The chemistry chapter lays the chemical foundation: heterogeneous Langmuir-Hinshelwood and Eley-Rideal mechanisms, modified Arrhenius and sticking-coefficient rate expressions, and coverage-dependent activation energies under the mean-field approximation. The backbone mechanism is that of Koop and Deutschmann for Pt-catalysed oxidation of CO, NO, NOx and C3H6. Because no elementary methanol/formaldehyde mechanism could be merged without violating thermodynamic consistency, two global lumped complete oxidation steps were appended instead.

The model is a 1D, isothermal, steady-state single-channel plug-flow reactor implemented in Cantera [3] as a chain of 200 Continuous-Stirred Tank Reactors (CSTRs) in series. Internal washcoat diffusion is treated explicitly via the Knudsen-regime effective diffusivity and flat-slab Thiele modulus, resulting in a per-slice, per-species effectiveness-factor multiplier. Axial dispersion, external mass transfer and thermal effects are excluded; external mass transfer is instead absorbed into a calibrated catalytic area parameter (Acat/L), fitted against the original Koop and Deutschmann profiles. The two lumped pre-exponentials were calibrated against experimental methanol data (Chantaravitoon, Chavadej, and Schwank) and the Torkashvand et al. formaldehyde mechanism.

Applied to a representative DMDF exhaust gas composition from Liu et al., the model shows the dual-fuel case needs roughly 1.3× the reactor length of diesel-only operation to reach full conversion. Crucially, when total hydrocarbon concentrations are matched, the two cases converge: the longer length is driven by the much higher methanol inlet concentration, not by any intrinsic disadvantage of methanol oxidation. A sensitivity study identifies Acat/L and the methanol pre-exponential as the dominant uncertainty sources, with the formaldehyde pre-exponential significant only in the dual-fuel case.

The thesis concludes that the doubled-design catalyst is likely sufficient for reducing methanol and formaldehyde to acceptable levels at the studied operating points, providing the first numerical basis for a previously unverified design. Key limitations include the decoupling of washcoat thickness from catalytic area (so thicker washcoat unphysically slows conversion), the isothermal assumption, the lumped rather than elementary treatment of methanol/formaldehyde, and the lack of experimental validation, which was identified as the most critical next step, alongside non-isothermal modelling and explicit external mass transfer. ... Read more

The maritime sector requires alternative power generation concepts to decarbonise and reduce greenhouse gas emissions while maintaining the operational performance required for deep-sea shipping. Ammonia is considered a promising carbon-free energy carrier for long-distance marine applications, but its low volumetric energy density, toxicity, and combustion behaviour introduce significant ship integration challenges. This study investigates how AmmoniaDrive, an ammonia-fuelled Solid Oxide Fuel Cell and Internal Combustion Engine combined cycle, can be applied effectively as a marine power generation system.

In AmmoniaDrive, ammonia is used in as the primary fuel for the SOFC system to generate electrical power. The remaining hydrogen-rich anode off-gas is subsequently used as a combustion enhancer in the ammonia-fuelled ICE. The electrical power is used for auxiliary loads and supports propulsion through an electrical machine, while the ICE provides the main propulsion power.

A car carrier was selected as the reference ship due to its standard route, predictable operating profile, high-value cargo, and potential ammonia bunkering at fixed ports. The base-case ship has a length of 199.9 m, a beam of 36.5 m, a service speed of 18 kn, and a cargo capacity of approximately 8,000 CEU and AmmoniaDrive was integrated into the base case without changing the main dimensions and while keeping the operating profile the same.

The results show that AmmoniaDrive can be technically integrated into a car carrier, but not just as a direct replacement for a conventional diesel propulsion system. The main design changes are caused by the ammonia storage and the ammonia power plant. To maintain the required round-trip autonomy, including reserve, the volume occupied by the tank quadruples with respect to the base case. Consequently, the available car deck area decreases by 7.40%.

AmmoniaDrive is a technically feasible concept for car carriers, provided that the ship is designed around the ammonia fuel system. Its feasibility is mainly governed by the cargo capacity loss, emission reduction potential, fuel autonomy, and the technology maturity.
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In 2023, the IMO introduced a new strategy to achieve net-zero greenhouse gas (GHG) emissions by or around 2050, establishing a clear target for ship owners and builders worldwide. In addition, measures are being taken to reduce harmful emissions such as NOx, SOx, and particulate matter. One promising sustainable fuel is ammonia, which offers a relatively high energy density, is easy to store, and emits only water and nitrogen during combustion. Although operating an internal combustion engine (ICE) on pure ammonia remains challenging, stable combustion can be achieved by adding a promoter fuel such as diesel or hydrogen.

A more novel propulsion concept is the use of Solid Oxide Fuel Cells (SOFCs), which electrochemically oxidize hydrogen to generate electricity with high efficiency and very low emissions. Hydrogen is produced by cracking ammonia at the high operating temperatures of the SOFC. However, SOFCs cannot utilize all supplied fuel without complex recirculation, resulting in an anode-off-gas (AOG) that still contains hydrogen.

Because ICEs provide higher power density, better transient response, and lower investment costs than SOFCs, combining both technologies is an attractive solution. In the AmmoniaDrive concept, ammonia is converted efficiently into electricity by the SOFC, while hydrogen in the SOFC anode-off-gas enhances ammonia combustion in the ICE. This hybrid configuration combines the efficiency of SOFCs with the operational flexibility of ICEs.

