Methanol premixed dual-fuel (PRDF) concepts can accelerate shipping defossilization, yet high methanol energy fraction (MEF) operation is often limited by combustion losses and knock behavior. The understanding of how boundary conditions—especially those accessible through retrofit-friendly control levers—influence the performance of methanol PRDF engines remains limited and impedes their high-MEF operation. This paper analyzes results from experiments on a marine-scale single-cylinder methanol PRDF engine at high load and high MEFs. The experiments established the influence of air excess ratio and trapped residual gases on combustion modes, efficiency, and emissions by adjusting the intake and exhaust pressures, respectively. A combined quantitative-qualitative analysis, including heat release morphology mapping, was used to link combustion behavior to performance and emissions. Decreasing intake pressure—richer operation via reduced air excess ratio—substantially improves combustion efficiency with only marginal compromise in heat losses. Increasing exhaust pressure leads to a weaker change in heat release shape than intake pressure, yet it achieves comparable gains in combustion efficiency by retaining hotter residual gas (RG) that promotes methanol combustion during the flame propagation-dominated stage. Heat release morphology shows stronger sensitivity to intake pressure for the sweeps conducted in this study, transitioning from single-peak and bell-shaped to double-peak and h-shaped profiles with increasing intake pressure. This transition indicates a shift from premixed autoignition toward flame propagation. Therefore, retrofit-friendly control levers can steer combustion mode and improve efficiency in high-MEF methanol PRDF operation. As such, this work provides a basis for design-of-experiment-driven optimization and control development.

Creating resilient and multi-layered transportation networks is of paramount importance for modern society, particularly considering the need to respond to a diverse array of risks. These resilient multilayer transport networks appear to share comparable properties with vital multilayer distribution systems found onboard large and complex ships. However, little is currently known regarding the similarities and differences in the design of multilayer networks found in various contexts, such as transportation infrastructure and shipboard distribution systems. This study introduces several multi-modal networks and elucidates their similarities and differences and their design processes. A case study details a typical topology of integrated onboard distribution systems, represented abstractly as a multilayer network to showcase said similarities and differences. The study concludes with the lessons learned from comparing transportation networks with vital onboard distribution systems and provides an outlook for future research into resilient shipboard systems.

Methanol has emerged as a promising sustainable fuel for shipping, with the premixed dual-fuel (PRDF) strategy holding strong potential for deploying it in marine internal combustion engines. However, achieving high methanol energy fractions (MEFs) remains challenging due to combustion stability issues, which limit efficiency and operating robustness. Experimental insights into high-MEF operation are scarce, particularly for large-bore engines, leaving critical knowledge gaps in understanding combustion and performance characteristics of methanol PRDF engines. This study addresses these gaps through an experimental investigation on a marine-scale single-cylinder engine, operating with up to 93% MEF and high-load conditions. Two distinct MEF operational ranges were identified, with different mechanisms limiting each boundary. Poor combustion performance and elevated unburned hydrocarbon emissions emerged as the primary factors limiting high MEFs and were more sensitive to pilot ignition timing than to ignition energy. Although energy from premixed combustion Phase I decreased from 25% at 79% MEF to 6.2% at 93% MEF at maximum load, advancing ignition by a shortened ignition delay (from 9.2 °CA to 4.4 °CA) improved combustion efficiency (from 87.9% to 92.7%) and gross indicated thermal efficiency (from 43.4% to 45.3%). A novel framework was applied to analyze heat release profiles, combining qualitative assessment with a quantitative methodology based on two morphology metrics. This approach revealed three distinct combustion modes—characterized by m-, h-, and n-shaped profiles—unique to methanol PRDF operation, each linked to specific underlying mechanisms, and provides a systematic tool for combustion mode classification.

