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{{Short description|Chemical reaction between a fuel and oxygen}}
{{redirect|Burning|the type of injury|Burn|combustion without external ignition|spontaneous combustion|the vehicle engine|internal combustion engine|other   uses|Burning (disambiguation)|and|Combustion (disambiguation)|and|Firing (disambiguation)}}
[[File:Fire, Fireplace, Rostov-on-Don, Russia.jpg|thumb|The [[flame]]s caused as a result of a [[fuel]] undergoing combustion (burning)]]
[[File:Regenerative thermal oxidizer.jpg|thumb|[[Regenerative thermal oxidiser|Air pollution abatement equipment]] provides combustion control for [[industrial processes]].]]

'''Combustion''', or '''burning''',<ref>colloquial meaning of burning is combustion accompanied by flames</ref> is a high-temperature [[exothermic]] [[redox]] [[chemical reaction]] between a [[fuel]] (the reductant) 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 (e.g., using a lit [[match]] to light a fire), the heat from a flame may provide enough energy to make the reaction self-sustaining. The study of combustion is known as '''combustion science'''.

Combustion is often a complicated sequence of [[elementary reaction|elementary]] [[Radical (chemistry)|radical reactions]]. [[Solid fuel]]s, such as [[wood]] and [[coal]], first undergo [[endothermic]] [[pyrolysis]] to produce gaseous fuels whose combustion then supplies the heat required to produce more of them. Combustion is often hot enough that [[incandescence|incandescent]] [[light]] in the form of either [[Smouldering|glowing]] or a [[flame]] is produced. A simple example can be seen in the combustion of [[hydrogen]] and [[oxygen]] into [[water]] [[vapor]], a reaction which is commonly used to fuel [[rocket engine]]s. This reaction releases 242{{nbsp}}[[Joule per mole|kJ/mol]] of heat and reduces the [[enthalpy]] accordingly (at constant temperature and pressure):

: <chem>2H_2(g){+}O_2(g)\rightarrow 2H_2O\uparrow</chem>

Uncatalyzed combustion in air requires relatively high temperatures. Complete combustion is [[stoichiometric]] concerning the fuel, where there is no remaining fuel, and ideally, no residual oxidant. Thermodynamically, the [[chemical equilibrium]] of combustion in air is overwhelmingly on the side of the products. However, complete combustion is almost impossible to achieve, since the chemical equilibrium is not necessarily reached, or may contain unburnt products such as [[carbon monoxide]], [[hydrogen]] and even [[carbon]] ([[soot]] or ash). Thus, the produced [[smoke]] is usually toxic and contains unburned or partially oxidized products. Any combustion at high temperatures in [[Atmosphere|atmospheric]] [[air]], which is 78 percent [[nitrogen]], will also create small amounts of several [[nitrogen oxides]], commonly referred to as [[NOx]], since the combustion of nitrogen is thermodynamically favored at high, but not low temperatures. Since burning is rarely clean, fuel gas cleaning or [[catalytic converter]]s may be required by law.

[[Fire]]s occur naturally, ignited by [[lightning]] strikes or by [[volcanic]] products. Combustion ([[fire]]) was the first controlled chemical reaction discovered by humans, in the form of [[campfire]]s and [[bonfire]]s, and continues to be the main method to produce energy for humanity. Usually, the fuel is [[carbon]], [[hydrocarbon]]s, or more complicated mixtures such as [[wood]] that contain partially oxidized hydrocarbons. The thermal energy produced from the combustion of either [[fossil fuel]]s such as [[coal]] or [[oil]], or from [[renewable fuel]]s such as [[firewood]], is harvested for diverse uses such as [[cooking]], production of [[electricity]] or industrial or domestic heating. Combustion is also currently the only reaction used to power [[rocket]]s. Combustion is also used to destroy ([[incineration|incinerate]]) waste, both nonhazardous and hazardous.

Oxidants for combustion have high oxidation potential and include atmospheric or pure [[oxygen]], [[chlorine]], [[fluorine]], [[chlorine trifluoride]], [[nitrous oxide]] and [[nitric acid]]. For instance, [[hydrogen]] burns in [[chlorine]] to form [[hydrogen chloride]] with the liberation of heat and light characteristic of combustion. Although usually not catalyzed, combustion can be catalyzed by [[platinum]] or [[vanadium]], as in the [[contact process]].

==Types==

===Complete and incomplete===
{{see also|pyrolysis}}

====Complete====
[[File:Methane-combustion.svg|thumb|The combustion of [[methane]], a [[hydrocarbon]]]]
In complete combustion, the reactant burns in oxygen and produces a limited number of products. When a [[hydrocarbon]] burns in oxygen, the reaction will primarily yield carbon dioxide and water. When elements are burned, the products are primarily the most common oxides. Carbon will yield [[carbon dioxide]], sulfur will yield [[sulfur dioxide]], and iron will yield [[iron(III) oxide]]. Nitrogen is not considered to be a combustible substance when oxygen is the [[Oxidizing agent|oxidant]]. Still, small amounts of various nitrogen oxides (commonly designated [[NOx|{{chem|NO|''x''}}]] species) form when the air is the oxidative.

Combustion is not necessarily favorable to the maximum degree of oxidation, and it can be temperature-dependent. For example, [[sulfur trioxide]] is not produced quantitatively by the combustion of sulfur. {{NOx}} species appear in significant amounts above about {{convert|2800|F|C}}, and more is produced at higher temperatures. The amount of {{NOx}} is also a function of oxygen excess.<ref name="NOx formation">[http://www.alentecinc.com/papers/NOx/The%20formation%20of%20NOx_files/The%20formation%20of%20NOx.htm The formation of NOx]. Alentecinc.com. Retrieved on 2010-09-28.</ref>

In most industrial applications and in [[fire]]s, [[air]] is the source of oxygen ({{chem|O|2}}). In the air, each mole of oxygen is mixed with approximately {{val|3.71|ul=mol}} of nitrogen. Nitrogen does not take part in combustion, but at high temperatures, some nitrogen will be converted to [[NOx#Thermal|{{chem|NO|''x''}}]] (mostly [[Nitric oxide|{{chem|NO}}]], with much smaller amounts of [[Nitrogen dioxide|{{chem|NO|2}}]]). On the other hand, when there is insufficient oxygen to combust the fuel completely, some fuel carbon is converted to [[carbon monoxide]], and some of the hydrogens remain unreacted. A complete set of equations for the combustion of a hydrocarbon in the air, therefore, requires an additional calculation for the distribution of oxygen between the carbon and hydrogen in the fuel.

