flame

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An exothermic reaction front or wave in a gaseous medium. Consider a uniform body of gas in which an exothermic chemical reaction (that liberates heat) is initiated by raising the temperature to a sufficiently high level; the reaction is started by a localized release of heat, as by a sufficiently energetic spark, and then spreads from the point of initiation. If the reaction is relatively slow, the whole gas will be involved before the initial region has finished reacting. If the reaction is relatively fast, the reaction zone will develop as a thin front or wave propagating into the unreacted gas, leaving fully reacted gas behind. If the front, in addition, shows luminosity (emission of light), the flame may be considered a classical example. However, perceptible emission of visible radiation is not essential to the definition.

Sufficient reaction rates may also be attained under special conditions (when the gas is very slowly heated inside a closed vessel) without very high temperatures if free radicals are generated in good concentration; this gives so-called cool flames.

The most common flame-producing reaction is combustion, which is broadly defined as a reaction between fuel and an oxidizer. The oxidizer is typically oxygen (usually in air), but a variety of other substances (for example, bromine with hydrogen) can play the same role in combination with the right fuel. While the overall theoretical reaction in a combustion flame—namely, fuel and oxidizer making fully oxidized products such as carbon dioxide and water vapor—is invariably simple, the actual reaction mechanism is typically very complex, involving many intermediate steps and compounds. Free radicals are generally present and figure prominently in the mechanism. See also Free radical.

An overall reaction involving just one reactant is chemical decomposition, for example, ozone decomposing into oxygen. Decomposition flames are usually simpler chemically than combustion flames.

Combustion flames are broadly divided into premixed flames and diffusion flames. Premixed flames occur when fuel and oxidizer are mixed before they burn. Diffusion flames occur when fuel and oxidizer mix and burn simultaneously. The intermediate case, with partial premixing, has been of relatively low theoretical and practical interest. Flames are further categorized on the basis of shape, time behavior (stationary or moving), flow regime (laminar or turbulent), buoyancy regime (forced convection or natural convection), presence or absence of confinement (as by combustion chamber walls), and flow complications (such as swirling flow and crosswind).

To communicate emotionally via e-mail. Just as people might differ about what is polite behavior and what is not, whether an e-mail message is flaming is also in the eye of the beholder. Vulgar cursing would definitely be flaming, however. See netiquette and holy war.

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Send an angry or harshly worded e-mail. Advertisers who send unsolicited electronic mail messages can expect some percentage of negative responses called a flame rate. Advertisers wishing to keep their flame rate to a minimum operate on an opt-in basis, sending e-mails only to persons who either request specific information or give advance permission for information to be sent. See also spam.

noun

The visible signs of combustion: blaze¹, conflagration, fire, flare-up. See hot/cold/lukewarm.

verb

To undergo combustion: blaze¹, burn, combust, flare. See hot/cold/lukewarm.

Definition: lover, passion
Antonyms: hate

[at MIT, orig. from the phrase flaming asshole]

1. vi. To post an email message intended to insult and provoke.

2. vi. To speak incessantly and/or rabidly on some relatively uninteresting subject or with a patently ridiculous attitude.

3. vt. Either of senses 1 or 2, directed with hostility at a particular person or people.

4. n. An instance of flaming. When a discussion degenerates into useless controversy, one might tell the participants “Now you're just flaming” or “Stop all that flamage!” to try to get them to cool down (so to speak).

The term may have been independently invented at several different places. It has been reported from MIT, Carleton College and RPI (among many other places) from as far back as 1969, and from the University of Virginia in the early 1960s.

It is possible that the hackish sense of ‘flame’ is much older than that. The poet Chaucer was also what passed for a wizard hacker in his time; he wrote a treatise on the astrolabe, the most advanced computing device of the day. In Chaucer's Troilus and Cressida, Cressida laments her inability to grasp the proof of a particular mathematical theorem; her uncle Pandarus then observes that it's called “the fleminge of wrecches.” This phrase seems to have been intended in context as “that which puts the wretches to flight” but was probably just as ambiguous in Middle English as “the flaming of wretches” would be today. One suspects that Chaucer would feel right at home on Usenet.

