combustion


combustion
combustive, adj.
/keuhm bus"cheuhn/, n.
1. the act or process of burning.
2. Chem.
a. rapid oxidation accompanied by heat and, usually, light.
b. chemical combination attended by production of heat and light.
c. slow oxidation not accompanied by high temperature and light.
3. violent excitement; tumult.
[1400-50; late ME ( < MF) < LL combustion- (s. of combustio). See COMBUST, -ION]

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Introduction

      rapid chemical reaction between substances that is usually accompanied by generation of heat and light in the form of flame. In most cases, oxygen comprises one of the reactants. Other physical phenomena that sometimes occur during combustion reactions are explosion and detonation.

      A brief treatment of combustion follows. For full treatment, see oxidation-reduction reaction: Combustion and flame (oxidation–reduction reaction).

      Combustion, one of the most important classes of chemical reaction, is often considered a climax phenomenon in the oxidation of certain types of substances. Although most flames have regions where reduction reactions are important, combustion is primarily the combining of combustible material with oxygen.

Chemical and physical aspects
      The chemical processes in combustion are most commonly initiated by such factors as heat, light, and sparks. As the combustible materials achieve the ignition temperature specific to the materials and the ambient pressure, the combustion reaction begins. The combustion spreads from the ignition source to the adjacent layer of gas mixture; in turn, each point of the burning layer serves as an ignition source for the next adjacent layer, and so on. Combustion terminates when equilibrium is achieved between the total heat energies of the reactants and the total heat energies of the products.

      Combustion may be propagated by complicated branched-chain reactions, as in hydrogen combustion. Other types of reactions, such as the combustion of carbon monoxide, are characterized by a fast interaction step between a hydroxyl radical (OH- ) and the carbon monoxide molecule (CO). Although the mechanisms of hydrocarbon combustion are not completely known, many of the steps involving hydrogen and oxygen atoms and hydroxyl and organic radicals are similar to those for hydrogen and carbon monoxide combustion.

      In addition to the chemical processes in combustion, physical processes that transfer mass and energy also occur. In gaseous combustion, for example, the diffusion of reactants and combustion products depends on their concentrations, pressure and temperature changes, and diffusion coefficients. Convection, which is also responsible for the transport of mass and energy, comprises buoyant and external forces, and turbulent and eddy motions.

      Combustion may also emit light energy, mostly in the infrared portion of the spectrum. The light emitted by a flame arises from the presence of particles in electronically excited states and from ions, radicals, and electrons.

Explosions
      An acceleration of a combustion reaction, whether caused by a rise in temperature or by an increase in the lengths of reaction chains, can lead to an explosion. In the former case a thermal explosion will occur when the rate of heat released by the reaction exceeds the rate of heat lost from the area. In the latter case a so-called chain explosion will occur when the probability of chain branching equals that of chain termination. When a combustion reaction accelerates progressively so that the flame front area advances at a supersonic velocity, compression from the shock wave causes an increase in temperature that results in self-ignition of the fuel. This phenomenon, called detonation, will not occur when energy loss from the reaction zone exceeds a certain limit.

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Universalium. 2010.

Synonyms:

Look at other dictionaries:

  • combustion — Combustion …   Thresor de la langue françoyse

  • COMBUSTION — La combustion recouvre des phénomènes très variés. La définition même du terme répond à deux tendances différentes. La première lui donne un sens très général. Elle englobe «combustion vive» et «combustion lente». La combustion de l’air dans les… …   Encyclopédie Universelle

  • combustion — COMBUSTION. s. f. Action de brûler entièrement. C est la combustion de l air qui fait la flamme. La combustion des cadavres étoit très dispendieuse chez les Romains. [b]f♛/b] Il se dit d Un incendie qui détruit totalement un édifice. J ai vu la… …   Dictionnaire de l'Académie Française 1798

  • Combustion — Com*bus tion (?; 106), n. [L. combustio: cf. F. combustion.] 1. The state of burning. [1913 Webster] 2. (Chem.) The combination of a combustible with a supporter of combustion, producing heat, and sometimes both light and heat. [1913 Webster]… …   The Collaborative International Dictionary of English

  • combustión — sustantivo femenino 1. Uso/registro: elevado. Acción y resultado de quemarse o arder un cuerpo: La combustión de la madera del almacén no permitió a los bomberos apagar el fuego. La combustión del carbón de la bodega llenó en seguida la casa de… …   Diccionario Salamanca de la Lengua Española

  • combustion — Combustion. s. f. Division, brouillerie & tumulte. Grande combustion. horrible combustion. tout le Royaume estoit en combustion. il a mis tout l Estat, toute la ville, toute la famille en combustion …   Dictionnaire de l'Académie française

  • combustión — Proceso de quemar u oxidación que se puede acompañar de luz y calor. El oxígeno por sí mismo no arde, pero facilita la combustión. La velocidad de combustión está determinada tanto por la concentración de oxígeno como por su presión parcial …   Diccionario médico

  • combustión — (Del lat. combustĭo, ōnis). 1. f. Acción y efecto de arder o quemar. 2. Biol. Oxidación de los alimentos en los seres vivos. 3. Quím. Reacción química entre el oxígeno y un material oxidable, acompañada de desprendimiento de energía y que… …   Diccionario de la lengua española

  • combustion — early 15c., from O.Fr. combustion (13c.), from L. combustionem (nom. combustio) a burning, noun of action from pp. stem of comburere to burn, from com , intensive prefix (see COM (Cf. com )), + *burere, faulty separation of amburere to burn… …   Etymology dictionary

  • combustion — [n] explosion; on fire agitation, candescence, disturbance, flaming, ignition, kindling, oxidization, thermogenesis, tumult, turmoil; concepts 521,676,724 …   New thesaurus

  • combustion — ► NOUN 1) the process of burning. 2) Chemistry rapid chemical combination with oxygen, involving the production of heat and light …   English terms dictionary


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