An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy .
75-549: The Lycoming IO-720 engine is a large displacement, horizontally opposed , eight-cylinder aircraft engine featuring four cylinders per side, manufactured by Lycoming Engines . There is no carbureted version of the engine, which would have been designated O-720 and therefore the base model is the IO-720. The IO-720 and the Jabiru 5100 are the only flat-eight configuration aircraft engines currently in production. The engine has
150-451: A fuel cell without side production of NO x , but this is an electrochemical engine not a heat engine. The word engine derives from Old French engin , from the Latin ingenium –the root of the word ingenious . Pre-industrial weapons of war, such as catapults , trebuchets and battering rams , were called siege engines , and knowledge of how to construct them
225-407: A fuel injection system which schedules fuel flow proportionally to the airflow, with fuel vaporization occurring at the intake ports. The engine has a displacement of 722 cubic inches (11.8 litres) and produces 400 hp (298 kW). The cylinders have air-cooled heads cast from aluminum alloy with a fully machined combustion chamber. The first IO-720 was type certified on 25 October 1961 to
300-400: A nuclear reaction is a process in which two nuclei , or a nucleus and an external subatomic particle , collide to produce one or more new nuclides . Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle, they then separate without changing the nature of any nuclide, the process is simply referred to as
375-472: A change in a nuclide induced by collision with another particle or to a spontaneous change of a nuclide without collision. Natural nuclear reactions occur in the interaction between cosmic rays and matter, and nuclear reactions can be employed artificially to obtain nuclear energy, at an adjustable rate, on-demand. Nuclear chain reactions in fissionable materials produce induced nuclear fission . Various nuclear fusion reactions of light elements power
450-482: A chemical reaction, but are not heat engines. Examples include: An electric motor uses electrical energy to produce mechanical energy , usually through the interaction of magnetic fields and current-carrying conductors . The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo . Traction motors used on vehicles often perform both tasks. Electric motors can be run as generators and vice versa, although this
525-454: A cold cylinder, which are attached to reciprocating pistons 90° out of phase. The gas receives heat at the hot cylinder and expands, driving the piston that turns the crankshaft . After expanding and flowing through the recuperator, the gas rejects heat at the cold cylinder and the ensuing pressure drop leads to its compression by the other (displacement) piston, which forces it back to the hot cylinder. Non-thermal motors usually are powered by
600-548: A few limited-production battery-powered electric vehicles have appeared, they have not proved competitive owing to costs and operating characteristics. In the 21st century the diesel engine has been increasing in popularity with automobile owners. However, the gasoline engine and the Diesel engine, with their new emission-control devices to improve emission performance, have not yet been significantly challenged. A number of manufacturers have introduced hybrid engines, mainly involving
675-409: A fully artificial nuclear reaction and nuclear transmutation was achieved by Rutherford's colleagues John Cockcroft and Ernest Walton , who used artificially accelerated protons against lithium-7, to split the nucleus into two alpha particles. The feat was popularly known as "splitting the atom ", although it was not the modern nuclear fission reaction later (in 1938) discovered in heavy elements by
750-412: A gas as in a Stirling engine , or steam as in a steam engine or an organic liquid such as n-pentane in an Organic Rankine cycle . The fluid can be of any composition; gas is by far the most common, although even single-phase liquid is sometimes used. In the case of the steam engine, the fluid changes phases between liquid and gas. Air-breathing combustion engines are combustion engines that use
825-464: A heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices. Stirling engines can be another form of non-combustive heat engine. They use the Stirling thermodynamic cycle to convert heat into work. An example is the alpha type Stirling engine, whereby gas flows, via a recuperator , between a hot cylinder and
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#1732798376278900-425: A heat engine). Chemical heat engines which employ air (ambient atmospheric gas) as a part of the fuel reaction are regarded as airbreathing engines. Chemical heat engines designed to operate outside of Earth's atmosphere (e.g. rockets , deeply submerged submarines ) need to carry an additional fuel component called the oxidizer (although there exist super-oxidizers suitable for use in rockets, such as fluorine ,
