Reducing CO2 emissions is an increasingly important issue. In
aviation, approaches such as e-propulsion only represent a solution for special
applications due to the low energy density of batteries. Because of the low-cost
and robust design of combustion engines, this concept is still the most suitable
for general aviation. For defossilization, besides e-fuels and bio-fuels, which
represent the so-called sustainable aviation fuels (SAF), hydrogen can serve as
a promising energy carrier for CO2 reduction. For this purpose, the
combustion process of a dual-fuel hydrogen–kerosene (Jet A-1) engine was
developed and investigated for use in small aircrafts. This study explores the
influence of hydrogen addition on combustion parameters, emissions, and
efficiency.
An advantage of this special design as dual-fuel engine (hydrogen and kerosene)
is the possibility of redundancy operation in the event of a H2 fuel
system failure as well as full operational capability of the aircraft in the
event of hydrogen supply difficulties at various airports. Besides test bench
investigations, 3D CFD simulations were performed to optimize hydrogen injector
position, ensure backfire-free operation, and improve mixture formation. In
addition to a low load and high load point, a high-altitude point was
investigated based on real flight data.
The maximum achievable hydrogen energy shares, limited by abnormal combustion,
and the respective CO2 reductions are shown. Furthermore, the
influence of the hydrogen mass distribution in the inlet ports was investigated
to achieve an advantage in the homogenization of the hydrogen–air mixture.
Finally, the efficiency losses in hydrogen dual-fuel mode compared to base
kerosene operation are shown in a detailed analysis.