Instruct: Given a question, retrieve documents that answer the question.
Query: What is the process of combustion?
Combustion processes which happen in very small volumes are considered micro-combustion. The high surface-to-volume ratio increases specific heat loss. Quenching distance plays a vital role in stabilizing the flame in such combustion chambers.
The combustion chamber of the W-series engine was in the upper part of the cylinder, not the head, the head having only tiny recesses for the valves. This arrangement was achieved by combining a cylinder head deck that was not perpendicular to the bore with a crowned piston, which was a novel concept in American production engines of the day. As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge-shaped combustion chamber with a pronounced quench area. The spark plugs were inserted vertically into the quench area, which helped to produce a rapidly moving flame front for more complete combustion.
A very wide variety of fuels may occur as gases, droplet fogs, or dust suspensions. Oxidants include halogens, ozone, hydrogen peroxide and oxides of nitrogen. Gaseous detonations are often associated with a mixture of fuel and oxidant in a composition somewhat below conventional flammability ratios. They happen most often in confined systems, but they sometimes occur in large vapor clouds. Other materials, such as acetylene, ozone, and hydrogen peroxide are detonable in the absence of dioxygen.
Polycyclic aromatic hydrocarbons are primarily found in natural sources such as creosote. They can result from the incomplete combustion of organic matter. PAHs can also be produced geologically when organic sediments are chemically transformed into fossil fuels such as oil and coal. PAHs are considered ubiquitous in the environment and can be formed from either natural or manmade combustion sources. The dominant sources of PAHs in the environment are thus from human activity: wood-burning and combustion of other biofuels such as dung or crop residues contribute more than half of annual global PAH emissions, particularly due to biofuel use in India and China. As of 2004, industrial processes and the extraction and use of fossil fuels made up slightly more than one quarter of global PAH emissions, dominating outputs in industrial countries such as the United States. Wildfires are another notable source. Substantially higher outdoor air, soil, and water concentrations of PAHs have been measured in Asia, Africa, and Latin America than in Europe, Australia, the U.S., and Canada.
Polycyclic aromatic hydrocarbons (PAHs) are aromatic hydrocarbons that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass). As pollutants, they are of concern because some compounds have been identified as carcinogenic, mutagenic, and teratogenic. PAHs are also found in cooked foods. Studies have shown that high levels of PAHs are found, for example, in meat cooked at high temperatures such as grilling or barbecuing, and in smoked fish.
The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, similar to the acid–base reaction. The oxidation alone and the reduction alone are each called a "half-reaction", because two half-reactions always occur together to form a whole reaction. When writing half-reactions, the gained or lost electrons are typically included explicitly in order that the half-reaction be balanced with respect to electric charge.
A thermonuclear weapon, or fusion weapon, is a second-generation nuclear weapon design which affords vastly greater destructive power than first-generation atomic bombs. Modern fusion weapons consist essentially of two main components: a nuclear fission primary stage (fueled by Uranium-235 or Plutonium-239) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium and tritium, or in modern weapons lithium deuteride. For this reason thermonuclear weapons are often colloquially called hydrogen bombs, or H-bombs.
The quark bomb explodes at the moment of construction at the factory. The rest of its existence is a slow process of quark fission, which turns the avalanche-like destruction of atoms into a slow, rhythmical, gradual destruction of 10 grams of copper dust - the best known explosive trigger. If the bomb is shot at, which destroys its mechanisms, then the unstoppable process of atomic fission begins at full strength. The only way to get rid of a quark bomb is to jettison it in deep space at least 3-4 light years from the nearest stellar body or nebula. Occasionally, quark fission can be transferred from one planet to another through tiny meteorites, dust particles, molecules of ionized gas, etc.
The notion of using a fission weapon to ignite a process of nuclear fusion can be dated back to 1942. At the first major theoretical conference on the development of an atomic bomb hosted by J. Robert Oppenheimer at the University of California, Berkeley, participant Edward Teller directed the majority of the discussion towards Enrico Fermi's idea of a "Super" bomb that would use the same reactions that powered the Sun itself.
Hydrogen is found in the first group and first period in the periodic table, i.e. it is the first element on the periodic table, making it the lightest element. Since hydrogen gas is so light, it rises in the atmosphere and is therefore rarely found in its pure form, H. In a flame of pure hydrogen gas, burning in air, the hydrogen (H) reacts with oxygen (O) to form water (HO) and releases energy.
Cast iron is made from pig iron, which is the product of smelting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are then added to the melt before the final form is produced by casting.
