To achieve the emission goals set out by the International Maritime Organization in 2018. Low or zerocarbon fuels will have to be used. Ammonia is considered to be a possible candidate since it doesn’t contain carbon. This thesis will attempt to study two methods that characterize the closed-cylinder process of an internal combustion engine; the Seiliger approach and Wiebe function. Two things are the main focus of this thesis. Namely, the application of these methods and how this process will be different for ammonia-diesel combustion compared to diesel combustion. The application will be done for a two-stroke compression ignition engine. The operating conditions that are considered are four load points 20%, 40%, 60%, and 100% at a constant engine speed. The application of this method means building an anti-causal and causal simulation model using Matlab Simulink. Both models simulate what happens in one cylinder during the closed-cylinder process, require the engine parameters as input, and produce the same results. The anti-causal model processes the pressure as a function of the crank angle to determine the combustion reaction rate. The causal model simulates the combustion reaction rate using a Wiebe function to determine the pressure. The Wiebe function is determined based on the reaction coordinate produced by the anti-causal model. By using the Wiebe function, the causal model produces smoother results than the anti-causal model. The Seiliger parameters are determined by using a Newton-Rhapson solver with the maximum pressure, maximum temperature, indicated work, and heat input as equivalence criteria. The results produced by this thesis generally show that the constructed method can produce accurate results. However, this accuracy is correlated to the operating conditions of the engine. As for the changes necessary for ammonia-diesel combustion. These changes have been provided on a conceptual level, with conceptual meaning in terms of equations and assumptions. These changes have not been implemented into a computer model that has been verified and validated. The fundamental difference for the constructed method according to this thesis is the fact that the combustion parameters; start and end of combustion for the two fuels have to be incorporated in the combustion model used for the anti-causal and causal model. This change has to be made, along with assumptions that the injected fuel evaporates and combusts almost simultaneously. This assumption is considered to be highly questionable for ammonia.

Ammonia can become an attractive alternative fuel source on-board of ships, since it does not produce SOx and carbon related emissions (including CO2, CO and soot). However, pure ammonia combustion is too slow to drive an internal combustion engine (ICE), a promoter fuel such as hydrogen is needed to speed up the combustion process. Since the SOFC can be used as a power generator and ammonia cracker, an interesting proposal is to have a hybrid ICE-SOFC power generation system on-board ships. A vast amount of papers concerning directly fueled ammonia SOFCs have been published throughout the years. This concept has already been extensively modeled and successfully tested on large-scale. On the other hand, not much is known about hydrogen-ammonia combustion inside an ICE. Although the flammability behaviour and chemical kinetics during combustion have been widely investigated. Publications concerning the in-cylinder combustion characteristics are scarce. Since there are already a number of working ammonia fueled SOFC models in the literature, the thesis will be mostly emphasised on the investigation of hydrogen-ammonia fueled internal combustion engines. Conducted experiments on automotive sized engines have shown that hydrogen-ammonia combustion during SI mode is possible, but not optimal because of the high auto-ignition resistance and low flame propagation speed of ammonia. Hence, poor engine efficiencies, low power densities and large amounts of unburned fuel are more likely to occur during spark ignition. Compression ignition on the other hand is largely affected by great amounts of NOx production inside the flame zone. The NOx is primarily produced from fuel-bound nitrogen, which can unlike the nitrogen (N2) in air easily re-bond with free oxygen during the combustion process. HCCI combustion is a promising candidate to overcome these disadvantages (i.e. low power density and high NOx emissions).