Internal combustion engine
The internal combustion engine is an engine in which the burning of a fuel occurs in a confined space called a combustion chamber. This exothermic reaction of a fuel with an oxidizer creates gases of high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause movement, for example by acting on pistons, rotors, or even by pressing on and moving the entire engine itself. 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. The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as Jet engines, most rockets and many gas turbines are also internal combustion engines. How exactly does a combustion engine work?
Watch this instructional video to find out more:
Demonstration of the internal combustion indirect or suction principle. This may not meet the definition of an engine, because the process does not repeat.
The first internal combustion engines did not have compression, but ran on what air/fuel mixture could be sucked or blown in during the first part of the intake stroke. The most significant distinction between modern internal combustion engines and the early designs is the use of compression and in particular of in-cylinder compression.
- 1509: Leonardo da Vincidescribed a compression-less engine. (His description may not imply that the idea was original with him or that it was actually built.)
- 1673: Christiaan Huygensdescribed a compression-less engine.
- 1780’s: Alessandro Voltabuilt 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.
- 17th century: Englishinventor Sir Samuel Morland used gunpowder to drive water pumps.
- 1794: Robert Streetbuilt a compression-less engine whose principle of operation would dominate for nearly a century.
- 1806: Swiss engineer François Isaac de Rivazbuilt an internal combustion engine powered by a mixture of hydrogen and oxygen.
- 1823: Samuel Brownpatented the first internal combustion engine to be applied industrially. It was compression-less and based on what Hardenberg calls the “Leonardo cycle,” which, as this name implies, was already out of date at that time. Just as today, early major funding, in an area where standards had not yet been established, went to the best showmen sooner than to the best workers.
- 1824: French physicist Sadi Carnotestablished the thermodynamic theory of idealized heat engines. This scientifically established the need for compression to increase the difference between the upper and lower working temperatures, but it is not clear that engine designers were aware of this before compression was already commonly used. It may have misled designers who tried to emulate the Carnot cycle in ways that were not useful.
- 1826April 1: The American Samuel Morey received a patent for a compression-less “Gas Or Vapor Engine”.
- 1838: a patent was granted to William Barnet (English). This was the first recorded suggestion of in-cylinder compression. He apparently did not realize its advantages, but his cycle would have been a great advance if developed enough.
- 1854: The Italians Eugenio Barsantiand Felice Matteucci patented the first working efficient internal combustion engine in London (pt. Num. 1072) but did not get into production with it. It was similar in concept to the successful Otto Langen indirect engine, but not so well worked out in detail.
- 1860: Jean Joseph Etienne Lenoir(1822 – 1900) produced a gas-fired internal combustion engine closely similar in appearance to a horizontal double-acting steam beam engine, with cylinders, pistons, connecting rods, and flywheel in which the gas essentially took the place of the steam. This was the first internal combustion engine to be produced in numbers. His first engine with compression shocked itself apart.
- 1862: Nikolaus Ottodesigned an indirect-acting free-piston compression-less engine whose greater efficiency won the support of Langen and then most of the market, which at that time, was mostly for small stationary engines fueled by lighting gas.
- 1870: In Vienna Siegfried Marcusput the first mobile gasoline engine on a handcart.
- 1876: Nikolaus Ottoworking with Gottlieb Daimler and Wilhelm Maybach developed a practical four-stroke cycle (Otto cycle) engine. The Germancourts, however, did not hold his patent to cover all in-cylinder compression engines or even the four stroke cycle, and after this decision in-cylinder compression became universal.
- 1879: Karl Benz, working independently, was granted a patentfor his internal combustion engine, a reliable two-stroke gas engine, based on Nikolaus Otto’s design of the four-stroke engine. Later Benz designed and built his own four-stroke engine that was used in his automobiles, which became the first automobiles in production.
- 1882: James Atkinsoninvented the Atkinson cycle Atkinson’s engine had one power phase per revolution together with different intake and expansion volumes making it more efficient than the Otto cycle.
- 1891 – Herbert Akroyd Stuartbuilds 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 Dieseldevelops his Carnot heat engine type motor burning powdered coal dust.
- 1893 February 23: Rudolf Diesel received a patent for the diesel engine.
- 1896: Karl Benzinvented the boxer engine, also known as the horizontally opposed engine, in which the corresponding pistons reach top dead centre 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 (see biodiesel).
- 1900: Wilhelm Maybachdesigned 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.
Early internal-combustion engines were used to power farm equipment similar to these models.
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 oxidisers such as nitrous oxide may be employed. Also see stoichiometry.
The most common fuel in use today are made up of hydrocarbons and are derived from mostly petroleum. These include the fuels known asdieselfuel, gasoline and petroleum gas, and rare use of propane gas. Most internal combustion engines designed for gasoline can run on natural gasor liquified petroleum gases without major modifications except for the fuel delivery components. Liquid and gaseous biofuels, such as Ethanol andbiodiesel, 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 onHydrogen gas.
All internal combustion engines must have a method for achieving ignition in their cylinders to create combustion. Engines use either an electricalmethod or a compression ignition system.
Gasoline Ignition Process
Electrical/Gasoline-type ignition systems (that can also run on other fuels as previously mentioned) generally rely on a combination of a lead-acid battery and an induction coil to provide a high voltage electrical spark to ignite the air-fuel mix in the engine’s cylinders. This battery can be recharged during operation using an electricity-generating device, such as an alternator or generator driven by the engine. Gasoline engines take in a mixture of air and gasoline and compress to less than 170 psi and use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder.
Diesel Engine Ignition Process
Compression ignition systems, such as the diesel engine and HCCI 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.
Once successfully ignited and burnt, the combustion products, hot gases, have more available energy than the original compressed fuel/air mixture (which had higher chemical energy). The available energy is manifested as high temperature and pressure which can be translated into work by the engine. In a reciprocating engine, the high pressure product gases inside the cylinders drive the engine’s pistons.
Once the available energy has been removed, the remaining hot gases are vented (often by opening a valve or exposing the exhaust outlet) and this allows the piston to return to its previous position (Top Dead Center – TDC). The piston can then proceed to the next phase of its cycle, which varies between engines. Any heat not translated into work is normally considered a waste product, and is removed from the engine either by an air or liquid cooling system.
An illustration of several key components in a typicalfour-stroke engine
The parts of an engine vary depending on the engine’s type. For a four-stroke engine, key parts of the engine include the crankshaft (purple), one or more camshafts (red and blue) and valves. For a two-stroke engine, there may simply be an exhaust outlet and fuel inlet instead of a valve system. In both types of engines, there are one or more cylinders (grey and green) and for each cylinder there is a spark plug (darker-grey), a piston (yellow) and a crank (purple). A single sweep of the cylinder by the piston in an upward or downward motion is known as a stroke and the downward stroke that occurs directly after the air-fuel mix in the cylinder is ignited is known as a power stroke.
A Wankel engine has a triangular rotor that orbits in an epitrochoidal (figure 8 shape) chamber around an eccentric shaft. The four phases of operation (intake, compression, power, exhaust) take place in separate locations, instead of one single location as in a reciprocating engine.
A Bourke Engine uses a pair of pistons integrated to a Scotch Yoke that transmits reciprocating force through a specially designed bearing assembly to turn a crank mechanism. Intake, compression, power, and exhaust all occur in each stroke of this yoke.
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.
Although the terms sometimes cause confusion, there is no real difference between an “engine” and a “motor.” At one time, the word “engine” (fromLatin, 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 combustion engines are often referred to as “motors.” (Anelectric engine refers to locomotive operated by electricity).
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.