Ammonia is considered one of the most promising hydrogen and energy carriers for decarbonizing deep-sea shipping and other remote heavy-duty applications. The AmmoniaDrive power plant concept uniquely combines Solid-Oxide Fuel Cell (SOFC) and Internal Combustion Engine (ICE) technology to address the issue of how to convert e-ammonia, produced from renewable resources, into useful on-board power safely and effectively, without the need for fossil fuels as combustion promotor. This paper introduces the AmmoniaDrive concept, outlines the challenging combustion properties of ammonia and ammonia-hydrogen mixtures and provides a short review of Compression Ignition ICE research for ammonia-fuelled engines. Three promising combustion concepts are introduced to give direction to further numerical and experimental research.

Waterborne transport is very important for moving freight and passengers globally. To make this transport more efficient, vessel design must adapt to changing missions, regulations and the occurrence of malfunctions. This paper presents the design of an intelligent decision-support framework to assist marine engineers and vessel operators in updating the system and control architecture of marine vessels before and during a mission. The connection between the system architecture and control design perspectives is enabled using a semantics-based technique. To this end, the multi-level vessel control system is described by a semantic database, a knowledge graph used to connect the components automatically, and quantitative service criteria. Considering the system architecture, the optimal modification is deduced using modularity and complexity criteria, originating from the field of network theory. On the control side, an intelligent automation supervisor is designed to make offline and online decisions regarding the energy deficit to execute a new mission and the active automation configuration during operation. For offline decisions, system architecture modifications are requested by the vessel designers to cover the energy deficit. During operation, switching between hardware and virtual sensors as well as switching between energy management controllers is implemented to handle the effects of sensor faults. The framework is successfully applied to a case study of a tugboat used to adapt to missions with different power requirements, while simulation results are used to indicate its application in supporting the decisions of vessel designers and human vessel operators.

Emerging clean fuels with high octane rating make spark ignition (SI) technology a promising candidate for heavy-duty applications. The conversion of existing diesel engines to SI operation can accelerate the adoption of these fuels. This study investigates the combustion characteristics of a 500 kWe marine lean-burn (LB) homogeneous charge SI engine with a flat cylinder head and a hemispherical bowl-in piston. It focuses on the relationship between fuel distribution and phasing across the distinct bowl-in and squish combustion phases and their impact on efficiency and emissions in multicylinder engines. The effects of air excess ratio, spark timing, and intake air temperature are systematically assessed. Dedicated measurements of methane and total unburned hydrocarbon emissions enable a comprehensive evaluation of combustion performance and emissions. Results confirm the presence of a slower squish phase, differing from conventional SI engines, and highlight the influence of the squish region's surface-to-volume ratio on flame propagation. The sensitivity of combustion behavior to control parameters such as air excess ratio and ignition timing is demonstrated, with notable differences: while richer mixtures advance bowl-in and squish phases, earlier ignition timing delays the squish phase. Despite this, both mixture enrichment and ignition timing advancement improved performance, increasing brake thermal efficiency by 25% and 10%, respectively. Methane emissions remained within typical ranges for marine SI engines and NO_x emissions met Tier III limits at nominal conditions; yet the persistent challenge of methane slip underscores the need for more comprehensive regulatory standards addressing both CH₄ and NO_x emissions.

Renewably produced methanol is a promising fuel for internal combustion engines in long-range transportation thanks to its scalability, liquid storage, and favorable combustion properties. However, the distinction between different injection and ignition strategies for methanol engines and the resulting combustion mechanisms has not been consistently defined. Moreover, diffusion combustion strategies are favored over premixed strategies in large engines because of higher methanol energy fractions, disregarding the advantages of premixed approaches, such as reduced nitrogen oxide emissions and retrofitting opportunities. To address ambiguity in terminology, this paper proposes a classification framework for injection and ignition strategies and applies it to methanol-fueled internal combustion engines. Subsequently, this review focuses on experimental studies of methanol-fueled heavy-duty engines, which are crucial for transitioning to renewable and sustainable energy in long-range transportation. This research summarizes the impact of the reviewed injection and ignition strategies on combustion characteristics, engine performance and emissions to identify key trends. Furthermore, this review highlights how specific design and operating parameters influence premixed dual-fuel combustion, offering insights into optimizing performance and emissions. While mono-fuel and premixed dual-fuel strategies with methanol can significantly promote methanol use in heavy-duty engines and reduce harmful emissions like nitrogen oxides, a rise in unburned hydrocarbon emissions may also be expected, necessitating further research in this area. Additionally, methanol injection location in premixed dual-fuel schemes affects its cooling effect, influencing volumetric and thermal efficiency. Overall, this study deepens our understanding of methanol's impact on heavy-duty engine performance, highlighting critical challenges to be addressed for advancing sustainable transportation.

