A combustion chamber is that part of an internal combustion engine or a reaction engine in which the fuel/air mix is burned. ICEs comprise reciprocating piston engines, rotary engines, gas turbines and jet turbines; the combustion process increases the internal energy of a gas, which translates into an increase in temperature, pressure, or volume depending on the configuration. In an enclosure, for example the cylinder of a reciprocating engine, the volume is controlled and the combustion creates an increase in pressure. In a continuous flow system, for example a jet engine combustor, the pressure is controlled and the combustion creates an increase in volume; this increase in pressure or volume can be used to do work, for example, to move a piston on a crankshaft or a turbine disc in a gas turbine. If the gas velocity changes, thrust is produced, such as in the nozzle of a rocket engine. At top dead centre the pistons of a petrol engine are flush with the top of the cylinder block; the combustion chamber may be a recess either in the top of the piston.
A design with the combustion chamber in the piston is called a Heron head, where the head is machined flat but the pistons are dished. The Heron head has proved more thermodynamically efficient than the hemispherical head. Intake valves permit the inflow of a fuel air mix. Head typesVarious shapes of combustion chamber have been used, such as: L-head for side-valve engines; the shape of the chamber has a marked effect on power output and emissions. Thisis best achieved with a compact rather than elongated chamber. Swirl & SquishThe intake valve/port is placed to give the mixture a pronounced "swirl" pattern above the rising piston, improving mixing and combustion; the shape of the piston top affects the amount of swirl. Another design feature to promote turbulence for good fuel/air mixing is "squish", where the fuel/air mix is "squished" at high pressure by the rising piston. Where swirl is important, combustion chambers in the piston may be favoured. Flame frontIgnition occurs around 15 degrees before top dead centre.
The spark plug must be sited. Good design should avoid narrow crevices where stagnant "end gas" can become trapped, as this gas may detonate violently after the main charge, adding little useful work and damaging the engine. Diesel engines fall into two broad classes: Direct injection, where the combustion chamber consists of a dished piston Indirect injection, where the combustion chamber is in the cylinder headDirect injection engines give better fuel economy but indirect injection engines can use a lower grade of fuel. Harry Ricardo was prominent in developing combustion chambers for diesel engines, the best known being the Ricardo Comet; the combustion chamber in gas turbines and jet engines is called the combustor. The combustor is fed with high pressure air by the compression system, adds fuel and burns the mix and feeds the hot, high pressure exhaust into the turbine components of the engine or out the exhaust nozzle. Different types of combustors exist, mainly: Can type: Can combustors are self-contained cylindrical combustion chambers.
Each "can" has liner, casing. Each "can" get an air source from individual opening. Cannular type: Like the can type combustor, can annular combustors have discrete combustion zones contained in separate liners with their own fuel injectors. Unlike the can combustor, all the combustion zones share a common air casing. Annular type: Annular combustors do away with the separate combustion zones and have a continuous liner and casing in a ring; the term combustion chamber is used to refer to an additional space between the firebox and boiler in a steam locomotive. This space is used to allow further combustion of the fuel. Large steam locomotives have a combustion chamber in the boiler to allow the use of shorter firetubes; this is because: Long firetubes have a theoretical advantage in providing a big heating surface but, beyond a certain length, this is subject to diminishing returns. Long firetubes are prone to sagging in the middle. Micro combustion chambers are the devices in which combustion happens at a small volume, due to which surface to volume ratio increases which plays a vital role in stabilizing the flame.
Cylinder head Engine displacement Combustor Variable compression ratio
Volkswagen AG, known internationally as the Volkswagen Group, is a German multinational automotive manufacturing company headquartered in Wolfsburg, Lower Saxony and indirectly majority owned by the Austrian Porsche-Piëch family. It designs and distributes passenger and commercial vehicles, motorcycles and turbomachinery and offers related services including financing and fleet management. In 2016, it was the world's largest automaker by sales, overtaking Toyota and keeping this title in 2017 and 2018, selling 10.8 million vehicles. It has maintained the largest market share in Europe for over two decades, it ranked seventh in the 2018 Fortune Global 500 list of the world's largest companies. Volkswagen Group sells passenger cars under the Audi, Bugatti, Porsche, SEAT, Škoda and the flagship Volkswagen marques, it is divided into two primary divisions, the Automotive Division and the Financial Services Division, as of 2008 had 342 subsidiary companies. Volkswagen has two major joint-ventures in China.