This study investigates the application of the AmmoniaDrive concept to a 14,000 TEU container vessel. The propulsion system consists of a low-speed two-stroke main engine directly driving the propeller, combined with an electric machine that enables power take-off (PTO), power take-in (PTI), and SOFC-only operation. The SOFC operates continuously, supplying electrical power during sailing, anchoring, and port stays. The system is evaluated for a voyage from Rotterdam to Shanghai via the Suez Canal, including four days in port or at anchor. Simulations consider high and low electrical power demand and three nominal power splits of 16.3%, 21.4%, and 30.4%.

The operational profile is simulated using a Matlab/Simulink model based on earlier work on the AmmoniaDrive concept. The original full-load model was extensively modified to simulate part-load operation of both the SOFC and the ICE. The SOFC model incorporates NTU-based heat exchangers, load-independent heat losses, a minimum cathode airflow, improved temperature control, and an optimized external ammonia cracking strategy using combustion of part of the anode-off-gas. The ICE model retains the five-point Seiliger cycle while incorporating load- and speed-dependent losses, auxiliary blowers for low-load operation, and electric machine models for hybrid power delivery.

The hybrid propulsion system is compared with a conventional reference system consisting of a main engine and generator sets. Fuel consumption is reduced by approximately 10%, 13%, and 16% for the low, medium, and high nominal power split configurations, respectively. Combined system efficiencies generally range from 55% to 70%, with higher power splits and lower propulsion loads resulting in better performance. System efficiency is primarily influenced by SOFC load, ICE load, operational power split, external cracking ratio, and fuel utilization.

Optimal SOFC load is generally between 85% and 100% at high sailing speeds, while the ICE supplies most transient power demand. At lower sailing speeds, SOFC load decreases only slightly, although electric machine limitations may restrict operation. Estimated NOx emissions decrease by 21–39%, depending mainly on the nominal power split. Although these estimates are based on published engine test-cycle data and do not account for hydrogen-ammonia combustion or part-load effects, a substantial reduction in NOx emissions is expected.

An alternative operating strategy, in which the SOFC continuously operates at full load while the ICE supplies all power variations, increases total fuel consumption by only 0.52% on average and slightly reduces NOx emissions. This strategy may improve load-following capability and reduce SOFC degradation. The study demonstrates that ammonia-fuelled SOFC-ICE hybrid systems can efficiently propel large container vessels under varying operating conditions, achieving fuel savings of 10–16% while providing a promising pathway towards cost-effective, CO₂-free shipping. ... Read more

The dredging industry, unlike any other industry, needs to become more sustainable. The trailing suction hopper dredger (TSHD) is a true work horse of the dredging industry, thus emission mitigation of this vessel type would be impactful. A potential candidate for the decarbonization of a THSD, mainly due the absence of carbon and the relatively high energy density, is to use ammonia as a fuel. The power demand profile of a TSHD could be described as capricious and the power density of the vessel type is usually high. To manage the power demand profile of the TSHD, a hybrid system is proposed, consisting of a solid oxide fuel cell (SOFC) and an internal combustion engine (ICE). The system could potentially be an efficient energy conversion system, while exhibiting sufficient transient power capabilities. To enable full provision of the demanded power over the dredger’s complete operational period, an Energy Storage System (ESS) will be added to the system as well. Compared to a conventional ICE-only design, the ammonia-fuelled energy system brings along more complex relations with regards to design and operational aspects. The integration of an ammonia-fuelled power generation system, together with an ESS, in a conceptual TSHD will therefore be investigated. The aim of this research is to clarify the implications on design and operations.

Interpretation of the existing literature mainly results in the usage of a spark-ignited ICE, an external ammonia cracker and a battery as ESS. It also becomes evident that the ICE-SOFC installed power ratio is an important factor, as the SOFC and ICE differ in design and operational characteristics. To obtain further case-specific implications, a time-based simulation approach is adopted. The purpose of the simulation is to investigate the effect of component sizing, to develop an energy management system and to analyse the performance of the system. A thermodynamic analysis of the system and scaling towards the desired operational profile are initially performed. The SOFC is then simulated through a 0D thermodynamic model, and the ICE is modelled too, with the help of a Mean Value Engine Model (MVEM), using a Seiliger cycle. The battery is subsequently simulated with a medium pass filter, concluding with the development of a rule-based energy management strategy. The design-related analysis is based on the following Key Performance Indicators (KPIs): the required energy capacity of the battery and the required onboard space for the drivetrain. While for the operations, the following KPI are assessed: the average system fuel efficiency, the correct balancing of the hydrogen flow, the compliance with the demanded energy during a dredging cycle and the safe operations of the battery.

