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

The maritime industry is a major contributor to global emissions, particularly carbon dioxide (CO₂) and nitrogen oxides (NOₓ), which has led to increasingly strict environmental regulations from organizations such as the International Maritime Organization and the Paris Agreement. These regulations are driving the search for sustainable alternatives to conventional fossil fuels in marine internal combustion engines. Methanol has emerged as a promising candidate due to its potential for renewable production, its liquid state under ambient conditions, and its ability to reduce harmful emissions compared to fuels like diesel. However, its adoption presents challenges, especially in fuel injection and mixture formation, due to its distinct physical properties such as high latent heat of vaporization, higher vapour pressure, and lower energy density. As most existing models are based on conventional fuels, there is a lack of understanding of methanol spray behaviour under realistic engine conditions.

This PhD thesis addresses these challenges by developing a computational fluid dynamics (CFD) framework using CONVERGE-CFD, incorporating both Reynolds-Averaged Navier–Stokes (RANS) and Large Eddy Simulation (LES) approaches. The framework is used to analyse methanol spray behaviour in conditions relevant to marine engines, covering both port fuel injection (PFI) and direct injection (DI). The study begins with a literature review that introduces a unified classification of methanol injection and ignition strategies, clarifying existing definitions and identifying knowledge gaps. The modelling framework is then validated using experimental data and applied to investigate atomization, evaporation, and spray dynamics under different injection conditions. Results show that while higher injection pressures improve atomization, evaporation remains limited, and spray-wall interactions play a dominant role in mixture formation.

Further analysis under direct injection conditions reveals unique spray phenomena specific to methanol, such as plume collapse and sweeping, which are successfully captured through careful model calibration. The research also examines methanol use in dual-fuel engines, highlighting the significant cooling effect caused by its high latent heat. This cooling can reduce local temperatures by up to 100 K, potentially hindering combustion and increasing variability. Overall, the study provides a validated and efficient modelling framework that improves understanding of methanol spray behaviour and supports the optimisation of methanol-fuelled marine engines, contributing to the transition toward more sustainable maritime energy systems. ... Read more

This thesis explores the potential of Variable Speed Generators (VSGs) within hybrid DC power systems for next-generation Anti-Submarine Warfare (ASW) frigates. As naval operations increasingly prioritise efficiency, emissions reduction, and adaptability to transient load variations, VSGs present a compelling alternative to conventional fixed-speed AC generators. While VSGs offer notable improvements in fuel efficiency, their transient performance under dynamic operating conditions remains a critical area of investigation. To assess these dynamics, a mean value simulation model was used and validated against Factory Acceptance Test (FAT) data and naval standards. The findings reveal a fundamental trade-off: although VSGs enhance fuel efficiency in steady-state operations, their transient response presents challenges, particularly in thermal management and stability. Slow turbocharger dynamics lead to prolonged inadequate air excess ratios during load transitions, resulting in incomplete combustion, excessive soot formation, and increased thermal stress. Additionally, VSGs exhibit difficulties in managing speed and voltage fluctuations during abrupt load changes. Despite these challenges, the study identifies several potential solutions, including electrically assisted turbochargers, advanced energy storage systems, and hybrid control strategies. These innovations can mitigate transient inefficiencies, enhancing both stability and responsiveness. In conclusion, while VSGs represent a significant advancement in naval power systems by combining fuel efficiency with operational flexibility, their successful integration requires targeted improvements in dynamic performance and system-level optimization. By addressing these limitations, VSGs can evolve into a more resilient and robust power solution for next-generation naval vessels. ... Read more

The development of shipboard DC power systems promises significant operational and economic benefits but faces major challenges in primary distribution, protection, and power scalability. As DC technology continues to mature, many aspects of shipboard implementation remain insufficiently defined to guarantee both safety and efficiency. Current regulatory standards are incomplete, and protection strategies often rely on outdated or inadequate frameworks. Unipolar and bipolar bus architectures each offer application-specific advantages, and the strategic placement of power electronics opens new possibilities for centralized and distributed switchboard designs. However, protection architectures still face limitations: breaker-based approaches rely on slow fuses, mechanical circuit breakers, or emerging solid-state circuit breakers, while power electronics–based protection, embedding protective functions within converters, remains underdeveloped. Furthermore, the low production rate of vessels and the varied power demands across applications often force designers to employ commercial off-the-shelf converters, raising challenges in modular topologies, scalability, and overall protection strategy.

