Fuel Analytics
By characterizing fuels in terms of their chemical composition and thermophysical properties, the Chemical Kinetics and Analytics Department creates the foundation for the investigation of the effects of the fuel composition on combustion and emission behavior. In particular, the analysis of synthetic fuels and fuel alternatives presents a challenge, as the chemical composition often differ greatly from conventional fuels.
For this purpose, the department has a state-of-the-art two-dimensional gas chromatograph (GCxGC) with coupled mass spectrometer and flame ionization detector available, with which the separation of even complex fuel matrices is possible due to the modulated series connection of two chromatography columns. This analysis is supported by 1H nuclear magnetic resonance spectroscopy (NMR), which enables precise determination of the hydrogen content of fuels. Thus, fuel samples can be precisely qualified and quantified on the molecular level, and the mass fractions of the individual chemical groups, the average molecular formula, and the C/H ratio can be determined.
In addition, crucial thermophysical parameters can be determined. These include distillation properties (e.g., initial boiling point, boiling curve, final boiling point), vapor pressure curves, kinematic viscosity and density (including low-temperature behavior down to -47 °C), freezing point, oxidation stability, surface tension, refractive index, and calorific value of the fuels under consideration. Especially in aviation, the low-temperature properties are of great importance and safety relevance.
The available analytical methods thus in part go far beyond those required in corresponding standards (e.g., ASTM or DIN) and provide individualized validation data for model-based optimization processes. The precise characterization of a fuel also forms the basis for the scientific interpretation of its combustion and emission behavior, as well as for the selection of suitable models for predicting the reaction kinetics of combustion and pollutant formation.
Literature
Jürgens, S.; Osswald, P.; Selinsek, M.; Piermartini, P.; Schwab, J.; Pfeifer, P.; Bauder, U.; Ruoff, S.; Rauch, B.; Köhler, M., Assessment of combustion properties of non-hydroprocessed Fischer-Tropsch fuels for aviation. Fuel Process. Technol. 2019, 193, 232-243.