The maritime sector faces major challenges to reduce its impact on global warming. The use of methanol as a fuel alternative is considered one of the more promising options to be implemented in a relatively short to medium time frame; based on the potential availability, emission reduction, energy density, potential to be synthetically produced, scalability of production, and its implementation on board ships (both new build and retrofitted).

This report investigates potential improvements of the injection system, to achieve complete evaporation in the air inlet of a port-fuel injection engine to avoid wall-wetting of the scavenger air receiver and inlet valve. As a result, the methanol-air mixture in the cylinder would become more homogeneous and able to provide 100% of the rated engine power. Earlier research indicated that the wall-wetting fuel film and its evaporation rate directly affect the air-fuel ratio of the in-cylinder mixture, stability of the combustion process, and overall engine performance. The study includes the development of an injection model simulating low-pressure port-fuel injection, similar to the system fitted on our Caterpillar test engine, and the development of a single-droplet evaporation model to gain inside into the evaporation process of 100% methanol.

Based on the performed experimental research, we conclude the average droplet size ranges between 100 and 120 μm. The average droplet speed was determined at ±35 m/s and the spray angle at 20°. At room temperature and pressure, the injection spray ended against the back-glass of the evaporation chamber, indicating almost none of the ethanol evaporates under these conditions. The injection length exceeds at least ±40 cm at atmospheric temperature and pressure, which is in line with the results of the single-droplet evaporation model.

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.

The maritime sector faces major challenges with increasing regulations from the International Maritime Organization (IMO) and national regulations for CO2, SOx and NOx. Innovative fuel types for maritime use are now under development by various stakeholders. Methanol shows considerable potential as one of the most promising for implementation in the short to medium term, based on the potential availability, emission reduction, and energy density. The Green maritime methanol (GMM) project is Netherlands based collaboration of important stakeholders such as shipbuilders, engine manufacturers and universities. Within this project, methanol is researched as a potential alternative combustion fuel for maritime vessels. For this purpose, the ”Dutch Caterpillar engine dealer” PON Power provided a G3508A engine available as a retrofit option. The engine is a turbocharged spark-ignited natural gas (NG) engine with 8 cylinders and a rated power of 500 kWe at 1500 rpm. After six months of rebuilding the engine, the spark-ignited (SI), port fuel injected (PFI) engine runs on 100% methanol. Tests with stable engine operation were achieved with 100% methanol at 25%, 50%, and 75% engine loading and a constant engine speed of 1500 rpm.
In this research, experiments and modelling have been performed to study combustion using 100% PFI methanol. Measurements are realized with varying: ignition timings, NOx emission settings, and manifold temperatures. Data collected during these measurements such as in-cylinder pressures, emissions, and temperatures, provided a comparison between running the engine on methanol or natural gas. In this comparison combustion stability is determined with the coefficient of variation (COV) of Pmax and of imep, optimum ignition timing is determined and engine efficiency is calculated and compared to NG. Modelling is accomplished with a TU Delft model of the G3508A SI engine adjusted for the use of 100% methanol as a fuel. A modified sub-model for the PFI and vaporization of methanol has been developed. These engine data will be used to validate the methanol engine model and to optimise the engine performance for further experimental runs and better understanding the use of methanol as a fuel.
The effect on the performance and the combustion when 100% methanol is used as fuel for a SI PFI engine compared to premixed injection of natural gas is shown in this work. The engine operates stably on methanol at 50% and 75% load within ignition timings of 16-24 °CA BTDC, but less stable than with NG. Heat release indicates an almost similar combustion duration, but shorter combustion duration is shown for methanol. Also with methanol, the crank angle where 50% of fuel is burnt (CA50) is shown earlier compared to NG. The faster premixed combustion, combined with a better found fuel consumption operating point, resulted in higher efficiencies for methanol compared to NG for the tested 50% and 75% load at comparable operating conditions.