This research addresses protection challenges through a multi-stage investigation into shipboard DC systems and power electronics for DC protection. First, a
use case–based categorization of short-circuit events in primary DC systems is proposed. A detailed fault inventory is compiled using a reference 5 MW superyacht model, providing simulation-based short-circuit data for diverse operational scenarios. The study contributes: (1) a comprehensive short-circuit inventory, (2) a qualitative fault categorization, and (3) design recommendations for power converters in shipboard DC systems. This work emphasizes that systematic fault classification is critical to understanding the impact of different short circuits and to guiding both protective device design and regulatory evolution.

In parallel, the thesis advances the state of the art in DC fault protection hardware. A high-speed solid-state circuit breaker (SSCB) is developed, integrating
a latching current limiter to prevent unnecessary tripping during transient overcurrents. Supported by a custom gate driver and controller, the SSCB prototype
achieves a clearing time of approximately 200 ns, substantially reducing system stress during faults. Both SPICE simulations and experimental tests confirm its
capability to properly operate under diverse fault conditions while requiring low complexity upgrades.

Finally, a proof-of-concept DC–DC converter with embedded protection is demonstrated. The proposed protection module, based on the electronic capacitor concept, is integrated into a 10 kW bidirectional LLC converter. Placed in series with the DC-link capacitor, the module significantly reduces processed power and conduction losses compared to conventional series-breaker configurations. Experimental validation confirms that the approach is compatible with fuse-based selectivity strategies while offering rapid fault isolation and reduced design complexity.

Collectively, this thesis provides a comprehensive framework, from system-level fault categorization to device-level protection design, supporting the safe and scalable adoption of shipboard DC systems. The proposed solutions and prototypes contribute to addressing essential protection challenges, favoring the widespread adoption of DC systems in various applications, by offering more efficient, compact, and safe DC systems, which ultimately play an important role in the transition of energy for transportation in general. ... Read more

This dissertation addresses the increasing global demand for reducing greenhouse gas emissions in the maritime industry. It provides methods and results on ship energy performance assessment and enhancement using high-frequency operational data. These methods can be used to inform operator decisions to increase operational performance, to assess modifications to power and propulsion systems and its control strategies and to evaluate hybrid propulsion and power generation systems for future ship design for ships with similar operating profiles and conditions. The developed methodologies can be implemented on a wide range of ship types and missions, particularly on vessels with highly uncertain mission profiles and operating conditions. The case in this work is the Holland class Ocean-going Patrol Vessels (OPV) of the Royal Netherlands Navy, which are multi-function ships, equipped with hybrid propulsion, that operate a very diverse operating profile worldwide.

First, this study examines the energy performance assessment of ships, discussing the limitations of existing energy efficiency measures such as the EEDI, EEXI, SEEMP, and CII, which do not fully account for operational and environmental uncertainties. It suggests a methodology to enrich datasets of operational data in case certain parameters are not logged, and it provides a number of qualitative and quantitative tools in the assessment of operational and environmental uncertainty, and energy performance, at a ship and component level. In this way, this methodology provides conclusions on design and operational decisions, such as the decision to equip vessels with hybrid propulsion.