Waterborne transportation has long been the backbone of global trade, with the reciprocating internal combustion engine (ICE) as the dominant power source. In the efforts to decarbonize shipping, methanol has emerged as a promising alternative fuel due to its easy storability and favorable combustion characteristics compared to non-carbon fuels such as hydrogen and ammonia. In the MENENS project, one of the research objectives is to better understand, further develop, and demonstrate different engine technologies that can employ methanol fuel in marine-sized engines. This study reviews maritime stakeholder research on methanol fuel for marine ICEs, emphasizing the chosen injection and ignition strategies across different engine technologies. In this paper, we aim to identify research gaps concerning methanol as a marine engine fuel, and provide insight into the initiatives and proposed research direction within MENENS.

Spark-ignition (SI) engines emerge as a viable solution for specific marine applications, offering low-noise operation and emissions mitigation, as well as great potential to utilize high-octane number alternative fuels, such as methanol, ammonia, and hydrogen. However, heavy-duty (HD) SI engines still face challenges such as knocking and combustion instability. Particularly for lean combustion conditions, these engines exhibit the most pronounced cyclic combustion variations. This paper investigates the combustion stability of a 500 kW marine lean-burn natural-gas (NG) engine, a promising candidate for reducing emissions in marine applications. We focus on analyzing in-cylinder pressure measurements to quantify combustion characteristics, emphasizing cycle-to-cycle combustion variation, and exploring the influence of operating parameters like spark timing (ST) and air excess ratio (λ). Our findings demonstrate a clear trade-off between NO_x and COV_IMEP emissions through variations in the λ and ST. We identified a transition zone characterized by an increasing number of late-burning cycles at higher λ, before partial burning cycles began at further dilution. Following this, we established a new threshold of 6% for COV_IMEP to determine unstable combustion. Notably, increasing dilution from a λ of 1.12 to 1.61 decreased NO_x emissions from 17.83 g/kWh to 0.16 g/kWh, well below IMO Tier III standards, while COV_IMEP increased from 1.72% to 13.42%. These insights highlight the potential for advancing SI technology for marine applications and the need for further research to optimize both combustion and emissions in such engines.

Reduced crewing concepts require a higher level of control and integration of platform systems. A clear reliability assessment of these systems in early design stages reduces the need for alternations in later design stages but remains challenging to perform. This paper addresses the design of reliable and integrated onboard systems such as cooling water, power distribution, and control systems. Current approaches to making platform systems more reliable, such as redundancy, modularity (independent subsystems) and reconfigurability, are analysed from a network theory perspective. Current graph measures do not align with experience-based requirements for improving system robustness. Our method combines the principles of network theory and experience-and rule-based system requirements to provide a comprehensive framework for a reliability comparison of integrated multilayer platform systems (distributing more than one type of flow). The robustness requirements are translated into network metrics to facilitate a quantitative trade-off typical to the early stages of the design process. The case study offers a preliminary view of the system topology of a notional naval vessel, consisting of power distribution, cooling water distribution and control systems. The network metrics facilitate an assessment of the system’s reliability compared to alternative system topologies with differentiating numbers of nodes, edges and density. This study finds varying dependencies of the robustness metrics on the network properties, shining new light on whether and how one should compare distribution system robustness.

