DLR researchers understand soot formation in engines
- Focus: Aeronautics, climate change
Aviation is not only responsible for carbon dioxide emissions; it also causes other emissions that have an impact on climate change, in particular soot particles. These are produced both on the ground and at cruising altitudes, where they act as condensation nuclei for ice crystals and lead to the formation of contrails, which may linger in the sky as contrail cirrus clouds. Reducing soot emissions by making engines as clean as possible requires a precise understanding of how soot is produced in engine combustion chambers, and how it is partially degraded there. Researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have now won a Distinguished Paper Award from the International Symposium on Combustion for their work on soot formation in engine combustion chambers.
"Cooperation between experiments and simulations is the key to the next generation of low-emission engines," says Klaus-Peter Geigle of the DLR Institute of Combustion Technology in Stuttgart. "The interplay between laser measurement technology and simulation has for the first time shown in detail how soot forms in an engine combustion chamber and is burned again, and which flow structures are responsible for this." The work was carried out as part of the EU-funded SOPRANO (Soot Processes and Radiation in Aeronautical inNOvative Combustors) project.
In order to minimise the formation of nitrogen oxides in current combustion chambers, the fuel is first burned with a fraction of the total air to ensure that as few nitrogen oxides as possible can form. The remaining air is then introduced quickly and then lean burned in another combustion zone. This is referred to as RQL (Rich Quench Lean) combustion. To keep soot emissions to a minimum, any soot that forms in the first zone must be oxidised as far as possible in the second zone, so that no pollutants leave the combustion chamber. Using the very latest high-speed laser measurement technology and innovative computer simulations, the DLR researchers have now examined this process in greater detail in collaboration with scientists from Algeria and the United States.
Their award-winning work was made possible by the unique interdisciplinary expertise of the DLR researchers in the fields of both optical measurement technology and soot simulation. Further work on this subject will be carried out in future. Researchers worldwide will use the unique dataset that has been created to verify their computational models. In addition to optimising the combustion chamber, alternative fuels can also be used to reduce the soot emissions of aircraft engines.