For the application of the ICE-SOFC system on a TSHD with a capacity of 25.000 m3, it can be concluded that a battery size of 10.0 MWh for the 50-50 ICE-SOFC configuration is required. The required capacity decreases, almost linearly, with increased installed ICE fractions, towards 4.38 MWh in the 80-20 ICE-SOFC configuration. The subsequent volume needed to integrate the ammonia-fuelled drivetrain shows a clear trend; at configuration with the power production ratio of 50-50 ICE-SOFC, the needed space is the largest. When the conclusions with regards to the operations are addressed, it can be stated that the operational profile of the TSHD can be managed by the ammonia-fuelled system. This holds for all the assessed configurations, if the system is controlled by the developed rule-based strategy. While supplying the demanded energy during operations, the integrated ICE-SOFC system shows an average system efficiency ranging from 43.8% towards 45.8%, at varying installed power ratios. When the power production ratio favours the SOFC, the total system efficiency increases. The average supply of hydrogen by the SOFC and average demand of hydrogen by the ICE can be balanced during operations, in each discussed configuration. When the battery performance is assessed, the safety limits of the State of Charge (SoC) and discharge/charge power are never crossed, showing that correct usage for each installed power ratio is possible. All in all, this research contributes towards a better understanding of the application of ammonia as a fuel in TSHDs. Further research is however still required to clarify the exact potential of this technology.
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The increasing numbers of anthropogenic emissions within the maritime sector have caused growing attention for emission-reducing technologies. A promising contributor to emission-reducing ship propulsion methods is Wind-Assisted Ship Propulsion (WASP). A WASP system creates additional forward thrust, assisting the main engine during sailing. The potential impact of WASP on fuel consumption and emissions within the Boskalis fleet remains uncertain. An analysis of the Boskalis fleet is conducted to find suitable vessel types for WASP application. The results of the multiple-criteria decision analysis show that the heavy marine transport vessels are interesting vessel types for WASP. A performance analysis and a general comparison of the existing WASP technologies show that the rotor sail is a suitable technology for these vessel types. Then, a 1-degree-of-freedom steady-state and time-domain model are developed to assess the impact of rotor sails on fuel consumption and emission reductions for the Triumph. These models are developed using operational ship data and estimations of propulsive power efficiencies. Results of the steady-state model indicate that fuel and emissions reductions reach between 3.4 – 5.0% annually for a representative voyage. Results of the time-domain model indicate trip-specific savings. These results suggest that the steady-state model is more suitable for estimating annual performance, while the time-domain model is suited for evaluating specific operating conditions. The Triumph could benefit from the installation of a rotor sail to reduce fuel consumption and emissions. Further development of the model is recommended to improve the accuracy of the assessment of the operational and environmental impact of WASP systems.
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The defossilization of marine power systems remains a central challenge in the ongoing energy transition of transportation. Despite the progress of alternative technologies, the reciprocating internal combustion engine (ICE) will continue to dominate marine applications in the foreseeable future due to its unparalleled robustness, reliability, and efficiency. Shipping’s transition toward carbon neutrality therefore relies on adapting this well-established technology to operate with sustainable fuels.

This dissertation addresses the growing need for sustainable marine fuels by exploring premixed combustion strategies to adopt methanol in marine engines. Because low reactivity of methanol limits its suitability for conventional compression ignition (CI) diesel engines, alternative premixed combustion concepts emerge. Lean-burn spark-ignition (LBSI) and premixed dual-fuel (PRDF) strategies share a premixed combustion concept and robust ignition control. In addition to new engine design architectures, the ability to convert existing diesel platforms to premixed methanol combustion with only relatively minor modifications makes these concepts highly attractive. Given the long operational lifespan of marine engines, such retrofit capability can smoothen and accelerate maritime defossilization. To inform the development of retrofit and next-generation methanol marine engines, this research offers an in-depth examination of these engine technologies, elucidating their potential and limitations.

The primary objective of this dissertation is to develop an experimentally based thermodynamic analysis framework for premixed methanol engine technologies, linking in-cylinder pressure-based and combustion-informed heat release analysis with engine performance indicators. This framework is tailored to the two premixed concepts of LBSI and PRDF. Building on these frameworks, the overarching goal of the thesis is to enhance the understanding of the performance of methanol-fueled premixed concepts, including their distinct combustion behavior, stability limits, efficiency, and emission characteristics. To this end, the frameworks are applied to two marine engine testbeds through targeted experimental campaigns: 1) a 34.7 liter multi-cylinder LBSI engine, and 2) a 4.1 liter single-cylinder PRDF engine.

To realize this research goal, this dissertation first reviews the research landscape of methanol engines and establishes the conceptual basis for the subsequent analysis frameworks. Beyond conducting a comprehensive literature review and identifying research gaps in SI and PRDF methanol operation, the review clarifies the inconsistent terminology used for injection, ignition, and combustion strategies for methanol use. To further address this, a unified classification framework is proposed that links injection and ignition strategies to combustion modes.

Building on this foundation, this thesis introduces a combustion chamber geometry-and concept-driven combustion characterization framework for LBSI multi-cylinder engines and applies it in experimental campaigns using natural gas as a fuel, as the LBSI engine cannot yet run on methanol. By resolving the distinct combustion phasing and linking it to engine performance indicators, this research shows that advancing the transition point at which the flame enters the squish region improves combustion stability as well as brake thermal and combustion efficiency, albeit with increased heat losses and NOx formation. The experimental framework integrates a multi-stage Wiebe formulation as an additional quantitative diagnostic tool for characterizing dual-stage combustion behavior. Because the combustion-phasing framework is rooted in the premixed flame-propagation dynamics associated with the chamber geometry, rather than in fuel-specific properties only, its qualitative conclusions are expected to remain valid for methanol LBSI operation. To this end, the diagnostic approach is deemed conceptually suited for direct application in future methanol-LBSI engine experiments.

