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Diesel Engine

Diesel engine

The diesel engine is a type of internal combustion engine; more specifically, it is a compression ignition engine, in which the fuel is ignited by being suddenly exposed to the high temperature and pressure of a compressed gas containing oxygen (usually atmospheric air), rather than a separate source of ignition energy (such as a spark plug), as is the case in the gasoline engine. This is known as the diesel cycle, after German engineer Rudolf Diesel, who invented it in 1892 and received the patent on February 23, 1893 (1893-02-23). Diesel intended the engine to use a variety of fuels including coal dust. He demonstrated it in the 1900 Exposition Universelle (World's Fair) using peanut oil (see biodiesel).

How diesel engines work

When a gas is compressed, its temperature rises (see the combined gas law); a diesel engine uses this property to ignite the fuel. Air is drawn into the cylinder of a diesel engine and compressed by the rising piston at a much higher compression ratio than for a spark-ignition engine, up to 25:1. The air temperature reaches 700–900 °C, or 1300–1650 °F. At the top of the piston stroke, diesel fuel is injected into the combustion chamber at high pressure, through an atomising nozzle, mixing with the hot, high-pressure air. The resulting mixture ignites and burns very rapidly. This contained explosion causes the gas in the chamber to heat up rapidly, which increases its pressure, which in turn forces the piston downwards. The connecting rod transmits this motion to the crankshaft, which is forced to turn, delivering rotary power at the output end of the crankshaft. Scavenging (pushing the exhausted gas-charge out of the cylinder, and drawing in a fresh draught of air) of the engine is done either by ports or valves. To fully realize the capabilities of a diesel engine, use of a turbocharger to compress the intake air is necessary; use of an aftercooler/intercooler to cool the intake air after compression by the turbocharger further increases efficiency. In very cold weather, diesel fuel thickens and increases in viscosity and forms wax crystals or a gel. This can make it difficult for the fuel injector to get fuel into the cylinder in an effective manner, making cold weather starts difficult at times, though recent advances in diesel fuel technology have made these difficulties rare. A commonly applied advance is to electrically heat the fuel filter and fuel lines. Other engines utilize small electric heaters called glow plugs inside the cylinder to warm the cylinders prior to starting. A small number use resistive grid heaters in the intake manifold to warm the inlet air until the engine reaches operating temperature. Engine block heaters (electric resistive heaters in the engine block) plugged into the utility grid are often used when an engine is shut down for extended periods (more than an hour) in cold weather to reduce startup time and engine wear. A vital component of any diesel engine system is the governor, which limits the speed of the engine by controlling the rate of fuel delivery. Older governors were driven by a gear system from the engine (and thus supplied fuel only linearly with engine speed). Modern electronically-controlled engines achieve this through the electronic control module (ECM) or electronic control unit (ECU) - the engine-mounted "computer". The ECM/ECU receives an engine speed signal from a sensor and then using its algorithms and look-up calibration tables stored in the ECM/ECU, it controls the amount of fuel and its timing (the "start of injection") through electric or hydraulic actuators to maintain engine speed. Controlling the timing of the start of injection of fuel into the pistons is key to minimising their emissions and maximising the fuel economy (efficiency) or the engine. The exact timing of starting this fuel injection into the cylinder is controlled electronically in most of today's modern engines. The timing is usually measured in units of crank angles before Top Dead Center (TDC) that the piston is at. For example, if the ECM/ECU initiates fuel injection when the piston is 10 degrees before TDC, the start of injection or "timing" is said to be 10 deg BTDC. The optimal timing will depend on both the engine design as well as its speed and load. Advancing (injecting when the piston is further away from TDC) the start of injection results in higher in-cylinder pressure and higher efficiency but also results in higher Nitrous Oxide (NOx) emissions. At the other extreme, very retarded start of injection or timing causes incomplete combustion. This results in higher Particulate Matter (PM) emissions and higher smoke.

Fuel injection in diesel engines

Early diesels often employed indirect injection in order to use simple, flat-top pistons, and made the positioning of the early, bulky diesel injectors easier, but all modern diesel engines employ some form of direct injection, coupled with more complicated bowl-in-piston designs. Modern engines also use a very highly pressurised fuel supply line, which replaces the older, noisier, and mechanically more complicated combined pump and selector valve assembly (see below).

Indirect Injection

An indirect injection diesel engine delivers fuel into a chamber off the combustion chamber, called a prechamber, where combustion begins and then spreads into the main combustion chamber. The prechamber is carefully designed to ensure adequate mixing of the atomized fuel with the compression-heated air. This has the effect of slowing the rate of combustion, which tends to reduce audible noise. It also softens the shock of combustion and produces lower stresses on the engine components. The addition of a prechamber, however, increases heat loss to the cooling system and thereby lowers engine efficiency.

