In the context of this thesis, the effect of various diesel-methanol blends in a diesel engine compared to conventional marine diesel oil is investigated by experiments and in-cylinder simulations. The main differences obtained between diesel and methanol are the lower heating value, heat of vaporization and cetane number. During the experiments, the engine was not able to run on M20 at loads lower than 153 [kW]. Pressure signal comparison between the cylinders showed that cylinder one shows better ignition properties for methanol operation compared to cylinder two, three and four. Higher COV's for IMEP and maximum pressure were obtained by methanol blends. Experiments with F76, M10 and M20 fuel have shown that methanol blends increase the specific fuel consumption and slightly decrease the engine efficiency. Specific NOx emissions decreased with 2.9 up to 14.2 [%] by methanol blends compared to F76. Due to the increased fuel consumption, the CO₂ emissions hardly reduced. Exhaust gas temperatures and CO emissions seems to decrease. The ignition delay of methanol blends increased up to 8 [degrees CA] for M20 while remaining the brake power constant. Moreover, the combustion duration and air excess ratio decreased by using methanol blends. A single droplet evaporation model is built to simulate the evaporation heat losses for methanol fuel during the in-cylinder process. Methanol has a longer evaporation time which is a disadvantage for diesel engine applications. By using the single droplet evaporation model combined with an injection model calibrated for dual fuel direct injection, the fuel spray evaporation heat is calculated for implementation in the single zone model. The results are calibrated by using the droplet diameter as a variable. In this way, the evaporation heat required for evaporation of methanol is simulated in the dual fuel single zone model. Heat release analysis shows that the premixed combustion phase of methanol blends is dominant compared to F76, while the diffusive combustion phase significantly reduces. For methanol blends, the residence time at high temperatures is lower due to the decreased combustion duration and elongated ignition delay. Unfortunately, the results from the dual fuel single zone model are strongly dependent on the position of the pressure signal. Results for the temperature of the mean cylinder two, three and four were not in line with the expectations. Cylinder one showed smoother heat release curves and its temperature result was in line with the expectations based on the exhaust gas temperature. More research to the effects of the fuel injectors on the heat release of methanol/diesel blends is recommended.

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).

The innovation of underwater exhaust systems on ships increases onboard space, reduces noise emission and allows for zero direct emissions. For defense vessels, stealth is increased as the heat signature reduces due to underwater exhaust. However, there is a disadvantage of dynamic back pressure at the exhaust outlet which deteriorates the performance of the engine. The waves at the exhaust outlet are dynamic consisting of different wave heights depending on sea state and period. These waves cause dynamic back pressure at the exhaust outlet. Experimental and simulation investigations on the effect of externally applied static back pressure due to submerged exhaust is already carried out. It was found that there is an increase in fuel consumption and thermal loading with an increase in static back pressure. But, the sea waves acting at the exhaust outlet is dynamic with fluctuating amplitude and wave period. No experimentally validated research is available in the public domain to understand the effect of externally applied dynamic back pressure due to sea waves on the diesel engine performance. Thus, in this master thesis, the effect of the externally applied dynamic back pressure due to underwater exhaust on the performance of the diesel engine is investigated. Experiments are performed on a pulse turbocharged 4-stroke marine diesel engine at the Netherlands Defence Academy. Effects of dynamic back pressure on engine performance at different sea-states are investigated. The impact of wave significant height and wave period on the performance of the diesel engine is examined separately. Along with the performance of the diesel engine, the effect of back pressure on the emissions are also investigated. In this research experiment, the diesel engine under selected load points is subjected to single and continuous waves of back-pressure with changing amplitudes of 45 mbar, 35 mbar and 25 mbar(Gauge) while the periods were varied between 2, 4, 6, and 8 seconds. The back pressure is replicated with the help of an electronically controlled butterfly valve turbine outlet placed after which controls the resistance to exhaust gas flow to the atmosphere. A Diesel Engine - B model developed at TU-Delft is adopted and verified with the help of measured data from the experiments. The adopted model is a mean value engine model implemented in MATLAB/Simulink environment. Current literature lacks studies on experimental validation of the effects of dynamic back pressure on a marine diesel engine. The verified model is used to simulate the performance with higher sea states which may not be possible to simulate on a test bench. This research showed that exhaust side parameters (e.g Exhaust receiver temperature) are more critical than the inlet side parameters (e.g. Inlet receiver temperature). Moreover, there is an increase in parameters progressively with increase in the amplitude of back-pressure. Above a wave period value, the engine performance parameters changed by approximately equal values irrespective of varying periods above it. The impact of steady state back pressure is found more severe on the diesel engine’s parameters and fuel consumption compared to externally applied dynamic back pressure of the same amplitude. The recorded emissions show an increase in the concentration of carbon monoxide (CO), carbon di-oxide (CO2), nitrous oxide (NO) and sulphur di oxide (SO2) in the exhaust with an increase in back pressure. On the other side, the oxygen concentration decreases with increase in the applied steady state and dynamic back pressure. Simulations suggested that the governor plays a crucial role in tackling the effects of dynamic back pressure by controlling the fuel flow to the diesel engine. The simulation results are also used to provide the applied back pressure ceiling limits in terms of air excess ratio and exhaust valve temperature for the test engine.

