New vessels need to remain fuel flexible in order to handle the uncertainties of the future regarding the available alternative fuels aiming to lower their environmental impact. On the other hand, it is even more challenging for existing vessels that are not fuel flexible to successfully improve their carbon impact. The current study examines the combustion characteristics of alternative maritime fuels including methanol and hydrogen in the compression-ignited internal combustion engines of Bravenes that burn diesel fuel, as well as the implications these fuels have on the environment and on safety when used onboard ships. The diesel fuel still acts as the main fuel but also as the ignition fuel for the injected additives. The purpose of the additives is for the substitution of diesel and to offer more complete combustion in the cylinders. Van Oord is already implementing the Fuelsave Marine+ technology on board Bravenes. This technology aims to reduce harmful emissions like ABe and greenhouse gases while also increasing engine efficiency in order to contribute to the overall energy transition effectively. Therefore, the primary goal of this research is to examine if there are any potential impacts of the technology on the efficiency, emissions, and fuel consumption of Bravenes engines.

The model used is able to characterize the combustion of the engine using the Seiliger combustion shape parameters a, b and c. These parameters consider the combustion efficiency, the ignition delay, and the heat fractions of the potential heat for the appropriate stages. The effects of the additives in small quantities can be seen in the combustion duration and the ignition delay of the combustion. In order to properly model the additional fuels effects some of the diesel mass needed to be substituted with methanol mass to provide the same energy content in the cylinder. Attention was also given to the proper selection of the KN&𝑋𝑏 parameters impacting the combustion shape parameters, and as a result the pressures and temperatures in the engine.

The results of the model for the diesel and diesel with additives operation predict a decrease in diesel fuel consumption which is a good indication of 𝐶𝑂2 emissions reduction. The peak cylinder pressures have increased with the additives injection and the peak temperatures as well which indicate an increase of 𝑁𝑂𝑥 emissions. The increase in the temperatures is not something expected in reality and could be due to a modeling effect. The indicated work of the engine combustion cycle also improved for the Fuelsave technology but due to the increase in peak pressures the mechanical efficiency decreased resulting in reduced effective efficiency. The selection of the Seiliger settings, which allowed
for a higher heat loss efficiency than was realistically anticipated, is another factor contributing to the decrease in effective efficiency. All in all, proper measurement campaign needs to be performed to show the clear effects of the technology as a retrofit solution on board existing vessels for efficiency and emission reduction.