Risk-based design of marine pressure hulls require computationally efficient and precise models predicting collapse pressures of ring stiffened cylindrical shells as a function of realistic geometrical imperfections. However, the empirical interframe collapse models commonly implemented in design codes do not explicitly depend on imperfections, and the existing analytical models are only valid for axisymmetrically imperfect shells. The goal is to derive an analytical model that explicitly depends on axisymmetric and asymmetric imperfections. In order to derive such a model, first the stress development is investigated using the nonlinear Finite Element Analysis (FEA) of twelve marine pressure hulls having axisymmetric imperfections only. The knowledge gained from these investigations is used to qualify three collapse models. One of them, the integral model introduced by the authors, is accurate and sufficiently precise. It uses a new definition of interframe collapse, which also allows for asymmetric imperfections.

@en

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.

@en

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.

@en

Hybrid propulsion and using liquefied natural gas (LNG) as the alternative fuel have been applied on automobiles and some small ships, but research investigating the fuel consumption and emissions over the total voyage of ocean-going cargo ships with a hybrid propulsion and different fuels is limited. This paper tries to fill the knowledge gap by investigating the influence of the ship mission profile, propulsion modes and effects of different fuels on the fuel consumption and emissions of the ship over the whole voyage, including transit in open sea and manoeuvring in close-to-port areas. Results show that propulsion control and electric power generation modes have a notable influence on the ship's fuel consumption and emissions during the voyage. During close-to-port manoeuvres, propelling the ship in power-take-in (PTI) mode and generating the electric power by auxiliary engines rather than the main engine will reduce the local NOx and HC (hydrocarbons) emissions significantly. Sailing the ship on LNG will reduce the fuel consumption, CO2 and NOx emissions notably while producing higher HC emissions than traditional fuels. The hybridisation of the ship propulsion and using LNG together with ship voyage optimisation, considering the ship mission, ship operations and sea conditions, will improve the ship's fuel consumption and emissions over the whole voyage significantly.@en

Naval ships are designed to operate and survive in hostile environments. As such, vulnerability reduction is a major topic of interest during the design of a naval ship. For modern naval ships the vulnerability is largely determined by the design and layout of distributed systems. The vulnerability of these systems needs to be assessed early on, as design decisions made in this stage are decisive for the vulnerability of the final ship. Various early stage methods for assessing vulnerability exist, but a clear structure on when to use what types of methods, how these methods relate to each other, and how these methods provide relevant answers, is still lacking. To address this gap, this paper introduces a framework for early stage design of distributed systems, in the context of vulnerability reduction. This framework supports in choosing the right vulnerability method at the right design stage. The framework considers an operationally oriented systems perspective on vulnerability, and a physically oriented ship perspective. In addition to that, early stage design is subdivided in concept exploration and concept definition, which have different purposes and contributions in the design process. The framework provides examples of methods that can be used to investigate vulnerability for the various perspectives and design stages. These examples consider methods that have been developed by joint Delft University of Technology (TU Delft) and the Netherlands Defence Materiel Organisation (DMO) research efforts, as well as other methods. Opportunities and challenges for integrating these methods between themselves and in the design process in general are discussed.@en

The increasing economic cost and environmental impact of maritime transportation necessitate the reduction of fossil fuel consumption of ocean-going cargo ships. Although fundamental ship propulsion system theory is well-known and is at a mature stage of development, there is still an enormous variety in the assessment methodology of (environmental) transport performance of ships. Furthermore, calibration of ship propulsion system model parameters with testbed, towing tank and full-scale measurement data is rare, as these measurements are both difficult and expensive. Finally, the effects of different power management strategies on the ultimate energy conversion effectiveness of typical cargo ships have rarely been investigated systematically. In this paper these three issues are discussed, addressed and solved for a representative benchmark chemical tanker. This ship was chosen to investigate the so-called energy conversion effectiveness under various propulsion control and electric power generation modes, as ample real ship data is available. The transport performance assessment of the ship's power plant is generalised for hybrid arrangements with either Power-Take-Off or Power-Take-In. The results show that an optimal combination of propulsion control, power management and voyage planning will further reduce the global fuel consumption and CO₂ emissions produced by the shipping industry.