Subsequently, this dissertation proposes a methodological analysis framework tailored to methanol PRDF operation. This framework enables both qualitative and quantitative analysis of heat release profiles and is applied in an experimental campaign on the single-cylinder test engine operating at high methanol energy fractions (MEFs). The qualitative analysis reveals three distinct combustion modes—characterized by m-, h-, and n-shaped profiles—unique to methanol PRDF operation, and associates them with specific underlying mechanisms. A systematic quantitative method based on two heat release morphology indicators—the Combustion Mechanism Index (CMI) and Phase Magnitude Ratio (PMR)—is proposed to map and classify these combustion modes. Methanol PRDF operation achieves lower NOx emissions than diesel-only (DO) baseline operation, but at the expense of higher NO2/NO ratios and substantial rise in CO and UHC emissions. While transitioning from DO to methanol PRDF offers potential efficiency gains for marine engines, especially under high-load operation, combustion losses remain the primary barrier. Building on the investigation of MEF effects and leveraging the developed framework, this thesis explores certain boundary conditions to assess their potential in mitigating methanol PRDF challenges. The parametric analysis of intake temperature and intake/exhaust pressures highlights the critical role of boundary conditions in enabling high-MEF, high-load PRDF operation, especially for diesel engines with mechanically controlled injection. Increasing intake temperature enhances combustion, allowing MEF to reach 93% without significant penalties in heat losses or NOx emissions. Similarly, reducing intake pressure enriches the mixture and improves combustion efficiency without compromising the high temperature related aspects. The morphological analysis during this reduction reveals a transition from h-shaped to bell-shaped heat release profiles, indicating a shift in the dominant combustion mechanism from flame propagation toward premixed autoignition.

On a final note, this dissertation aims not only to advance understanding of premixed methanol combustion in large-bore engines but also to provide practical diagnostic methodologies that support research and development of marine power systems powered by sustainable fuels. Therefore, the developed frameworks are intended to be refined and expanded to other engines and fuels, and as such this thesis contributes to more sustainable shipping. ... Read more

This thesis aims to determine whether a battery pack, hydrogen or methanol is the most suitable climate-neutral energy carrier for the next generation of Rijkswaterstaat patrol vessels. The highest plausible required energy storage capacity in three distinct operating region types was estimated. Through iteration of the ship resistance and the power plant weight, the technical feasibility of each carrier was tested in all three region types. It was found that the implementation of alternative energy carriers will require an increase in vessel size and weight if the current operational autonomy is to be maintained. For relatively small operating regions with strict speed limitations, batteries are the most suited carrier, while methanol is best suited for large patrol regions where patrol vessels operate at higher speeds.
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The maritime industry is undergoing a rapid transformation driven by decarbonisation and digitalisation, leading to increasingly integrated and complex onboard systems. Ensuring the robustness of these systems, defined here as a ship’s ability to maintain vital functions despite random component or connection failures, is critical, particularly during early design stages where modifications are less costly. This paper presents a novel robustness evaluation method adapted to ship concept design, utilising network theory to model interdependencies across electrical, control, and data acquisition systems. The method incorporates metrics adapted to maritime engineering, enabling efficient assessment of multiple system configurations and identification of vulnerable components. Applied to five inland vessel concepts varying in automation levels, the results confirm that redundant control options substantially improve robustness, and that elasticity-based metrics provide consistent robustness comparisons across networks of differing sizes. Conversely, classical metrics such as natural connectivity and effective graph resistance potentially exhibit sensitivity to network size, limiting their applicability. The study emphasises the importance of integrating robustness evaluation into early design processes to inform the development of safer, more reliable autonomous vessels. It highlights potential directions for future research, including enhanced failure modelling and statistically based simulations. ... Read more

The maritime industry faces increasing pressure to reduce its environmental impact, particularly through the reduction of greenhouse gas emissions. This thesis investigates the feasibility and technical implications of operating large, low-speed, two-stroke marine engines on hydrogen using low-pressure direct injection. The study addresses the lack of specialized combustion models for hydrogen in large marine engines by developing a tailored in-cylinder thermodynamic combustion model.

A comprehensive literature review highlights hydrogen's unique combustion characteristics, such as high flame speeds, low ignition energy, and wide flammability range, along with associated challenges like pre-ignition, knocking, and NOx emissions. Existing combustion strategies and injection technologies, particularly those adapted from natural gas-fueled engines, are evaluated for their applicability to hydrogen combustion.

The developed combustion model integrates a Seiliger cycle representation enhanced by temperature-dependent thermodynamic properties. It systematically assesses the effects of hydrogen combustion on key engine parameters, including pressure rise rate, peak cylinder pressures, and temperatures, under various operational scenarios. The results highlight the importance of combustion phasing and air-excess ratios in managing hydrogen combustion characteristics, indicating that careful optimisation of injection timing and combustion strategy is crucial to ensure safe and efficient engine operation. Although the model reveals risks associated with aggressive combustion scenarios, such as exceeding mechanical design limits due to high peak pressures, it provides a structured framework for identifying realistic operating conditions for hydrogen LPDI combustion.