Direct injection

Modern diesel engines make use of one of the following direct injection methods:

Common rail direct injection

The common rail system on its prototype was already developed in late sixties with Mr. Hiber in Switzerland. After that, Ganser of the Swiss Federal Institute of Technology focusing on his research the common rail technology was advanced. In mid nineties, Dr. Shohei Itoh and Masahiko Miyaki, Japanese automotive parts manufacturer Denso Corporation, developed the Common Rail Fuel System for Heavy Duty Vehicles and finally turned into its first practical use on their ECD-U2 common Rail system, which was mounted on the HINO RAISING RANGER truck and sold for general use in 1995. Later in 1997 the German automotive parts manufacturer Robert Bosch GmbH extended its use for passenger car. Today the common rail system is responsible for a revolution in diesel engine technology. Delphi Automotive Systems of the US also make common-rail systems. Different car makers refer to their common rail engines by different names, e.g. DaimlerChrysler's CDI, Ford Motor Company's TDCi (most of these engines are manufactured by PSA), Fiat Group's (Fiat, Alfa Romeo and Lancia) JTD, Renault's DCi, GM/Opel's CDTi (most of these engines are manufactured by Fiat, other by Isuzu), PSA Peugeot Citroen's HDI, Toyota's D-4D, and so on. In older diesel engines, a distributor-type injection pump, regulated by the engine, supplies bursts of fuel to injectors which are simply nozzles through which the diesel is sprayed into the engine's combustion chamber. As the fuel is at low pressure and there cannot be precise control of fuel delivery, the spray is relatively coarse and the combustion process is relatively crude and inefficient. In common rail systems, the distributor injection pump is eliminated. Instead an extremely high pressure pump stores a reservoir of fuel at high pressure - up to 1,800 bar (180 MPa) - in a "common rail", basically a tube which in turn branches off to computer-controlled injector valves, each of which contains a precision-machined nozzle and a plunger driven by a solenoid. Driven by a computer (which also controls the amount of fuel to the pump), the valves, rather than pump timing, control the precise moment when the fuel injection into the cylinder occurs and also allow the pressure at which the fuel is injected into the cylinders to be increased. As a result, the fuel that is injected atomises easily and burns cleanly, reducing exhaust emissions and increasing efficiency. In addition, the engine's Electronic Control Unit (ECU) can inject a small amount of diesel just before the main injection event ("pilot" injection) that reduces noise and vibration, as well as optimises injection timing and quantity for variations in fuel quality, cold starting, and so on. Most European automakers have common rail diesels in their model lineups, even for commercial vehicles. Some Japanese manufacturers, such as Toyota, Nissan and recently Honda, have also developed common rail diesel engines.

Unit direct injection

This also injects fuel directly into the cylinder of the engine. However, in this system the injector and the pump are combined into one unit positioned over each cylinder. Each cylinder thus has its own pump, feeding its own injector, which prevents pressure fluctuations and allows more consistent injection to be achieved. This type of injection system, also developed by Bosch, is used by Volkswagen AG in cars, and most major diesel engine manufactures, in large commercial engines (Cat, Cummins, Detroit Diesel). With recent advancements, the pump pressure has been raised to 2,050 bar (205 MPa), allowing injection parameters similar to common rail systems.

Types of diesel engines

There are two classes of diesel engines: two-stroke and four-stroke. Most diesels generally use the four-stroke cycle, with some larger diesels operating on the two-stroke cycle. Normally, banks of cylinders are used in multiples of two, although any number of cylinders can be used as long as the load on the crankshaft is counterbalanced to prevent excessive vibration. The inline-6 is the most prolific in medium- to heavy-duty engines, though the V8 and straight-4 are also common.