Secondly, this research introduces a digital twin modelling approach for energy performance prediction using high-frequency operational data. This steady state approach combines statistical and well established first-principle techniques to model system components and compensate for the accuracy of sensors and uncertainties linked to information provided by the manufacturers and shipbuilder. Results demonstrate the effectiveness of the adopted approach to predict carbon intensity over more than seventy different and diverse actual sailing intervals with high accuracy. The model shows not only a mean absolute percentage error of less than 5% on predicting instant fuel consumption on both mechanical and electrical modes, but also a carbon intensity prediction accuracy within 2.5% with a 95% confidence interval, which justifies a significant improvement over traditional models.

Finally, this study examines the design optimisation of ship energy systems. Building on the conclusions of the previous chapters, it examines the topology selection and sizing problem for the case study class of vessels. This chapter proposes a robust multi-objective optimisation framework using actual sailing profiles. It proves its robustness using actual sailing profiles of different vessels of the same class, and it examines new designs with environmental, financial and technical objectives. Results highlight the importance of accounting for realistic operational and environmental conditions in the design of ship energy systems, but also the environmental and financial benefits of design by optimisation methods.

As a final note and recommendation, this dissertation encourages the collection and use of operational data in design and operational decisions, and it offers tools and directions in which carbon emissions of ship operations can be reduced in a financially and technically viable manner. ... Read more

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

The company H2 Marine Solutions has designed a zero-emission hydrogen powered boat. This boat is compared to its fossil fuel counterpart more than twice as heavy. The reason for this is that the system components that are used in the hybrid powertrain of the hydrogen powered boat are heavier. The main question of this research is: How can we establish the optimal energy and power of the system components of a hybrid power system with optimal energy management for a zero-emission hydrogen powered boat for different operational profiles? This results in a sizing and control optimization problem. Because these two problems are coupled this is a multi-objective double-layer optimization problem. The most popular strategy to solve this problem is with the control problem nested in the sizing problem \cite{Hybrid-ship}. The most popular algorithms to solve these problems are evolutionary algorithms.

Unfortunately due to the complexity of these algorithms and due to lack of time the sizing and control problems are solved separately in this research. First, the system components of the plant are described and modeled. The components that are modeled are the battery, the fuel cells, and the DC/DC converter. To find the optimal energy management strategy an online optimization strategy is used. This is done because the problem is solved in real-time than and could be used in a real application. The strategy that is chosen to solve the control problem is the Equivalent Consumption Minimization Strategy (ECMS). This strategy translates the electrical energy from the battery into equivalent hydrogen consumption. For every timestep, the equivalent consumption is minimized by the ECMS. Because there are different variants of ECMS three of these variants are discussed and compared in the research. Also, two rule-based energy management strategies are compared. The sizing problem is described by linear equality and inequality constraints. The problem is solved by the Linprog function in Matlab. The objective of the sizing problem is to minimize the weight of the system components. The input in the sizing problem is the energy and power demand of the most energy intensive operational profile. After solving the sizing and control problem the results are combined and the different operational profiles are used as input to show the robustness of the optimization.

The three different energy management strategies all minimize the instantaneous equivalent consumption but show different behaviors when controlling the system components. The optimal energy management strategy is the Smooth Adaptive Penalty (SAP)-ECMS. With this controller, the fuel cells work on a steady operating point and ramp up and down the output power smoothly when necessary. Due to this behavior, the average efficiency of the fuel cell is the highest, and the hydrogen consumption is the lowest compared to the other controllers. The results of the sizing problem show that the weight will decrease when a bigger fuel cell is used in combination with a smaller battery. The consideration between a bigger fuel cell and a smaller battery is a consideration between lower weight and more hydrogen consumption. When a bigger fuel cell is used it is recommended to implement an optimal energy management strategy such as the SAP-ECMS to control the output power of the system components. This is preferable above a rule-based controller which can not find the optimal operating point at all timesteps. Even better energy management strategies may exist or could be made by combining different ECMS's. When the sizing and control problem are solved in a nested strategy more accurate results could be achieved. ... Read more