A hot (usually luminous) zone of gas and/or particulate matter in gaseous suspension that is undergoing combustion.

LearnThatWord.com is a free vocabulary and spelling program where you only pay for results!

1. the luminous, irregular appearance usually accompanying combustion, or an appearance resembling it.
2. to render sterile by exposure to a flame.

• f. cell — the excretory cell in cestodes and trematodes; their number and arrangement is a basis for identification.
• f. figure — in skin lesions such as insect bite reactions, eosinophilic granulomas; characterized by areas of altered collagen surrounded by eosinophils and eosinophilic cytoplasmic granules.
• f. follicle — inactive hair follicles with excessive trichilemmal keratinization.
• f. retardants — see fire retardant.

• Behavior or Personality

For other uses, see Flame (disambiguation).

Flames of charcoal.

Laminar flame of a burning candle.

A flame (from Latin flamma) is the visible (light-emitting), gaseous part of a fire. It is caused by a highly exothermic reaction (for example, combustion, a self-sustaining oxidation reaction) taking place in a thin zone.^[1] If a fire is hot enough to ionize the gaseous components, it can become a plasma.^[2]

Contents 1 Mechanism 2 Flame color 3 Flame temperature 3.1 Common flame temperatures 3.2 Hottest flame temperature 3.3 Cool flames 4 Flames in microgravity 5 References 6 See also 7 External links

Mechanism

Color and temperature of a flame are dependent on the type of fuel involved in the combustion, as, for example, when a lighter is held to a candle. The applied heat causes the fuel molecules in the candle wax to vaporize. In this state they can then readily react with oxygen in the air, which gives off enough heat in the subsequent exothermic reaction to vaporize yet more fuel, thus sustaining a consistent flame. The high temperature of the flame causes the vaporized fuel molecules to decompose, forming various incomplete combustion products and free radicals, and these products then react with each other and with the oxidizer involved in the reaction. Sufficient energy in the flame will excite the electrons in some of the transient reaction intermediates such as CH and C₂, which results in the emission of visible light as these substances release their excess energy (see spectrum below for an explanation of which specific radical species produce which specific colors). As the combustion temperature of a flame increases (if the flame contains small particles of unburnt carbon or other material), so does the average energy of the electromagnetic radiation given off by the flame (see blackbody).

Other oxidizers besides oxygen can be used to produce a flame. Hydrogen burning in chlorine produces a flame and in the process emits gaseous hydrogen chloride (HCl) as the combustion product.^[3] Another of many possible chemical combinations is hydrazine and nitrogen tetroxide which is hypergolic and commonly used in rocket engines. Fluoropolymers can be used to supply fluorine as an oxidizer of metallic fuels, e.g. in the magnesium/teflon/viton composition.

The chemical kinetics occurring in the flame are very complex and involves typically a large number of chemical reactions and intermediate species, most of them radicals. For instance, a well-known chemical kinetics scheme, GRI-Mech,^[4] uses 53 species and 325 elementary reactions to describe combustion of biogas.

There are different methods of distributing the required components of combustion to a flame. In a diffusion flame, oxygen and fuel diffuse into each other; where they meet the flame occurs. In a premixed flame, the oxygen and fuel are premixed beforehand, which results in a different type of flame. Candle flames (a diffusion flame) operate through evaporation of the fuel which rises in a laminar flow of hot gas which then mixes with surrounding oxygen and combusts.

Flame color

Spectrum of the blue (premixed, i.e., complete combustion) flame from a butane torch showing molecular radical band emission and Swan bands. Note that virtually all the light produced is in the blue to green region of the spectrum below about 565 nanometers, accounting for the bluish color of sootless hydrocarbon flames.

Different flame types of a Bunsen burner depend on oxygen supply. On the left a rich fuel with no premixed oxygen produces a yellow sooty diffusion flame; on the right a lean fully oxygen premixed flame produces no soot and the flame color is produced by molecular radicals, especially CH and C2 band emission. The purple color is an artifact of the photographic process^{[citation needed]}

Flame color depends on several factors, the most important typically being blackbody radiation and spectral band emission, with both spectral line emission and spectral line absorption playing smaller roles. In the most common type of flame, hydrocarbon flames, the most important factor determining color is oxygen supply and the extent of fuel-oxygen pre-mixing, which determines the rate of combustion and thus the temperature and reaction paths, thereby producing different color hues.