The amount of air required for complete combustion is known as the "theoretical air" or "stoichiometric air".<ref>{{cite report |url=https://books.google.com/books?id=jqkXAAAAYAAJ&pg=RA1-PA26R |title=Central Boiler Plants |year=1989 |page=Glossary 26 |publisher=US Department of the Army |id=TM 5-650}}</ref> The amount of air above this value actually needed for optimal combustion is known as the "excess air", and can vary from 5% for a natural gas boiler, to 40% for [[anthracite]] coal, to 300% for a [[gas turbine]].<ref>{{cite web |title=Engineering Toolbox: Optimal Combustion Processes - Fuel vs. Excess Air |url=https://www.engineeringtoolbox.com/fuels-combustion-efficiency-d_167.html |access-date=15 May 2023 |date=2003 }}</ref>

====Incomplete====
{{see also|Charring}}
Incomplete combustion will occur when there is not enough oxygen to allow the fuel to react completely to produce carbon dioxide and water. It also happens when the combustion is quenched by a heat sink, such as a solid surface or flame trap. As is the case with complete combustion, water is produced by incomplete combustion; however, [[carbon]] and [[carbon monoxide]] are produced instead of carbon dioxide.

For most fuels, such as diesel oil, coal, or wood, [[pyrolysis]] occurs before combustion. In incomplete combustion, products of pyrolysis remain unburnt and contaminate the smoke with noxious particulate matter and gases. Partially oxidized compounds are also a concern; partial oxidation of ethanol can produce harmful [[acetaldehyde]], and carbon can produce toxic carbon monoxide.

The designs of combustion devices can improve the quality of combustion, such as [[Oil burner|burners]] and [[internal combustion engines]]. Further improvements are achievable by [[catalytic]] after-burning devices (such as [[catalytic converter]]s) or by the simple partial return of the [[exhaust gas]]es into the combustion process. Such devices are required by [[environmental legislation]] for cars in most countries. They may be necessary to enable large combustion devices, such as [[thermal power station]]s, to reach legal [[emission standards]].

The degree of combustion can be measured and analyzed with test equipment. [[HVAC]] contractors, [[firefighters]] and [[engineers]] use combustion analyzers to test the [[Fuel efficiency|efficiency]] of a burner during the combustion process. Also, the efficiency of an internal combustion engine can be measured in this way, and some U.S. states and local municipalities use combustion analysis to define and rate the efficiency of vehicles on the road today.

Carbon monoxide is one of the products from [[incomplete combustion]].<ref>{{cite web|title=Incomplete combustion process|url=https://www.greenfacts.org/glossary/ghi/incomplete-combustion-processes.htm}}</ref> The formation of carbon monoxide produces less heat than formation of carbon dioxide so complete combustion is greatly preferred especially as carbon monoxide is a poisonous gas. When breathed, carbon monoxide takes the place of oxygen and combines with some of the hemoglobin in the blood, rendering it unable to transport oxygen.<ref>{{cite web|title=Burning showing incomplete combustion|url=https://www.sciencelearn.org.nz/resources/747-what-is-fire}}</ref>

====Problems associated with incomplete combustion====

=====Environmental problems=====
These oxides combine with [[water]] and [[oxygen]] in the atmosphere, creating [[nitric acid]] and [[sulfuric acids]], which return to Earth's surface as acid deposition, or "acid rain." Acid deposition harms aquatic organisms and kills trees. Due to its formation of certain nutrients that are less available to plants such as calcium and phosphorus, it reduces the productivity of the ecosystem and farms. An additional problem associated with [[nitrogen oxides]] is that they, along with [[hydrocarbon]] pollutants, contribute to the formation of [[ground level ozone]], a major component of smog.<ref name="education.seattlepi.com">{{cite web|title=Environmental Problems associated with incomplete combustion |date= 25 February 2014|url= http://education.seattlepi.com/environmental-problems-associated-combustion-hydrocarbons-5621.html}}</ref>

=====Human health problems=====
Breathing [[carbon monoxide]] causes headache, dizziness, vomiting, and nausea. If carbon monoxide levels are high enough, humans become unconscious or die. Exposure to moderate and high levels of carbon monoxide over long periods is positively correlated with the risk of heart disease. People who survive severe [[carbon monoxide poisoning]] may suffer long-term health problems.<ref>{{cite web|title=Carbon Monoxide Poisoning|date=8 December 2020|url=https://ephtracking.cdc.gov/showCoRisk.action}}</ref> Carbon monoxide from the air is absorbed in the lungs which then binds with [[hemoglobin]] in human's red blood cells. This reduces the capacity of red blood cells that carry oxygen throughout the body.

===Smoldering===
[[Smoldering]] is the slow, low-temperature, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. It is a typically incomplete combustion reaction. Solid materials that can sustain a smoldering reaction include coal, [[cellulose]], [[wood]], [[cotton]], [[tobacco]], [[peat]], [[Plant litter|duff]], [[humus]], synthetic foams, charring [[polymers]] (including [[polyurethane foam]]) and [[dust]]. Common examples of smoldering phenomena are the initiation of residential fires on [[upholstered furniture]] by weak heat sources (e.g., a cigarette, a short-circuited wire) and the persistent [[combustion of biomass]] behind the flaming fronts of [[wildfire]]s.

===Spontaneous===
[[Spontaneous combustion]] is a type of combustion that occurs by self-heating (increase in temperature due to [[exothermic]] internal reactions), followed by thermal runaway (self-heating which rapidly accelerates to high temperatures) and finally, ignition.
For example, phosphorus self-ignites at room temperature without the application of heat. Organic materials undergoing bacterial [[composting]] can generate enough heat to reach the point of combustion.<ref>{{cite web |url=http://www.soilandmulchproducernews.com/index.php/frontpage-articles-hidden/160-a-perfect-storm-mulch-fire-dynamics-and-prevention |title=A Perfect Storm: Mulch Fire Dynamics and Prevention |publisher=Soilandmulchproducernews.com |access-date=2018-07-12 |archive-date=2018-07-01 |archive-url=https://web.archive.org/web/20180701011314/http://www.soilandmulchproducernews.com/index.php/frontpage-articles-hidden/160-a-perfect-storm-mulch-fire-dynamics-and-prevention |url-status=dead }}</ref>

===Turbulent===
Combustion resulting in a turbulent flame is the most used for industrial applications (e.g. [[gas turbine]]s, [[gasoline engine]]s, etc.) because the turbulence helps the mixing process between the fuel and [[oxidizer]].

