[edit] History
A colorized automobile engine
Early internal-combustion engines were used to power farm equipment similar to these models.
The first internal combustion engines did not have compression, but ran on air/fuel mixture 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 Vinci described a compression-less engine.
1673: Christiaan Huygens described a compression-less engine.
[2]
17th century: English inventor Sir Samuel Morland used gunpowder to drive water pumps.
1780's: Alessandro Volta built a toy electric pistol
([5]) in which an electric spark exploded a mixture of air and hydrogen, firing a cork from the end of the gun.
1794: Robert Street built a compression-less engine whose principle of operation would dominate for nearly a century.
1806: Swiss engineer François Isaac de Rivaz built an internal combustion engine powered by a mixture of hydrogen and oxygen.
1823: Samuel Brown patented 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was compression-less and based on what Hardenberg calls the "Leonardo cycle," which, as this name implies, was already out of date at that time.
1824: French physicist Sadi Carnot established 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.
1826 April 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.
1854: The Italians Eugenio Barsanti and Felice Matteucci patented the first working efficient internal combustion engine in London (pt. Num. 1072) but did not go 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.
1862: Nikolaus Otto designed 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 Marcus put the first mobile gasoline engine on a handcart.
1876: Nikolaus Otto working with Gottlieb Daimler and Wilhelm Maybach developed a practical four-stroke cycle (Otto cycle) engine. The German courts, 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.
Karl Benz
1879: Karl Benz, working independently, was granted a patent for 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 Atkinson invented the Atkinson cycle engine. 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 Stuart built his oil engine, leasing rights to Hornsby of England to build them. They build the first cold start, compression ignition engines. In 1892, they installed the first ones in a water pumping station. An experimental higher-pressure version produced self-sustaining ignition through compression alone in the same year.
1892: Rudolf Diesel developed his Carnot heat engine type motor burning powdered coal dust.
1893 February 23: Rudolf Diesel received a patent for the diesel engine.
1896: Karl Benz invented 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 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.
[edit] Applications
Internal combustion engines are most commonly used for mobile propulsion in automobiles, equipment, and other portable machinery. In mobile equipment internal combustion is advantageous, since it can provide high power to weight ratios together with excellent fuel energy-density. These engines have appeared in transport in almost all automobiles, trucks, motorcycles, boats, and in a wide variety of aircraft and locomotives, generally using petroleum . 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 (i.e. 12 V generators) and by industry.
[edit] Operation
Four-stroke cycle (or Otto cycle)1. intake2. compression3. power4. exhaust
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. Also see stoichiometry.
The most common modern fuels are made up of hydrocarbons and are derived from mostly petroleum. These include the fuels known as dieselfuel, gasoline and petroleum gas, and the rarer use of propane gas. Most internal combustion engines designed for gasoline can run on natural gas or liquefied 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 achieve ignition in their cylinders to create combustion. Typically engines use either a spark ignition (SI) method or a compression ignition (CI) system. In the past other methods using hot tubes or flames have been used.
[edit] 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 185 psi and use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder.
[edit] 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 old engines, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions.
[edit] Energy
Once 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.
[edit] Parts
An illustration of several key components in a typical four-stroke engine
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 passes from the carburetor to the the cylinder, where it is ignited; this 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 occur in each stroke.
[edit] Classification
The fundamental difference between an engine and a motor is that a motor converts electricity into mechanical energy whereas an engine converts thermal energy into mechanical energy. At one time, the word "engine" (from Latin, via Old French, ingenium, "ability") meant any piece of machinery — a sense the persists in expressions such as siege engine. 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." (An electric engine refers to locomotive operated by electricity).
However, many people consider engines as those things which generate their power from within, and motors as requiring an outside source of energy to perform their work.
[edit] Principles of operation
[edit] Beare Head
The Beare Head Six Stroke was named such after its inventor. The Beare Head Six Stroke combines both a four stroke engine bottom end, plus a two stroke slanted top end, thus 4+2= Six Stroke. It is a piston valve with auxiliary low pressure valves. With the hybrid of two- and four-stroke technology, the device supposedly achieves increased torque and power output, better fuel economy and cleaner burning with reduced emissions, longer service intervals, and considerably reduced tooling costs when compared with a conventional OHC four-stroke design.
The technology was sold to an Australian company in 2004 http://www.jack-brabham-engines.com
[edit] Bourke Engine
In this engine, two diametrically opposed cylinders are linked to the crank by the crank pin that goes through the common scotch yoke. The cylinders and pistons are so constructed that there are, as in the usual two stroke cycle, two power strokes per revolution. However, unlike the common two stroke engine, the burnt gases and the incoming fresh air do not mix in the cylinders, contributing to a cleaner, more efficient operation.
The scotch yoke mechanism also has low side thrust and thus greatly reduces friction between pistons and cylinder walls. The Bourke engine'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.
[edit] Controlled Combustion Engine
These are also cylinder based engines and may be either single- or two-stroke but use, instead of a crankshaft and piston rods, two gear connected, counter rotating concentric cams to convert reciprocating motion into rotary movement.
These cams practically cancel out sideward forces that would otherwise be exerted on the cylinders by the pistons, greatly improving mechanical efficiency.
The number of lobes of the cams (always an odd number not less than 3) determines the piston travel versus the torque delivered. In this engine, there are two cylinders that are 180 degrees apart for each pair of counter-rotating cams. For single-stroke versions there are as many cycles per cylinder pair as there are lobes on each cam, and twice as many for two-stroke engines.
[edit] Wankel
Main article: Wankel engine
The Wankel engine (Rotary engine) does not have piston strokes so is more properly called a four-phase than a four-stroke engine.
It operates with the same separation of phases as the four-stroke engine, with the phases taking place in separate locations in the engine. This engine provides three power 'strokes' per revolution per rotor, typically giving it a greater power-to-weight ratio than piston engines. This type of engine is most notably used in the current Mazda RX-8, the earlier RX-7, and other models.
[edit] Gas turbine
Main article: Gas turbine
Gas turbines cycles (notably jet engines), do not 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 (normally air) 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. The exhaust gas may be used to provide thrust, supplying only sufficient power to the turbine to compress incoming air (jet engine); or as much energy as possible can be supplied to the turbine (gas turbine proper).
[edit] Disused methods
In some old non-compressing internal combustion engines: In the first part of the piston downstroke a fuel/air mixture was sucked or blown in.
In the rest of the piston downstroke the inlet valve closed and the fuel/air mixture fired. In the piston upstroke the exhaust valve was open. This was an attempt at imitating the way a piston steam engine works.
[edit] Fuels and oxidizers
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 fluidised 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 also often colloquially referred to as 'gas engines'.
The main limitations on fuels are that it must be easily transportable through the fuel system to the combustion chamber, and that the fuel release sufficient energy in the form of heat upon combustion to make use of the engine practical.
The oxidiser 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 so that they do not need air from the atmosphere. Some race cars carry nitrous oxide as oxidizer. Other chemicals such as chlorine or fluorine have been used experimentally, but have not been found to be practical.
Diesel engines are generally heavier, noisier and more powerful at lower speeds than gasoline engines. They are also more fuel-efficient in most circumstances and are used in heavy road vehicles, some automobiles (increasingly so for their increased fuel efficiency over gasoline engines), ships, railway 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 have taken over about 40% of the market since the 1990s. 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.
[edit] Hydrogen engine
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 known green house gas GHG, 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 due to the second law of thermodynamics.
Although there are multiple ways of producing free hydrogen, those require converting 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 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 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 has other issues, such as the high price of the sodium borohydride, the raw material. Sodium borohydride is renewable and could become cheaper if more widely produced.)
