Reactive Flows

The use of combustion processes, the most important example of a chemically reactive flow, is one of the oldest and at the same time one of the most successful technologies to serve humans. In spite of all efforts made in the development of alternative sources of energy, currently more than 80 % of the energy supplies of the world still rely on combustion processes. Because of their broad spectrum of application (heat, electricity, transport and chemistry), the fossil fuels that are currently used annually worldwide have taken about one million years of the Earth’s history to form. The pollutants that are produced through this, such as CO2, nitrogen oxides and soot, lead to undesirable changes in the atmosphere and biosphere of the Earth, as will be described in Section 10.4. Reactive flows and thus also combustion processes are determined by a complex multi-dimensional and time-dependent interaction between a large number of chemical elementary reactions and transport processes for mass, momentum and energy, as well as phase boundary effects. Empirical methods to develop or improve environmentally friendly and efficient new processes have been largely exhausted. Rather a new approach is necessary. This approach no longer consists of describing reactive flows summarily, rather of assembling the microscopic processes and thereby deriving the visible macroscopic processes. In this manner it is possible, for example, to explain the origin of the formation of pollutants, the incomplete progression of combustion or the mode of functioning of catalysts.