The company has operations in 150 countries and operates 100 production facilities across 27 countries. Volkswagen was founded in 1937; the company's production grew in the 1950s and 1960s, in 1965 it acquired Auto Union, which subsequently produced the first post-war Audi models. Volkswagen launched a new generation of front-wheel drive vehicles in the 1970s, including the Passat and Golf. Volkswagen acquired a controlling stake in SEAT in 1986, making it the first non-German marque of the company, acquired control of Škoda in 1994, of Bentley and Bugatti in 1998, Scania in 2008 and of Ducati, MAN and Porsche in 2012; the company's operations in China have grown in the past decade with the country becoming its largest market. In June 2018, Volkswagen Trucks and Buses which comprises the MAN, RIO truck brands are renamed to TRATON AG but the marques will not change, said by Andreas Renschler. Volkswagen Aktiengesellschaft is a public company and has a primary listing on the Frankfurt Stock Exchange, where it is a constituent of the Euro Stoxx 50 stock market index, secondary listings on the Luxembourg Stock Exchange, SIX Swiss Exchange.
It has been traded in the United States via American depositary receipts since 1988 on the OTC Marketplace. Volkswagen delisted from the London Stock Exchange in 2013; the state of Lower Saxony holds 12.7 % of the company's shares. Volkswagen was founded on 28 May 1937 in Berlin as the Gesellschaft zur Vorbereitung des Deutschen Volkswagens mbH by the National Socialist Deutsche Arbeitsfront; the purpose of the company was to manufacture the Volkswagen car referred to as the Porsche Type 60 the Volkswagen Type 1, called the Volkswagen Beetle. This vehicle was designed by Ferdinand Porsche's consulting firm, the company was backed by the support of Adolf Hitler. On 16 September 1938, Gezuvor was renamed Volkswagenwerk GmbH. Shortly after the factory near Fallersleben was completed, World War II started and the plant manufactured the military Kübelwagen and the related amphibious Schwimmwagen, both of which were derived from the Volkswagen. Only a small number of Type 60 Volkswagens were made during this time.
The Fallersleben plant manufactured the V-1 flying bomb, making the plant a major bombing target for the Allied forces. After the war in Europe, in June 1945, Major Ivan Hirst of the British Army Royal Electrical and Mechanical Engineers took control of the bomb-shattered factory, restarted production, pending the expected disposal of the plant as war reparations. However, no British car manufacturer was interested. To build the car commercially would be a uneconomic enterprise". In 1948, the Ford Motor Company of USA was offered Volkswagen, but Ernest Breech, a Ford executive vice president said he didn't think either the plant or the car was "worth a damn." Breech said that he would have considered merging Ford of Germany and Volkswagen, but after the war, ownership of the company was in such dispute that nobody could hope to be able to take it over. As part of the Industrial plans for Germany, large parts of German industry, including Volkswagen, were to be dismantled. Total German car production was set at a maximum of 10% of the 1936 car production numbers.
The company survived by producing cars for the British Army, in 1948 the British Government handed the company back over to the German state, it was managed by former Opel chief Heinrich Nordhoff. Production of the Type 60 Volkswagen started after the war due to the need to rebuild the plant and because of the lack of raw materials, but production grew in the 1950s and 1960s; the company began introducing new models based on the Type 1, all with the same basic air-cooled, rear-engine, rear-drive platform. These included the Volkswagen Type 2 in 1950, the Volkswagen Karmann Ghia in 1955, the Volkswagen Type 3 in 1961, the Volkswagen Type 4 in 1968, the Volkswagen Type 181 in 1969. In 1960, upon t
Volkswagen. It is the flagship marque of the Volkswagen Group, the largest automaker by worldwide sales in 2016 and 2017; the group's main market is in China, which delivers 40 % of its profits. Volkswagen translates to "people's car" in German; the company's current international advertising slogan is just "Volkswagen", referencing the name's meaning. Volkswagen was established in 1937 by the German Labour Front in Berlin. In the early 1930s cars were a luxury: most Germans could afford nothing more elaborate than a motorcycle. Only one German out of 50 owned a car. Seeking a potential new market, some car makers began independent "people's car" projects – the Mercedes 170H, Adler AutoBahn, Steyr 55, Hanomag 1.3L, among others. The trend was not new, as Béla Barényi is credited with having conceived the basic design in the mid-1920s. Josef Ganz developed the Standard Superior. In Germany, the company Hanomag mass-produced the 2/10 PS "Kommissbrot", a small, cheap rear-engined car, from 1925 to 1928.