Advantages and disadvantages versus spark-ignition engines

Diesel engines are more efficient than gasoline/petrol engines of the same power (by approx. 15%), resulting in lower fuel consumption. Naturally aspirated diesel engines are more massive than gasoline/petrol engines of the same power for two reasons; the first is that it takes a larger capacity diesel engine than a gasoline engine to produce the same power. This is essentially because the diesel cannot operate as quickly - the "rev limit" is lower - because getting the fuel-air mixture into a diesel engine is more difficult than a gasoline engine [http://www.perkins.com/perkins/cda/articleDisplay/1,4094,7___32_____7_10020408,00.html]. The second reason is that a diesel engine must be stronger to withstand the higher combustion pressures needed for ignition. Yet it is this same build quality that has allowed some enthusiasts to acquire significant power increases with turbocharged engines through fairly simple and inexpensive modifications. A gasoline engine of similar size cannot put out a comparable power increase without extensive alterations because the stock components would not be able to withstand the higher stresses placed upon them. Since a diesel engine is already built to withstand higher levels of stress, it makes an ideal candidate for performance tuning with little expense. However it should be said that any modification that raises the amount of fuel and air put through a diesel engine will increase its operating temperature which will reduce its life and service interval requirements. In addition, sending additional fuel to the cylinders will wash away lubricating oil faster. These things are issues with newer, lighter, "high performance" diesel engines which aren't "overbuilt" to the degree of older engines and are being pushed to provide greater power in smaller engines. The addition of a turbocharger or supercharger to the engine (see turbodiesel) greatly assists in increasing fuel economy and power output. Boost pressures can be higher on diesels than gasoline engines, and the higher compression ratio allows a diesel engine to be more efficient than a comparable spark ignition engine, although the calorific value of the fuel is slightly lower at 45.3 megajoules per kilogram to gasoline at 45.8 MJ/kg. The increased fuel economy of the diesel over the petrol engine means that the diesel produces less carbon dioxide (CO₂) per unit distance. The recent development of biofuel alternatives to fossil fuels has unleashed the ability to produce a net-sum of zero emissions of CO₂, as it is re-absorbed into plants and then comes full circle, being used to produce the fuel. Diesel engines can produce black soot from their exhaust. This consists of unburned carbon compounds. Modern diesel engines catch the soot in a particle filter, which when saturated is automatically regenerated by burning the particles. Other problems associated with the exhaust gases (nitrogen oxide, sulfurous fumes) can be mitigated with further investment and equipment. The lack of an electrical ignition system greatly improves the reliability. The high durability of a diesel engine is also due to its overbuilt nature (see above) as well as the diesel's combustion cycle, which creates less-violent changes in pressure when compared to a spark-ignition engine, a benefit that is magnified by the lower rotating speeds in diesels. Unfortunately, due to the greater compression force required and the increased weight of the stronger components, starting a diesel engine is a harder task. More torque is required to push the engine through compression. Either an electrical starter or an air start system is used to start the engine turning. On large engines, pre-lubrication and slow turning of an engine, as well as heating, are required to minimize the possibility of damaging the engine during initial start-up and running. Some smaller military diesels can be started with an explosive cartridge that provides the extra power required to get the machine turning. In the past, Caterpillar and John Deere used a small gasoline "pony" motor in their tractors to start the primary diesel motor. The pony motor heated the diesel to aid in ignition and utilized a small clutch and transmission to actually spin up the diesel engine. Even more unusual was an International Harvester design in which the diesel motor had its own carburetor and ignition system, and started on gasoline. Once warmed up, the operator moved two levers to switch the motor to diesel operation, and work could begin. These engines had very complex cylinder heads (with their own gasoline combustion chambers) and in general were vulnerable to expensive damage if special care was not taken (especially in letting the engine cool before turning it off).

Automobile racing

Although the weight and lower output of a diesel engine tend to keep them away from automotive racing applications, there are many diesels being raced in classes that call for them, mainly in truck racing, as well in types of racing where these drawbacks are less severe, such as land speed record racing. [http://www.cumminsracing.com/ Diesel engined dragsters] even exist, despite the diesel's drawbacks being central to performance in this sport. In 1952, [http://www.cummins.com/eu/pages/en/whoweare/cumminshistory.cfm Cummins Diesel] won the pole at the Indianapolis 500 race with a supercharged 3 liter diesel car, relying on torque and fuel efficiency to overcome weight and low peak power, and led most of the race until the badly situated air intake of the car swallowed enough debris from the track to disable the car.

Dieseling in spark-ignition engines

A gasoline (spark ignition) engine can sometimes act as a compression ignition engine under abnormal circumstances, a phenomenon typically described as "pinging" or "pinking" (during normal running) or "dieseling" (when the engine continues to run after the electrical ignition system is shut off). This is usually caused by hot carbon deposits within the combustion chamber that act as would a "glow plug" within a diesel or model aircraft engine. Excessive heat can also be caused by improper ignition timing and/or fuel/air ratio which in turn overheats the exposed portions of the spark plug within the combustion chamber.

Fuel and fluid characteristics

Diesel engines can operate on a variety of different fuels, depending on configuration, though the eponymous diesel fuel derived from crude oil is most common. Good-quality diesel fuel can be synthesised from vegetable oil and alcohol. Biodiesel is growing in popularity since it can frequently be used in unmodified engines, though production remains limited. Petroleum-derived diesel is often called "petrodiesel" if there is need to distinguish the source of the fuel. The engines can work with thicker, heavier oil, or oil with higher viscosity, as long as it is heated to ease pumping and injection. These fuels are cheaper than clean, refined diesel oil, although they are dirtier. The biofuels straight vegetable oil (SVO) and waste vegetable oil (WVO) can fall into this category. Moving beyond that, use of low-grade fuels can lead to serious maintenance problems. Most diesel engines that power ships like supertankers are built so that the engine can safely use low grade fuels. Ethanol is also used in some cases, since it has a high octane rating which means it can be highly compressed before spontaneously igniting. One way this is used is in E95 fuel which actually contains 5% gasoline along with 95% ethanol. Normal diesel fuel is more difficult to ignite than gasoline because of its higher flash point, but once burning, a diesel fire can be extremely fierce.

