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Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion does not always result in fire, because a flame is only visible when substances undergoing combustion vaporize, but when it does, a flame is a characteristic indicator of the reaction. While activation energy must be supplied to initiate combustion, the heat from a flame may provide enough energy to make the reaction self-sustaining. The study of combustion is known as combustion science.
A flame is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction made in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density, they are then considered plasma.
A premixed flame is a flame formed under certain conditions during the combustion of a premixed charge of fuel and oxidiser. Since the fuel and oxidiser—the key chemical reactants of combustion—are available throughout a homogeneous stoichiometric premixed charge, the combustion process once initiated sustains itself by way of its own heat release. The majority of the chemical transformation in such a combustion process occurs primarily in a thin interfacial region which separates the unburned and the burned gases. The premixed flame interface propagates through the mixture until the entire charge is depleted. The propagation speed of a premixed flame is known as the flame speed which depends on the convection-diffusion-reaction balance within the flame, i.e. on its inner chemical structure. The premixed flame is characterised as laminar or turbulent depending on the velocity distribution in the unburned pre-mixture.
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The Combustion Institute is an educational non-profit, international, scientific and engineering society whose purpose is to promote research in combustion science. The institute was established in 1954, and its headquarters are in Pittsburgh, Pennsylvania, United States. The current president of The Combustion Institute is Philippe Dagaut (2021-).
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A cool flame is a flame having a typical temperature of about 400 °C (752 °F). In contrast to an ordinary hot flame, the reaction is not vigorous and releases little heat, light, or carbon dioxide. Cool flames are difficult to observe and are uncommon in everyday life, but they are responsible for engine knock – the undesirable, erratic, and noisy combustion of low-octane fuels in internal combustion engines.
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In Combustion, G equation is a scalar field equation which describes the instantaneous flame position, introduced by Forman A. Williams in 1985 in the study of premixed turbulent combustion. The equation is derived based on the Level-set method. The equation was first studied by George H. Markstein, in a restrictive form for the burning velocity.
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In combustion, Zeldovich–Liñán model is a two-step reaction model for the combustion processes, named after Yakov Borisovich Zeldovich and Amable Liñán. The model includes a chain-branching and a chain-breaking reaction. The model was first introduced by Zeldovich in 1948 and later analysed by Liñán using activation energy asymptotics in 1971. The mechanism with a quadratic or second-order recombination that were originally studied reads as
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Clavin–Garcia equation or Clavin–Garcia dispersion relation provides the relation between the growth rate and the wave number of the perturbation superposed on a planar premixed flame, named after Paul Clavin and Pedro Luis Garcia Ybarra, who derived the dispersion relation in 1983. The dispersion relation accounts for Darrieus–Landau instability, Rayleigh–Taylor instability and diffusive–thermal instability and also accounts for the temperature dependence of transport coefficients.
Matalon–Matkowsky–Clavin–Joulin theory refers to a theoretical hydrodynamic model of a premixed flame with a large-amplitude flame wrinkling, developed independently by Moshe Matalon & Bernard J. Matkowsky and Paul Clavin & Guy Joulin. The theory, for the first time, calculated the burning rate of the curved flame that differs from the burning rate of the planar flame due to flame stretch, associated with the flame curvature and the strain imposed on the flame by the flow field.
References
- 1 2 Oran, E. S. (2015). A tribute to Dr. George H. Markstein (1911–2011). Combustion and Flame, 1(162), 1–2.
- ↑ Markstein, G. H. (1988). Experimental and theoretical studies of flame-front stability. In Dynamics of curved fronts (pp. 413–423). Academic Press.
- ↑ Markstein, G. H. 1950 Project squid. the structure of flames burning in tubes. part 1. flame structure in slow-burning mixtures of hydrocarbons, air and nitrogen. Tech. Rep.. Cornell Aeronautical Lab. Buffalo NY.
- ↑ Orloff, L., De Ris, J., & Markstein, G. H. (1975, January). Upward turbulent fire spread and burning of fuel surface. In Symposium (International) on Combustion (Vol. 15, No. 1, pp. 183–192). Elsevier.
- ↑ "Silver Combustion Medal | The Combustion Institute". June 24, 2016.
- ↑ "Bernard Lewis Gold Medal | The Combustion Institute". June 24, 2016.
- ↑ "Awards | Eastern States Section of the Combustion Institute". ESSCI.