In Czechoslovakia, the Hans Ledwinka's penned Tatra T77, a popular car amongst the German elite, was becoming smaller and more affordable at each revision. Ferdinand Porsche, a well-known designer for high-end vehicles and race cars, had been trying for years to get a manufacturer interested in a small car suitable for a family, he built a car named the "Volksauto" from the ground up in 1933, using many popular ideas and several of his own, putting together a car with an air-cooled rear engine, torsion bar suspension, a "beetle" shape, the front hood rounded for better aerodynamics. In 1934, with many of the above projects still in development or early stages of production, Adolf Hitler became involved, ordering the production of a basic vehicle capable of transporting two adults and three children at 100 km/h, he wanted all German citizens to have access to cars. The "People's Car" would be available to citizens of the Third Reich through a savings plan at 990 Reichsmarks —about the price of a small motorcycle.
Despite heavy lobbying in favour of one of the existing projects, it soon became apparent that private industry could not turn out a car for only 990 RM. Thus, Hitler chose to sponsor an state-owned factory using Ferdinand Porsche's design; the intention was that ordinary Germans would buy the car by means of a savings scheme, which around 336,000 people paid into. However, the entire project was financially unsound, only the Nazi party made it possible to provide funding. Prototypes of the car called the "KdF-Wagen", appeared from 1938 onwards; the car had its distinctive round shape and air-cooled, flat-four, rear-mounted engine. The VW car was just one of many KdF programs, which included things such as outings; the prefix Volks— was not just applied to cars, but to other products in Germany. On 28 May 1937, Gesellschaft zur Vorbereitung des Deutschen Volkswagens mbH, or Gezuvor for short, was established by the Deutsche Arbeitsfront in Berlin. More than a year on 16 September 1938, it was renamed to Volkswagenwerk GmbH.
Erwin Komenda, the longstanding Auto Union chief designer, part of Ferdinand Porsche's hand-picked team, developed the car body of the prototype, recognizably the Beetle known today. It was one of the first cars designed with the aid of a wind tunnel—a method used for German aircraft design since the early 1920s; the car designs were put through rigorous tests, achieved a record-breaking million miles of testing before being deemed finished. The construction of the new factory started in May 1938 in the new town of "Stadt des KdF-Wagens", purpose-built for the factory workers; this factory had only produced a handful of cars by the time war started in 1939. None were delivered to any holder of the completed saving stamp books, though one Type 1 Cabriolet was presented to Hitler on 20 April 1944. War changed production to military vehicles—the Type 82 Kübelwagen utility vehicle, the amphibious Schwimmwagen—manufactured for German forces; as was common with much of the production in Nazi Germany during the war, slave labor was utilized in the Volkswagen plant, e.g. from Arbeitsdorf concentration camp.