975-500: A heavy and light nucleus; while reactions between two light nuclei are the most common ones. Neutrons , on the other hand, have no electric charge to cause repulsion, and are able to initiate a nuclear reaction at very low energies. In fact, at extremely low particle energies (corresponding, say, to thermal equilibrium at room temperature ), the neutron's de Broglie wavelength is greatly increased, possibly greatly increasing its capture cross-section, at energies close to resonances of
1050-460: A large scale required efficient electrical generators and electrical distribution networks. To reduce the electric energy consumption from motors and their associated carbon footprints , various regulatory authorities in many countries have introduced and implemented legislation to encourage the manufacture and use of higher efficiency electric motors. A well-designed motor can convert over 90% of its input energy into useful power for decades. When
1125-489: A majority of the models. Several three-cylinder, two-stroke-cycle models were built while most engines had straight or in-line cylinders. There were several V-type models and horizontally opposed two- and four-cylinder makes too. Overhead camshafts were frequently employed. The smaller engines were commonly air-cooled and located at the rear of the vehicle; compression ratios were relatively low. The 1970s and 1980s saw an increased interest in improved fuel economy , which caused
1200-438: A more powerful oxidant than oxygen itself); or the application needs to obtain heat by non-chemical means, such as by means of nuclear reactions . All chemically fueled heat engines emit exhaust gases. The cleanest engines emit water only. Strict zero-emissions generally means zero emissions other than water and water vapour. Only heat engines which combust pure hydrogen (fuel) and pure oxygen (oxidizer) achieve zero-emission by
1275-560: A nuclear power plant uses the heat from the nuclear reaction to produce steam and drive a steam engine, or a gas turbine in a rocket engine may be driven by decomposing hydrogen peroxide . Apart from the different energy source, the engine is often engineered much the same as an internal or external combustion engine. Another group of noncombustive engines includes thermoacoustic heat engines (sometimes called "TA engines") which are thermoacoustic devices that use high-amplitude sound waves to pump heat from one place to another, or conversely use
1350-563: A pressure just above atmospheric to drive the piston helped by a partial vacuum. Improving on the design of the 1712 Newcomen steam engine , the Watt steam engine, developed sporadically from 1763 to 1775, was a great step in the development of the steam engine. Offering a dramatic increase in fuel efficiency , James Watt 's design became synonymous with steam engines, due in no small part to his business partner, Matthew Boulton . It enabled rapid development of efficient semi-automated factories on
1425-564: A previously unimaginable scale in places where waterpower was not available. Later development led to steam locomotives and great expansion of railway transportation . As for internal combustion piston engines , these were tested in France in 1807 by de Rivaz and independently, by the Niépce brothers . They were theoretically advanced by Carnot in 1824. In 1853–57 Eugenio Barsanti and Felice Matteucci invented and patented an engine using
1500-608: A railroad electric locomotive , rather than an electric motor. Some motors are powered by potential or kinetic energy, for example some funiculars , gravity plane and ropeway conveyors have used the energy from moving water or rocks, and some clocks have a weight that falls under gravity. Other forms of potential energy include compressed gases (such as pneumatic motors ), springs ( clockwork motors ) and elastic bands . Historic military siege engines included large catapults , trebuchets , and (to some extent) battering rams were powered by potential energy. A pneumatic motor
1575-569: A return to smaller V-6 and four-cylinder layouts, with as many as five valves per cylinder to improve efficiency. The Bugatti Veyron 16.4 operates with a W16 engine , meaning that two V8 cylinder layouts are positioned next to each other to create the W ;shape sharing the same crankshaft. The largest internal combustion engine ever built is the Wärtsilä-Sulzer RTA96-C , a 14-cylinder, 2-stroke turbocharged diesel engine that
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#17327983762781650-724: A small gasoline engine coupled with an electric motor and with a large battery bank, these are starting to become a popular option because of their environment awareness. Exhaust gas from a spark ignition engine consists of the following: nitrogen 70 to 75% (by volume), water vapor 10 to 12%, carbon dioxide 10 to 13.5%, hydrogen 0.5 to 2%, oxygen 0.2 to 2%, carbon monoxide : 0.1 to 6%, unburnt hydrocarbons and partial oxidation products (e.g. aldehydes ) 0.5 to 1%, nitrogen monoxide 0.01 to 0.4%, nitrous oxide <100 ppm, sulfur dioxide 15 to 60 ppm, traces of other compounds such as fuel additives and lubricants, also halogen and metallic compounds, and other particles. Carbon monoxide
