Hydrogen economy is spreading across the maritime sector in response to increasingly stringent regulations for shipping emissions. The challenging on-board hydrogen logistics are often mitigated with hydrogen carriers such as methanol. Research on methanol reforming to hydrogen for fuel cell feed is conducted mostly in steady state, overlooking dynamic reactor operation and its effects on the power production system. Forced reactor operations induce fluctuations of CO content in the reformate potentially harmful to the PEM fuel cell, and drops in methanol conversion causing inefficient operation. In present research, simulations with a physical 2D unsteady model of a packed bed methanol steam reforming reactor resulted in methanol conversion drop durations of up to a minute. Additionally, temporary increases of CO content up to 112% were observed. Throughput ramp ups most notably impact the conversion, while ramp downs negatively affect selectivity. The investigation on reactor geometry concludes that larger tube diameters increase transient time and CO spikes, while they decrease with reactor length. Amplified unsteady effects are also observed with larger changes in input process variables. The results imply that heat transfer rate to the reactor are most often the detrimental factor for transient effects and durations in practice. Following this work, inclusion of realistic heating methods is recommended, instead of uniform tube temperatures used in present simulations. Heating system characteristics are necessary for realistic evaluation of the methanol reformer constraint on fuel cell feed demand in fully integrated systems.

The maritime sector aims to achieve short and medium-term sustainability targets through the conversion of Internal Combustion Engines to methanol operation. For small to medium sized engines, Port Fuel Injection (PFI) is the most viable injection method to achieve this conversion. However, the knowledge of the behaviour of methanol in combustion engines, particularly its spray characteristics under PFI conditions, is limited. To better understand liquid methanol sprays, this paper studies the injection of methanol in marine PFI conditions through Computational Fluid Dynamics (CFD) modelling. The CFD models use the Lagrangian-Eulerian (LE) coupling method within the Reynolds Averaged Navier Stokes (RANS) turbulence framework. Numerical results were validated using dedicated methanol experiments from the literature for both high and low injection pressures. Subsequently, this predictive CFD framework was used in a number of different injection pressures with scaled injection quantities that represent marine applications. Moreover, we demonstrated that high injection pressure improves atomisation and, thus, evaporation prior to wall impingement. This work strongly contributes to our understanding of marine PFI methanol engines by modelling fuel quantities relevant for ship applications. Our approach can be implemented in full engine simulations to solve evaporation challenges often found in small-bore methanol marine engines.

Methanol is a promising alternative fuel, which can assist in reducing emissions in heavy-duty dual-fuel (DF) compression ignition (CI) engines. In medium and large bore marine engines, DF operation is achieved through either direct injection (DI) or port fuel injection (PFI) of methanol with diesel acting as a DI pilot fuel for ignition. However, the injection of methanol presents a significant challenge due to its high latent heat of vaporization and decreased lower heating value (LHV) compared to diesel. Therefore, for the same energy content operation, methanol requires around eight times the amount of heat to evaporate completely in comparison to diesel, which results in lower in-cylinder temperatures. This charge cooling effect leads to a strong negative temperature gradient influencing ignition and flame propagation. This paper aims to quantify the cooling effect of methanol in a heavy-duty dual-fuel DICI engine environment. The presented methodology uses Computational Fluid Dynamics (CFD) simulations to model methanol sprays with validation originating from the Engine Combustion Network (ECN) Spray D experimental data. The CFD models operate within the Lagrangian-Eulerian framework in CONVERGE-CFD using the Reynolds Averaged Navier Stokes turbulence modelling. Compared to diesel, injecting methanol with the same energy content exhibited up to 100 K more decreased temperature within the mixture. Consequently, this cooled mixture may pose challenges to combustion stability due to the intense temperature gradients. Nonetheless, lower mixture temperature decreases NOx emissions, which can prove beneficial for high methanol energy fractions in dual-fuel DICI engines.