In a laboratory under normal gravity conditions and with a closed oxygen valve, a Bunsen burner burns with yellow flame (also called a safety flame) at around 1,000 °C (1,800 °F). This is due to incandescence of very fine soot particles that are produced in the flame. With increasing oxygen supply, less blackbody-radiating soot is produced due to a more complete combustion and the reaction creates enough energy to excite and ionize gas molecules in the flame, leading to a blue appearance. The spectrum of a premixed (complete combustion) butane flame on the right shows that the blue color arises specifically due to emission of excited molecular radicals in the flame, which emit most of their light well below ~565 nanometers in the blue and green regions of the visible spectrum.

The colder part of a diffusion (incomplete combustion) flame will be red, transitioning to orange, yellow, and white as the temperature increases as evidenced by changes in the blackbody radiation spectrum. For a given flame's region, the closer to white on this scale, the hotter that section of the flame is. The transitions are often apparent in fires, in which the color emitted closest to the fuel is white, with an orange section above it, and reddish flames the highest of all.^[5] A blue-colored flame only emerges when the amount of soot decreases and the blue emissions from excited molecular radicals become dominant, though the blue can often be seen near the base of candles where airborne soot is less concentrated.^[6]

Specific colors can be imparted to the flame by introduction of excitable species with bright emission spectrum lines. In analytical chemistry, this effect is used in flame tests to determine presence of some metal ions. In pyrotechnics, the pyrotechnic colorants are used to produce brightly colored fireworks.

Flame temperature

A flame test for sodium. Note that the yellow color in this gas flame does not arise from the blackbody emission of soot particles (as the flame is clearly a blue premixed complete combustion flame) but instead comes from the spectral line emission of sodium atoms, specifically the very intense sodium D lines.

When looking at a flame's temperature there are many factors which can change or apply. One important one is that a flame's color does not necessarily determine a temperature comparison because black-body radiation is not the only thing that produces or determines the color seen; therefore it is only an estimation of temperature. Here are other factors that determine its temperature:

• Adiabatic flame; i.e., no loss of heat to the atmosphere (may differ in certain parts).
• Atmospheric pressure
• Percentage oxygen content of the atmosphere.
• The fuel being burned (i.e., depends on how quickly the process occurs; how violent the combustion is.)
• Any oxidation of the fuel.
• Temperature of atmosphere links to adiabatic flame temperature (i.e., heat will transfer to a cooler atmosphere more quickly).
• How stoichiometric the combustion process is (a 1:1 stoichiometricity) assuming no dissociation will have the highest flame temperature... excess air/oxygen will lower it and likewise not enough air/oxygen.

In fires (particularly house fires), the cooler flames are often red and produce the most smoke. Here the red color compared to typical yellow color of the flames suggests that the temperature is lower. This is because there is a lack of oxygen in the room and therefore there is incomplete combustion and the flame temperature is low, often just 600–850 °C (1,112–1,562 °F). This means that a lot of carbon monoxide is formed (which is a flammable gas if hot enough) which is when in Fire and Arson investigation there is greatest risk of backdraft. When this occurs flames get oxygen, carbon monoxide combusts and temporary temperatures of up to 2,000 °C (3,632 °F) occur.^{[citation needed]}

Flame temperatures of common items include a candle at 1,400 °C (2,600 °F),^[7] a blow torch – at around 1,600 °C (2,900 °F) a propane torch at 1,995 °C (3,620 °F), or a much hotter oxyacetylene combustion at 3,000 °C (5,400 °F).

