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This paper presents thermodynamic (energy and exergy) analysis and comparison of two different marine propulsion steam turbines based on their operating parameters from exploitation. The first turbine did not possess steam reheating and had only two cylinders (high-pressure and low-pressure cylinders), while the second turbine possesses steam reheating and has one additional cylinder (intermediate-pressure cylinder). In the literature at the moment, there cannot be found a direct and exact comparison of these two marine steam turbines and their cylinders based on real exploitation conditions. Along with energy and exergy analyses, the research it is investigated the sensitivity of exergy parameters to the ambient temperature change for both turbines and each cylinder. It is also presented the influence of the steam reheating process on the energy and exergy efficiency of the entire power plant. For both observed turbines and their cylinders it is valid that relative losses and efficiencies (both energy and exergy) are reverse proportional. The operation of an intermediate pressure cylinder from a steam turbine with reheating is the closest to optimal. Due to the different origins of losses considered in energy and exergy analyses, each analysis detects different turbine cylinders as the most problematic ones. The steam reheating process decreases losses and increases efficiencies (both energy of each turbine cylinder and the whole turbine. The whole turbine with reheating has an energy efficiency equal to 81.46% and an exergy efficiency equal to 86.48%, while the whole turbine without reheating has energy and exergy efficiencies equal to 76.47% and 80.94%, respectively. Exergy parameters of a steam turbine without reheating as well as its cylinders are much more influenced by the ambient temperature change in comparison to the steam turbine with reheating and its cylinders. The steam reheating process will increase the efficiency of the whole power plant in real exploitation conditions between 10% and 12%.

Ship motions affect the propulsion system, which causes fluctuations in the power system. Mutually, the power system variations impact the ship velocity by generating speed changes in the propeller. Therefore, interconnecting the ship hydrodynamic and power system has paramount importance in designing and analysing an all-electric ship (AES). The lack of an integrated model that can be evaluated in various operating conditions, such as manoeuvring, is evident. This paper explores the required perceptions for the power system and hydrodynamic analysis of an AES. Then, an integrated theoretical model comprising both the ship motion and power system is proposed. In addition to providing an accurate model for the ship in varying situations, this study demonstrates that the ship speed estimation during a ship route change differs from when the interconnections are overlooked. In the light of this determination, a straightforward enhancement for the ship speed control system is proposed. The effects of this modification on the ship power system are explored using the proposed model. The developed model is examined in different scenarios, and its advantages are discussed. It is shown that this model is suitable for employing in the model-based design of AESs.

Objectius de Desenvolupament Sostenible::14 - Vida Submarina Objectius de Desenvolupament Sostenible::6 - Aigua Neta i Sanejament Objectius de Desenvolupament Sostenible::13 - Acció per al Clima

When the marine propulsion system with double-cylinder turbines (DCT) works, the phenomena of nonlinear instability such as structural impact, vibration, and noise often occur. The instability is the result of the combined effects of the symmetrical layout and unsymmetrical load. The purpose of this paper is to reveal the instability mechanism of this type of propulsion system theoretically. First, based on the theory of finite-width journal bearing and gear transmission principle, a lateral–torsional–axial model considering the inertial effects of DCT and the ship propeller is established. Second, the vibration characteristics of the system are studied by numerical analysis. At last, dynamic evolution laws of the coupled system with layout and load parameters are investigated, and the instability mechanism is revealed. The results indicate that the dynamic characteristics of the system show obvious load ratio-controlled zone and layout angle-controlled zone with the changing of the parameters. Furthermore, the vibration condition of the gear pairs on the low-load side is worse than that on the high-load side. Finally, as the stability of the system decreases, the influence of the oil whip gradually increases. The research is of great significance for quantifying the stability of the propulsion system and predicting the system stability.