The company would admit in 1998. German historians estimated. Many of the slaves were reported to have been supplied from the concentration camps upon request from plant managers. A lawsuit was filed in 1998 by survivors for restitution for the forced labor. Volkswagen would set up a voluntary restitution fund; the company owes its post-war existence to one man, wartime British Army officer Major Ivan Hirst, REME. In April 1945, KdF-Stadt and its bombed factory were captured by the Americans, subsequently handed over to the British, within whose occupation zone the town and fa
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels. In most petrol engines, the fuel and air are mixed after compression; the pre-mixing was done in a carburetor, but now it is done by electronically controlled fuel injection, except in small engines where the cost/complication of electronics does not justify the added engine efficiency. The process differs from a diesel engine in the method of mixing the fuel and air, in using spark plugs to initiate the combustion process. In a diesel engine, only air is compressed, the fuel is injected into hot air at the end of the compression stroke, self-ignites; the first practical petrol engine was built in 1876 in Germany by Nikolaus August Otto, although there had been earlier attempts by Étienne Lenoir, Siegfried Marcus, Julius Hock and George Brayton. With both air and fuel in a closed cylinder, compressing the mixture too much poses the danger of auto-ignition — or behaving like a diesel engine.
Because of the difference in burn rates between the two different fuels, petrol engines are mechanically designed with different timing than diesels, so to auto-ignite a petrol engine causes the expansion of gas inside the cylinder to reach its greatest point before the cylinder has reached the "top dead center" position. Spark plugs are set statically or at idle at a minimum of 10 degrees or so of crankshaft rotation before the piston reaches T. D. C, but at much higher values at higher engine speeds to allow time for the fuel-air charge to complete combustion before too much expansion has occurred - gas expansion occurring with the piston moving down in the power stroke. Higher octane petrol burns slower, therefore it has a lower propensity to auto-ignite and its rate of expansion is lower. Thus, engines designed to run high-octane fuel can achieve higher compression ratios. Most modern automobile petrol engines have a compression ratio of 10.0:1 to 13.5:1. Engines with a knock sensor can and have C.
R higher than 11.1:1 and approaches 14.0:1 and engines without a knock sensor have C. R of 8.0:1 to 10.5:1. Petrol engines run at higher rotation speeds than diesels due to their lighter pistons, connecting rods and crankshaft and due to petrol burning more than diesel; because pistons in petrol engines tend to have much shorter strokes than pistons in diesel engines it takes less time for a piston in a petrol engine to complete its stroke than a piston in a diesel engine. However, the lower compression ratios of petrol engines give petrol engines lower efficiency than diesel engines. Most petrol engines have 20% thermal efficiency, nearly half of diesel engines; however some newer engines are reported to be much more efficient than previous spark-ignition engines. Petrol engines have many applications, including: Automobiles Motorcycles Aircraft Motorboats Small engines, such as lawn mowers and portable engine-generators Before the use of diesel engines became widespread, petrol engines were used in buses, lorries and a few railway locomotives.
Examples: Bedford OB bus Bedford M series lorry GE 57-ton gas-electric boxcab locomotive Petrol engines may run on the four-stroke cycle or the two-stroke cycle. For details of working cycles see: Four-stroke cycle Two-stroke cycle Wankel engine Common cylinder arrangements are from 1 to 6 cylinders in-line or from 2 to 16 cylinders in V-formation. Flat engines – like a V design flattened out – are common in small airplanes and motorcycles and were a hallmark of Volkswagen automobiles into the 1990s. Flat 6s are still used in many modern Porsches, as well as Subarus. Many flat engines are air-cooled. Less common, but notable in vehicles designed for high speeds is the W formation, similar to having 2 V engines side by side. Alternatives include rotary and radial engines the latter have 7 or 9 cylinders in a single ring, or 10 or 14 cylinders in two rings. Petrol engines may be air-cooled, with fins; the coolant was water, but is now a mixture of water and either ethylene glycol or propylene glycol.
These mixtures have lower freezing points and higher boiling points than pure water and prevent corrosion, with modern antifreezes containing lubricants and other additives to protect water pump seals and bearings. The cooling system is slightly pressurized to further raise the boiling point of the coolant. Petrol engines use spark ignition and high voltage current for the spark may be provided by a magneto or an ignition coil. In modern car engines the ignition timing is managed by an electronic Engine Control Unit; the most common way of engine rating is what is known as the brake power, measured at the flywheel, given in kilowatts or horsepower. This is the actual mechanical power output of the engine in a complete form; the term "brake" comes from the use of a brake in a dynamometer test to load the engine. For accuracy, it is important to understand what is meant by complete. For example, for a car engine, apart from friction and thermodynamic losses inside the engine, power is absorbed by the water pump and radiator fan, thus reducing the power available at the flywheel to move the car along.