===Micro-gravity===
[[Image:Microgravity Burning.jpg|thumb|Colourized gray-scale composite image of the individual frames from a video of a backlit fuel droplet burning in microgravity]]

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.<ref>[https://web.archive.org/web/20011118103426/http://spaceflight.nasa.gov/history/shuttle-mir/science/mg/nm21460011.htm Shuttle-Mir History/Science/Microgravity/Candle Flame in Microgravity (CFM) – MGBX].  Spaceflight.nasa.gov (1999-07-16). Retrieved on 2010-09-28.</ref>). 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 (electronics)|thermal management of electronic systems]], multiphase flow boiling dynamics, and many others).

===Micro-combustion===
Combustion processes that 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 chamber]]s.

==Chemical equations==

===Stoichiometric combustion of a hydrocarbon in oxygen===

Generally, the [[chemical equation]] for [[Stoichiometry|stoichiometric]] combustion of a [[hydrocarbon]] in oxygen is:
:<math chem="">\ce{C}_x \ce{H}_y + \left(x+{y\over 4}\right)\ce{O2->} x\ce{CO2} + {y\over 2} \ce{H2O}</math>

For example, the stoichiometric combustion of [[methane]] in oxygen is:
:<chem>\underset{methane}{CH4} + 2O2 -> CO2 + 2H2O</chem>

===Stoichiometric combustion of a hydrocarbon in air===

If the stoichiometric combustion takes place using air as the oxygen source, the [[nitrogen]] present in the air ([[Atmosphere of Earth]]) can be added to the equation (although it does not react) to show the stoichiometric composition of the fuel in air and the composition of the resultant flue gas. Treating all non-oxygen components in air as nitrogen gives a 'nitrogen' to oxygen ratio of 3.77, i.e. (100% &minus; {{chem|O|2}}%) / {{chem|O|2}}% where {{chem|O|2}}% is 20.95% vol:
:<math chem="">\ce{C}_x \ce{H}_y + z\ce{O2} + 3.77z\ce{N2 ->} x\ce{CO2} + {y\over 2} \ce{H2O} + 3.77z\ce{N2}</math>
where <math>z = x + {y\over 4}</math>.

For example, the stoichiometric combustion of methane in air is:
:<math chem="">\ce{\underset{methane}{CH4} + 2O2} + 7.54\ce{N2-> CO2 + 2H2O} + 7.54\ce{N2}</math>

The stoichiometric composition of methane in air is 1 / (1 + 2 + 7.54) = 9.49% vol.

The stoichiometric combustion reaction for C{{sub|α}}H{{sub|β}}O{{sub|γ}} in air:
:<math chem>\ce{C_\mathit{\alpha}H_\mathit{\beta}O_\mathit{\gamma}} + \left ( \alpha + \frac{\beta}{4} -\frac{\gamma}{2} \right ) \left ( \ce{O_2} + 3.77 \ce{N_2} \right ) \longrightarrow \alpha \ce{CO_2} + \frac{\beta}{2} \ce{H_2O} + 3.77 \left ( \alpha + \frac{\beta}{4} -\frac{\gamma}{2} \right ) \ce{N_2}</math>

The stoichiometric combustion reaction for C{{sub|α}}H{{sub|β}}O{{sub|γ}}S{{sub|δ}}:

:<math chem>\ce{C_\mathit{\alpha}H_\mathit{\beta}O_\mathit{\gamma}S_\mathit{\delta}} + \left ( \alpha + \frac{\beta}{4} -\frac{\gamma}{2} + \delta \right ) \left ( \ce{O_2} + 3.77 \ce{N_2} \right ) \longrightarrow \alpha \ce{CO_2} + \frac{\beta}{2} \ce{H_2O} + \delta \ce{SO_2} + 3.77 \left ( \alpha + \frac{\beta}{4} -\frac{\gamma}{2} + \delta \right ) \ce{N_2}</math>

The stoichiometric combustion reaction for C{{sub|α}}H{{sub|β}}O{{sub|γ}}N{{sub|δ}}S{{sub|ε}}:

:<math chem>\ce{C_\mathit{\alpha}H_\mathit{\beta}O_\mathit{\gamma}N_\mathit{\delta}S_\mathit{\epsilon}} + \left ( \alpha + \frac{\beta}{4} -\frac{\gamma}{2} + \epsilon \right ) \left ( \ce{O_2} + 3.77 \ce{N_2} \right ) \longrightarrow \alpha \ce{CO_2} + \frac{\beta}{2} \ce{H_2O} + \epsilon \ce{SO_2} + \left ( 3.77 \left ( \alpha + \frac{\beta}{4} -\frac{\gamma}{2} + \epsilon \right ) + \frac{\delta}{2} \right ) \ce{N_2}</math>

The stoichiometric combustion reaction for C{{sub|α}}H{{sub|β}}O{{sub|γ}}F{{sub|δ}}:

:<math chem>\ce{C_\mathit{\alpha}H_\mathit{\beta}O_\mathit{\gamma}F_\mathit{\delta}} + \left ( \alpha + \frac{\beta-\delta}{4} -\frac{\gamma}{2} \right ) \left ( \ce{O_2} + 3.77 \ce{N_2} \right ) \longrightarrow \alpha \ce{CO_2} + \frac{\beta-\delta}{2} \ce{H_2O} + \delta \ce{HF} + 3.77 \left ( \alpha + \frac{\beta-\delta}{4} -\frac{\gamma}{2} \right ) \ce{N_2}</math>

===Trace combustion products===

Various other substances begin to appear in significant amounts in combustion products when the [[Adiabatic flame temperature|flame temperature]] is above about {{val|1600|ul=K}}. When excess air is used, nitrogen may oxidize to {{chem|link=nitric oxide|NO}} and, to a much lesser extent, to {{chem|link=nitrogen dioxide|NO|2}}. {{chem|link=carbon monoxide|CO}} forms by [[disproportionation]] of {{CO2}}, and {{chem|link=hydrogen|H|2}} and {{chem|link=hydroxyl radical|OH}} form by disproportionation of {{H2O}}.