Current EEDI (Energy Efficiency Design Index) regulations striving to reduce the installed engine power on new ships for a low EEDI may lead to underpowered ships having insufficient power when operating in adverse sea conditions. In this paper, the operational safety of a low-powered ocean-going cargo ship operating in adverse sea conditions has been investigated using an integrated ship propulsion, manoeuvring and sea state model. The ship propulsion and manoeuvring performance, especially the dynamic engine behaviour, when the ship is sailing in heavy weather and turning into head sea, have been studied. According to the results, the dynamic engine behaviour should be considered when assessing the ship operational safety, as the static engine operating envelope is inadequate for the safety assessment. The impact of PTO/PTI (power-take-off/in) operation and changing propeller pitch on the ship thrust availability in adverse sea conditions have also been investigated. To protect the engine from mechanical and thermal overloading, compressor surge and over-speeding during dynamic ship operations and/or in high sea states, the engine and propeller should be carefully controlled. The paper shows that if in (heavy) adverse weather the propeller pitch can be reduced or if the shaft generator can work as a motor (PTI), more thrust can be developed which can significantly improve the operational safety of the ship.

Analysis of ship propulsion system performance is often performed using detailed hydrodynamic models to assess load changes, which are subsequently compared to static engine limits, or by detailed engine models that are rarely integrated with sufficiently detailed propulsion models for load change estimation. To investigate the dynamic engine (overloading) behaviour and ship propulsion performance under various heavy operating conditions, a Mean Value First Principle Parametric (MVFPP) engine model is integrated into a ship propulsion system model in this paper. An upgraded thermodynamic-based MVFPP model for two-stroke marine diesel engines is presented, in particular a newly developed MVFPP gas exchange model. Based on the integrated propulsion system model of a benchmark ocean-going chemical tanker, the engine dynamic behaviour during ship acceleration, deceleration and crash stop has been investigated. Results show that, during dynamic processes, the engine could be thermally overloaded even if the engine power trajectory is inside the static engine operating envelope. The paper contributes to finding proper indicators for thermal overloading of modern two-stroke marine diesel engines. It is demonstrated that when matching the engine with the propeller and designing the ship propulsion control system, not only the static engine operating envelope, but also the dynamic engine behaviour should be considered.

The current literature on solid oxide fuel cell and internal combustion engine (SOFC-ICE) integration is focused on the application of advanced combustion technologies operating as bottoming cycles to generate a small load share. This integration approach can pose challenges for ships such as restricted dynamic capabilities and large space and weight requirements. Furthermore, the potential of SOFC-ICE integration for marine power generation has not been explored. Consequently, the current work proposes a novel approach of SOFC-ICE integration for maritime applications, which allows for high-efficiency power generation while the SOFC anode-off gas (AOG) is blended with natural gas (NG) and combusted in a marine spark-ignited (SI) engine for combined power generation. The objective of this paper is to investigate the potential of the proposed SOFC-ICE integration approach with respect to system efficiency, emissions, load sharing, space and weight considerations and load response. In this work, a verified zero-dimensional (0-D) SOFC model, engine experiments and a validated AOG-NG mean value engine model is used. The study found that the SOFC-ICE integration, with a 67–33 power split at 750 kWe power output, yielded the highest efficiency improvement of 8.3% over a conventional marine natural gas engine. Simulation results showed that promising improvements in efficiency of 5.2%, UHC and NOx reductions of about 30% and CO₂ reductions of about 12% can be achieved from a 33–67 SOFC-ICE power split with comparatively much smaller increments in size and weight of 1.7 times. Furthermore, the study concluded that in the proposed SOFC-ICE system for maritime applications, a power split that favours the ICE would significantly improve the dynamic capabilities of the combined system and that the possible sudden and large load changes can be met by the ICE.