Alternative Fuels

Coordinator: Dr. P. Le Clercq

Alternative fuels have become a major topic for energy supply and mobility and are nowadays more relevant than ever before. In Germany this topic is closely interlinked with the adopted energy turn (Energiewende): Among others, at least 60% of the gross final consumption of energy and 80% of the electricity consumption shall be covered by renewable energies by 2050. Here, alternative fuels are of particular importance in several respects: As fuel in internal combustion engines and aero engines, as fuel for decentralized power plants and as storage medium for excess energy from wind and solar power plants. Just like their feedstocks and conversion process, the produced synthetic fuels are very diverse, for instance, bio-alcohols, hydrogen, fuels from gasification and fermentation processes or, Fischer-Tropsch products. According to their strongly varying compositions, the combustion characteristics of alternative fuels are quite different so that new or adapted combustion concepts must be developed. For future power plants and propulsion systems, fuel flexibility is one of the most important requirements.

The DLR Institute of Combustion Technology performs research in the development of technologies for the production and use of alternative fuels for power and heat generation and for propulsion. Efficiency and reliability are in the focus as well as climate and environmental compatibility. In cooperation with the DLR Institute of Technical Thermodynamic, a further research focus is on the analysis of the availability and the potential further usage of alternative fuels.

More specifically, regarding alternative aviation fuels the stringent specifications which have to be met by jet fuel have led to the development of a robust approval process for the qualification of new fuels and blend stocks. This process is very costly in time and effort. Consequently, DLR-VT is also active in the pre-screening of potential alternative fuels. This allows stakeholders to gather information concerning key combustion properties to assess the technical suitability prior to engaging in such a long process.

Designing the composition of synthetic fuels plays an increasing role, i.e. the optimization of the composition with respect to the physical and chemical properties like specific energy content, combustion characteristics, environmental compatibility as well as aspects concerning production and storage. Regarding the combustion characteristics of aero-engines or stationary gas turbines, good flame stability and low emissions are primary objectives of the research. Because the fuel composition has a significant influence on all combustion characteristics and because of the high diversity of potential fuels, an optimization of the fuels cannot be achieved by empirical methods, but has to be based on a deep understanding of the underlying physical and chemical process chains.

It is therefore a major goal of the institute to develop tools for the optimization and characterization of the combustion properties of alternative fuels. These tools are based on chemical-kinetics modeling, numerical simulation of the combustion process and experimental investigations using advanced laser measuring techniques. A further goal is the development of gas turbine combustors for decentralized combined heat and power plants which enable a clean, efficient and reliable operation with a large variety of alternative fuels.

The most important research topics in our institute related to this subject are:   

  • Chemical analysis of alternative fuels and their pollutant emissions in combustion processes.
  • Development of numerical simulation and laser measurement techniques for combustion processes with alternative fuels.
  • Development of detailed chemical-kinetics reaction mechanisms for alternative fuels and their reduction for the implementation in CFD (Computational Fluid Dynamics) codes.
  • Validation measurements for chemical-kinetics mechanisms and numerical simulations of gas turbine-relevant model combustors.
  • Development of chemical-kinetics, numerical and, diagnostic methods for gasification processes.
  • Experimental and numerical research work for the development of fuel-flexible burners.
  • Screening of alternative fuels.
  • Usage of alternative fuels in micro gas turbines for decentralized energy supply.
 Comparison of the intensity of soot radiation from a spray flame operated with conventional kerosene and synthetic fuel (Gas-to-Liquid fuel, GtL). Due to a lower content of aromatics, the GtL produces less soot.
zum Bild Comparison of the intensity of soot radiation from a spray flame operated with conventional kerosene and synthetic fuel (Gas-to-Liquid fuel, GtL). Due to a lower content of aromatics, the GtL produces less soot.


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