This research thus offers critical insights into the technical feasibility and practical limitations of hydrogen combustion in large two-stroke marine engines, contributing valuable guidance for future development and experimental validation efforts. ... Read more

The maritime industry faces growing pressure to reduce greenhouse gas (GHG) emissions and transition toward sustainable propulsion technologies. This thesis investigates the feasibility of employing ammonia and hydrogen as alternative fuels in dual-fuel configurations with diesel for large two-stroke internal combustion engines (ICEs). A voyage simulation model of a post-Panamax container ship (the Duisburg Testcase) was developed in MATLAB Simulink to evaluate fuel performance under voyage conditions. The research includes a review of the properties of ammonia and hydrogen, the development of dualfuel engine models based on the Seiliger process, and the integration of these models into a timedomain voyage simulator. Simulations were performed for diesel, diesel–ammonia, and diesel–hydrogen operation to compare fuel consumption and efficiency. Results show that both ammonia and hydrogen can be more energy efficient relative to conventional diesel operation. Ammonia offers promising scalability and easier storage, while hydrogen achieves higher efficiency but presents greater challenges regarding storage and safety. The developed simulation framework provides a tool for evaluating and optimizing dual-fuel propulsion systems, supporting the maritime sector’s transition to cleaner energy solutions. ... Read more

This review examines research on marine lean burn spark ignition (SI) engines powered with natural gas (NG), focusing on a 500 kWe engine with a flat cylinder head and hemispherical bowl-in piston. These engines demonstrate cylinder flow regimes that significantly affect combustion and heat transfer. The current heat-transfer models can’t capture and assess how cylinder flow regimes influence combustion and heat transfer, as they’re validated on conventional engine testbeds. This creates a gap in accurately simulating heat transfer for marine SI engines, underscoring the need for targeted model assessment. Here, these heat-transfer models are applied, compared, and evaluated under full-scale, multi-cylinder, lean-burn conditions to assess modeling accuracy and sensitivity to key parameters. By identifying which correlation best predicts in-cylinder heat loss, this review lays the groundwork for more reliable thermal modeling and optimized natural-gas spark-ignition (NG-SI) retrofit strategies. ... Read more

Understanding the failure behavior of thin-walled steel structures under large-deformation plasticity and fracture is crucial for assessment of accidental loading conditions. This thesis will experimentally determine the crack propagation direction in a thin steel sheet under different combinations of in-plane strain, which is essential for improving simulations. Necking and crack angles in a commercially available ductile steel sheet (DC01) are determined under various stress conditions, ranging from uniaxial to equi-biaxial tension. A state-of-the-art formability testing method (Marciniak) is adapted to meet the specific needs of this project. Through tensile testing, the Lankford Parameters of DC01 steel are determined, with which a theoretical assumption of the crack angle can be made using Hills theory (1952). By varying the specimen and carrier dimensions, the strain ratio range of −1/2 to near 1 is tested. A Digital Image Correlation (DIC) system is used to measure deformations and strains during the whole deforming process. Pictures taken from the DIC system and post-mortem section cuts allow for the determination of the crack angle with respect to the in-plane and through-thickness directions. The resulting crack angles agree with the theoretical angles determined by Hill (1952) when the frame of reference of determining the crack angles are rotated. ... Read more

To more effectively reduce carbon emissions from ships during op- eration, utilizing hydrogen as a fuel for ship engines has emerged as a promising direction. Given the unique physical properties of hydrogen, targeted modifications to existing engines are necessary for adaptation. In hydrogen-fueled engines, the injection system is a critical component. This study aims to adjust the design parameters of a novel injector to match large two-stroke ship engines and to theoretically demonstrate the feasibility of this novel injector for use in large two-stroke engines fueled by hydrogen.Currently, the ma- jority of hydrogen-fueled engines are four-stroke engines, typically employing high-pressure injection. However, high-pressure injection tends to shorten the lifespan of the injection system, consequently reducing the overall lifespan of the engine. Therefore, this study proposes a low-pressure injection scheme, combined with in-cylinder direct injection, to mitigate the risk of unintended ignition. Given the high autoignition temperature of hydrogen, spark ignition is employed to facilitate ignition. A critical step in evaluating feasibility is determining the appropriate injection timing.Initially, it was es- tablished that hydrogen should be injected after the commencement of the compression stroke to achieve optimal mixing. Subsequently, the study analyzed the in-cylinder pressure variations during the compression stroke to identify the feasible injection window. Finally, the design parameters of the injector were configured to align with these conditions. The findings theoretically demonstrate that this injector can achieve low-pressure direct injection in large two-stroke hydrogen engines.Due to time constraints, the study did not inves- tigate the effects of different injection angles and positions on the engine. Nonetheless, the theoretical analysis confirms the feasibil- ity of employing low-pressure direct injection in large two-stroke hydrogen engines. ... Read more

The problem of global warming is becoming every day more and more pressing, leading to the necessity of reducing harmful emissions especially in the shipping sector. Most ships sail with Internal Combustion Engines, reason why it is beneficial to keep using this system, with the prospect of being able, though, to cut down on the emissions. This can be done implementing new fuels, such as PODE and methanol. These two fuels can largely reduce the emissions without the need for major changes to the engine system. Also, they can be produced in an ”eco-friendly” way, reducing the emissions also during the production process. In this study, the working characteristics of a dual fuel engine, considering methanol and PODE are analysed, as well as the production process of PODE from methanol, process that happens on board of the vessel itself. For the dual fuel engine the analysis showed that different ratios of methanol and PODE can be considered for the dual fuel engine and that this system can deliver the required power output. The plant design resulted in a plant consisting of two reactors and a separation system. At last, the necessary fuel can be produced by a plant that is small enough to fit on the ship and not have to reduce the capacity of the vessel significantly. ... Read more