Diesel applications

The vast majority of modern heavy road vehicles (trucks), ships, large-scale portable power generators, most farm and mining vehicles, and many long-distance locomotives have diesel engines. However, in the U.S. they are not as popular in passenger vehicles as they are in Europe as they are perceived as being heavier, noisier, of having performance characteristics which makes them slower to accelerate, and of being more expensive than petrol vehicles. In addition, before the mandatory reduction of sulphur in on-road diesel fuel to 15 parts per million, which will start at 15 Oct 2006 (2006-10-15) in the U.S. (1 June 2006 (2006-06-01) in Canada), diesel fuel used in North America has higher sulphur content than the fuel used in Europe, effectively limiting diesel use to industrial vehicles. 2006-06-01 In Europe, where tax rates in many countries make diesel fuel much cheaper than petrol, diesel vehicles are very popular and newer designs have significantly narrowed differences between petrol and diesel vehicles in the areas mentioned. One anecdote tells of Formula One driver Jenson Button, who was arrested while driving a diesel-powered BMW coupe at 230 km/h (about 140 mph) in France, where he was too young to have a petrol-engined car hired to him. Button dryly observed in subsequent interviews that he had actually done BMW a public relations service, as nobody had believed a diesel could be driven that fast. The BMW diesel lab in Steyr, Austria is led by Ferenc Anisits and is considered to be a leader in development of automotive diesel engines. Similarly, Mercedes Benz had a successful run of diesel-powered passenger cars in the late 1970s and 1980s. After a hiatus in the 1990s with relatively few diesel cars in its lineup, Mercedes Benz has revived diesel cars in its newer ranges with an emphasis on high performance versus the older models' lack thereof. ;High-Speed :High-speed (approximately 1200 rpm and greater) engines are used to power lorries (trucks), buses, tractors, cars, yachts, compressors, pumps and small generators. ;Medium-Speed :Large electrical generators are driven by medium speed engines, (approximately 300 to 1200 rpm) optimised to run at a set speed and provide a rapid response to load changes. ;Low-Speed : The largest diesel engines are used to power ships. These monstrous engines have power outputs over 80,000 kW, turn at about 60 to 100 rpm, and are up to 15 m tall. They often run on cheap low-grade fuel, which require extra heat treatment in the ship for tanking and before injection due to their low volatility. Companies such as Burmeister & Wain and Wärtsilä (e.g., Sulzer Diesels) design such large low speed engines. They are unusually narrow and tall due to the addition of a crosshead bearing. Today (2005), the Wärtsilä-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world, with cylinder bores of 960 mm (37.8 in) and stroke of 2500 mm (98.4 in), producing up to 80,080 kW (107,389 hp) in the 14-cylinder configuration. The zeppelins Graf Zeppelin II and Hindenburg were propelled by reversible diesel engines. The direction of operation was changed by shifting gears on the camshaft. From full power forward, the engines could be brought to a stop, changed over, and brought to full power in reverse in less than 60 seconds. This was done before reversible pitch propellers for aircraft had been perfected. A few airplanes have been built that use diesel engines, such as the Junkers-powered Blohm & Voss Ha 139 of the late 1930s. This is quite rare because of the high importance of power-weight ratios in aeronautical applications, and the development of kerosene-powered jet engines and the closely-related turboprop engines. However, this may change in the near future. The newer automotive diesels have power-weight ratios comparable to the ancient spark-ignition designs common in general aviation aircraft, and have better fuel efficiency. Their use of electronic ignition, fuel injection, and sophisticated engine management systems also makes them far easier to operate than mass-produced spark-ignition aircraft engines, most of which still use carburetors. Combined with Europe's very favourable tax treatment of diesel fuel compared to petrol, these factors have led to considerable interest in diesel-powered small general aviation planes, and several manufacturers have recently begun selling diesel engines for this purpose. The Diamond Twin Star is currently one of the very few general aviation aircraft manufactured with diesel engines. It can be twice as efficient as a comparable twin aircraft due to the diesel engines made by Thielert. Another major advantage for aviation users is that diesel engines can be fuelled with jet fuel, which is produced in a much greater quantity than avgas. See aircraft engine. Also, some motorcycles have been built using diesel engines.

Current and future developments

Already, many common rail and unit injection systems employ new injectors using stacked piezoelectric crystals in lieu of a solenoid, which gives finer control of the injection event. Variable geometry turbochargers have flexible vanes, which move and let more fuel into the engine depending on load. This technology increases both performance and fuel economy A technique called accelerometer pilot control (APC) uses a sensor called an accelerometer to provide feedback on the engine's level of noise and vibration and thus instruct the ECU to inject the minimum amount of fuel that will produce quiet combustion and still provide the required power (especially while idling.) The next generation of common rail diesels are expected to use variable injection geometry, which allows the amount of fuel injected to be varied over a wider range, and variable valve timing similar to that on gasoline engines. At least in the US, diesels will slowly face displacement by tougher emissions regulations. Other methods to achieve even more efficient combustion, such as HCCI (homogeneous charge compression ignition), are being studied.