1725-453: A source of water power to provide additional power to watermills and water-raising machines. In the medieval Islamic world , such advances made it possible to mechanize many industrial tasks previously carried out by manual labour . In 1206, al-Jazari employed a crank - conrod system for two of his water-raising machines. A rudimentary steam turbine device was described by Taqi al-Din in 1551 and by Giovanni Branca in 1629. In
1800-429: A strict definition (in practice, one type of rocket engine). If hydrogen is burnt in combination with air (all airbreathing engines), a side reaction occurs between atmospheric oxygen and atmospheric nitrogen resulting in small emissions of NO x . If a hydrocarbon (such as alcohol or gasoline) is burnt as fuel, CO 2 , a greenhouse gas , is emitted. Hydrogen and oxygen from air can be reacted into water by
1875-431: A torque include the familiar automobile gasoline and diesel engines, as well as turboshafts . Examples of engines which produce thrust include turbofans and rockets . When the internal combustion engine was invented, the term motor was initially used to distinguish it from the steam engine—which was in wide use at the time, powering locomotives and other vehicles such as steam rollers . The term motor derives from
1950-443: A type of nuclear scattering , rather than a nuclear reaction. In principle, a reaction can involve more than two particles colliding , but because the probability of three or more nuclei to meet at the same time at the same place is much less than for two nuclei, such an event is exceptionally rare (see triple alpha process for an example very close to a three-body nuclear reaction). The term "nuclear reaction" may refer either to
2025-561: A water-powered mill was built in Kaberia of the kingdom of Mithridates during the 1st century BC. Use of water wheels in mills spread throughout the Roman Empire over the next few centuries. Some were quite complex, with aqueducts , dams , and sluices to maintain and channel the water, along with systems of gears , or toothed-wheels made of wood and metal to regulate the speed of rotation. More sophisticated small devices, such as
2100-416: Is a machine that converts potential energy in the form of compressed air into mechanical work . Pneumatic motors generally convert the compressed air to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor. Pneumatic motors have found widespread success in
2175-534: Is highly toxic, and can cause carbon monoxide poisoning , so it is important to avoid any build-up of the gas in a confined space. Catalytic converters can reduce toxic emissions, but not eliminate them. Also, resulting greenhouse gas emissions, chiefly carbon dioxide , from the widespread use of engines in the modern industrialized world is contributing to the global greenhouse effect – a primary concern regarding global warming . Some engines convert heat from noncombustive processes into mechanical work, for example
2250-710: Is not always practical. Electric motors are ubiquitous, being found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools , and disk drives . They may be powered by direct current (for example a battery powered portable device or motor vehicle), or by alternating current from a central electrical distribution grid. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of large ships, and for such purposes as pipeline compressors, with ratings in
2325-428: Is reached with a coolant temperature of around 110 °C (230 °F). Earlier automobile engine development produced a much larger range of engines than is in common use today. Engines have ranged from 1- to 16-cylinder designs with corresponding differences in overall size, weight, engine displacement , and cylinder bores . Four cylinders and power ratings from 19 to 120 hp (14 to 90 kW) were followed in
Lycoming IO-720 - Misplaced Pages Continue
2400-534: Is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine). " Combustion " refers to burning fuel with an oxidizer , to supply the heat. Engines of similar (or even identical) configuration and operation may use a supply of heat from other sources such as nuclear, solar, geothermal or exothermic reactions not involving combustion; but are not then strictly classed as external combustion engines, but as external thermal engines. The working fluid can be