Power is abso
Indirect injection in an internal combustion engine is fuel injection where fuel is not directly injected into the combustion chamber. In the last decade, gasoline engines equipped with indirect injection systems, wherein a fuel injector delivers the fuel at some point before the intake valve, have fallen out of favor to direct injection. However, certain manufacturers such as Volkswagen and Toyota have developed a'dual injection' system, combining direct injectors with port injectors, combining the benefits of both types of fuel injection. Direct injection allows the fuel to be metered into the combustion chamber under high pressure which can lead to greater power, fuel efficiency; the issue with direct injection is that it leads to greater amounts of particulate matter and with the fuel no longer contacting the intake valves, carbon can accumulate on the intake valves over time. Adding indirect injection keeps fuel spraying on the intake valves, reducing or eliminating the carbon accumulation on intake valves and in low load conditions, indirect injection allows for better fuel-air mixing.
This system is used in higher cost models due to the added expense and complexity. Port injection refers to the spraying of the fuel onto the back of the intake port, which speeds up its evaporation. An indirect injection diesel engine delivers fuel into a chamber off the combustion chamber, called a prechamber, where combustion begins and spreads into the main combustion chamber; the prechamber is designed to ensure adequate mixing of the atomized fuel with the compression-heated air. The purpose of the divided combustion chamber is to speed up the combustion process, in order to increase the power output by increasing engine speed; the addition of a prechamber, increases heat loss to the cooling system and thereby lowers engine efficiency. The engine requires glow plugs for starting. In an indirect injection system the air moves fast, mixing the air; this simplifies injector design and allows the use of smaller engines and less toleranced designs which are simpler to manufacture and more reliable.
Direct injection, by contrast, uses fast-moving fuel. The optimisation of the in-cylinder air flow is much more difficult than designing a prechamber. There is much more integration between the design of the engine, it is for this reason that car diesel engines were all indirect injection until the ready availability of powerful CFD simulation systems made the adoption of direct injection practical. Cylinder head of a small Kubota indirect injection diesel engine, it consists of a spherical chamber located in the cylinder head and separated from the engine cylinder by a tangential throat. About 50% of the air enters the swirl chamber during the compression stroke of the engine, producing a swirl. After combustion, the products return through the same throat to the main cylinder at much higher velocity. So more heat loss to walls of the passage takes place; this type of chamber finds application in engines in which fuel control and engine stability are more important than fuel economy. These are Ricardo chambers, named after Sir Harry Ricardo.
This chamber is connected to the engine cylinder by small holes. It occupies 40% of the total cylinder volume. During the compression stroke, air from the main cylinder enters the precombustion chamber. At this moment, fuel is injected into the precombustion chamber and combustion begins. Pressure increases and the fuel droplets are forced through the small holes into the main cylinder, resulting in a good mix of the fuel and air; the bulk of the combustion takes place in the main cylinder. This type of combustion chamber has multi-fuel capability because the temperature of the prechamber vaporizes the fuel before the main combustion event occurs; the air cell is a small cylindrical chamber with a hole in one end. It is mounted more or less coaxially with the injector, said axis being parallel to the piston crown, with the injector firing across a small cavity, open to the cylinder into the hole in the end of the air cell; the air cell is mounted so as to minimise thermal contact with the mass of the head.
A pintle injector with a narrow spray pattern is used. At its top dead centre the majority of the charge mass is contained in the air cell; when the injector fires, the jet of fuel ignites. This results in a jet of flame shooting back out of the air cell directly into the jet of fuel still issuing from the injector; the heat and turbulence give excellent fuel mixing properties. Since the majority of the combustion takes place outside the air cell in the cavity, which communicates directly with the cylinder, there is less heat loss involved in transferring the burning charge into the cylinder. Air cell injection can be considered as a compromise between indirect and direct injection, gaining some of the efficiency advantages of direct injection while retaining the simplicity and ease of development of indirect injection. Air cell chambers are named Lanova air chambers; the Lanova combustion system was developed by the Lanova company, founded in 1929 by Franz Lang, Gotthard Wielich and Albert Wielich.