Modern diesel facts

(Source: Robert Bosch GmbH) Fuel passes through the injector jets at speeds of nearly 1500 miles per hour (2400 km/h) – as fast as the top speed of a jet plane. Fuel is injected into the combustion chamber in less than 1.5 milliseconds (one and a half thousandths of a second) – about as long as a camera flash. The smallest quantity of fuel injected is one cubic millimetre – about the same volume as the head of a pin. The largest injection quantity at the moment for automobile diesel engines is around 70 cubic millimetres. If the camshaft of a six-cylinder engine is turning at 4500 rpm, the injection system has to control and deliver 225 injection cycles per second. On a demonstration drive, a Volkswagen 1-liter diesel-powered car used only 0.89 liters of fuel in covering 100 kilometers – making it probably the most fuel-efficient car in the world. Bosch’s high-pressure fuel injection system was one of the main factors behind the prototype’s extremely low fuel consumption. Production record-breakers in fuel economy include the Volkswagen Lupo 3L TDI and the Audi A2 3L 1.2 TDI with standard consumption figures of 3 liters of fuel per 100 kilometers. Their high-pressure diesel injection systems are also supplied by Bosch. In 2001, nearly 36% of newly registered cars in Western Europe had diesel engines. Austria leads the league table of registrations of diesel-powered cars with 66%, followed by Belgium with 63% and Luxembourg with 58%. Germany, with 34.6% in 2001, was in the middle of the league table. By way of comparison: in 1996, diesel-powered cars made up only 15% of the new car registrations in Germany. In 1998, for the very first time in the history of the legendary 24-hour race at the Nürburgring, a diesel-powered car was the overall winner – the BMW works team 320d, fitted with modern high-pressure diesel injection technology from Bosch.

External links

-
- [http://auto.howstuffworks.com/diesel.htm/ HowStuffWorks Article]
- [http://www.bath.ac.uk/~ccsshb/12cyl/ The Most Powerful Diesel Engine in the World]
- [http://www.cumminsracing.com Cummins Racing, home of the world's fastest diesel dragster...]
- [http://www.thedieselstop.com The Diesel Stop - Information on the Power Stroke Diesel]
- [http://www.northtexaspowerstrokes.com North Texas Power Stroke Association - Ford/International Power Stroke Diesel Enthusiasts]
- [http://www.rolls-royce.com/marine/product/diesel/default.jsp Rolls-Royce corporate website - diesel engines]
- [http://www.tdiclub.com TDIClub.com - TDI Enthusiasts]
- [http://www.turbodieselregister.com Turbodiesel Register - Dodge/Cummins Turbodiesel Enthusiasts]
- [http://www.volvo.com/volvopenta/global/en-gb Volvo Penta - manufacturer of marine and industrial diesel engines]
- [http://www.best-generator.com/ Best Engine - Manufacturer of Diesel Engine]
- [http://www.centurion-engines.com Centurion Engines - aeronautical applications]
- [http://www.wartsila.com/ Wärtsilä - manufacturer of diesel power plants]
- [http://www.cat.com/cda/layout?m=37532&x=7 Caterpillar - manufacturer of Caterpiller (Cat) diesel engines as well as construction equipment]
- [http://www.cummins.com Cummins - manufacturer of Cummins diesel engines]
- [http://www.detroitdiesel.com Detroit Diesel - manufacturer of diesel engines]
- [http://www.internationaldelivers.com/ -International/Navistar- manufacturer of International and Ford PowerStroke diesel engines, as well as heavy duty trucks]
- [http://www.perkins.com Perkins - manufacturer of diesel engines]
- [http://www.deutz.de Deutz - manufacturer of esoteric diesel engines]
- [http://www.deere.com John Deere - manufacturer of diesel engines and farm and construction equipment]
- [http://www.yanmar.com Yanmar - manufacturer of diesel engines, specilzing in those for marine use]
- [http://www.komatsu.com/kdl Komatsu Diesel - manufacturer of diesel engines]
- http://www.sisudiesel.com/ - Sisu Diesel
- [http://wagoneers.com/ wagoneers.com - see Mercedes Diesels and DIESELS] Category:Piston engines ko:디젤 엔진 ja:ディーゼルエンジン

Internal combustion engine

The internal combustion engine is a heat engine in which combustion occurs in a confined space called a combustion chamber. Combustion of a fuel creates high temperature/pressure gases, which are permitted to expand. The expanding gases are used to directly move a piston, turbine blades, rotor(s), or the engine itself thus doing useful work. Internal combustion engines can be powered by any fuel that can be combined with an "oxidizer" in the chamber. By way of contrast, an external combustion engine such as a steam engine does work when the combustion process heats a separate working fluid, such as water or steam, which then in turn does work. Jet engines, most rockets and many gas turbines are strictly classed as internal combustion engines, but the term internal combustion engine is also used to refer specifically to reciprocating engines, Wankel engines and similar designs in which combustion is intermittent. Today, in some published discussions, internal combustion engine is abbreviated to the acronym ICE.

History

Wankel engine English inventor Sir Samuel Morland used gunpowder to drive water pumps in the 17th century. For more conventional, reciprocating internal combustion engines the fundamental theory for two-stroke engines was established by Sadi Carnot in France in 1824, whilst the American Samuel Morey received a patent on April 1, 1826 for a "Gas Or Vapor Engine". The Italians Eugenio Barsanti and Felice Matteucci patented the first working, efficient version of an internal combustion engine in 1854 in London (pt. Num. 1072). Despite these and other attempts, it wasn't until 1859 that the Frenchman Étienne Lenoir (1822 - 1900) designed an engine that ran on a mixture of explosive gas and air. In 1860, Jean Joseph Etienne Lenoir produced a gas-fired internal combustion engine not dissimilar in appearance to a steam beam engine. This closelly resembled a horizontal double acting steam engine, with cylinders, pistons, connecting-rods and fly wheel in which the gas essentially took the place of the steam. In 1870 in Vienna Siegfried Marcus put the first mobile gasoline engine on a handcart. Nikolaus Otto working with Gottlieb Daimler and Wilhelm Maybach in the 1870's developed the four-stroke cycle (Otto cycle) engine.