This thesis aims at gaining insights into the operational principles of the diesel engine injection systems and reproducing the dynamic of fuel injection in the diesel engines. Two popular fuel injection systems are modeled in this thesis, including the mechanical injection system and the common-rail injection system.

In the GasDrive project, a solid oxide fuel cell and a reciprocating gas engine are used to provide electrical and mechanical power for a ship. One of the goals of the GasDrive project is to broaden the limits between knock and misfire for the gas engine. Extending the operating limit could be achieved by addition of anode-off gas. Before anode-off gas can be used in combustion together with natural gas in the GasDrive project, the combustion characteristics of anode-off gas must be known. In this thesis, a literature review is conducted in order to explore similar gasses. One such gas is producer gas, on which both experimental and numerical studies have been conducted by other researchers. To investigate the performance of anode-off gas, an altered in-cylinder model was used. The model is verified using producer gas as a fuel, with the experimental data from producer gas combustion in an IC engine. The model functions properly and is used to investigate anode-off gas combustion.
In modelling the combustion of anode-off gas, multiple parameters are kept constant and similar to that of producer gas. These parameters include the Vibe parameters, engine geometry, air excess ratio, T1, p1, and stoichiometric gas mass fraction from the previous cycle. The combustion duration relative to producer gas is modelled based on the ratio of turbulent flame speeds. This turbulent flame speed is a combination of laminar flame speed and turbulence intensity. At first the SOC is kept constant as well, only altering the EOC for different combustion durations. The maximum power output is 79 kWe for anode-off gas with a 50% fuel utilization rate. The maximum efficiency is 20%. The peak pressure is 104 bar, which is higher than for producer gas, but falls within the limits of what the engine can handle. The peak temperature is 2847 K, which is more than 700 K higher than producer gas. The engine, it is believed, can not handle this temperature. The lowest peak temperature is reached for anode-off gas with a 85% fuel utilization rate and is 2652 K. This is still outside normal engine operating temperatures. Combustion of anode-off gas under stoichiometric conditions in an IC engine is therefore not feasible. Increasing the air excess ratio could resolve this issue, but can not be done in the current model without having experimental data on anode-off gas. The fuel consumption is 6-18 times higher than conventional fuels, also showing that anode-off gas combustion would not be an advantage over conventional fuels. More power at lower temperatures can be reached when retarding start of combustion, achieving MBT timing. Peak power is achieved using anode-off gas with a 50% fuel utilization rate and is 82 kWe. The corresponding peak temperature is 2822 K, which is also outside normal operating conditions of IC engines. Based on the modelling results, it can be said that combustion of anode-off gas is possible in a IC engine, but power outputs will be lower than conventional fuels and fuel consumption will be higher.