For example, when {{val|1|ul=mol}} of [[propane]] is burned with {{val|28.6|ul=mol}} of air (120% of the stoichiometric amount), the combustion products contain 3.3% {{chem|O|2}}. At {{val|1400|ul=K}}, the [[Chemical equilibrium|equilibrium]] combustion products contain 0.03% {{chem|NO}} and 0.002% {{chem|OH}}. At {{val|1800|ul=K}}, the combustion products contain 0.17% {{chem|NO}}, 0.05% {{chem|OH}}, 0.01% {{chem|CO}}, and 0.004% {{chem|H|2}}.<ref name="EquiWeb">{{cite web |url=http://www.crct.polymtl.ca/equiweb.php |title=Equilib-Web |date=8 March 2022 |first1=Christopher W. |last1=Bale |first2=Eve |last2=Bélisle |access-date=15 May 2023 |publisher=Centre for Research in Computational Thermochemistry, Polytechnique Montreal}}</ref>

[[Diesel engines]] are run with an excess of oxygen to combust small [[Particle|particles]] that tend to form with only a stoichiometric amount of oxygen, necessarily producing [[NOx|nitrogen oxide]] emissions. Both the United States and European Union [[Emission standard|enforce limits]] to vehicle nitrogen oxide emissions, which necessitate the use of special [[catalytic converter]]s or treatment of the exhaust with [[urea]] (see [[Diesel exhaust fluid]]).

===Incomplete combustion of a hydrocarbon in oxygen===

The incomplete (partial) combustion of a [[hydrocarbon]] with oxygen produces a gas mixture containing mainly {{chem|CO|2}}, {{chem|CO}}, {{H2O}}, and {{chem|H|2}}. Such gas mixtures are commonly prepared for use as protective atmospheres for the [[Heat treating|heat-treatment]] of metals and for [[Carburizing|gas carburizing]].<ref>ASM Committee on Furnace Atmospheres, ''Furnace atmospheres and carbon control'', Metals Park, OH [1964].</ref> The general reaction equation for incomplete combustion of one [[Mole (unit)|mole]] of a hydrocarbon in oxygen is:

: <chem>\underset{fuel}{C_\mathit{x} H_\mathit{y}} + \underset{oxygen}{\mathit{z} O2} -> \underset{carbon \ dioxide}{\mathit{a}CO2} + \underset{carbon\ monoxide}{\mathit{b}CO} + \underset{water}{\mathit{c}H2O} + \underset{hydrogen}{\mathit{d}H2}</chem>

When ''z'' falls below roughly 50% of the stoichiometric value, [[Methane|{{chem|CH|4}}]] can become an important combustion product; when ''z'' falls below roughly 35% of the stoichiometric value, elemental [[carbon]] may become stable.

The products of incomplete combustion can be calculated with the aid of a [[material balance]], together with the assumption that the combustion products reach [[Chemical equilibrium|equilibrium]].<ref>{{cite journal | title = Exothermic atmospheres | journal = Industrial Heating | page = 22 | date = June 2013 | url = http://www.industrialheating.com/articles/91142-exothermic-atmospheres | access-date = 5 July 2013 | archive-date = 9 November 2023 | archive-url = https://web.archive.org/web/20231109214347/https://www.industrialheating.com/articles/91142-exothermic-atmospheres | url-status = dead }}</ref><ref name="ExoCalc">[http://www.industrialheating.com/ExoCalc] ExoCalc</ref> For example, in the combustion of one [[Mole (unit)|mole]] of propane ({{chem|C|3|H|8}}) with four moles of {{chem|O|2}}, seven moles of combustion gas are formed, and ''z'' is 80% of the stoichiometric value. The three elemental balance equations are:
* Carbon: <math>a + b = 3</math>
* Hydrogen: <math>2c + 2d = 8</math>
* Oxygen: <math>2a + b + c = 8</math>

These three equations are insufficient in themselves to calculate the combustion gas composition.
However, at the equilibrium position, the [[water-gas shift reaction]] gives another equation:

: <chem>CO + H2O -> CO2 + H2</chem>; <math>K_{eq} = \frac{a \times d}{b \times c}</math>

For example, at {{val|1200|ul=K}} the value of ''K{{sub|eq}}'' is 0.728.<ref name="ReacWeb">{{cite web|url=http://www.crct.polymtl.ca/reacweb.htm |title=Reaction-Web |publisher=Crct.polymtl.ca |access-date=2018-07-12}}</ref> Solving, the combustion gas consists of 42.4% {{H2O}}, 29.0% {{CO2}}, 14.7% {{chem|H|2}}, and 13.9% {{chem|CO}}. Carbon becomes a stable phase at {{val|1200|ul=K}} and {{val|1|ul=atm}} pressure when z is less than 30% of the stoichiometric value, at which point the combustion products contain more than 98% {{chem|H|2}} and {{chem|CO}} and about 0.5% {{chem|CH|4}}.

Substances or materials which undergo combustion are called [[fuel]]s. The most common examples are natural gas, propane, [[kerosene]], [[Diesel fuel|diesel]], petrol, charcoal, coal, wood, etc.

===Liquid fuels===

Combustion of a [[liquid fuel]] in an oxidizing atmosphere actually happens in the gas phase. It is the vapor that burns, not the liquid. Therefore, a liquid will normally catch fire only above a certain temperature: its [[flash point]]. The flash point of liquid fuel is the lowest temperature at which it can form an ignitable mix with air. It is the minimum temperature at which there is enough evaporated fuel in the air to start combustion.

=== Gaseous fuels ===
Combustion of gaseous fuels may occur through one of four distinctive types of burning: [[diffusion flame]], [[premixed flame]], [[autoignitive reaction front]], or as a [[detonation]].<ref name=":0">{{Cite journal|last=Bradley|first=D|date=2009-06-25|title=Combustion and the design of future engine fuels|journal=Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science|language=en|volume=223|issue=12|pages=2751–2765|doi=10.1243/09544062jmes1519|s2cid=97218733}}</ref> The type of burning that actually occurs depends on the degree to which the [[fuel]] and [[oxidizer]] are mixed prior to heating: for example, a diffusion flame is formed if the fuel and oxidizer are separated initially, whereas a premixed flame is formed otherwise. Similarly, the type of burning also depends on the pressure: a detonation, for example, is an autoignitive reaction front coupled to a strong shock wave giving it its characteristic high-pressure peak and high [[detonation velocity]].<ref name=":0" />

===Solid fuels===
[[File:disfig1.svg|thumb|upright=1.5|A general scheme of [[polymer]] combustion]]

The act of combustion consists of three relatively distinct but overlapping phases:
* '''Preheating phase''', when the unburned [[fuel]] is heated up to its flash point and then [[fire point]]. Flammable gases start being evolved in a process similar to [[dry distillation]].
* '''Distillation phase''' or '''gaseous phase''', when the mix of evolved flammable gases with oxygen is ignited. Energy is produced in the form of heat and light. [[Flame]]s are often visible. Heat transfer from the combustion to the solid maintains the evolution of flammable vapours.
* '''Charcoal phase''' or '''solid phase''', when the output of flammable gases from the material is too low for the persistent presence of flame and the [[charring|charred]] fuel does not burn rapidly and just glows and later only [[Smouldering|smoulders]].