In the USA, the Lanova system was used by Mack Trucks. An example is the Mack-Lanova ED diesel engine fitted to the Mack NR truck. Smaller diesels can be produced; the injection pressure required is low, so the injector is cheaper to produce. The injection direction is of less importance. Indirect injection is much simpler to manufacture.
A car is a wheeled motor vehicle used for transportation. Most definitions of car say they run on roads, seat one to eight people, have four tires, transport people rather than goods. Cars came into global use during the 20th century, developed economies depend on them; the year 1886 is regarded as the birth year of the modern car when German inventor Karl Benz patented his Benz Patent-Motorwagen. Cars became available in the early 20th century. One of the first cars accessible to the masses was the 1908 Model T, an American car manufactured by the Ford Motor Company. Cars were adopted in the US, where they replaced animal-drawn carriages and carts, but took much longer to be accepted in Western Europe and other parts of the world. Cars have controls for driving, passenger comfort, safety, controlling a variety of lights. Over the decades, additional features and controls have been added to vehicles, making them progressively more complex; these include rear reversing cameras, air conditioning, navigation systems, in-car entertainment.
Most cars in use in the 2010s are propelled by an internal combustion engine, fueled by the combustion of fossil fuels. Electric cars, which were invented early in the history of the car, began to become commercially available in 2008. There are benefits to car use; the costs include acquiring the vehicle, interest payments and maintenance, depreciation, driving time, parking fees and insurance. The costs to society include maintaining roads, land use, road congestion, air pollution, public health, health care, disposing of the vehicle at the end of its life. Road traffic accidents are the largest cause of injury-related deaths worldwide; the benefits include on-demand transportation, mobility and convenience. The societal benefits include economic benefits, such as job and wealth creation from the automotive industry, transportation provision, societal well-being from leisure and travel opportunities, revenue generation from the taxes. People's ability to move flexibly from place to place has far-reaching implications for the nature of societies.
There are around 1 billion cars in use worldwide. The numbers are increasing especially in China and other newly industrialized countries; the word car is believed to originate from the Latin word carrus or carrum, or the Middle English word carre. In turn, these originated from the Gaulish word karros, it referred to any wheeled horse-drawn vehicle, such as a cart, carriage, or wagon. "Motor car" is attested from 1895, is the usual formal name for cars in British English. "Autocar" is a variant, attested from 1895, but, now considered archaic. It means "self-propelled car"; the term "horseless carriage" was used by some to refer to the first cars at the time that they were being built, is attested from 1895. The word "automobile" is a classical compound derived from the Ancient Greek word autós, meaning "self", the Latin word mobilis, meaning "movable", it entered the English language from French, was first adopted by the Automobile Club of Great Britain in 1897. Over time, the word "automobile" fell out of favour in Britain, was replaced by "motor car".
"Automobile" remains chiefly North American as a formal or commercial term. An abbreviated form, "auto", was a common way to refer to cars in English, but is now considered old-fashioned; the word is still common as an adjective in American English in compound formations like "auto industry" and "auto mechanic". In Dutch and German, two languages related to English, the abbreviated form "auto" / "Auto", as well as the formal full version "automobiel" / "Automobil" are still used — in either the short form is the most regular word for "car"; the first working steam-powered vehicle was designed — and quite built — by Ferdinand Verbiest, a Flemish member of a Jesuit mission in China around 1672. It was a 65-cm-long scale-model toy for the Chinese Emperor, unable to carry a driver or a passenger, it is not known with certainty if Verbiest's model was built or run. Nicolas-Joseph Cugnot is credited with building the first full-scale, self-propelled mechanical vehicle or car in about 1769, he constructed two steam tractors for the French Army, one of, preserved in the French National Conservatory of Arts and Crafts.