2475-707: The Antikythera Mechanism used complex trains of gears and dials to act as calendars or predict astronomical events. In a poem by Ausonius in the 4th century AD, he mentions a stone-cutting saw powered by water. Hero of Alexandria is credited with many such wind and steam powered machines in the 1st century AD, including the Aeolipile and the vending machine , often these machines were associated with worship, such as animated altars and automated temple doors. Medieval Muslim engineers employed gears in mills and water-raising machines, and used dams as
2550-662: The Volkswagen Beetle , the Citroën 2CV , some Porsche and Subaru cars, many BMW and Honda motorcycles . Opposed four- and six-cylinder engines continue to be used as a power source in small, propeller-driven aircraft . The continued use of internal combustion engines in automobiles is partly due to the improvement of engine control systems, such as on-board computers providing engine management processes, and electronically controlled fuel injection. Forced air induction by turbocharging and supercharging have increased
2625-407: The club and oar (examples of the lever ), are prehistoric . More complex engines using human power , animal power , water power , wind power and even steam power date back to antiquity. Human power was focused by the use of simple engines, such as the capstan , windlass or treadmill , and with ropes , pulleys , and block and tackle arrangements; this power was transmitted usually with
2700-733: The combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston , which turns a crankshaft . Unlike internal combustion engines, a reaction engine (such as a jet engine ) produces thrust by expelling reaction mass , in accordance with Newton's third law of motion . Apart from heat engines, electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air , and clockwork motors in wind-up toys use elastic energy . In biological systems, molecular motors , like myosins in muscles , use chemical energy to create forces and ultimately motion (a chemical engine, but not
2775-399: The oxygen in atmospheric air to oxidise ('burn') the fuel, rather than carrying an oxidiser , as in a rocket . Theoretically, this should result in a better specific impulse than for rocket engines. A continuous stream of air flows through the air-breathing engine. This air is compressed, mixed with fuel, ignited and expelled as the exhaust gas . In reaction engines , the majority of
2850-429: The pistons or turbine blades or a nozzle , and by moving it over a distance, generates mechanical work . An external combustion engine (EC engine) is a heat engine where an internal working fluid is heated by combustion of an external source, through the engine wall or a heat exchanger . The fluid then, by expanding and acting on the mechanism of the engine produces motion and usable work . The fluid
2925-471: The 13th century, the solid rocket motor was invented in China. Driven by gunpowder, this simplest form of internal combustion engine was unable to deliver sustained power, but was useful for propelling weaponry at high speeds towards enemies in battle and for fireworks . After invention, this innovation spread throughout Europe. The Watt steam engine was the first type of steam engine to make use of steam at
3000-454: The CAR 13 standard as amended to 15 June 1956 including 13-1, 13-2, 13-3, 13-4. In 2009 a new IO-720-A1B cost US$ 113,621, with a rebuilt engine retailing for US$ 75,435 and a factory overhaul priced at US$ 66,289. Data from Lycoming Specialty Datasheet and TYPE CERTIFICATE DATA SHEET NO. 1E15, Revision 6 Engine Available energy sources include potential energy (e.g. energy of
3075-500: The Earth's gravitational field as exploited in hydroelectric power generation ), heat energy (e.g. geothermal ), chemical energy , electric potential and nuclear energy (from nuclear fission or nuclear fusion ). Many of these processes generate heat as an intermediate energy form; thus heat engines have special importance. Some natural processes, such as atmospheric convection cells convert environmental heat into motion (e.g. in
Lycoming IO-720 - Misplaced Pages Continue
3150-483: The German scientists Otto Hahn , Lise Meitner , and Fritz Strassmann . Nuclear reactions may be shown in a form similar to chemical equations, for which invariant mass must balance for each side of the equation, and in which transformations of particles must follow certain conservation laws, such as conservation of charge and baryon number (total atomic mass number ). An example of this notation follows: To balance
3225-521: The Latin verb moto which means 'to set in motion', or 'maintain motion'. Thus a motor is a device that imparts motion. Motor and engine are interchangeable in standard English. In some engineering jargons, the two words have different meanings, in which engine is a device that burns or otherwise consumes fuel, changing its chemical composition, and a motor is a device driven by electricity , air , or hydraulic pressure, which does not change