@en

This paper demonstrates the usefulness of an automatic topology generator that uses genetic algorithm techniques to generate many alternative system designs and in doing so enables design space exploration for on-board energy distribution systems. This will provide better insight in the relation between design requirements (e.g. budget), system design solutions and important perfor-mance characteristics like ship survivability in early design stages. The basic idea is to apply proven techniques as used for ship configuration (i.e. hull and layout design) to the design of “ship service systems”. The case study will consist of multiple, interconnected systems on board an Ocean-going Patrol Vessel that distribute electric power, chilled water and mechanical (propulsion) power.@en

Several studies address early design of land-based and automotive energy distribution systems using network theory. Energy distribution systems on board of high-risk maritime craft are however rarely investigated in this way. In this article a method for automatically generating network topologies for vital energy distribution systems on board of ships is presented. The method combines fundamentals of network theory with marine engineering heuristics to introduce a generic yet realistic framework for node and edge differentiation. The framework is combined with a genetic algorithm to enable Automatic Topology Generation for design space exploration. The developed ATG tool enables trade-off analysis by visualising a Pareto front of optimal design solutions with respect to the opposing design objectives of system robustness and the “claim” of the systems on the ship (i.e. weight and space requirements, costs and operability). A novel robustness metric for vital on-board energy distribution systems is presented that enables the assessment of system reconfigurability. A critical review of this metric is provided in the article as well, as robustness as a design objective is particularly hard to capture. The method can be used by system designers as a decision support tool in early-stage ship/on-board system design.@en

Owing to new regulations starting from 2025, all commercial canal boats have to comply to zero local emission standards in Amsterdam. It is therefore vital that a clear emission indicator is made available for vessels with a varying operational profile, such as canal boats. In this paper, it is argued that current indicators, such as the Energy Efficiency Design Index, are not suitable for these (passenger) vessels. This paper proposes environmental performance indicators that can quantify emissions, (non-dimensional) energy and fuel usage based on an operational profile set in the design phase. This profile includes part load operation and auxiliary consumers and it can compare new designed concepts with current baseline vessels based on the ‘benefit for society’ of different vessel types. In the proposed environmental performance indicators, several operational modes can be defined, in contrast with the currently proposed Energy Efficiency Design Index, which is a point index at 75% of installed power. To gauge not only local emissions but also global emissions, the environmental performance indicator methodology is used to determine a minimum efficiency from any power generation method. This minimum efficiency follows from a comparison between baseline vessels and concepts that are more energy efficient and emission friendly. The proposed environmental performance indicators were validated using measurements on typical propulsion configurations of canal boats in Amsterdam. Three full electric concepts were designed and compared with the measured baseline vessels. As full electric concepts do not have local emissions, the method of power generation must satisfy the requirement to have less global emissions than the mechanical baseline. Furthermore, an energy efficiency of at least 33% is calculated from a fossil-fuelled land-based power plant (including transport) to the boundary from quay to boat to be required for newly designed electric concepts to be more energy efficient than the mechanical baseline.@en

Mean value diesel engine models are widely used since they focus on the main engine performance and can operate on a time scale that is longer than one revolution, and as a consequence use time steps that are much longer than crank-angle models. Mean Value First Principle (MVFP) models are not primarily intended for engine development but are used for systems studies that are become more important for engine users. In this paper two new variants of Seiliger processes, which characterize the engine in-cylinder process with finite stages are investigated, in particular their ability to correctly model the heat release by a finite number of combustion parameters. MAN 4L20/27 engine measurements are used and conclusions were drawn which Seiliger variant should be used and how to model the combustion shape for more engines. Then expressions to calculate the combustion parameters have been obtained by using a multivariable regression fitting method. The mean value diesel engine model has been corrected and applied to the simulation of a ship propulsion system which contains a modern MAN 18V32/40 diesel engine in its preliminary design stage and the simulation results have shown the capability of the integration of MVFP model into a larger system.@en

After-treatment technologies are adopted in automobiles and ships to meet strict emission regulations, which increase exhaust back pressure. Furthermore, underwater exhaust systems are employed on board ships to save space, and reduce noise and pollution on working decks. However, water at exhaust outlet creates a flow resistance for the exhaust gases, which adds to the back pressure. High back pressure reduces the operating limits of an engine, increases fuel consumption, and can lead to exhaust smoke. While the effects of back pressure were recognized earlier, there is a lack of experimentally validated research on the performance limits of a turbocharged, marine diesel engine against high back pressure for the entire operating window. The focus of this research is to provide a comprehensive understanding of back pressure effects on marine diesel engine performance, and to identify limits of acceptable back pressure along with methods to tackle high back pressure. In this work, a pulse turbocharged, medium speed, diesel engine was tested at different loads and engine speeds; against different values of static back pressure. Additionally, mean value model simulations could be validated and were used to compare the performance of a pulse and constant pressure turbocharged engine against high back pressures of 1 meter water-column (mWC), and for two different values of valve overlap. Using the validated simulation model, the conceptual basis for the engine smoke limit as well as for thermal overloading is investigated. A methodology applying the conceptual basis to define boundaries of acceptable back pressures has been presented in this paper. A combination of pulse turbocharger systems and small valve overlap showed to significantly improve back pressure handling capabilities of engines.