Applications

Internal combustion engines are most commonly used for mobile propulsion systems. 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 cars, motorbikes, many 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 gas turbines. They are also used for electric generators and by industry. For low power mobile and many non-mobile applications an electric motor is a competitive alternative. In the future, electric motors may also become competitive for most mobile applications. However, the high cost and weight and poor energy density of batteries and lack of affordable onboard electric generators such as fuel cells has largely restricted their use to specialist applications.

Operation

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 fuels in use today are made up of hydrocarbons and are derived from petroleum. These include the fuels known as diesel, gasoline and liquified petroleum gas. Most internal combustion engines designed for gasoline can run on natural gas or liquified petroleum gases without modifications except for the fuel delivery components. Liquid and gaseous biofuels of adequate formulation can also be used. 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 hydrocarbons, which also produces carbon dioxide, a major cause of global warming, as well as carbon monoxide, resulting from incomplete combustion. The big disadvantage of hydrogen in many situations its storage. Liquid hydrogen has extremely low density- 14 times lower than water and requires extensive insulation, whilst gaseous hydrogen requires very heavy tankage. While hydrogen is light and therefore has a higher specific energy, the volumetric efficiency is still roughly five times lower than petrol. This is why hydrogen must be compressed if there is to be a useful amount of stored energy. All internal combustion engines must have a means of ignition to promote combustion. Most engines use either an electrical or a compression heating ignition system. Electrical ignition systems generally rely on 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 alternator driven by the engine. Compression heating ignition systems (Diesel engines and HCCI engines) rely on the heat created in the air by compression in the engine's cylinders to ignite the fuel. 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 a waste product and is removed from the engine either by an air or liquid cooling system.

Parts

heat 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 epitroichoidal (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.

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. 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."

Principles of operation

electric motor Reciprocating:
- Two-stroke engine
- Four-stroke engine
- Bourke Engine Rotary:
- Demonstrated:
- Wankel engine
- Proposed:
- orbital engine
- quasiturbine 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, 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. 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.

Fuel and oxidiser types

Fuels used include gasoline (aka petrol), Liquified Petroleum Gas, Vapourized Petroleum Gas, Compressed Natural Gas, hydrogen, diesel fuel, JP18 (jet fuel), landfill gas, biodiesel, peanut oil, ethanol, methanol (methyl or wood alcohol). Engines that use gases for fuel are called gas engines and those that use liquid hydrocarbons are called oil engines. However, gasoline engines are often called gas engines for short. The only limitations are that the fuel 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, but can be pure oxygen, nitrous oxide or hydrogen peroxide. Other chemicals such as chlorine or fluorine have seen experimental use; but mostly are impractical. 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 more so for their increased fuel-efficiency over gasoline engines), 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. Tractor vaporising oil

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.
- 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 , "Electrical Igniter for Gas Engines", on 16 August 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. Larger gasoline engines such as used in cars have mostly moved to Fuel injection systems. LPG engines use a mix of Fuel injection systems and closed loop carburetors. 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. 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.

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. 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. 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.

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. Diesel engines produce a wide range of pollutants including aerosols of many small particles that are believed to penetrate deeply into human lungs.
- Many fuels contain sulfur leading to sulfur oxides (SOx) in the exhaust, promoting acid rain.
- The high temperature of combustion creates greater proportions of nitrogen oxides (NOx), demonstrated to be hazardous to both plant and animal health.
- Net carbon dioxide production is not a necessary feature of engines, but since most engines are run from fossil fuels this 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 only produce water, in theory.

Bibliography

- Singer, Charles Joseph; Raper, Richard, A history of technology : The Internal Combustion Engine, edited by Charles Singer ... [et al.], Clarendon Press, 1954-1978. pp.157-176[http://proxy.bib.uottawa.ca:2398/cgi/t/text/pageviewer-idx?c=acls&cc=acls&idno=heb02191.0005.001&q1=bicycle&frm=frameset&seq=5]

External links

- [http://www.keveney.com/Engines.html Animated Engines] - explains a variety of types
- [http://auto.howstuffworks.com/engine3.htm How Internal Combustion Works] - with animation Category:Energy conversion Category:Engines ja:内燃機関

Compression ignition engine

How diesel engines work

Fuel injection in diesel engines

Indirect Injection

Direct injection

Modern diesel engines make use of one of the following direct injection methods:

Common rail direct injection

Unit direct injection

Types of diesel engines

Advantages and disadvantages versus spark-ignition engines

Automobile racing

Dieseling in spark-ignition engines

Fuel and fluid characteristics

Diesel applications

Current and future developments

Modern diesel facts

External links

Fuel

:For information on the band, see Fuel (band). :For the workstation, see SGI Fuel. Fuel is material with one type of energy which can be transformed into another usable energy. A common example is potential energy being converted into kinetic energy, (as heat and mechanical work). In many cases this is just something that will burn.