This graduation thesis studies the CI combustion of ammonia and hydrogen in an ICE. It contains a review of the literature and a modeling study of the ignition and cylinder performance of the AmmoniaDrive test engine. AmmoniaDrive is a NWO-funded research project that aims to decarbonize shipping by introducing an ammonia-fuelled SOFC-ICE power plant for ships and other heavy-duty applications.
Ammonia (NH3) has unfavorable properties for combustion, such as a high heat of vaporization, narrow flammability limits, a high flame quenching distance, low flame speed, and most important: a high resistance to autoignition. Those properties have to be overcome and hydrogen (H2) is known to be capable of playing a role. As the properties of hydrogen are extremely high combustion speed, very wide flammability limits and a very short flame quenching distance. Unfortunately, both ammonia and hydrogen have a high resistance to autoignition, while CI engines need a fuel with low resistance to auto-ignition. For this reason, a carbon-based fuel, like DME or HVO, is considered necessary to achieve ignition.
The state-of-the-art experimentally achieved combustion concepts are an homogeneous charge compression ignition (HCCI) combustion concept of Pochet et al. [2020a] and an reactivity controlled compression ignition (RCCI) combustion concept of Chiera et al. [2022]. The HCCI combustion concept is fueled by NH3 and H2, without a carbon-based fuel. However, it requires a compression ratio (CR) of 22, a high intake temperature, and is limited by the maximum pressure rise rate (MPRR). The RCCI combustion concept is fueled by NH3 and diesel. This concept can achieve up to 81%e NH3, but still requires 19%e diesel.
A modeling study is done to investigate how to improve the CI combustion strategies, taking into consideration the context of AmmoniaDrive. The modeling study consists of two closed volume single-zone thermodynamic reactor models: the ignition model and the engine cylinder model. The ignition model is a constant volume model, resembling top dead center (TDC) conditions. The engine cylinder model simulates a closed volume from bottom dead center (BDC) to 90 CAD after TDC and incorporates volume change and the heat loss. Bothmodels make use of the chemical kinetic mechanism of Shrestha et al. [2018] to incorporate the combustion reaction. Due to the limitation imposed by the available species in chemical kinetic mechanisms, the carbon-based fuel in the modeling study is DME. For the future, hydrotreated vegetable oil (HVO) seems a more favorable carbon-based fuel, based on experimental results in a constant volume combustion chamber (CVCC) of Hernandez et al. [2023].
The results of the two models indicate that an HCCI combustion concept of ammonia and hydrogen, without a carbon-based fuel, will not ignite within the engine limits of the AmmoniaDrive test engine. An HCCI combustion concept of ammonia, hydrogen, with DME will ignite, but has a limited power output due to the MPRR. An RCCI combustion concept with stratification of DME throughout the cylinder looks promising based on the engine cylinder model results. Stratifying DME concentration, and with that the fuel reactivity, is likely to reduce the MPRR. This would allow for a higher power output due to the possibility to injectmore fuel energy without exceeding the engine limits.
Combining the literature and modeling results, it is likely that an RCCI combustion concept with ammonia, hydrogen, and HVO will lead to a higher power output and a decreased required amount of carbon-based fuel, whilst staying within engine limits. ... Read more