His inventions were, handicapped by problems with water supply and maintaining steam pressure. In 1801, Richard Trevithick built and demonstrated his Puffing Devil road locomotive, believed by many to be the first demonstration of a steam-powered road vehicle, it was unable to maintain sufficient steam pressure for long periods and was of little practical use. The development of external combustion engines is detailed as part of the history of the car but treated separately from the development of true cars. A variety of steam-powered road vehicles were used during the first part of the 19th century, including steam cars, steam buses and steam rollers. Sentiment against them led to the Locomotive Acts of 1865. In 1807, Nicéphore Niépce and his brother Claude created what was the world's first internal combustion engine, but they chose to install it in a boat on the river Saone in France. Coincidentally, in 1807 the Swiss inventor François Isaac de Rivaz designed his own'de Rivaz internal combustion engine' and used it to develop the world's first vehicle to be powered by such an engine.
Europe is a continent located in the Northern Hemisphere and in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west and the Mediterranean Sea to the south, it comprises the westernmost part of Eurasia. Since around 1850, Europe is most considered to be separated from Asia by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas and the waterways of the Turkish Straits. Although the term "continent" implies physical geography, the land border is somewhat arbitrary and has been redefined several times since its first conception in classical antiquity; the division of Eurasia into two continents reflects East-West cultural and ethnic differences which vary on a spectrum rather than with a sharp dividing line. The geographic border does not follow political boundaries, with Turkey and Kazakhstan being transcontinental countries. A strict application of the Caucasus Mountains boundary places two comparatively small countries and Georgia, in both continents.
Europe covers 2 % of the Earth's surface. Politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a total population of about 741 million as of 2016; the European climate is affected by warm Atlantic currents that temper winters and summers on much of the continent at latitudes along which the climate in Asia and North America is severe. Further from the sea, seasonal differences are more noticeable than close to the coast. Europe, in particular ancient Greece, was the birthplace of Western civilization; the fall of the Western Roman Empire in 476 AD and the subsequent Migration Period marked the end of ancient history and the beginning of the Middle Ages. Renaissance humanism, exploration and science led to the modern era. Since the Age of Discovery started by Portugal and Spain, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at various times the Americas all of Africa and Oceania and the majority of Asia.
The Age of Enlightenment, the subsequent French Revolution and the Napoleonic Wars shaped the continent culturally and economically from the end of the 17th century until the first half of the 19th century. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to radical economic and social change in Western Europe and the wider world. Both world wars took place for the most part in Europe, contributing to a decline in Western European dominance in world affairs by the mid-20th century as the Soviet Union and the United States took prominence. During the Cold War, Europe was divided along the Iron Curtain between NATO in the West and the Warsaw Pact in the East, until the revolutions of 1989 and fall of the Berlin Wall. In 1949 the Council of Europe was founded, following a speech by Sir Winston Churchill, with the idea of unifying Europe to achieve common goals, it includes all European states except for Belarus and Vatican City. Further European integration by some states led to the formation of the European Union, a separate political entity that lies between a confederation and a federation.
The EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The currency of most countries of the European Union, the euro, is the most used among Europeans. In classical Greek mythology, Europa was a Phoenician princess; the word Europe is derived from her name. The name contains the elements εὐρύς, "wide, broad" and ὤψ "eye, countenance", hence their composite Eurṓpē would mean "wide-gazing" or "broad of aspect". Broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. There have been attempts to connect Eurṓpē to a Semitic term for "west", this being either Akkadian erebu meaning "to go down, set" or Phoenician'ereb "evening, west", at the origin of Arabic Maghreb and Hebrew ma'arav. Michael A. Barry, professor in Princeton University's Near Eastern Studies Department, finds the mention of the word Ereb on an Assyrian stele with the meaning of "night, sunset", in opposition to Asu " sunrise", i.e. Asia.
The same naming motive according to "cartographic convention" appears in Greek Ἀνατολή. Martin Litchfield West stated that "phonologically, the match between Europa's name and any form of the Semitic word is poor." Next to these hypotheses there is a Proto-Indo-European root *h1regʷos, meaning "darkness", which produced Greek Erebus. Most major world languages use words derived from Europa to refer to the continent. Chinese, for example, uses the word Ōuzhōu. In some Turkic languages the Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa; the prevalent definition of Europe as a geographical term has been in use since the mid-19th century. Europe is taken to be bounded by large bodies of water