Progressing targets on GHG emission reduction urge the the Netherlands Ministry of Defense (NL MoD) to reduce the use of fossil fuels, as they announced to contribute to the Paris agreement by reducing its dependency on fossil fuels by at least 70% by the year 2050. However, without sacrificing striking power, because future naval combatants need to perform their operations on the highest end of the violence spectrum and need to have sufficient autonomy to perform their operations at sea independent of logistic supply lines. The Royal Netherlands Navy (RNLN) is investigating the replacement of the Air Defense and Command Frigate (LCF) between 2030 and 2040 by a Large Surface Combatant. As it will be impossible to achieve substantial reduction of GHG emissions through energy-saving technologies, sustainable fuels need to be implemented in the design. In this thesis, the impact of sustainable fuel choice on the design of Large Surface Combatants with a displacement of around 6000 tonnes is assessed. In particular, the current and future developments of sustainable methanol and diesel have been reviewed from existing literature and are examined on the replacement Large Surface Combatant: specifically their advantages, disadvantages, production routes, future production cost estimates and availability to give an understanding which pathways can help the NL MoD to achieve their stated GHG emissions reduction goals. Furthermore, three different design concepts are presented with respect to fuel composition from which the impact of the established fuels is quantitatively examined. First, sustainable diesel is a drop-in fuel, which makes blending of sustainable diesel with fossil diesel possible in the existing infrastructure allowing a gradual transfer from fossil diesel to sustainable diesel. However, the production is less efficient in a well-to-wake approach and the cost of Bio-diesel and E-diesel is 5% to 30% more expensive with a mean estimated additional cost of 6 €/GJ compared to methanol. Secondly, operating on methanol has a significant impact on the design of a large surface combatant: the specific energy of methanol is more than twice as low as diesel and the ship needs a longer machinery space to allow for a diesel engine propulsion configuration. This results in a increase in displacement of 20%. Finally, navies could consider a two-fuel strategy: sail on methanol during operations with limited autonomy, typically in peace time, and operate on diesel during operations with high autonomy, during war time operations. In this case the design needs to include both diesel and methanol fuel systems and additional space for methanol safety measures. This results in a increase in displacement of 4%. However, the range when operating on methanol is reduced to 2187 nm compared to a 5000 nm baseline range. Assessing the impact of sustainable methanol and diesel for Large Surface Combatants at this level of detail and considering a two-fuel strategy is novel for the field. The results can be used by the Royal Netherlands Navy to compare the different concepts and serve as an indicative substantiation in the acquisition of a new Large Surface Combatant. Moreover, it can help in forming the strategy to migrate future naval combatants from current fossil fuels to future sustainable fuels. ... Read more

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. ... Read more

The shipping industry is forced to reduce its emissions and underwater radiated noise in order to decrease the impact on the environment and limit global warming. Moreover, a low acoustic signature can be lifesaving for a navy ship, especially during submarine on mine threats. To be able to operate as flexible as possible under these threats, a flexible propulsion plant is required. A diesel engine with a controllable pitch propeller (CPP) is contributing to this. A method to reduce the emissions and noise of such a plant is to improve the control strategy. Often this is tested with numerical models. However, frequently they contain many simplifications of reality, for example, the neglection of several hydrodynamic effects. Hardware In the Loop (HIL) takes these effects into account by replacing a software part of the model with a hardware component. In this research, the CPP is the scaled hardware part. A feasibility study is performed to determine whether a propeller open water HIL setup can be used to simulate the dynamic behaviour of the propulsion plant. Therefore, a comparison is made between full and model scale numerical simulation of a diesel engine with a CPP controlled by adaptive pitch control (APC). To reduce the pitch actuations with the APC strategy a Kalman filterwith deadband is implemented. Full-scale simulations with irregular waves demonstrated that the pitch actuations could be reduced during acceleration and at a constant speed. The validated full-scale model is Froude scaled and implemented in a model of the open water HIL setup. The results of the full and model scale simulations are very similar. Thus, the HIL setup can be used to simulate the dynamic behaviour of a propulsion plant. However, the hardware limitations such as the backlash in the CPP blades, the low sample rate of the actual pitch and the Froude dissimilarity of the acceleration of the towing tank need to be resolved to ensure the scaled simulations are representative for the actual, full scale, vessel. Due to these limitations, it is not possible to use the setup at this moment to perform experiments and improve novel control strategies. If these physical limitations of the current HIL setup are overcome, the effect of the propeller and the pitch control strategy during turns can be investigated by performing experiments with oblique inflow. ... Read more