Today, alternative fuels are seen as a critical area of sustainable technological growth in maritime transport. The International Maritime Organisation (IMO), the United Nations body for maritime issues and other international bodies are in the process of amending and updating the regulations applicable to the shipping industry. Greece is ready to enter the era of liquefied natural gas (LNG) and electricity as marine fuels, as Eastern Mediterranean projects are heading towards adopting these alternative fuels. This study aims to explore the intention of the Greek stakeholders in accepting and using LNG and electricity as alternative fuels. The research objectives are to identify, analyse and evaluate the determinants that influence the intention to accept, diffuse and use alternative fuels, LNG and electricity for marine propulsion, and develop, construct and validate a hybrid model that can be used for future study. This research will clarify possible challenges or barriers to the implementation of technology by stakeholders and contribute to a deeper understanding of the green shipping network. It will also highlight the role of key players in the diffusion phase of technological innovation and the technology itself and its characteristics. Moreover, this research will suggest a unified model using the expansive Technology Acceptance Model (TAM) in conjunction with the Innovation Diffusion Theory (IDT) and external variables affecting LNG and electricity 1) to investigate the intent of implementing the use of such alternative fuels and 2) to inform policymakers concerning sustainable shipping.

This article presents the third and last part of the problem of diagnosing the fatigue of marine propulsion shafts in terms of energy with the use of the action function, undertaken by the authors. Even the most perfect physical models of real objects, observed under laboratory conditions and developed based on the results of their research, cannot be useful in diagnostics without properly transferring the obtained results to the scale of the real object. This paper presents the method of using dimensional analyses and the Buckingham theorem (the so-called π theorem) to determine the dimensionless numbers of the dynamic similarity of the physical model of the propulsion shaft and its real ship counterpart, which enable the transfer of the results of the research on the energy processes accompanying the ship propulsion shaft fatigue from the physical model to the real object.

Marine propulsion shafting systems are exposed to torsional vibrations originating from excitations in their prime movers and propellers. It is essential to analyse their steady state response in the earliest stage of ship design. The paper describes the implementation of SimulationX software based upon simulation modelling for these calculations. This software can be used either by the design office of the shipyard or by the classification society for verification within the plan approval phase. Some specifics of the input data preparation are briefly discussed. In addition, the simulation results depend on the modelling approach chosen. For these reasons, the real two-stroke Diesel engine ship propulsion system was chosen and several different models were implemented for system modelling. SimulationX calculation results are compared with those of two well-known and field-proven programs that use an analytical approach. Finally, the results are compared with the measurements performed on the actual newly built ship. Discussion reviews the selected SimulationX model, and its verification and validation in the case of engine cylinders with normal ignition.

In this paper, methods for removing corrosion product deposits from the primary circuit of light-water reactors with pressurized coolant under transient operating conditions are considered. The analysis of these methods, which are successfully used in the main types of light-water reactors, such as PWRs, VVERs, and nuclear marine propulsion reactors, has shown that the promising lines for their development are the selection of chemical reagents that do not violate the water chemistry of the coolant and provide the effective removal (disintegration or dissolution) of corrosion product deposits and experimental validation of their use. To disintegrate the deposits in the VVER-type reactors, hydrazine can be used; hydrazine and ammonia can be used for this purpose in marine nuclear propulsion reactors. The formation on the surface of fuel assemblies of bonaccordite (Ni2FeBO5) as a result of coolant boiling is a serious problem that may arise during the purification of the primary circuit from corrosion product deposits under transient conditions in the PWRs. To prevent the formation of this compound, it is proposed to adjust the water chemistry of the primary coolant so that the pH value of the medium is at 7.4 throughout the entire reactor’s operational period. The mutual influence of the methods for removing corrosion product deposits under transient operating conditions of nuclear reactors and the technology of injecting zinc into the primary circuit coolant has been analyzed. It has been shown that the technological solutions proposed can complement each other and, despite widespread applications of the zinc-injection technology, the purification methods still remain topical under transient operating conditions of the reactor. The purification methods under investigation have proven their applicability to the basic light-water reactors, such as PWRs and VVERs, as well as nuclear marine propulsion reactors.

The paper addresses the main long-standing approaches to the development of marine gas turbine engines and propulsion plants as well as prospective lines in their development. The paper presents the results of UEC-Saturn work in the field of designing and engineering facilities development for marine gas turbine manufacturing in Russia. The key issues of converting aircraft gas turbine engines for application as a part of marine propulsion plants have been addressed.