==Combustion management==
Efficient [[Industrial furnace|process heating]] requires recovery of the largest possible part of a fuel's [[heat of combustion]] into the material being processed.<ref>{{cite journal | title = Calculating the heat of combustion for natural gas | journal = Industrial Heating | page = 28 | date = September 2012 | url = http://www.industrialheating.com/articles/90561-calculating-the-heat-of-combustion-for-natural-gas | access-date = 5 July 2013 | archive-date = 10 July 2013 | archive-url = https://web.archive.org/web/20130710085624/http://www.industrialheating.com/articles/90561-calculating-the-heat-of-combustion-for-natural-gas | url-status = dead }}</ref><ref name="HeatCalc">[http://www.industrialheating.com/HeatCalc] HeatCalc</ref> There are many avenues of loss in the operation of a heating process. Typically, the dominant loss is [[sensible heat]] leaving with the [[Exhaust gas|offgas]] (i.e., the [[flue gas]]). The temperature and quantity of offgas indicates its heat content ([[enthalpy]]), so keeping its quantity low minimizes heat loss.

In a perfect furnace, the combustion air flow would be matched to the fuel flow to give each fuel molecule the exact amount of oxygen needed to cause complete combustion. However, in the real world, combustion does not proceed in a perfect manner. Unburned fuel (usually {{chem|CO}} and {{chem|H|2}}) discharged from the system represents a heating value loss (as well as a safety hazard). Since combustibles are undesirable in the offgas, while the presence of unreacted oxygen there presents minimal safety and environmental concerns, the first principle of combustion management is to provide more oxygen than is theoretically needed to ensure that all the fuel burns. For methane ({{chem|CH|4}}) combustion, for example, slightly more than two molecules of oxygen are required.

The second principle of combustion management, however, is to not use too much oxygen. The correct amount of oxygen requires three types of measurement: first, active control of air and fuel flow; second, offgas oxygen measurement; and third, measurement of offgas combustibles. For each heating process, there exists an optimum condition of minimal offgas heat loss with acceptable levels of combustibles concentration. Minimizing excess oxygen pays an additional benefit: for a given offgas temperature, the [[NOx]] level is lowest when excess oxygen is kept lowest.<ref name="NOx formation" />

Adherence to these two principles is furthered by making material and heat balances on the combustion process.<ref>{{cite journal | title = Making a material balance | journal = Industrial Heating | page = 20 | date = November 2012 | url =  http://www.industrialheating.com/articles/90764-making-a-material-balance | access-date = 5 July 2013}}</ref><ref name="MatBalCalc">[http://www.industrialheating.com/MatBalCalc] MatBalCalc</ref><ref>{{cite journal | title = Making a heat balance | journal = Industrial Heating | page = 22 | date = December 2012 | url =  http://www.industrialheating.com/articles/90812-making-a-heat-balance | access-date = 5 July 2013}}</ref><ref name="HeatBalCalc">[http://www.industrialheating.com/HeatBalCalc] HeatBalCalc</ref> The [[material balance]] directly relates the [[air/fuel ratio]] to the percentage of {{chem|O|2}} in the combustion gas. The heat balance relates the heat available for the charge to the overall net heat produced by fuel combustion.<ref>{{cite journal | title = Available combustion heat | journal = Industrial Heating | page = 22 | date = April 2013 | url =  http://www.industrialheating.com/articles/91014-available-combustion-heat | access-date = 5 July 2013}}</ref><ref name="AvailHeatCalc">[http://www.industrialheating.com/availheatcalc] AvailHeatCalc</ref> Additional material and heat balances can be made to quantify the thermal advantage from preheating the combustion air,<ref>{{cite journal | title = Making a system balance (Part 2) | journal = Industrial Heating | page = 24 | date = March 2012 | url =  http://www.industrialheating.com/articles/90954-making-a-system-balance-part-2 | access-date = 5 July 2013}}</ref><ref name="SysBalCalc2">[http://www.industrialheating.com/SysBalCalc2] SysBalCalc2</ref> or enriching it in oxygen.<ref>{{cite journal | title = Making a system balance (Part 1) | journal = Industrial Heating | page = 22 | date = February 2012 | url =  http://www.industrialheating.com/articles/90897-making-a-system-balance-part-1 | access-date = 5 July 2013}}</ref><ref name="SysBalCalc">[http://www.industrialheating.com/sysbalcalc] SysBalCalc</ref>

==Reaction mechanism==
{{More citations needed section|date=January 2017}}
Combustion in oxygen is a [[chain reaction]] in which many distinct [[Radical (chemistry)|radical]] intermediates participate. The high energy required for initiation is explained by the unusual structure of the [[dioxygen]] molecule. The lowest-energy configuration of the dioxygen molecule is a stable, relatively unreactive diradical in a [[triplet oxygen|triplet spin state]]. Bonding can be described with three bonding electron pairs and two antibonding electrons, with [[Spin (physics)|spins]] aligned, such that the molecule has nonzero total angular momentum. Most fuels, on the other hand, are in a singlet state, with paired spins and zero total angular momentum. Interaction between the two is quantum mechanically a "[[forbidden transition]]", i.e. possible with a very low probability. To initiate combustion, energy is required to force dioxygen into a spin-paired state, or [[singlet oxygen]]. This intermediate is extremely reactive. The energy is supplied as [[heat]], and the reaction then produces additional heat, which allows it to continue.

Combustion of hydrocarbons is thought to be initiated by hydrogen atom abstraction (not proton abstraction) from the fuel to oxygen, to give a hydroperoxide radical (HOO). This reacts further to give hydroperoxides, which break up to give [[hydroxyl radical]]s. There are a great variety of these processes that produce fuel radicals and oxidizing radicals. Oxidizing species include singlet oxygen, hydroxyl, monatomic oxygen, and [[hydroperoxyl]]. Such intermediates are short-lived and cannot be isolated. However, non-radical intermediates are stable and are produced in incomplete combustion. An example is [[acetaldehyde]] produced in the combustion of [[ethanol]]. An intermediate in the combustion of carbon and hydrocarbons, [[carbon monoxide]], is of special importance because it is a [[Poison|poisonous gas]], but also economically useful for the production of [[syngas]].

