel engines produce a wide range of pollutants including aerosols of many small particles (PM10) that are believed to penetrate deeply into human lungs. Engines running on liquefied petroleum gas (LPG) are very low in emissions as LPG burns very clean and does not contain sulphur or lead.


Internal combustion engine efficiency

The efficiency of various types of internal combustion engines vary. It is generally accepted that most gasoline fueled internal combustion engines, even when aided with turbochargers and stock efficiency aids, have a mechanical efficiency of about 20 percent. Most internal combustion engines waste about 36 percent of the energy in gasoline as heat lost to the cooling system and another 38 percent through the exhaust. The rest, about six percent, is lost to friction. Most engineers have not been able to successfully harness wasted energy for any meaningful purpose, although there are various add on devices and systems that can greatly improve combustion efficiency.

Hydrogen Fuel Injection, or HFI, is an engine add on system that is known to improve fuel economy of internal combustion engines by injecting hydrogen as a combustion enhancement into the intake manifold. Fuel economy gains of 15 percent to 50 percent can be seen. A small amount of hydrogen added to the intake air-fuel charge increases the octane rating of the combined fuel charge and enhances the flame velocity, thus permitting the engine to operate with more advanced ignition timing, a higher compression ratio, and a leaner air-to-fuel mixture than otherwise possible. The result is lower pollution with more power and increased efficiency. Some HFI systems use an on board electrolyzer to generate the hydrogen used. A small tank of pressurized hydrogen can also be used, but this method necessitates refilling.

There has also been discussion of new types of internal combustion engines, such as the Scuderi Split Cycle Engine, that utilize high compression pressures in excess of 2000 psi and combust after top-dead-center (the highest & most compressed point in a internal combustion piston stroke). Such engines are expected to achieve efficiency as high as 50-55%.


  1. Thinkquest, Huygens.] Retrieved July 16, 2008.
  2. Tony Williams, 101 Ingenious Kiwis (Reed Publishing NZ Ltd, 2006), p. 83.


  • Hardenberg, Horst O. 1999. The Middle Ages of the Internal Combustion Engine. Warrendale, PA: SAE International Publishing. ISBN 0768003911.
  • Heywood, John. 1988. Internal Combustion Engine Fundamentals. New York: McGraw-Hill Science/Engineering/Math. ISBN 007028637X.
  • Stone, Richard. 1999. Introduction to Internal Combustion Engines. Warrendale, PA: SAE International Publishing. ISBN 0768004950.
  • Taylor, Charles Fayette. 1985. The Internal Combustion Engine in Theory and Practice. Cambridge, MA: The MIT Press. ISBN 0262700263.

External links

All links retrieved April 18, 2014.




Research begins here...