Fuels

Solid fuels

burn There are many different types of fuel. Solid fuels include coal, wood and peat. All these types of fuel are combustible, they create fire and heat. Coal was burnt by steam trains to heat water into steam to move parts and provide power. Peat and wood are mainly used for domestic and industrial heating, though peat has been used for power generation, and wood-burning steam locomotives were common in times past. Steam power is becoming more and more desirable as oil and gas supplies begin to run out, this is because of the wide number of possible things that can burn to heat water.

Liquid and gas fuels

Non-solid fuels include petroleum and gas (both fuel types have myriad varieties including petrol (gasoline) and natural gas). The former is widely used in the internal combustion engine while both are used in power generation.

Nuclear fuels

In a nuclear reaction a radioactive fuel will undergo fission. This provides a useful source of energy without combustion. Also, in stars (and our sun), hydrogen (a gas) is the fuel for the nuclear fusion.

Other fuel

nuclear fusion Hydrogen also features as an upcoming fuel for automobiles with Oxygen in the Fuel Cell. This involves a reaction where the hydrogen and oxygen react to produce water (H₂O) and electrical energy, which then can supply an electrical motor in order to run a car (or a variety of other uses). In this reaction the chemical energy of the chemicals is converted into electrical energy due to redox. Carbohydrates, fats, and proteins, derived from food, are the fuels for biological systems. For instance, glucose (a simple carbohydrate) combines with oxygen to produce water, carbon-dioxide, and a release of energy. In the bodies of most animals, the released energy is used by the muscles.

Fuel values

Main article: Fuel value. The fuel value is the quantity of potential energy in a food or other substance.

Temperature

Temperature is the physical property of a system which underlies the common notions of "hot" and "cold"; the material with the higher temperature is said to be hotter. Physically, temperature is a measure of the random agitation of matter and ambiant photons, under the effect of thermal fluctuations. It is a fundamental parameter in thermodynamics and it is conjugate to entropy. More quantitatively, the order of magnitude of the fluctuations of the energy associated with an atom, molecule or another elementary constituant of a physical system is

k_B T

, where

k_B

is Boltzmann's constant, and T is temperature, expressed in Kelvins.

Overview

The formal properties of temperature are studied in thermodynamics and statistical mechanics. The temperature of a system at thermodynamic equilibrium is defined by a relation between the amount of heat

\delta Q

incident on the system during an infinitesimal quasistatic transformation, and the variation

\delta S

of its entropy during this transformation. :

\delta S = \frac

Contrarly to entropy and heat, whose microscopic definitions are valid even far away from thermodynamic equilibrium temperature can only be defined at thermodynamic equilibrium, or local thermodynamic equilibrium (see below). As a system receives heat its temperature rises, similarly a loss of heat from the system tends to decrease its temperature (at the - uncommon - exception of negative temperature, see below). When two systems are at the same temperature, no heat transfer occurs between them. When a temperature difference does exist, heat will tend to move from the higher-temperature system to the lower-temperature system, until they are at thermal equilibrium. This heat transfer may occur via conduction, convection or radiation (see heat for additional discussion of the various mechanisms of heat transfer). Temperature is also related to the amount of internal energy and enthalpy of a system. The higher the temperature of a system, the higher its internal energy and enthalpy are. Temperature is an intensive property of a system, meaning that it does not depend on the system size or the amount of material in the system. Other intensive properties include pressure and density. By contrast, mass and volume are extensive properties, and depend on the amount of material in the system.

Role of temperature in nature

Temperature plays an important role in almost all fields of science, including physics, chemistry, and biology. Many physical properties of materials including the phase (solid, liquid, gaseous or plasma), density, solubility, vapor pressure, and electrical conductivity depend on the temperature. Temperature also plays an important role in determining the rate and extent to which chemical reactions occur. This is one reason why the human body has several elaborate mechanisms for maintaining the temperature at 37 °C, since temperatures only a few degrees higher can result in harmful reactions with serious consequences. Temperature also controls the type and quantity of thermal radiation emitted from a surface. One application of this effect is the incandescent light bulb, in which a tungsten filament is electrically heated to a temperature at which significant quantities of visible light are emitted. Temperature-dependence of the speed of sound in air c, density of air ρ and acoustic impedance Z vs. temperature °C

Temperature measurement

Main article: Temperature measurement Temperature measurement using modern scientific thermometers and temperature scales goes back at least as far as the early 18th century, when Gabriel Fahrenheit adapted a thermometer (switching to mercury) and a scale both developed by Ole Christensen Rømer. Fahrenheit's scale is still in use, alongside the Celsius scale and the Kelvin scale.