To keep the global warming of the Earth to a minimum, the greenhouse gas emissions need to be reduced. Van Oord aims to be carbon neutral by 2050; therefore, Van Oord is exploring alternative fuels. Ammonia is a promising option to use as a fuel due to the forty times lower well-to-wake emissions than MGO when it is produced with green energy. There is no carbon content in ammonia. Furthermore, the expected cost of using ammonia as a fuel is lower than other competitive 'green' fuels, such as hydrogen or methanol, due to the lower storage or fuel fabrication cost of ammonia. The goal of this research is to determine if and when it is economically viable to use ammonia as a fuel to decarbonize a trailing suction hopper dredger (TSHD). This is expressed in cost per dredged material [€/m^3].
Ammonia needs to be handled, stored and consumed taking into account safety precautions to have a safe operable ship. Additionally, ammonia has poor combustion characteristics, and therefore a promoter such as hydrogen (7-11%) or MGO (40-60%) is necessary to initiate the combustion. Additionally, internal combustion engines (ICE) using ammonia as a fuel are expected to have a low transient load capability. Therefore, if there is no MGO present, the dynamic loading capability of the ICE with the load variation of the dredging process is a challenge. The same challenge applies for a Solid oxide fuel cell (SOFC), where the SOFC does hardly have transient load capabilities.
A TSHD currently has an ICE capable of dynamic loading, and the main reasons for this transient load is the change in propulsion power, which is dependent on the friction of the draghead and the sailing speed of the vessel. Furthermore, a sudden change in mixture density in the dredging tube during dredging will result in a sudden transient load. To cope with these transient loads, the energy supply on board of a TSHD must have transient load capabilities.
A fuel consumption model has been developed to compare five drive train configurations for the dredging project Kustlijnzorg with an operational profile of 30 days with respect to the original drivetrain. The total power demand [kW] and the transient load [kW/s] was included on a boolean way in this model. When the power demand or the transient load was too high then the model would stop. By means of this model, the main particulars of the engines, fuel cells and batteries regarding power and energy were determined. The output of this model was the amount of fuel consumed during 30 days. This fuel consumption model was validated with another project.
The Construction Industry Research and Information Association (CIRIA) has developed a method to valuate a TSHD. With this CIRIA methods, the value of a conventional TSHD is determined and compared with the value of the ammonia driven configurations. The value of a new vessel that operates on ammonia can be estimated with the help of a sustainability factor. It is found that the weekly cost of the vessel is mainly dependent on; the value of the vessel, which is dependent on the installed power and cost of technology, the fuel consumption, the cost of fuel and the carbon tax.
Currently, it is not economically feasible to use ammonia as a fuel to decarbonize a TSHD. So, not with an ICE or SOFC. However, when green ammonia is used in combination with a SOFC, then a TSHD can be fully decarbonized. In order to make ammonia an economically feasible option for a TSHD, the price of MGO and carbon has to increase, or the price of the SOFC and ammonia (grey and green) has to decrease significantly.
Currently it is unclear if the carbon tax in the future applies to tank-to-wake (TTW) or well-to-wake (WTW) emissions. If the WTW emissions are taxed, then grey ammonia is never a better choice than MGO in terms of cost. Which is also the case when considering the CO2 equivalent emissions.
To conclude, it is currently not economically feasible to decarbonize a TSHD using ammonia as a fuel based on the cost per dredged material [€/m^3]. The limited transient load capabilities of drive train configurations on ammonia, need a battery or MGO to cope with the transient load of a TSHD. Future progress in the technology or developments in the reduction of transient loads could make ammonia as a fuel for a TSHD a better option. Finally, future developments in the price of: carbon, ammonia and MGO can make it economically feasible to decarbonize a TSHD.
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As a big contributor to the the global emissions, the maritime sector strives to bring down its greenhouse gasses and hazardous emissions by enforcing increasing strict rules on the exhaust gasses. This gives major challenges to the maritime sector to develop greener modes of transportation. This report investigates the in-cylinder starting conditions of spark ignited gas engines, as the starting conditions have a large influence on the efficiency and NOx emissions of gas engines. The investigation is based on experiments performed on a Caterpillar G3508 gas engine. These experiments gave an insight on the starting temperature, pressure and residual mass. With the acquired knowledge on the starting conditions, we improved the induction and volumetric efficiency prediction of a state of the art 0-dimensional engine model [15]. Another contribution of this paper is the development of a way to establish the volumetric efficiency from the amount of oxygen in the exhaust gas, for a natural gas engine. We used this method to check the improvements made to the engine model. Out of the performed experiments, we concluded that the induced inlet mass temperature decreases with increasing power or mass flow. The insight found about the starting pressure for this engine is that the trapped pressure increases in relation to the manifold pressure with increasing power or mass flow. Together with an improved residual mass prediction, these insights resulted in an increase of the volumetric efficiency prediction accuracy by 2% at low powers and 10% at high power. ... Read more

With the increasing concerns of the emission of greenhouse gases and other pollutants and the push towards sustainable and greener means of transportation, there is a need for new drive systems running on alternative fuels. One fuel that holds significant potential as a marine fuel for the future is methanol. When produced utilising carbon capture methods and green energy, it has the potential to be a net zero fuel. Among other high-potential future fuels, methanol has the added benefit of being liquid at room temperature. Additionally, methanol has the potential to be utilised in novel drive systems, such as the combination of a solid oxide fuel cell (SOFC) and a reciprocating internal combustion engine (ICE). This concept utilises the high efficiency and negligible NOx formation of the SOFC, while the ICE provides dynamic load capabilities. This study concentrates on the electrical efficiency of this type of plant for maritime applications.
This work presents an in MATLAB & Simulink constructed first principles based model of a methanol fuelled SOFC-ICE combined cycle. The zero-dimensional SOFC model consists of a temperature controlled methanator which maintains an external reforming ratio of 0.5; a cell mass balance; a cell energy balance, and an electrochemical model. The ICE model core consists of a turbocharged five-state Seiliger cycle. It simulates Wärtsilä 12V31DF fuelled with methanol and dehydrated hydrogen-rich anode of gas (AOG). The SOFC efficiency and its separate losses are evaluated for different temperatures, current densities, fuel utilisation factors UF and steam-to-fuel ratio’s in combined cycle operations. Additionally, the standalone SOFC performance, without the use of waste heat from the ICE and disuse of residual fuel in the AOG, is evaluated, but only for the nominal condition. The ICE efficiency and losses are evaluated for a power range between 1% and 100%. By varying the ammount of cells, the following power splits PSOFC/PICE have been evaluated: 0/100 25/75; 50/50; 75/25 and 100/0. The combined cycle performance is evaluated for different temperatures and current densities.
This study found that while varying the steam-to-fuel ratio and fuel utilisation factor (UF) have minimal impact on the electrical efficiency of the SOFC in combined cycle operations, temperature and current density have a significant effect on the efficiency of the SOFC. For a steam-to-fuel ratio of 1:1, a UF of 0.8, a current density of 5000 A · m−2 and a mean cell temperature of 1073K an efficiency of 58.6% was obtained. The standalone SOFC, or 100/0 power split, obtained an efficiency of 48.4%. The stand-alone ICE genset, or 0/100 power split, operates at a nominal efficiency of 42.3%. When the ICE is used in a direct drive configuration, it corresponds to an efficiency of 43.6%. The combined cycle obtained efficiencies of 45.4%, 49.1% and 53.4% for 25/75, 50/50 and 75/25 power splits, respectively. These results are compared to the results of a similar study investigating an ammonia-fuelled SOFCICE combined cycle for maritime applications, which reported efficiencies of 47%, 50% and 52% for 25/75, 50/50 and 75/25 power splits, respectively, under similar operating conditions.
The efficiency gain of the methanol-fuelled 75/25 configuration compared to the direct drive is limited. This raises the questions about whether the added complexity of introducing an SOFC is justified for the limited efficiency gain. The highest efficiency was obtained with the methanol-fuelled 75/25 power split, but due to the large proportion of SOFC power, it is less tolerant to dynamics in the load, making it questionable whether it can fully meet the dynamic power demand of a ship. Therefore, the 50/50 power split configuration is expected to be the most viable option in terms of both technological feasibility and efficiency gain. A change in the power split to 100/0 results in a decrease in system efficiency due to the lack of waste heat from the ICE and the inability to utilise residual fuel in the exhaust. When considering efficiency, the values for the ammonia fuelled and methanol fuelled plant are similar.
The 50/50 powersplit configuration is 5.6 percentpoints more efficient than the methanol fuelled direct drive ICE and 1.2 percentpoints more efficient than the methanol-fuelled standalone SOFC. This clearly shows the synergistic benefits of combining a methanol-fuelled SOFC with an ICE. However, when compared to the ammonia fuelled combined cycle with 50/50 power split, it is 0.9 percentpoints less efficient. Nevertheless, it is important to exercise caution when drawing further conclusions from this last figure as the model has been constructed at a system level and no thorough uncertainty analysis has been conducted. Furthermore, the requirements regarding the power and energy density are strongly dependent on the type of ship and its operational profile. Therefore, future research should include the implementation of dynamic load capabilities in the model to evaluate its technological feasibility and overall net efficiency gain in various operational profiles of ships. Also, further research is required on the methanol-fuelled ICE cylinder process and the heat integration of the combined cycle.
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Introduction - Hydrofoils are often used for high-performance craft. They enable the hull to rise out of the water and reduce drag. A recurring problem is ventilation, this is the presence of a cavity filled with ambient air on the lifting surface. Ventilation causes the lift of the hydrofoil to decrease drastically. A lot of research has been done on ventilation behaviour. Ventilation remains a stochastic phenomenon to this day. The same operational conditions do not yield the same flow behaviour, a correlation between the pressure on the lifting surface and ventilation behaviour might exist. This research is an intermediate step towards finding a correlation between pressure on the surface of a foil and ventilation, making ventilation repeatable. The main goal of this research is to find out if a full surface pressure reconstruction can aid the search for a correlation between pressure and ventilation.

