Combustion

Combustion is a chemical process in which a substance reacts rapidly with an oxidizer, usually oxygen in the air, releasing heat and often light. It is typically exothermic and requires three elements: a fuel, an oxidizer, and sufficient heat to reach the activation temperature. Once initiated, the reaction propagates through the fuel and oxidizer.

In its most common form, combustion is represented by a hydrocarbon reacting with oxygen to form oxides of carbon and water, releasing energy. For example, methane reacts with oxygen to produce carbon dioxide and water: CH4 + 2 O2 → CO2 + 2 H2O. The flame zone is a region where reactive species and heat sustain the reaction. If the supply of fuel or oxygen is limited, incomplete combustion can occur, producing carbon monoxide, soot, and other byproducts.

Combustion can be rapid, as in flames or explosions, or slow, as in oxidation processes that do not involve flame. Flames are characterized by a visible emission of light and a distinct temperature profile, while flameless, diffusion, and autoignition processes can occur under different conditions.

The products of combustion depend on the fuel and conditions; complete combustion typically yields CO2 and H2O, while incomplete combustion yields CO, soot, and other partially oxidized species. The energy released powers many technologies, including internal combustion engines, gas turbines, and furnaces, and is also a major source of heat and light.

Safety and environmental considerations are important, as combustion can produce pollutants such as CO, NOx, particulate matter, and greenhouse gases. Efficiency improvements and emission controls are active areas of science and engineering.