Whirling vibration is an important part of the calculations of the design of a marine shaft. In fact, all classification societies require a propulsion shafting whirling vibration calculation giving the range of critical speeds, i.e., free whirling vibration calculation. However, whirling vibration is a source of fatigue failure of the bracket and aft stern tube bearings, destruction of high-speed shafts with universal joints, noise, and hull vibrations. There are numerous uncertainties in the calculation of whirling vibration, namely, in the shafting system modeling and in the determination of excitement and damping forces. Moreover, whirling vibration calculation mathematics is much more complex than torsional or axial calculations. The marine propulsion shaft can be studied as a selfsustained vibration system, which can be modeled using the Van der Pol equation. In this document, a new way to solve the Van der pol equation is presented. The proposed method, based on a variational approach without local minima extra to the solution, converges for whatever initial point and parameter in the Van der Pol equation.

This paper presents a steady-state sensitivities analysis of four well-known propulsion control techniques: shaft speed, torque, power and integrative torque–power controllers applied to a ducted marine propeller driven by an electrical motor. Also, this work proposes a variation in the latter technique and analyzes its sensitivities as well. The control loop scheme follows the structure of propulsion control in a dynamic positioning system. The sensitivity concept is used to perform the analysis, which consists of a normalization of the equilibrium point with respect to its reference value. The effect of inaccuracies between the control model and plant parameters over the equilibrium points is considered and analyzed in three scenarios for each controller. Simulations with a ducted propeller model are performed to provide further information about sensitivities, and the results are compared by using performance measurements based on the mean absolute error. The results provide detailed information on each controller’s characteristics in steady state in the whole operation range regarding shaft speed, torque, power and thrust.

This paper discusses the aerodynamic analysis and design of a novel, hubless, contra-rotating, rim-driven fan (RDF) device. Rim-driven thruster technology has been used for marine propulsion for decades, yet RDF technology has not been comparably developed for aerospace applications. This paper demonstrates that an innovative two-stage contra-rotating RDF configuration provides the potential for a significant increase in the available thrust and efflux velocity when compared with existing technologies. The analysis was conducted for an RDF device with a relatively small fan diameter of 120 mm. However, the findings of this study can be equally applied to the performance of much larger and more powerful RDF propulsion units. This would also include devices having multiple contra-rotating paired stages, for example, four, six, or more rotors to permit higher-pressure ratios and exhaust airspeeds suitable for large modern aircraft propulsion.

Stringent environmental regulations and increasing oil prices showcase the need for renewable energy sources like solar in marine transportation. The application of solar energy in electric propulsion systems is growing tremendously. Power electronics-based inverters help in harvesting direct current (DC) power into alternating current (AC) power. A multilevel inverter (MLI) is a popular power electronic converter producing the desired output voltage from several DC input voltage sources like batteries, supercapacitors, and solar panels. An MLI consists of several switches whose action results in severe harmonic issues. Specific harmonic elimination in MLI is a challenging job and is resolved conventionally by the Newton-Raphson method. However, nowadays, soft computing techniques are used to solve nonlinear equations optimally. In this manuscript, minimization of total harmonic distortion in MLI has been taken as an optimization problem and is solved using teaching-learning‐based optimization (TLBO). The TLBO algorithm is applied to compute the optimum switching angles for MLI to produce the required fundamental output voltage with less harmonic distortion. As it does not require any algorithm-specific parameters, TLBO is an effective method to obtain optimum MLI solutions. A 21-level symmetric MLI is simulated and is used to evaluate the performance of the TLBO algorithm. The simulation results are validated using an experimental model of proposed MLI with a Xilinx Spartan-SA field programmable gate array‐based controller. This research outcome bears testimony to TLBO optimization's efficiency in improving the quality of the power generated in ships using renewable sources.

This paper discusses two approaches to FEM-based calculation of marine propulsion shafts made of polymeric composites: one approach represents the composite as a homogeneous material, whereas the other approach represents it as a real sandwich structure made up by monolayers with different properties.

