In the European Union-funded ‘High Biofuel Blends in Aviation’ (HBBA) study, Markus Köhler, DLR Institute of Combustion Technology, Stuttgart, Germany, and colleagues investigated the chemical and physical properties of biofuels with a focus on blends, i.e., mixtures of conventional kerosene with biofuels. The study analyzed particularly promising biofuels, according to source, production process, and approval status.
An airliner turbine can cost up to several million euro. Should it be operated using non-certified fuel for research purposes, for example, it may not be reinstalled in an aircraft. This means that bridging the gap between tests on a laboratory scale to actual implementation in an aircraft represents a huge challenge for researchers. For the first time, the scientists have investigated biofuels on a special test rig at Lufthansa Technik in Hamburg, where a dismounted aero-engine is available especially for research purposes. Using this engine, the scientists examined and compared three different fuels: pure biofuel, a blend consisting of 50 % biofuel and 50 % conventional fuel, as well as conventional kerosene as a reference.
The test engine is suspended from the ceiling in a hangar. The exhaust gas stream enters a large tunnel behind the engine, where samples were taken. The laboratory analyses showed that biofuels are well suited for use in aero-engines.
The certification of a completely new fuel is an extremely elaborate and lengthy process. Blends of biofuels and conventional kerosene represent an important intermediate stage – some of their properties correspond to those of normal kerosene, which means that not all parameters required for the combustion process have to be completely re-examined. They are also an important step toward so-called designer fuels. Such fuels are composed in such a way that their properties are as optimal as possible in terms of environmental friendliness and technical characteristics. Research in this field is a major focus for the DLR Institute of Combustion Technology.
- Institute of Combustion Technology of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), Stuttgart, Germany
- Lufthansa Technik, Hamburg, Germany
- Bundeswehr Research Institute for Materials, Fuels and Lubricants (Wehrwissenschaftliches Institut für Werk- und Betriebsstoffe; WiWeB), Erding, Germany