3300-454: The best-known neutron reactions are neutron scattering , neutron capture , and nuclear fission , for some light nuclei (especially odd-odd nuclei ) the most probable reaction with a thermal neutron is a transfer reaction: Some reactions are only possible with fast neutrons : Either a low-energy projectile is absorbed or a higher energy particle transfers energy to the nucleus, leaving it with too much energy to be fully bound together. On
3375-436: The chemical composition of its energy source. However, rocketry uses the term rocket motor , even though they consume fuel. A heat engine may also serve as a prime mover —a component that transforms the flow or changes in pressure of a fluid into mechanical energy . An automobile powered by an internal combustion engine may make use of various motors and pumps, but ultimately all such devices derive their power from
3450-447: The combustion energy (heat) exits the engine as exhaust gas, which provides thrust directly. Typical air-breathing engines include: The operation of engines typically has a negative impact upon air quality and ambient sound levels . There has been a growing emphasis on the pollution producing features of automotive power systems. This has created new interest in alternate power sources and internal-combustion engine refinements. Though
3525-424: The course of a reaction ( exothermic reaction ) or kinetic energy may have to be supplied for the reaction to take place ( endothermic reaction ). This can be calculated by reference to a table of very accurate particle rest masses, as follows: according to the reference tables, the 3 Li nucleus has a standard atomic weight of 6.015 atomic mass units (abbreviated u ), the deuterium has 2.014 u, and
3600-489: The efficiency of a motor is raised by even a few percentage points, the savings, in kilowatt hours (and therefore in cost), are enormous. The electrical energy efficiency of a typical industrial induction motor can be improved by: 1) reducing the electrical losses in the stator windings (e.g., by increasing the cross-sectional area of the conductor , improving the winding technique, and using materials with higher electrical conductivities , such as copper ), 2) reducing
3675-496: The electrical losses in the rotor coil or casting (e.g., by using materials with higher electrical conductivities, such as copper), 3) reducing magnetic losses by using better quality magnetic steel , 4) improving the aerodynamics of motors to reduce mechanical windage losses, 5) improving bearings to reduce friction losses , and 6) minimizing manufacturing tolerances . For further discussion on this subject, see Premium efficiency ). By convention, electric engine refers to
3750-632: The energy and the flux of the incident particles, and the reaction cross section . An example of a large repository of reaction rates is the REACLIB database, as maintained by the Joint Institute for Nuclear Astrophysics . In the initial collision which begins the reaction, the particles must approach closely enough so that the short-range strong force can affect them. As most common nuclear particles are positively charged, this means they must overcome considerable electrostatic repulsion before
3825-551: The energy production of the Sun and stars. In 1919, Ernest Rutherford was able to accomplish transmutation of nitrogen into oxygen at the University of Manchester, using alpha particles directed at nitrogen N + α → O + p. This was the first observation of an induced nuclear reaction, that is, a reaction in which particles from one decay are used to transform another atomic nucleus. Eventually, in 1932 at Cambridge University,
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#17327983762783900-486: The energy released is 0.0238 × 931 MeV = 22.2 MeV . Expressed differently: the mass is reduced by 0.3%, corresponding to 0.3% of 90 PJ/kg is 270 TJ/kg. This is a large amount of energy for a nuclear reaction; the amount is so high because the binding energy per nucleon of the helium-4 nucleus is unusually high because the He-4 nucleus is " doubly magic ". (The He-4 nucleus is unusually stable and tightly bound for
3975-404: The engine. Another way of looking at it is that a motor receives power from an external source, and then converts it into mechanical energy, while an engine creates power from pressure (derived directly from the explosive force of combustion or other chemical reaction, or secondarily from the action of some such force on other substances such as air, water, or steam). Simple machines , such as
4050-750: The equation above for mass, charge and mass number, the second nucleus to the right must have atomic number 2 and mass number 4; it is therefore also helium-4. The complete equation therefore reads: or more simply: Instead of using the full equations in the style above, in many situations a compact notation is used to describe nuclear reactions. This style of the form A(b,c)D is equivalent to A + b producing c + D. Common light particles are often abbreviated in this shorthand, typically p for proton, n for neutron, d for deuteron , α representing an alpha particle or helium-4 , β for beta particle or electron, γ for gamma photon , etc. The reaction above would be written as Li(d,α)α. Kinetic energy may be released during