This paper examines the environmental impact of Natural Gas (NG) as a transportation fuel, particularly for marine transportation use. The aim is to provide a systematic evaluation of Greenhouse Gas (GHG) emissions in the upstream fuel supply chain of NG fuel in British Columbia (BC), Canada. The recent introduction of Liquefied Natural Gas (LNG) fuel for ferry operations in western Canada presents a major step towards the large-scale adoption of NG as a cleaner and lower-cost fuel. This makes a systematic approach for accurate Lifecycle Assessment (LCA) of GHG emissions for the NG/LNG fuel more important and urgent. An analysis using operation and fuel consumption data from vessels with different engine technologies and types of fuel shows that the diesel cycle NG engine will produce 2% less CO 2e emissions in comparison to the low sulphur petroleum diesel engine, while other NG engine technologies, such as the lean-burn Otto cycle engine or dual-fuel gas engine, will result in 4% higher CO 2e emissions. This study clears doubts on well-to-pump (WTP) NG emissions, supports the wide adoption of NG fuel and promotes further pump-to-propeller (PTP) emission improvements in marine propulsion.

For a sea-going ship to be built new or reconstructed, the main propulsion plant (MPP) consisting of a marine diesel engine (MDE), driving the ship propeller, is mandatory to be calculated with the torsional vibrations (TVs) in accordance with the Rules for the Classification and Construction of Sea-Going Ships, such as Russian Maritime Register of Shipping (RMR), DNV, ABS, and VR. The TV calculations (TVC) are conducted at normal working regimes and at misfire regimes (called by Normal or Misfire regimes relatively) with only one of cylinders of MDE while engine speed range covers from the minimum to maximum values of the operation speeds. The TVC on the MPP are incredibly sophisticated calculations and are conducted with special software for TVC. The paper presents the algorithms and software for automatic calculating the TVs (SATVC) basing on the made mathematical models, algorithms and coded in LabView by authors. The SATVC was automatic calculated the freedom TVs (FTVs), excited torsional moments (ETM), excited TVs (ETVs), permitted torsional pressures (PTP), and common management (CTVC). In the article were shown the probated results of TVC using the SATVC for the MPP on MV.HR.34000 DWT which built in Pha Rung Shipyard, Viet Nam.

The propulsion system of a medium-voltage dc (MVDC) ship is subject to large thrust/torque variations due to interactions of the ship and the propeller with sea waves. These variations induce steep power fluctuations on the MVDC bus, adversely impacting the stability, efficiency and power quality. Hybrid energy storage system (HESS) is a promising solution for mitigating these power fluctuations. Dictating the energy that the HESS components must deliver/absorb, the energy management strategy (EMS) impacts the size/capacity of the energy storage system (ESS). Based on this consideration, sizing and EMS of a battery/supercapacitor (SC) HESS are jointly optimised by using a deep reinforcement learning-based method. The proposed method splits the power between the HESS components such that while the operational constraints are satisfied, energy storage size and losses are minimised. Its features are adaptability to varying sea states, real-time implementation feasibility, while obviating the requirement for knowledge of the ship propulsion power profile. The efficacy of the joint sizing/EMS on reducing the ESS size is validated by comparing the sizes when battery-only, SC-only and HESS are employed in the MVDC shipboard power system. Real-time implementation feasibility and adaptability to various ship propulsion power profiles is confirmed through real-time simulations.

This study presents the electromagnetic, thermal and mechanical analysis of a 750 kW, 1200 rpm, 690 V surface permanent magnet motor aimed at marine propulsion (azimuth thruster). Based on a preliminary machine design, key electromagnetic design aspects including magnet demagnetisation and magnet loss reduction by tangential and axial segmentation are assessed. Then, three different cooling solutions are evaluated via computational fluid dynamics simulations combining the use of a water-jacket surrounding the stator, wafters attached to the rotor structure and the addition of an inner fan. Subsequently, the dynamic design analysis method is applied in order to check the machine's response to shock loadings due to underwater explosions. Finally, a machine prototype is successfully manufactured and tested, showing the proper fulfilment of the design requirements.