Common flame temperatures

This section may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (September 2009)

This is a rough guide to flame temperatures for various common substances (in 20 °C air at 1 atm. pressure):

Material burned	Flame temperature (°C)
Charcoal fire	750–1,200
Methane (natural gas)	900–1,500
Propane blowtorch	1,200–1,700
Candle flame	~1,100 (majority), hot spots may be 1300–1400
Magnesium	1,900–2,300
Hydrogen torch	Up to ~2,000
Acetylene blowlamp/blowtorch	Up to ~2,300
Oxyacetylene	Up to ~3,300
Backdraft flame peak	1,700–1,950
Bunsen burner flame	900–1,600 (depending on the air valve)

Material burned	Max. flame temperature (°C, in air, diffusion flame)[5]
Wood	1027
Gasoline	1026
Methanol	1200
Kerosene	990
Animal fat	800–900
Charcoal (forced draft)	1390

Hottest flame temperature

Cyanogen produces a very hot flame with a temperature of over 4,525 °C (8,180 °F) when it burns in oxygen.^[8] Dicyanoacetylene, a compound of carbon and nitrogen with chemical formula C₄N₂ burns in oxygen with a bright blue-white flame at a temperature of 5260 K (4990 °C, 9010 °F), and at up to 6000 K in ozone.^[9] This high flame temperature is also the result of the absence of hydrogen, and, therefore, water as a combustion product. Because of its high specific heat, water vapor as a combustion product tends to lower the flame temperature of hydrogen containing compounds. The endothermic dissociation of water at high temperatures above 2000 °C also prevents flame temperatures to rise above 3000 to 4000 °C.

Cool flames

Main article: Cool flame

At temperatures as low as 120 °C, fuel-air mixtures can react chemically and produce very weak flames called cool flames. The phenomenon was discovered by Humphry Davy in 1817. The process depends on a fine balance of temperature and concentration of the reacting mixture, and if conditions are right it can initiate without any external ignition source. Cyclical variations in the balance of chemicals, particularly of intermediate products in the reaction, give oscillations in the flame, with a typical temperature variation of about 100 K, or between "cool" and full ignition. Sometimes the variation can lead to explosion.^[10][11]

Flames in microgravity

In zero gravity, convection does not carry the hot combustion products away from the fuel source, resulting in a spherical flame front.

In 2000, experiments by NASA confirmed that gravity plays an indirect role in flame formation and composition.^[12] The common distribution of a flame under normal gravity conditions depends on convection, as soot tends to rise to the top of a flame (such as in a candle in normal gravity conditions), making it yellow. In microgravity or zero gravity environment, such as in orbit, natural convection no longer occurs and the flame becomes spherical, with a tendency to become bluer and more efficient. There are several possible explanations for this difference, of which the most likely is the hypothesis that the temperature is sufficiently evenly distributed that soot is not formed and complete combustion occurs.^[13] Experiments by NASA reveal that diffusion flames in microgravity allow more soot to be completely oxidized after they are produced than do diffusion flames on Earth, because of a series of mechanisms that behave differently in microgravity when compared to normal gravity conditions.^[14] These discoveries have potential applications in applied science and industry, especially concerning fuel efficiency.

