A study on electrofuels in aviation
Creators: name: Goldmann, Andreas
name: Sauter, Waldemar
name: Oettinger, Marcel
name: Kluge, Tim
name: Schröder, Uwe
name: Seume, Jörg R.
name: Friedrichs, Jens
name: Dinkelacker, Friedrich
Publisher: name: Basel : MDPI AG
Year: 2018
Subjects: subject: Aviation
subject: Combustion
subject: Electrofuels
subject: Fuel synthesis
subject: Renewable green fuels
subject: Turbine
subject: Adiabatic flame temperature
subject: Aircraft engines
subject: Ammonia
subject: Drops
subject: Emission control
subject: Energy efficiency
subject: Gas emissions
subject: Greenhouse gases
subject: Hydrogen
subject: Methanol fuels
subject: Strain rate
subject: Turbines
subject: Auto-ignition delay time
subject: Comparative evaluations
subject: Extinction strain rate
subject: Green fuel
subject: Laminar flame speed
subject: Physicochemical property
subject: Sustainable solution
subject: Alternative fuels
subject: Dewey Decimal Classification::600 | Technik::620 | Ingenieurwissenschaften und Maschinenbau

description: With the growth of aviation traffic and the demand for emission reduction, alternative fuels like the so-called electrofuels could comprise a sustainable solution. Electrofuels are understood as those that use renewable energy for fuel synthesis and that are carbon-neutral with respect to greenhouse gas emission. In this study, five potential electrofuels are discussed with respect to the potential application as aviation fuels, being n-octane, methanol, methane, hydrogen and ammonia, and compared to conventional Jet A-1 fuel. Three important aspects are illuminated. Firstly, the synthesis process of the electrofuel is described with its technological paths, its energy efficiency and the maturity or research need of the production. Secondly, the physico-chemical properties are compared with respect to specific energy, energy density, as well as those properties relevant to the combustion of the fuels, i.e., autoignition delay time, adiabatic flame temperature, laminar flame speed and extinction strain rate. Results show that the physical and combustion properties significantly differ from jet fuel, except for n-octane. The results describe how the different electrofuels perform with respect to important aspects such as fuel and air mass flow rates. In addition, the results help determine mixture properties of the exhaust gas for each electrofuel. Thirdly, a turbine configuration is investigated at a constant operating point to further analyze the drop-in potential of electrofuels in aircraft engines. It is found that electrofuels can generally substitute conventional kerosene-based fuels, but have some downsides in the form of higher structural loads and potentially lower efficiencies. Finally, a preliminary comparative evaluation matrix is developed. It contains specifically those fields for the different proposed electrofuels where special challenges and problematic points are seen that need more research for potential application. Synthetically-produced n-octane is seen as a potential candidate for a future electrofuel where even a drop-in capability is given. For the other fuels, more issues need further research to allow the application as electrofuels in aviation. Specifically interesting could be the combination of hydrogen with ammonia in the far future; however, the research is just at the beginning stage.