Solid and heavy liquid fuels also undergo a great number of [[pyrolysis]] reactions that give more easily oxidized, gaseous fuels. These reactions are endothermic and require constant energy input from the ongoing combustion reactions. A lack of oxygen or other improperly designed conditions result in these noxious and carcinogenic pyrolysis products being emitted as thick, black smoke.

The rate of combustion is the amount of a material that undergoes combustion over a period of time. It can be expressed in grams per second (g/s) or kilograms per second (kg/s).

Detailed descriptions of combustion processes, from the chemical kinetics perspective, require the formulation of large and intricate webs of elementary reactions.<ref>{{cite book|last1=Law|first1=C.K.|title=Combustion Physics|date=2006|publisher=Cambridge University Press|location=Cambridge, UK|isbn=9780521154215}}</ref> For instance, combustion of hydrocarbon fuels typically involve hundreds of chemical species reacting according to thousands of reactions.

The inclusion of such mechanisms within computational flow solvers still represents a pretty challenging task mainly in two aspects. First, the number of degrees of freedom (proportional to the number of chemical species) can be dramatically large; second, the source term due to reactions introduces a disparate number of time scales which makes the whole [[dynamical system]] stiff. As a result, the direct numerical simulation of turbulent reactive flows with heavy fuels soon becomes intractable even for modern supercomputers.<ref>{{cite book|last1=Goussis|first1=D.|last2=Maas|first2=U.|title=Turbulent Combustion Modeling|date=2011|publisher=Springer Science|pages=193–220}}</ref>

Therefore, a plethora of methodologies have been devised for reducing the complexity of combustion mechanisms without resorting to high detail levels. Examples are provided by:
* The Relaxation Redistribution Method (RRM)<ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|last2=Karlin|first2=Ilya|title=Adaptive simplification of complex multiscale systems|journal=Phys. Rev. E|date=2011|volume=83|issue=3|pages=036706|doi=10.1103/PhysRevE.83.036706|pmid=21517624|arxiv = 1011.1618 |bibcode = 2011PhRvE..83c6706C |s2cid=7458232}}</ref><ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|last2=Asinari|first2=Pietro|last3=Visconti|first3=Filippo|title=Fast computation of multi-scale combustion systems|journal=Phil. Trans. Roy. Soc. A|date=2011|volume=369|issue=1945|pages=2396–2404|doi=10.1098/rsta.2011.0026|pmid=21576153|arxiv = 1011.3828 |bibcode = 2011RSPTA.369.2396C |s2cid=14998597}}</ref><ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|title=Approximation of slow and fast dynamics in multiscale dynamical systems by the linearized Relaxation Redistribution Method|journal=Journal of Computational Physics|date=2012|volume=231|issue=4|doi=10.1016/j.jcp.2011.11.007|arxiv = 1102.0730 |bibcode = 2012JCoPh.231.1751C|pages=1751–1765|s2cid=16979409}}</ref><ref>{{cite journal|last1=Kooshkbaghi|first1=Mahdi|last2=Frouzakis|first2=E. Christos|last3=Chiavazzo|first3=Eliodoro|last4=Boulouchos|first4=Konstantinos|last5=Karlin|first5=Ilya|title=The global relaxation redistribution method for reduction of combustion kinetics|journal=The Journal of Chemical Physics|date=2014|volume=141|issue=4|doi=10.1063/1.4890368|pmid=25084876|page=044102|bibcode = 2014JChPh.141d4102K |s2cid=1784716 |url=https://iris.polito.it/bitstream/11583/2553537/1/JChemPhys_2014a.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://iris.polito.it/bitstream/11583/2553537/1/JChemPhys_2014a.pdf |archive-date=2022-10-09 |url-status=live}}</ref>
* The Intrinsic Low-Dimensional Manifold (ILDM) approach and further developments<ref>{{cite journal|last1=Maas|first1=U.|last2=Pope|first2=S.B.|title=Simplifying chemical kinetics: intrinsic low-dimensional manifolds in composition space|journal=Combust. Flame|date=1992|volume=88|issue=3–4|pages=239–264|doi=10.1016/0010-2180(92)90034-m}}</ref><ref>{{cite journal|last1=Bykov|first1=V.|last2=Maas|first2=U|title=The extension of the ILDM concept to reaction–diffusion manifolds|journal=Combust. Theory Model.|date=2007|volume=11|issue=6|pages=839–862|doi=10.1080/13647830701242531|bibcode=2007CTM....11..839B|s2cid=120624915}}</ref><ref>{{cite journal|last1=Nafe|first1=J.|last2=Maas|first2=U.|title=A general algorithm for improving ILDMs|journal=Combust. Theory Model.|date=2002|volume=6|issue=4|pages=697–709|doi=10.1088/1364-7830/6/4/308|bibcode = 2002CTM.....6..697N |s2cid=120269918}}</ref>
* The invariant-constrained equilibrium edge preimage curve method.<ref>{{cite journal|last1=Ren|first1=Z.|last2=Pope|first2=S.B.|last3=Vladimirsky|first3=A.|last4=Guckenheimer|first4=J.M.|title=The invariant constrained equilibrium edge preimage curve method for the dimension reduction of chemical kinetics|journal=J. Chem. Phys.|volume=124|issue=11|doi=10.1063/1.2177243|pmid=16555878|bibcode = 2006JChPh.124k4111R|page=114111|year=2006}}</ref>
* A few variational approaches<ref>{{cite journal|last1=Lebiedz|first1=D|title=Entropy-related extremum principles for model reduction of dissipative dynamical systems|journal=Entropy|date=2010|volume=12|issue=4|pages=706–719|bibcode = 2010Entrp..12..706L |doi = 10.3390/e12040706 |doi-access=free}}</ref><ref>{{cite journal|last1=Reinhardt|first1=V.|last2=Winckler|first2=M.|last3=Lebiedz|first3=D.|title=Approximation of slow attracting manifolds in chemical kinetics by tra trjectory-based optimization approaches|journal=J. Phys. Chem. A|date=112|pages=1712–1718|doi=10.1021/jp0739925|pmid=18247506|volume=112|issue=8|bibcode=2008JPCA..112.1712R|url=http://archiv.ub.uni-heidelberg.de/volltextserver/7352/1/modelred_optimization.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://archiv.ub.uni-heidelberg.de/volltextserver/7352/1/modelred_optimization.pdf |archive-date=2022-10-09 |url-status=live}}</ref>
* The Computational Singular perturbation (CSP) method and further developments.<ref>{{cite book|last1=Lam|first1=S.H.|last2=Goussis|first2=D.|title=Conventional Asymptotic and Computational Singular Perturbation for Symplified Kinetics Modelling|date=1991|publisher=Springer|location=Berlin}}</ref><ref>{{cite journal|last1=Valorani|first1=M.|last2=Goussis|first2=D.|last3=Najm|first3=H.N.|title=Higher order corrections in the approximation of low-dimensional manifolds and the construction of simplified problems with the csp method|journal=J. Comput. Phys.|date=2005|volume=209|issue=2|pages=754–786|doi=10.1016/j.jcp.2005.03.033|bibcode = 2005JCoPh.209..754V }}</ref>
* The Rate Controlled Constrained Equilibrium (RCCE) and Quasi Equilibrium Manifold (QEM) approach.<ref>{{cite journal|last1=Keck|first1=J.C.|last2=Gillespie|first2=D.|title=Rate-controlled partial-equilibrium method for treating reacting gas mixtures|journal=Combust. Flame|date=1971|volume=17|issue=2|pages=237–241|doi=10.1016/S0010-2180(71)80166-9}}</ref><ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|last2=Karlin|first2=Ilya|title=Quasi-equilibrium grid algorithm: geometric construction for model reduction|journal=J. Comput. Phys.|date=2008|volume=227|issue=11|pages=5535–5560|doi=10.1016/j.jcp.2008.02.006|arxiv = 0704.2317 |bibcode = 2008JCoPh.227.5535C |s2cid=973322}}</ref>
* The G-Scheme.<ref>{{cite journal|last1=Valorani|first1=M.|last2=Paolucci|first2=S.|title=The G-Scheme: a framework for multi-scale adaptive model reduction|journal=J. Comput. Phys.|date=2009|volume=228|issue=13|pages=4665–4701|doi=10.1016/j.jcp.2009.03.011|bibcode = 2009JCoPh.228.4665V }}</ref>
* The Method of Invariant Grids (MIG).<ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|last2=Karlin|first2=Ilya|last3=Gorban|first3=Alexander|title=The role of thermodynamics in model reduction when using invariant grids|journal=Commun. Comput. Phys.|date=2010|volume=8|issue=4|pages=701–734|doi=10.4208/cicp.030709.210110a|bibcode=2010CCoPh...8..701C|url=http://www.math.le.ac.uk/people/ag153/homepage/ChiaKarGor2010.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.math.le.ac.uk/people/ag153/homepage/ChiaKarGor2010.pdf |archive-date=2022-10-09 |url-status=live|citeseerx=10.1.1.302.9316}}</ref><ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|last2=Karlin|first2=Ilya|last3=Frouzakis|first3=Christos E.|last4=Boulouchos|first4=Konstantinos|title=Method of invariant grid for model reduction of hydrogen combustion|journal=Proceedings of the Combustion Institute|date=2009|volume=32|doi=10.1016/j.proci.2008.05.014|pages=519–526|arxiv=0712.2386|s2cid=118484479}}</ref><ref>{{cite journal|last1=Chiavazzo|first1=Eliodoro|last2=Karlin|first2=Ilya|last3=Gorban|first3=Alexander|last4=Boulouchos|first4=Konstantinos|title=Coupling of the model reduction technique with the lattice Boltzmann method for combustion simulations|journal=Combust. Flame|date=2010|volume=157|issue=10|pages=1833–1849|doi=10.1016/j.combustflame.2010.06.009}}</ref>