Method - The test geometry is a NACA0012 surface-piercing hydrofoil with pressure measured using 2 rows of 15 pressure tappings. Extension pieces are used to obtain the span-wise pressure distribution while keeping the submerged span constant. The test program has three sets: all vertical runs (Set 1), high roll angle runs (Set 2), and runs with ventilation (Set 3). During the experiment, the loads are measured with force transducers on a frame that measures forces in 6 degrees of freedom. The calibration of the force transducers is performed prior to the experiment. The calibration of the pressure sensors is done first using a 9 meter water column before the experiment and during the experiment in the towing tank, extra re-calibration (stepped runs) data is collected. The collected force measurement data is processed to attain the lift and drag coefficients. The pressure measurements are translated to the pressure coefficient and placed in a matrix on the right location of the lifting surface.

Results - Based on repeated experimental runs the percentage differences are obtained on sensor and array levels. 30% of the sensors have a percentage difference of more than 10%, while the maximum difference for an entire array is 2.5%. A cross-check between the upper and lower arrays showed a percentage difference above 15% for 28% of the sensors, with a maximum difference of 1.2% at the array level. The pressure distributions at 0∘ roll angle, from Set 1, match the general pressure distribution characteristics. Comparing the 3D lift coefficient computed from the pressure measurements to that of the force data or an empirical method yields ambiguous results. The 3D lift coefficient based on the pressure measurement is within a 4% difference to Xfoil. The result of the high roll angle runs, Set 2, show the effect free-surface proximity has on the chord-wise pressure distribution. For the shallowest pressure reconstructions, close to the free-surface, the pressure distribution shows a minor peak near the leading edge after which the curve drops to near zero quickly. The operational conditions do not affect the quality of measurements. During two runs ventilation occurred, this is Set 3. The time-traces of the three forwardmost sensors show a dip prior to ventilation, with one sensor displaying an oscillating response. It is hypothesised that this is the position where ventilation is induced, but based on the results this can not be proven. All sensor response follows the same pattern when the ventilation bursts over the surface. The set-up is able to capture quick pressure changes.

Conclusion -The percentage difference is too high for too many sensors. On the array level, however, the difference is considered small enough. The results of set 1 are in good agreement with known data. The results obtained at 60∘ roll angle are concluded to be of the same quality as for 0∘ roll. The method is capable of providing results in a wide range of operational conditions. Based on the ventilation runs, no correlation to pressure reading has been found. The time-traces of the sensors near the leading edge of these runs do show fluctuations prior to ventilation. With more ventilation runs available, it is highly likely that a correlation can be established. Due to the slim data set, it is possible that the conclusions drawn will be refuted in the future when a larger data set is available. Currently, the goal has not been achieved, and it cannot be stated with certainty that the method used here to attain a full surface pressure reconstruction can be used to correlate pressure to ventilation. ... Read more

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. ... Read more