4125-636: The first half of the 20th century, a trend of increasing engine power occurred, particularly in the U.S. models. Design changes incorporated all known methods of increasing engine capacity, including increasing the pressure in the cylinders to improve efficiency, increasing the size of the engine, and increasing the rate at which the engine produces work. The higher forces and pressures created by these changes created engine vibration and size problems that led to stiffer, more compact engines with V and opposed cylinder layouts replacing longer straight-line arrangements. Optimal combustion efficiency in passenger vehicles
4200-691: The forces multiplied and the speed reduced . These were used in cranes and aboard ships in Ancient Greece , as well as in mines , water pumps and siege engines in Ancient Rome . The writers of those times, including Vitruvius , Frontinus and Pliny the Elder , treat these engines as commonplace, so their invention may be more ancient. By the 1st century AD, cattle and horses were used in mills , driving machines similar to those powered by humans in earlier times. According to Strabo ,
4275-403: The form of rising air currents). Mechanical energy is of particular importance in transportation , but also plays a role in many industrial processes such as cutting, grinding, crushing, and mixing. Mechanical heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a mechanical heat engine in which heat from
4350-528: The free-piston principle that was possibly the first 4-cycle engine. The invention of an internal combustion engine which was later commercially successful was made during 1860 by Etienne Lenoir . In 1877, the Otto cycle was capable of giving a far higher power-to-weight ratio than steam engines and worked much better for many transportation applications such as cars and aircraft. The first commercially successful automobile, created by Karl Benz , added to
4425-466: The hand-held tool industry and continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome efficiency deficiencies before being seen as a viable option in the transportation industry. A hydraulic motor derives its power from a pressurized liquid . This type of engine is used to move heavy loads and drive machinery. Nuclear reaction In nuclear physics and nuclear chemistry ,
4500-411: The heat of a combustion process. The internal combustion engine is an engine in which the combustion of a fuel (generally, fossil fuel ) occurs with an oxidizer (usually air) in a combustion chamber . In an internal combustion engine the expansion of the high temperature and high pressure gases, which are produced by the combustion, directly applies force to components of the engine, such as
4575-444: The helium-4 nucleus has 4.0026 u. Thus: In a nuclear reaction, the total (relativistic) energy is conserved . The "missing" rest mass must therefore reappear as kinetic energy released in the reaction; its source is the nuclear binding energy . Using Einstein's mass-energy equivalence formula E = mc , the amount of energy released can be determined. We first need the energy equivalent of one atomic mass unit : Hence,
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#17327983762784650-525: The interest in light and powerful engines. The lightweight gasoline internal combustion engine, operating on a four-stroke Otto cycle, has been the most successful for light automobiles, while the thermally more-efficient Diesel engine is used for trucks and buses. However, in recent years, turbocharged Diesel engines have become increasingly popular in automobiles, especially outside of the United States, even for quite small cars. In 1896, Karl Benz
4725-510: The nuclei involved. Thus low-energy neutrons may be even more reactive than high-energy neutrons. While the number of possible nuclear reactions is immense, there are several types that are more common, or otherwise notable. Some examples include: An intermediate energy projectile transfers energy or picks up or loses nucleons to the nucleus in a single quick (10 second) event. Energy and momentum transfer are relatively small. These are particularly useful in experimental nuclear physics, because
4800-483: The one hand, it is the difference between the sums of kinetic energies on the final side and on the initial side. But on the other hand, it is also the difference between the nuclear rest masses on the initial side and on the final side (in this way, we have calculated the Q-value above). If the reaction equation is balanced, that does not mean that the reaction really occurs. The rate at which reactions occur depends on