The basic principle of the Teller–Ulam configuration is the idea that different parts of a thermonuclear weapon can be chained together in "stages", with the detonation of each stage providing the energy to ignite the next stage. At a bare minimum, this implies a "primary" section that consists of an implosion-type fission bomb (a "trigger"), and a "secondary" section that consists of fusion fuel. The energy released by the "primary" compresses the "secondary" through a process called "radiation implosion", at which point it is heated and undergoes nuclear fusion. This process could be continued, with energy from the secondary igniting a third fusion stage; Russia's AN602 "Tsar Bomba" is thought to have been a three-stage fission-fusion-fusion device. Theoretically by continuing this process thermonuclear weapons with arbitrarily high yield could be constructed. This contrasts with fission weapons which are limited in yield.
The stability of the atmosphere in Earth is not a consequence of chemical equilibrium. Oxygen is a reactive compound, and should eventually combine with gases and minerals of the Earth's atmosphere and crust. Oxygen only began to persist in the atmosphere in small quantities about 50 million years before the start of the Great Oxygenation Event. Since the start of the Cambrian period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume. Traces of methane (at an amount of 100,000 tonnes produced per year) should not exist, as methane is combustible in an oxygen atmosphere.
Examples of energy transformation include generating electric energy from heat energy via a steam turbine, or lifting an object against gravity using electrical energy driving a crane motor. Lifting against gravity performs mechanical work on the object and stores gravitational potential energy in the object. If the object falls to the ground, gravity does mechanical work on the object which transforms the potential energy in the gravitational field to the kinetic energy released as heat on impact with the ground. Our Sun transforms nuclear potential energy to other forms of energy; its total mass does not decrease due to that in itself (since it still contains the same total energy even if in different forms), but its mass does decrease when the energy escapes out to its surroundings, largely as radiant energy.
The color of the smoke indicates the results to the people assembled in St Peter's Square. Dark smoke (fumata nera) indicates that the ballot did not result in an election, while white smoke (fumata bianca) announces that a new pope was chosen. Originally, in the event a pope was not elected, damp straw was added to the fire to create dark smoke. In the event a new pope was elected, the ballots were burned alone, creating white smoke.
In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH, which are co-enzymes used in the electron transport chain. It is named as such because the beta carbon of the fatty acid undergoes oxidation to a carbonyl group. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although very long chain fatty acids are oxidized in peroxisomes.
The extremely high temperatures of lava flows (1200 °C; 2200 °F) cause sea water to decompose into hydrogen and oxygen. The hydrogen combines with chloride ions dissolved in sea water, forming hydrogen chloride gas (hydrochloric acid). The rapidly rising plume of gas also carries with it fine particles of volcanic glass. The hydrochloric acid and other contaminants can precipitate out rapidly and the plume may become relatively safe a few hundred meters away, however, laze plumes should be shown a degree of respect as they can and have killed people who come in contact with them. The USGS has reported that, in 2000, two people were killed by exposure to laze clouds.
The aerosol of electronic cigarettes is generated when the e-liquid reaches a temperature of roughly 100–250 °C within a chamber.
The user inhales the aerosol, commonly called vapor, which has only one property in common with cigarette smoke, nicotine (not a carcinogen when vaped, but harmful to kid's growth process). The aerosol can provide a flavor profile ranging from a simple tobacco to a complex dessert and offers an alternative to combustible tobacco smoking which meets a number of the pleasure benchmarks sought by those who appreciate nicotine. In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas. Vapor from an e-cigarette simulates tobacco smoke, but the process of burning tobacco does not occur. The aerosol is made-up of liquid sub-micron particles of condensed vapor, which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals. The chemicals in the aerosol give rise to the issue of safety of electronic cigarettes. After a puff, inhalation of the aerosol travels from the device into the mouth and lungs. A 2014 review found that the particles emitted by e-cigarettes are comparable in size and number to particles in cigarette smoke, with the majority of them in the ultrafine range. The particles are of the ultrafine size which can go deep in the lungs and then into the systemic circulation. Studies show that the quantities of metals emitted are minimal and permissible by medicinal standards.
