Combustion and flame: Combustion and flame Introduction - combustion: Introduction - combustion Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame. Types : Types Smoldering combustion : Smoldering combustion 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. Solid materials that can sustain a smoldering reaction include coal, cellulose, wood . Rapid combustion: Rapid combustion Rapid combustion is a form of combustion, otherwise known as a fire, in which large amounts of heat and light energy are released, which often results in a flame. This is used in a form of machinery such as internal combustion engines . Turbulent combustion: Turbulent combustion Combustion resulting in a turbulent flame is the most used for industrial application (e.g. gas turbines, gasoline engines, etc.) because the turbulence helps the mixing process between the fuel and oxidizer . Microgravity : Microgravity Combustion processes behave differently in a microgravity environment than in Earth-gravity conditions due to the lack of buoyancy. For example, a candle's flame takes the shape of a sphere . Fuels : Fuels Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner . Most fuels used by humans undergo combustion , a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air. Types : Types LIQUID FUELS: LIQUID FUELS Combustion of a liquid fuel in an oxidizing atmosphere actually happens in the gas phase. It is the vapour that burns, not the liquid. Therefore, a liquid will normally catch fire only above a certain temperature: its flash point. SOLID FUELS: SOLID FUELS Solid fuel refers to various types of solid material that are used as fuel to produce energy and provide heating , oih sually released through combustion.Solid fuels include wood , charcoal, peat, coal, Hexamine fuel tablets, and pellets made from wood, corn,wheat , rye and other grains . FLAME: FLAME A flame is the visible (light-emitting), gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone . If a fire is hot enough to ionize the gaseous components, it can become a plasma .