===Kinetic modelling===

The kinetic modelling may be explored for insight into the reaction mechanisms of thermal decomposition in the combustion of different materials by using for instance [[Thermogravimetric analysis]].<ref>{{cite journal|last1=Reyes|first1=J.A.|last2=Conesa|first2=J.A.|last3=Marcilla|first3=A.|title=Pyrolysis and combustion of polycoated cartons recycling. kinetic model and ms analysis|journal=Journal of Analytical and Applied Pyrolysis|date=2001|volume=58-59|pages=747–763|doi=10.1016/S0165-2370(00)00123-6}}</ref>

==Temperature==
[[File:Zoom lunette ardente.jpg|thumb|[[Antoine Lavoisier]] conducting an experiment related to combustion generated by amplified sunlight]]
Assuming perfect combustion conditions, such as complete combustion under [[adiabatic]] conditions (i.e., no heat loss or gain), the adiabatic combustion temperature can be determined. The formula that yields this temperature is based on the [[first law of thermodynamics]] and takes note of the fact that the [[heat of combustion]] is used entirely for heating the fuel, the combustion air or oxygen, and the combustion product gases (commonly referred to as the ''[[flue gas]]'').

In the case of [[fossil fuels]] burnt in air, the combustion temperature depends on all of the following:
* the [[Heat of combustion|heating value]];
* the [[air-fuel ratio|stoichiometric air to fuel ratio]] <math>{\lambda}</math>;
* the [[specific heat capacity]] of fuel and air;
* the air and fuel inlet temperatures.

The adiabatic combustion temperature (also known as the ''[[adiabatic flame temperature]]'') increases for higher heating values and inlet air and fuel temperatures and for stoichiometric air ratios approaching one.

Most commonly, the adiabatic combustion temperatures for coals are around {{convert|2200|C|0|abbr=on}} (for inlet air and fuel at ambient temperatures and for <math>\lambda = 1.0</math>), around {{convert|2150|C|0|abbr=on}} for oil and {{convert|2000|C|0|abbr=on}} for [[natural gas]].<ref>{{cite journal | title = Adiabatic flame temperature | journal = Industrial Heating | page = 20 | date = May 2013 | url =  http://www.industrialheating.com/articles/91062-adiabatic-flame-temperature | access-date = 5 July 2013}}</ref><ref name="AFTCalc">[http://www.industrialheating.com/AFT-Calc] AFTCalc</ref>

In industrial [[Industrial furnace|fired heaters]], [[power station]] [[steam generator]]s, and large [[gas turbine|gas-fired turbines]], the more common way of expressing the usage of more than the stoichiometric combustion air is ''percent excess combustion air''. For example, excess combustion air of 15 percent means that 15 percent more than the required stoichiometric air is being used.

