Combustion is defined as the burning of a fuel and oxidant to produce heat and/or work. It is the major energy release mechanism in the Earth and key to humankind's existence. Combustion includes thermal, hydrodynamic, and chemical processes. It starts with the mixing of fuel and oxidant, and sometimes in the presence of other species or catalysts. The fuel can be gaseous, liquid, or solid and the mixture may be ignited with a heat source. When ignited, chemical reactions of fuel and oxidant take place and the heat release from the reaction creates a self-sustained process. The combustion products include heat, light, chemical species, pollutants, mechanical work, and plasma. Sometimes, a low-grade fuel, e.g., coal, biomass, or coke, can be partially burned to produce higher-grade fuel, e.g., methane. The partial burning process is called gasification. Various combustion systems, e.g., furnaces, combustors, boilers, reactors, and engines, are developed to utilize combustion heat, chemical species, and work.
Advanced measurement and control equipment has traditionally been used as a tool for the analysis of a combustion system. The analysis can lead to lower energy use and pollutant emissions by the system. Recently, the computational codes, including kinetics and fluid dynamics codes, have been used as an added tool for combustion analysis. In recent years, concerns over the availability of energy sources and the impacts of combustion processes on global environments, have attracted more and more attention; this concern has been heightened with recognition that fossil fuels have a finite supply. Thus, efficient and responsive use of our energy sources has become a primary concern for human society.