The hydrodynamic analysis of flapping foil inspired by the thunniform fish propulsion is carried out numerically. The hydrodynamic performances of 2D and 3D rigid oscillating foils are analysed for...

According to the analysis of the problems about the operation of marine propulsion shafting in steady state, the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearings in two-dimensional space are established, and a coupling mathematical model of the marine propulsion shafting in steady operating state is proposed. Then the simulation of a real ship is carried out, and the variation laws of some special parameters such as bearing load and deflection are obtained. Finally, the results of simulation are verified by experimental data of a real ship, which can provide the mathematical model and analysis method for the research on the characteristics of ship propulsion shafting condition in steady state.

An intelligent floating raft system (IFRS) for marine propulsion shafting is designed and introduced in detail in this paper. IFRS includes floating raft, air spring mounting system, and emergency protection device. The mechanical characteristics of IFRS are modeled and analyzed. The test rig is built and the deformation of IFRS and alignment of shafting are tested and monitored. According to the alignment principles, IFRS can meet the alignment requirements. When encountering extreme working conditions, the emergency protection device of IFRS can ensure the safety of marine propulsion shafting. Also, the IFRS and hull coupling finite element simulation is carried out. More low-frequency modes are excited when IFRS is used.

Considering the recent introduction of restrictions on air pollutant onboard ships and the increasing interest towards more energy efficient naval transportation, an effort is made in the present thesis to assess the possible design of a novel engine unit. More specifically, in the current regulation context, Gas Turbines are a promising alternative to current diesel engines, thanks to lighter fuel requirements, low NOx pollutants and the potential to run in combined cycle architecture with cogeneration strategies. While their application has shown clear advantages and drawbacks on large ships, there seems to be little if no data concerning smaller units. The present work tries to assess the possible design of a radial turbine for an engine to be employed onboard ships as a Mini Gas Turbine, i.e. up to 5 MW output power, taking into account cycle, aerodynamic and structural design. To this purpose, a platform was built in Ansys Workbench to perform Computational Fluid Dynamics and thermo-mechanical Finite Element simulations aimed to design and optimize such a novel radial turbine.

The interaction between ship propulsion machinery, propellers and the highly dynamic environment which is the sea is a complex yet highly relevant subject. During a storm, for example, waves and ship motions may cause the propeller to draw air, or ventilate, resulting in rapid changes in propeller thrust and load torque. These fluctuations propagate through the propulsion system, potentially causing excessive loads on propulsion machinery, while also reducing the ship's manoeuvrability. A profound understanding of these complex interactions still lacks. One result of this knowledge gap is the limited acceptance of new technologies for ship propulsion, especially those technologies known to have limited transient capabilities. In this paper, hardware in the loop (HIL) is proposed as a solution to this knowledge gap. Paying specific attention to propeller ventilation, HIL is used to identify new aspects of interaction between engine and propeller, thus demonstrating the added value of HIL for ventilation studies.

The importance of mathematical and numerical simulation in marine engineering is growing together with the complexity of the designed systems. In general, simulation a makes it possible to improve the engineering design, reducing working time and costs of production as well. In this respect, the implementation of a simulation model for cycloidal propellers is presented. Cycloidal thrusters are being increasingly used in marine applications. Their best performance concerns low-speed applications, due to their ability to steer thrust in any direction. The proposed simulator is able to assess the performance of cycloidal propellers in terms of the generated thrust and torque, without resorting to consuming and demanding computational tools, such as CFD methods. This feature makes the presented model particularly suitable for the simulation in the time domain of the maneuverability of surface units, equipped with cycloidal propellers. In this regard, after embodying the implemented model in an already existing simulation platform for maneuverability, we show the most significant outputs concerning some simulated maneuvers, performed at cruise speed.