References

1. ^ Law, C. K. (2006). "Laminar premixed flames". Combustion physics. Cambridge, England: Cambridge University Press. p. 300. ISBN 0-521-87052-6. http://books.google.com/?id=vWgJvKMXwQ8C&pg=RA300. 
2. ^ Verheest, Frank (2000). "Plasmas as the fourth state of matter". Waves in Dusty Space Plasmas. Norwell MA: Kluwer Academic. p. 1. ISBN 0-7923-6232-2. http://books.google.com/?id=LBpPMbADNCgC&pg=PA1. 
3. ^ "Reaction of Chlorine with Hydrogen". Archived from the original on 2008-08-20. http://web.archive.org/web/20080820080559/http://genchem.chem.wisc.edu/demonstrations/Inorganic/pages/Group67/chlorine_and_hydrogen.htm. 
4. ^ Gregory P. Smith, David M. Golden, Michael Frenklach, Nigel W. Moriarty, Boris Eiteneer, Mikhail Goldenberg, C. Thomas Bowman, Ronald K. Hanson, Soonho Song, William C. Gardiner, Jr., Vitali V. Lissianski, and Zhiwei Qin. "GRI-Mech 3.0". http://www.me.berkeley.edu/gri_mech/. 
5. ^ ^{a b} Christopher W. Schmidt, Steve A. Symes (2008). The analysis of burned human remains. Academic Press. pp. 2–4. ISBN 0-12-372510-0. http://books.google.com/?id=Q7Pb2wXV2woC&pg=PA4. 
6. ^ Jozef Jarosinski, Bernard Veyssiere (2009). Combustion Phenomena: Selected Mechanisms of Flame Formation, Propagation and Extinction. CRC Press. p. 172. ISBN 0-8493-8408-7. http://books.google.com/?id=hadB8msSl1EC&pg=PA172. 
7. ^ Temperatures in flames and fires. Doctorfire.com. Retrieved on 2011-11-13.
8. ^ Thomas, N.; Gaydon, A. G.; Brewer, L., A. G.; Brewer, L. (1952). "Cyanogen Flames and the Dissociation Energy of N2". The Journal of Chemical Physics 20 (3): 369–374. Bibcode 1952JChPh..20..369T. doi:10.1063/1.1700426. 
9. ^ Kirshenbaum, A. D.; and A. V. Grosse (May 1956). "The Combustion of Carbon Subnitride, NC₄N, and a Chemical Method for the Production of Continuous Temperatures in the Range of 5000–6000°K". Journal of the American Chemical Society 78 (9): 2020. doi:10.1021/ja01590a075. 
10. ^ Pearlman, Howard; Chapek, Richard M. (24 April 2000). "Cool Flames and Autoignition in Microgravity". NASA. http://www.grc.nasa.gov/WWW/RT/RT1999/6000/6711wu.html. Retrieved 13 May 2010. 
11. ^ Jones, John Clifford (September 2003). "Low temperature oxidation". Hydrocarbon process safety: a text for students and professionals. Tulsa, OK: PennWell. pp. 32–33. ISBN 978-1-59370-004-1. 
12. ^ Spiral flames in microgravity, National Aeronautics and Space Administration, 2000.
13. ^ Candle Flame in Microgravity. NASA
14. ^ C. H. Kim et al. Laminar Soot Processes Experiment Shedding Light on Flame Radiation. NASA, HTML

See also

• Fire
• Flame detector
• Plasma (physics)
• Pyranoscope

External links

• A candle flame strongly influenced and moved about by an electric field due to the flame having ions.
• Ultra-Low Emissions Low-Swirl Burner

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - flamme
v. intr. - flamme
v. tr. - flamme

idioms:

• flame gun    apparat der fremkalder en flamme brugt til at dræbe ukrudt
• flame out    blusse op
• flame thrower    flammekaster
• flame up    flamme op, blive blussende rød
• go up in flames    gå op i flammer

Nederlands (Dutch)
vlam, geliefde, glans, oranjerood, hartstocht, soort mot, vlammen, uitbarsten, gloeien, signaleren d.m.v. vuur, doen vlammen, flamberen, schitteren, als een vlam wiegen, door vlammen overbrengen

Français (French)
n. - flamme (littér), (fig) feu, (Culin) à feu (doux/vif), rouge feu (couleur), torpille/flamme (e-mail)
v. intr. - flamboyer, flamber, brûler, s'enflammer, lancer une guerre d'insultes sur e-mail
v. tr. - (Culin) flamber, envoyer un message injurieux par e-mail

idioms:

• flame gun    chalumeau
• flame out    enflammer
• flame thrower    lance-flammes
• flame up    s'enflammer, s'emporter, flamboyer
• go up in flames    s'enflammer

Deutsch (German)
n. - Flamme
v. - flammen, glühen

idioms:

• flame gun    Flämmgerät
• flame out    ausbrennen
• flame thrower    Flammenwerfer
• flame up    aufflammen, (fig) in Wut geraten, anfangen zu brennen
• go up in flames    in Flammen aufgehen

Ελληνική (Greek)
n. - φλόγα, (καθομ.) αγαπημένη, ερωμένη, (Η/Υ) προσβλητικό ηλεκτρονικό μήνυμα
v. - φλέγομαι, φλογίζομαι, λαμπαδιάζω, κορώνω, ανάβω, (Η/Υ) κατακεραυνώνω με προσβλητικό μήνυμα

idioms:

