Greenhouse gas emissions released in the combustion of fossil fuels are a key driver of climate change. The diesel engine combustion process, which is the state-of-the-art for marine en-gines, also results in increased sulfur oxides (SOX) and nitrogen oxide (NOX) emissions. In the long term, one way to avoid emissions from shipping is to use renewable energies. The nec-essary expansion of renewable energies, the technical conversion of the fleet and the estab-lishment of a global and gap-free supply infrastructure are challenges that cannot be overcome in the short term. For this reason, it makes sense to look at transitional technologies that will not make ships emission-free but will significantly reduce emissions.
One possibility is the use of liquefied natural gas (LNG). Despite slightly reduced efficiency compared to the diesel process, CO2 savings of around 20 % can be achieved compared to the burning of diesel or heavy fuel oil due to the lower C/H ratio of the natural gas.
Studies on the single-cylinder engine test bed at TUHH demonstrated that propeller operation with medium-speed four-stroke dual fuel (DF) engines on the design propeller curve is possi-ble. In Addition, the strict IMO Tier III NOX limits could also be met in the part load range. The consumption and mission measurements show that operation at nominal pitch is not only pos-sible but also reasonable. Towards high mean effective pressures, the efficiency of the engine also increases in the part-load range and fuel consumption as well as CO2 emissions are re-duced. The LNG engine test bed at TUHH has all the key components of an LNG infrastructure onboard ships. Thus, not only the combustion of natural gas could be investigated, but also the operational boundary conditions. On the one hand, it was shown that fluctuating gas qual-ities favor knocking combustion, which can be counteracted within limits by early adjustment of the pilot injection timing. On the other hand, it became clear that the injection period towards high mean effective pressures becomes so long that methane slip can occur during valve over-lap.