@en

The understanding, modelling and analysis of the behaviour of a non-linear ship propulsion plant are of great importance for conceptual system design, component selection, selection of control strategy and for propulsion control system tuning. Conceptual propulsion system design activities, such as deciding the combinator curve, require a relatively simple steady state simulation model, while propulsion controller design and tuning requires a non-linear time domain simulation model which captures the intricacies of the propulsion plant. In this paper a linearised model of the uncontrolled ship propulsion system is derived which can be used for analysis of propulsion system behaviour in waves and for initial controller design and tuning. Furthermore a thorough analysis is made of the conditions under which local instability of the system can occur. In a follow up paper the linearised model is extended and verified by means of comparison with a non-linear model. There it is furthermore used to investigate the effect of engine governor settings on a propulsion plant when sailing in waves at different encounter frequencies. The authors believe that, due to its transparency and clear link to well known parameters and variables, the linearised core propulsion system model as derived in this paper should appeal to marine system engineers, control engineers and hydrodynamicists alike. The linearised model should however not be seen as the replacement for a non-linear model, but rather as an additional tool that can be used.@en

The understanding, modelling and analysis of the behaviour of a ship propulsion plant are of great importance for conceptual system design, component selection, selection of control strategy and for propulsion control system tuning. Some of these activities require a relatively simple steady state simulation model, while other activities require a non-linear time domain simulation model which captures the intricacies of the plant, its components and the related controllers. In this paper a linearised model from an earlier publication is taken as a basis for further development. First of all a diesel engine and a hydraulic pitch actuating system are added to the model. Secondly a shaft speed controller is added to the system. Subsequently the controlled propulsion system is verified by scrutinising Bode plots and step responses. After this the linearised model is used to investigate the relation between parameter settings in the engine governor and actual system behaviour in regular waves. This provides the basis for understanding the behaviour of the propulsion system in irregular waves.@en

Een groot aantal modellen van het erfgoed stammen uit de negentiende eeuw. Waar en hoe die apparaten voor het onderwijs aan de Polytechnische School zijn gebruikt of dat zij pas veel later zijn verkregen is niet bekend. Het zijn over het algemeen kleinere machines die hoogstwaarschijnlijk voor demonstratie- en onderwijsdoeleinden zullen zijn gebruikt. @en

An overview is given of mechanical, electrical and hybrid propulsion arrangements. The relation between propulsion concepts and power generation is explained and elaborated in energy flow diagrams. A general procedure for analyzing propulsion and power generation concepts is presented, using energy conversion effectiveness and based upon a selection of operational modes and a mission profile reflecting the use of those modes. Potential matching problems when switching between propulsion modes are identified and possible solutions given.@en

Gearboxes are a necessary part of almost any propulsion train and their percentual losses are usually assumed to be small and constant. However, in low-load and part-load conditions, gearbox losses may be significant. With the current trend of slow steaming, the performance of gearboxes is once again in focus. In order to estimate the performance of maritime gearboxes, an evaluation of losses was done using a thermal network. The analysis was done for a standard double-input single-output maritime gearbox and over the entire range of torque and revolutions per minute. Results indicate that the transmission losses are not negligible in low-load condition; in fact they may as high as 10% of delivered power. Further results show that the maximum temperature in the teeth contact can reach 70 °C but this might be an overestimate. Finally, using the investigated thermal network models, a simplified model of transmission losses is proposed together with the fit coefficients for the torque and revolutions per minute.@en

In this paper we describe a generic way of sizing main dimensions of primary equipment for marine applications. Contrary to a straight fit through a database the method tries to develop expressions in which, apart from the main specifications in terms of power and speed, the selection of the main machine parameters has an influence on the ultimate overall dimensions of the component. The result is a “rubber” design model that uses in an intelligent way the first principles underlying the design of machines and that can be used in preliminary design of complex maritime objects. The method will be illustrated for components as diverse as electric machines, gearboxes and diesel engines but is thought to be generally applicable.@en

Design of a hybrid diesel-fuelled PEMFC system for application onboard naval ships is challenging for mul-tiple reasons. The fact that new technologies are used is only one of them. Less obvious, but also very challeng-ing is for instance choosing the ratio between installed battery capacity and fuel cell power. This ratio is a typi-cal design issue for hybrid systems. Dynamic models are necessary to find an optimal solution to this issue. In this paper the developed dynamic models are discussed, some in more detail, after which simulation results will be shown.@en