The amount of oxygen in the atmosphere has fluctuated over the last 600 million years, reaching a peak of 35% during the Carboniferous period, significantly higher than today's 21%. Two main processes govern changes in the atmosphere: plants use carbon dioxide from the atmosphere, releasing oxygen and the breakdown of pyrite and volcanic eruptions release sulfur into the atmosphere, which oxidizes and hence reduces the amount of oxygen in the atmosphere. However, volcanic eruptions also release carbon dioxide, which plants can convert to oxygen. The exact cause of the variation of the amount of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are associated with rapid development of animals. Today's atmosphere contains 21% oxygen, which is high enough for rapid development of animals.The climate of the late Precambrian showed some major glaciation events spreading over much of the earth. At this time the continents were bunched up in the Rodinia supercontinent. Massive deposits of tillites and anomalous isotopic signatures are found, which gave rise to the Snowball Earth hypothesis. As the Proterozoic Eon drew to a close, the Earth started to warm up. By the dawn of the Cambrian and the Phanerozoic, life forms were abundant in the Cambrian explosion with average global temperatures of about 22 °C.
Any substance consisting of two or more different types of atoms (chemical elements) in a fixed stoichiometric proportion can be termed a "chemical compound"; the concept is most readily understood when considering pure chemical substances. It follows from their being composed of fixed proportions of two or more types of atoms that chemical compounds can be converted, via chemical reaction, into compounds or substances each having fewer atoms. The ratio of each element in the compound is expressed in a ratio in its chemical formula. A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using the standard abbreviations for the chemical elements, and subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is HO. In the case of non-stoichiometric compounds, the proportions may be reproducible with regard to their preparation, and give fixed proportions of their component elements, but proportions that are not integral [e.g., for palladium hydride, PdH (0.02 < x < 0.58)].
Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium (NH), nitrite (NO), nitrate (NO), nitrous oxide (NO), nitric oxide (NO) or inorganic nitrogen gas (N). Organic nitrogen may be in the form of a living organism, humus or in the intermediate products of organic matter decomposition. The processes in the nitrogen cycle is to transform nitrogen from one form to another. Many of those processes are carried out by microbes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth. For example, the nitrogenous wastes in animal urine are broken down by nitrifying bacteria in the soil to be used as new. The diagram {besides} alongside shows how these processes fit together to form the nitrogen cycle.
In addition to pre-combustion and oxy-fuel combustion technologies, post-combustion is a promising technology which can be used to extract CO emission from biomass fuel resources. During the process, CO is separated from the other gases in the flue gas stream after the biomass fuel is burnt and undergo separation process. Because it has the ability to be retrofitted to some existing power plants such as steam boilers or other newly built power stations, post-combustion technology is considered as a better option than pre-combustion technology. According to the fact sheets "U.S. CONSUMPTION OF BIO-ENERGY WITH CARBON CAPTURE AND STORAGE" released in March 2018, the efficiency of post-combustion technology is expected to be 95% while pre-combustion and oxy-combustion capture CO2 at an efficient rate of 85% and 87.5% respectively.
When the fuel in a flame combusts, the energy released by the combustion process is deposited in combustion products, usually molecular fragments called free radicals. The combustion products are excited to a very high temperature called the adiabatic flame temperature (that is, the temperature before any heat has been transferred away from the combustion products). This temperature is usually much higher than the temperature of the air in the flame or which an object inserted into the flame can reach. When the combustion products lose this energy by radiative emission, the radiation can thus be more intense than that of a lower-temperature blackbody inserted into the flame. The exact emission process involved varies with the material, the type of fuels and oxidizers, and the type of flame, though in many cases it is well established that the free radicals undergo radiative recombination. This energetic light emitted directly from the combustion products may be observed directly (as with a blue gas flame), depending on the wavelength, or it may then cause fluorescence in the candoluminescent material. Some free-radical recombinations emit ultraviolet light, which is only observable through fluorescence.
The term 'micro' gravity refers to a gravitational state that is 'low' (i.e., 'micro' in the sense of 'small' and not necessarily a millionth of Earth's normal gravity) such that the influence of buoyancy on physical processes may be considered small relative to other flow processes that would be present at normal gravity. In such an environment, the thermal and flow transport dynamics can behave quite differently than in normal gravity conditions (e.g., a candle's flame takes the shape of a sphere.). Microgravity combustion research contributes to the understanding of a wide variety of aspects that are relevant to both the environment of a spacecraft (e.g., fire dynamics relevant to crew safety on the International Space Station) and terrestrial (Earth-based) conditions (e.g., droplet combustion dynamics to assist developing new fuel blends for improved combustion, materials fabrication processes, thermal management of electronic systems, multiphase flow boiling dynamics, and many others).
The quality of combustion can be improved by the designs of combustion devices, such as burners and internal combustion engines. Further improvements are achievable by catalytic after-burning devices (such as catalytic converters) or by the simple partial return of the exhaust gases into the combustion process. Such devices are required by environmental legislation for cars in most countries and may be necessary to enable large combustion devices, such as thermal power stations, to reach legal emission standards.