TY - JOUR

T1 - A Study on Electrofuels in Aviation

AU - Goldmann, Andreas

AU - Sauter, Waldemar

AU - Oettinger, Marcel

AU - Kluge, Tim

AU - Schröder, Uwe

AU - Seume, Joerg R.

AU - Friedrichs, Jens

AU - Dinkelacker, Friedrich

N1 - Funding information: Acknowledgments: This research was supported by the Lower Saxonian Ministry for Science and Culture as part of the research program MOBILISE (Mobility in Engineering and Science). The authors gratefully acknowledge the substantial contribution of the DLR Institute of Propulsion Technology and MTU Aero Engines AG for providing the TRACE code.

PY - 2018/2

Y1 - 2018/2

N2 - 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.

AB - 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.

KW - Aviation

KW - Combustion

KW - Electrofuels

KW - Fuel synthesis

KW - Renewable green fuels

KW - Turbine

UR - http://www.scopus.com/inward/record.url?scp=85051401628&partnerID=8YFLogxK

U2 - 10.3390/en11020392

DO - 10.3390/en11020392

M3 - Article

AN - SCOPUS:85051401628

VL - 11

JO - ENERGIES

JF - ENERGIES

SN - 1996-1073

IS - 2

M1 - 11020392

ER -