The scientific aim of this paper is to analyse the topicality of the turbocharger explosions and to attempt to answer the question of whether some technical characteristics of the engine can be perceived as directly connected with the risk of the turbocharger explosion. Moreover, our objective was also to calculate the turbocharger explosion probability. This article presents the results of a quantitative and qualitative analysis of 42 explosions of marine main engine turbochargers occurring between 1977 and 2022. The number of explosions was analysed, and the average and instantaneous frequencies of turbocharger explosions each year were determined. An analysis was performed of the number of explosions with respect to the age and type of ship on which the accident occurred. An analysis of the contribution of different types of main engine to the studied population of explosions was also carried out. Criteria such as the number of strokes, engine speed, type of crank-piston mechanism, cylinder arrangement, engine power per cylinder, and number of cylinders were considered. An analysis was carried out of the disasters that had occurred, considering the contribution of the various engine manufacturers. An integrated distribution of the number of turbocharger explosions by year was presented, considering the engine speed, the maximum continuous rating of the engine, and the engine design. The analysis did not indicate a significant correlation between the type of ship and the number of explosions that occurred. More than half of the analysed population of explosions (median) occurred on vessels no older than 15 years. It is highly likely that engine type does not directly affect the number of turbocharger explosions and the risk of explosions. On the other hand, it is not possible to exclude the influence of the individual characteristics of an engine built to a particular manufacturer’s design on the magnitude of the risk of a turbocharger exploding during engine operation. Considering the number of ships worldwide, the probability of an explosion in a given year on a given ship is not less than 1.61 × 10−7.

After steam engine-based propulsion systems became outdated due to the poor efficiency issue, gas turbine and diesel engine-based propulsion systems found popularity. The efficiency of combustion engines is optimum only when it is operated close to the rated load. It also suffers from vibrations, higher fuel consumption, frequent maintenance requirements, and a lack of flexible and redundant operations. Few hybrid propulsion systems such as thermal combined and gas-electric came into existence to address these issues. However, they required geared transmission system, deteriorating efficiency and increasing the maintenance requirements. Hence, electrification of marine systems is considered crucial to empower future marine propulsion systems (MPS). This paper reviews the merits and demerits of contemporary multilevel inverter (MLI) topologies, which are potentially believed to enhance the performance of electric propulsion systems (EPS) for marine applications. A detailed comparison and simulation results of contemporary MLI topologies to drive the MPS are presented with their respective five-level configurations. Simulations of different five-level MLIs for the load of 5 MVA are done using PLECS software.

Following the successful commercialization of road-going electric vehicles, zero-emission electric marine vessels are gaining industry focus for absolute battery operation. Due to the low energy density of lithium-ion batteries, low propulsion-powered marine vessels operated frequently over short distances are found suitable for complete battery propulsion. In this paper, a modular multilevel converter (MMC) with symmetrically decentralized onboard battery banks is proposed as a marine traction inverter for a multi-purpose harbor vessel. A novel mathematical model of the marine vessel is proposed to size the propulsion motor, and generate torque-speed commands corresponding to vessel speed during the maneuver. A brief analytical discussion has presented on the selection of motor-converter configuration for marine propulsion application, considering three-phase low-voltage permanent magnet synchronous motor (PMSM) with a two-level inverter and three-phase medium-voltage PMSM with MMC. A short endurance marine drive cycle is simulated with low-speed high torque three-phase PMSM driven by MMC with integrated battery modules (BM). This study leveraged MATLAB/Simulink environment to analyze the operational performance of MMC and BMs during various phases of the short endurance marine drive cycle.

The double-cylinder turbines' (DCT) propulsion system is widely applied to large-scale ships, while the instability mechanism of the system lacks theoretical and scientific research. Based on gear transmission principle and finite width journal bearings theory, the lateral-torsional-axial model of the system considering multiple nonlinear and time-varying factors is established. The effects of the unsymmetrical load parameters on the stability of the coupled system have been explored and quantified. Results indicate that the phenomenon of instability gradually occurs with the increase of excitation frequency, the decrease of load ratio between the two inputs or the decrease of input load value, and the vibration of the gear pair on the low load side is more severe. Furthermore, the vibration amplitude is related not only to the load parameters but also to the distance between the gear pair and the load input disk. Finally, the influence of the oil whip on the system stability is crucial, especially when the system is in an unstable state. This study puts forward the stability boundary of the DCT propulsion system and provides a theoretical reference for the optimization and adjustment of the load parameters.