In recent years, ships are expected to improve energy efficiency and reduce carbon emissions. For naval vessels, it is important to be able to maintain their mission profile. It is therefore required to provide real-time advice to the ship’s crew on the optimal speed and propulsion mode settings that include the actual environmental conditions. This paper proposes a novel machine learning approach to establish the ship’s fuel consumption per mile for the actual environmental conditions and develop fuel consumption curves for the various propulsion configurations. The proposed approach uses a multi-layer perceptron (MLP) model to establish the ocean parameters based on the own ship data, with an accuracy of 4.150 %. Using these ocean parameters combined with the own ship data, the fuel per mile is predicted and fuel consumption curves are established using an MLP-model, with an accuracy of 1.551 %. This thesis shows that the proposed approach makes it possible to help a ship’s crew make well informed decisions to reduce their CO2 emissions in real time while still meeting their mission profile. The proposed approach is especially useful for military operators since there is no need for external data sources. Further research is identified to optimize the proposed approach using a dataset containing a higher variety and number of environmental conditions and propulsion modes to improve and validate the fuel consumption curves for the entire spectrum of speeds, environmental conditions and propulsion modes. ... Read more

The time a naval combatant can be deployed for a mission is limited by its dependency on supplies. At a certain point the ship needs to leave the area of operations to be replenished in a harbour or by a support ship. Moreover, the Royal Netherlands Navy has a societal obligation to reduce its environmental impact, in particular on global warming. Therefore, the Royal Netherlands Navy (RNLN) wants to reduce the fossil fuel dependency of its fleet significantly [50]. One of the methods to reduce fossil fuel dependency of ships is to reduce their energy requirement.
The operational profile of fast naval combatants for the RNLN requires that the ships operate on the diesel engines for 90 percent of the time, often in part load. In part load, the turbocharger cannot supply the engine with the right amount of charge air. This results in a limited operating envelope for the diesel engine, and a decreased efficiency in part load. This is caused by the matching of a turbocharger, which is a compromise between high efficiency in the design point, and off design performance. However, in part load, advanced charge air configurations can potentially resolve this and improve the results as shown by Grimmelius et al. [15] and Zhang et al. [56]
This study investigates the effect of advanced charge air configurations on the efficiency and acceleration performance of diesel engines in hybrid configurations aboard fast naval combatants. First, two mean value first principle diesel engine models based on the work of Geertsma et al. [12] were used to model the diesel engine. Next, the models were partly validated with ship data. We found that an approach using compressor maps and a motion based turbocharger model was most accurate. Then, a parallel-sequential turbocharger and a hybrid electric turbocharger were incorporated into the model. A hybrid turbocharger is a turbocharger with an electric machine coupled to the turbocharger shaft. The electric machine can increase the turbocharger speed to boost the charge air pressure in motor mode. Also, in generator mode excessive power from the turbocharger shaft can be taken out and utilized elsewhere. It was concluded that the application of advanced charge air configurations can significantly improve the engine efficiency in part load. For example, in a diesel hybrid propulsion configuration with power take-off this can lead to an efficiency increase of almost 10% at 20% load in comparison with a single charged engine. Furthermore, hybrid turbocharging enables extending the operating envelope of a parallel-sequential turbocharged engine with up to 25% at 60% engine speed. This enables the engine to deliver constant torque from 600 to 1000 rpm. With these concepts therefore, both improved efficiency and improved acceleration performance can be achieved.
... Read more