4875-649: The power output of smaller displacement engines that are lighter in weight and more fuel-efficient at normal cruise power.. Similar changes have been applied to smaller Diesel engines, giving them almost the same performance characteristics as gasoline engines. This is especially evident with the popularity of smaller diesel engine-propelled cars in Europe. Diesel engines produce lower hydrocarbon and CO 2 emissions, but greater particulate and NO x pollution, than gasoline engines. Diesel engines are also 40% more fuel efficient than comparable gasoline engines. In
4950-543: The product nucleus is metastable, this is indicated by placing an asterisk ("*") next to its atomic number. This energy is eventually released through nuclear decay . A small amount of energy may also emerge in the form of X-rays . Generally, the product nucleus has a different atomic number, and thus the configuration of its electron shells is wrong. As the electrons rearrange themselves and drop to lower energy levels, internal transition X-rays (X-rays with precisely defined emission lines ) may be emitted. In writing down
5025-475: The reaction can begin. Even if the target nucleus is part of a neutral atom , the other particle must penetrate well beyond the electron cloud and closely approach the nucleus, which is positively charged. Thus, such particles must be first accelerated to high energy, for example by: Also, since the force of repulsion is proportional to the product of the two charges, reactions between heavy nuclei are rarer, and require higher initiating energy, than those between
5100-426: The reaction equation, in a way analogous to a chemical equation , one may, in addition, give the reaction energy on the right side: For the particular case discussed above, the reaction energy has already been calculated as Q = 22.2 MeV. Hence: The reaction energy (the "Q-value") is positive for exothermal reactions and negative for endothermal reactions, opposite to the similar expression in chemistry . On
5175-594: The reaction mechanisms are often simple enough to calculate with sufficient accuracy to probe the structure of the target nucleus. Only energy and momentum are transferred. Energy and charge are transferred between projectile and target. Some examples of this kind of reactions are: Usually at moderately low energy, one or more nucleons are transferred between the projectile and target. These are useful in studying outer shell structure of nuclei. Transfer reactions can occur: Examples: Reactions with neutrons are important in nuclear reactors and nuclear weapons . While
5250-417: The same reason that the helium atom is inert: each pair of protons and neutrons in He-4 occupies a filled 1s nuclear orbital in the same way that the pair of electrons in the helium atom occupy a filled 1s electron orbital ). Consequently, alpha particles appear frequently on the right-hand side of nuclear reactions. The energy released in a nuclear reaction can appear mainly in one of three ways: When
5325-442: The thousands of kilowatts . Electric motors may be classified by the source of electric power, by their internal construction, and by their application. The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on
5400-523: Was designed to power the Emma Mærsk , the largest container ship in the world when launched in 2006. This engine has a mass of 2,300 tonnes, and when running at 102 rpm (1.7 Hz) produces over 80 MW, and can use up to 250 tonnes of fuel per day. An engine can be put into a category according to two criteria: the form of energy it accepts in order to create motion, and the type of motion it outputs. Combustion engines are heat engines driven by
5475-436: Was granted a patent for his design of the first engine with horizontally opposed pistons. His design created an engine in which the corresponding pistons move in horizontal cylinders and reach top dead center simultaneously, thus automatically balancing each other with respect to their individual momentum. Engines of this design are often referred to as “flat” or “boxer” engines due to their shape and low profile. They were used in
5550-463: Was merely a water pump, with the engine being transported to the fire by horses. In modern usage, the term engine typically describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform mechanical work by exerting a torque or linear force (usually in the form of thrust ). Devices converting heat energy into motion are commonly referred to simply as engines . Examples of engines which exert
5625-473: Was often treated as a military secret. The word gin , as in cotton gin , is short for engine . Most mechanical devices invented during the Industrial Revolution were described as engines—the steam engine being a notable example. However, the original steam engines, such as those by Thomas Savery , were not mechanical engines but pumps. In this manner, a fire engine in its original form
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