Units of temperature

The basic unit of temperature (symbol: T) in the International System of Units (SI) is the kelvin (K). One kelvin is formally defined as 1/273.16 of the temperature of the triple point of water (the point at which water, ice and water vapor exist in equilibrium). The temperature 0 K is called absolute zero and corresponds to the point at which the molecules and atoms have the least possible thermal energy. An important unit of temperature in theoretical physics is the Planck temperature (1.4 × 10³² K). In the field of plasma physics, because of the high temperatures encountered and the electromagnetic nature of the phenomena involved, it is customary to express temperature in electronvolts (eV) or kiloelectronvolts (keV), where 1 eV = 11,605 K. In the study of QCD matter one routinely meets temperatures of the order of a few hundred MeV, equivalent to about 10¹² K. For everyday applications, it is often convenient to use the Celsius scale, in which 0 °C corresponds to the temperature at which water freezes and 100 °C corresponds to the boiling point of water at sea level. In this scale a temperature difference of 1 degree is the same as a 1 K temperature difference, so the scale is essentially the same as the kelvin scale, but offset by the temperature at which water freezes (273.15 K). Thus the following equation can be used to convert from degrees Celsius to kelvins. :

\mathrm

In the United States, the Fahrenheit scale is widely used. On this scale the freezing point of water corresponds to 32 °F and the boiling point to 212 °F. The following formula can be used to convert from Fahrenheit to Celsius: :

\mathrm

See temperature conversion formulas for conversions between most temperature scales. ¹ Only the kelvin, Celsius, Fahrenheit, and Rankine scales are in use today.
² Some numbers in this table have been rounded off.
³ Normal human body temperature is 36.8 °C ±0.7 °C, or 98.2 °F ±1.3 °F.

Negative temperatures

:See main article: Negative temperature. For some systems and specific definitions of temperature, it is possible to obtain a negative temperature. A system with a negative temperature is not colder than absolute zero, but rather it is, in a sense, hotter than infinite temperature (sic).

Articles about temperature ranges:

- 10⁻¹² K = 1 picokelvin (pK)
- 10⁻⁹ K = 1 nanokelvin (nK)
- 10⁻⁶ K = 1 microkelvin (µK)
- 10⁻³ K = 1 millikelvin (mK)
- 10⁰ K = 1 kelvin
- 10¹ K = 10 kelvins
- 10² K = 100 kelvins
- 10³ K = 1,000 kelvin = 1 kilokelvin (kK)
- 10⁴ K = 10,000 kelvins = 10 kK
- 10⁵ K = 100,000 kelvins = 100 kK
- 10⁶ K = 1 megakelvin (MK)
- 10⁹ K = 1 gigakelvin (GK)
- 10¹² K = 1 terakelvin (TK) See Orders of magnitude (temperature).

Theoretical foundation of temperature

Zeroth-law definition of temperature

While most people have a basic understanding of the concept of temperature, its formal definition is rather complicated. Before jumping to a formal definition, let us consider the concept of thermal equilibrium. If two closed systems with fixed volumes are brought together, so that they are in thermal contact, changes may take place in the properties of both systems. These changes are due to the transfer of heat between the systems. When a state is reached in which no further changes occur, the systems are in thermal equilibrium. Now a basis for the definition of temperature can be obtained from the so-called zeroth law of thermodynamics which states that if two systems, A and B, are in thermal equilibrium and a third system C is in thermal equilibrium with system A then systems B and C will also be in thermal equilibrium (being in thermal equilibrium is a transitive relation; moreover, it is an equivalence relation). This is an empirical fact, based on observation rather than theory. Since A, B, and C are all in thermal equilibrium, it is reasonable to say each of these systems shares a common value of some property. We call this property temperature. Generally, it is not convenient to place any two arbitrary systems in thermal contact to see if they are in thermal equilibrium and thus have the same temperature. Also, it would only provide an ordinal scale. Therefore, it is useful to establish a temperature scale based on the properties of some reference system. Then, a measuring device can be calibrated based on the properties of the reference system and used to measure the temperature of other systems. On

Diesel engine

How diesel engines work

Fuel injection in diesel engines

Indirect Injection

Direct injection

Common rail direct injection

Unit direct injection

Types of diesel engines

Advantages and disadvantages versus spark-ignition engines

Automobile racing

Dieseling in spark-ignition engines

Fuel and fluid characteristics

Diesel applications

Current and future developments

Modern diesel facts

See also

External links

Internal combustion engine

History

Applications

Operation

Parts

Classification

Principles of operation

Engine cycle

Fuel and oxidiser types

Cylinders

Ignition system

Fuel systems

Engine configuration

Engine capacity

Engine pollution

Bibliography

External links

Compression ignition engine

How diesel engines work

Fuel injection in diesel engines

Indirect Injection

Direct injection

Common rail direct injection

Unit direct injection

Types of diesel engines

Advantages and disadvantages versus spark-ignition engines

Automobile racing

Dieseling in spark-ignition engines

Fuel and fluid characteristics

Diesel applications

Current and future developments

Modern diesel facts

See also

External links

Fuel

Fuels

Solid fuels

Liquid and gas fuels

Nuclear fuels

Other fuel

Fuel values

See also

Temperature

Overview

Role of temperature in nature

Temperature measurement

Units of temperature

Negative temperatures

Articles about temperature ranges:

Theoretical foundation of temperature

Zeroth-law definition of temperature