==Instabilities==
Combustion instabilities are typically violent pressure oscillations in a combustion chamber. These pressure oscillations can be as high as 180{{nbsp}}dB, and long-term exposure to these cyclic pressure and thermal loads reduces the life of engine components. In rockets, such as the F1 used in the Saturn V program, instabilities led to massive damage to the combustion chamber and surrounding components. This problem was solved by re-designing the fuel injector. In liquid jet engines, the droplet size and distribution can be used to attenuate the instabilities. Combustion instabilities are a major concern in ground-based gas turbine engines because of {{NOx}} emissions. The tendency is to run lean, an equivalence ratio less than 1, to reduce the combustion temperature and thus reduce the {{NOx}} emissions; however, running the combustion lean makes it very susceptible to combustion instability.

The [[Thermoacoustic hot air engine|Rayleigh Criterion]] is the basis for analysis of thermoacoustic combustion instability and is evaluated using the Rayleigh Index over one cycle of instability<ref>John William Strutt, 3rd Baron Rayleigh, Sc.D., F.R.S.., Honorary Fellow of Trinity College, Cambridge; "The Theory of Sound", §322h, 1878:</ref>

<div style="text-align:center;"><math>G(x)=\frac{1}{T}\int_{T}q'(x,t)p'(x,t)dt</math></div>

where q' is the heat release rate perturbation and p' is the pressure fluctuation.<ref>A. A. Putnam and W. C. Dennis (1953) "Organ-pipe oscillations in a flame-filled tube", ''Fourth Symposium (International) on Combustion'', The Combustion Institute, pp. 566–574.</ref><ref>E. C. Fernandes and M. V. Heitor, [https://books.google.com/books?id=Je_hG6UfnogC&q=rayleigh+thermoacoustic+ "Unsteady flames and the Rayleigh criterion"] in F. Culick,  M. V. Heitor, and J. H. Whitelaw, ed.s, ''Unsteady Combustion'' (Dordrecht, the Netherlands:  Kluwer Academic Publishers, 1996), p. 4</ref>
When the heat release oscillations are in phase with the pressure oscillations, the Rayleigh Index is positive and the magnitude of the thermoacoustic instability is maximised. On the other hand, if the Rayleigh Index is negative, then thermoacoustic damping occurs. The Rayleigh Criterion implies that thermoacoustic instability can be optimally controlled by having heat release oscillations 180 degrees out of phase with pressure oscillations at the same frequency.<ref>Dowling, A. P. (2000a). "Vortices, sound and flame – a damaging combination". ''The Aeronautical Journal of the RaeS''</ref><ref>{{cite journal |doi=10.1080/00102202.2012.714020 |title=Temperature Response of an Acoustically Forced Turbulent Lean Premixed Flame: A Quantitative Experimental Determination |year=2013 |last1=Chrystie |first1=Robin S. M. |last2=Burns |first2=Iain S. |last3=Kaminski |first3=Clemens F. |journal=Combustion Science and Technology |volume=185 |pages=180–199|s2cid=46039754 }}</ref> This minimizes the Rayleigh Index.

==See also==
{{col-begin}}
{{col-break}}
'''Related concepts'''
* [[Air–fuel ratio]]
* [[Autoignition temperature]]
* [[Chemical looping combustion]]
* [[Deflagration]]
* [[Detonation]]
* [[Dust explosion]]
* [[Explosion]]
* [[Fire]]
* [[Flame]]
* [[Global warming]]
* [[Heterogeneous combustion]]
* [[Markstein number]]
* [[Phlogiston theory]] (historical)
* [[Spontaneous combustion]]

{{col-break}}

'''Machines and equipment'''
* [[Boiler]]
* [[Bunsen burner]]
* [[External combustion engine]]
* [[Furnace (house heating)|Furnace]]
* [[Gas turbine]]
* [[Internal combustion engine]]
* [[Rocket engine]]

'''Scientific and engineering societies'''
* [[International Flame Research Foundation]]
* [[The Combustion Institute]]

'''Other'''
* [[Combustible dust]]
* [[Combustion of biomass|Biomass burning]]
* [[List of light sources]]
* [[Open burning of waste]]
* [[Stubble burning]]
{{col-end}}

== References ==
{{reflist|colwidth=30em}}

==Further reading==
{{Wiktionary}}
* {{cite book |last1=Poinsot |first1=Thierry |last2=Veynante |first2=Denis |url=http://elearning.cerfacs.fr/combustion/onlinePoinsotBook/buythirdedition/index.php |title=Theoretical and Numerical Combustion |edition=3rd |publisher=European Centre for Research and Advanced Training in Scientific Computation |year=2012 |access-date=2011-11-18 |archive-date=2017-09-12 |archive-url=https://web.archive.org/web/20170912201709/http://elearning.cerfacs.fr/combustion/onlinePoinsotBook/buythirdedition/index.php |url-status=dead }}
* {{cite book | editor1-last = Lackner | editor1-first = Maximilian | editor2-last = Winter | editor2-first = Franz | editor3-last = Agarwal | editor3-first = Avinash K. | url = http://as.wiley.com/WileyCDA/WileyTitle/productCd-3527324496.html | title = Handbook of Combustion, 5 volume set | publisher = [[Wiley-VCH]] | year = 2010 | isbn = 978-3-527-32449-1 | access-date = 2010-04-29 | archive-date = 2011-01-17 | archive-url = https://web.archive.org/web/20110117003038/http://as.wiley.com/WileyCDA/WileyTitle/productCd-3527324496.html | url-status = dead }}
* {{cite book| editor-last = Baukal | editor-first = Charles E. | title = Oxygen-Enhanced Combustion | publisher = [[CRC Press]] | year = 1998}}
* {{cite book | last1 = Glassman | first1 = Irvin | last2 = Yetter| first2 = Richard | title = Combustion | edition = Fourth}}
* {{cite book | last = Turns | first = Stephen | title = An Introduction to Combustion: Concepts and Applications | year = 2011}}
* {{cite book | last1 = Ragland | first1 = Kenneth W | last2 = Bryden | first2 = Kenneth M. | title = Combustion Engineering | edition = Second | year = 2011}}
* {{cite book | editor-last = Baukal| editor-first = Charles E. Jr | title = The John Zink Hamworthy Combustion Handbook: Three-Volume Set | edition = Second | contribution = Industrial Combustion | year = 2013}}
* {{cite book | last = Gardiner | first = W. C. Jr | title = Gas-Phase Combustion Chemistry | year = 2000 | edition = Revised}}

{{Firelighting}}
{{Fire}}

{{Authority control}}

[[Category:Combustion| ]]
[[Category:Chemical reactions]]