• flame gun    φλογοβόλο
• flame out    εκτοξεύω φλόγες
• flame thrower    (στρατ.) φλογοβόλο (όπλο)
• flame up    (ανα)φλέγομαι, λαμπαδιάζω, κορώνω
• go up in flames    γίνομαι παρανάλωμα του πυρός

Italiano (Italian)
fiammeggiare, fiamma

idioms:

• flame gun    lanciafiamme
• flame out    fiammeggiare
• flame thrower    lanciafiamme
• go up in flames    andare in fiamme

Português (Portuguese)
n. - chama (f)
v. - incendiar

idioms:

• flame gun    lança-chamas (m)
• flame out    queimar de novo, enfurecer-se
• flame thrower    lança-chamas (m) (Mil.)
• flame up    enfurecer-se, enrubescer
• go up in flames    incendiar-se

Русский (Russian)
огонь, пламя, вспыхивать, вспышка, предмет страсти, пассия

idioms:

• flame gun    огнемет
• flame out    вспыхнуть, гибель
• flame thrower    огнемет
• flame up    вспыхнуть
• go up in flames    загореться

Español (Spanish)
n. - correo electrónico ofensivo
v. intr. - pasarse mandando y recibiendo correo electrónico
v. tr. - mandar correo electrónico ofensivo

idioms:

• flame gun    lanzallamas
• flame out    arder, encenderse
• flame thrower    lanzallamas
• flame up    inflamarse
• go up in flames    incendiarse, quemarse

Svenska (Swedish)
n. - flamma, eld (bildl.), käresta (vard.), offensiv e-mail
v. - flamma, signalera med eld, värma i en låga, lysa upp med flammor, bränna med eldspruta, flambera, skicka offensiv e-mail, skicka e-mail i ett (i det oändliga)

中文（简体）(Chinese (Simplified))
火焰, 热情, 火舌, 燃烧, 闪耀, 爆发, 焚烧, 激动, 面红

idioms:

• flame gun    喷火枪
• flame out    突然冒火焰
• flame thrower    喷火器, 火焰喷射器
• flame up    爆发
• go up in flames    着火, 烧毁, 消失, 不成功

中文（繁體）(Chinese (Traditional))
n. - 火焰, 熱情, 火舌
v. intr. - 燃燒, 閃耀, 爆發
v. tr. - 焚燒, 激動, 面紅

idioms:

• flame gun    噴火槍
• flame out    突然冒火焰
• flame thrower    噴火器, 火焰噴射器
• flame up    爆發
• go up in flames    著火, 燒毀, 消失, 不成功

한국어 (Korean)
n. - 불길, 불쾌한 전자메일
v. intr. - 불길을 내다, (얼굴)붉어지다, 전자메일을 쓰다
v. tr. - ~을 태우다, ~을 흥분 시키다, 불쾌한 전자메일을 보내다

idioms:

• flame out    (비행기의) 제트 엔진의 갑작스런 정지
• flame up    불꽃같이 빛나다, 얼굴이 확 붉어지다
• go up in flames    건물이 타오르다

日本語 (Japanese)
n. - 炎, 燃えるような輝き, 情熱
v. - 炎を出す, 燃え上がる, 炎のように輝く, ぱっと赤らむ, かっと怒り出す

idioms:

• flame gun    火炎除草機
• flame out    突然燃え上がる, 突然燃焼停止する
• flame thrower    火炎放射器
• flame up    燃え上がる, かっとなる, 赤面する
• go up in flames    燃え上がる

العربيه (Arabic)
‏(الاسم) شعله , لهب, بريد الكتروني مزعج (فعل) يلتهب, يرسل بريد الكتروني مزعج, يطول في رساله الكترونيه‏

עברית (Hebrew)
n. - ‮להבה, אש, זוהר‬
v. intr. - ‮פרץ (רגש), התכעס, בער, זהר כלהבה‬
v. tr. - ‮הבעיר, אותת באש‬

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