A traditional propeller can easily become entangled with floating objects while operating. In this paper, we present a newly developed electromagnetic-valve-control-based water-jet propulsion system (ECWPS) for an unmanned surface cleaning vessel that can be flexibly controlled via a micro control unit (MCU). The double-structure was adapted to the unmanned surface cleaning vessel for floating-collection missions. Computational fluid dynamics (CFD) software for operating effect simulation was also used to reveal the working principle of the ECWPS under different conditions. Neglecting the assembly technique, the design level, controlling strategy, and maneuvering performance of the ECWPS reached unprecedented levels. The ECWPS mainly consists of an electromagnetic-valve array (EA), pipeline network, control system, and water-jet source. Both CFD analyses and experimental results show that the hydraulic characteristic of the ECWPS was predicted reasonably, which has enormous practical value and development prospects.

A Nonlinear Model Predictive Control (NMPC) scheme is proposed for the optimal transient power-split problem of a hybrid diesel-electric marine propulsion plant. The NMPC scheme directly controls the torque output of the diesel engine and the electric motor generator ensuring that certain constraints concerning the engine overloading are applied. In this way, fuel consumption and NOx emissions can be reduced. The modeling for the controller design was based on experimental data gathered from the hybrid plant and on first principles for the diesel engine behavior and battery charging. The controller was experimentally tested in real-time operation. Results showed that controller rejected successfully load disturbances and maintained the desired rotational speed of the powertrain as well as the desirable state of charge in battery within limits.

This paper is about condition based maintenance and technical diagnostic on specifically object-cylinder units of two stroke low speed diesel engine MAN B&W 8K80MC-C. It describes: the way of controlling direct parameters (pressure and temperature) taken from the engine, measuring the pressure in engine cylinders via electronic device "PREMET" and visual control of cylinder liners and pistons. Analyzing the data we got clear conclusion about needs of preventive action or possibility of extension of exploitation without maintenance for certain period. Practice confirms that it is possible to extend the period between two overhauls while maintaining engine performance within the limits prescribed by the manufacturer and the values of the parameters obtained on the test drive, as well as reduce maintenance costs.

Operational rules and control strategies of the chemically recuperated gas turbine (CRGT) in the marine propulsion are investigated in this paper. The Minimization of Gibbs free energy method is used to calculate the diesel-steam reforming reaction which products synthetic hydrogen rich fuels, and a universal model of the chemical regenerator which is easily applied to different application environments is created. The hydrogen production and hydrogen molar fraction are investigated to verify that the CRGT improve the combustion performances under low working conditions. Off-design calculations are performed to derive proper operational rules, and transient calculations are performed to investigate the best control strategies for the systems. The modelling approach of the chemical regenerator can be generally used in the chemically recuperated gas turbine. The elaborate operational rules can greatly improve the thermal efficiencies under every working condition. The system using synchronous control strategies have better regulation speed and operation stability than that using asynchronous control strategies.

[Objectives]In view of the lack of complete definition, confusion about denotation of basic concepts of waterjet and pumpjet and confusion of product appellations both at home and abroad at present,[Methods]the common and special characteristics of the two propulsors were refined out and their differences distinguished based on the analysis of their working principle and concrete structures,the definitions of waterjet propulsion and pumpjet propulsion were proposed and their common characteristics, special characteristics and differences were pointed out.[Results]The waterjet and pumpjet are all pump-type propulsors,all of which rely on the matching design of rotors and stators on the flow field inside a duct to produce an axial jet. The first design index of waterjet is high efficiency and the rapidity shall be ensured primarily,whose design result is a waterjet. The first design index of pumpjet is low noise (the acoustic stealth)shall be ensured primarily,whose design result is a pumpjet.[Conclusions]This definition not only includes and distinguishes all existing waterjets and pumpjets,but also points out the problems of some foreign pump-type propulsor's nomenclature and classification. This definition helps the public understand and distinguish between waterjet propulsion and pumpjet propulsion.

Marine cycloidal propeller, as a special type of marine propulsion system, is used for ships that require high maneuverability, such as tugs and ferries. In a marine cycloidal propeller, the thrust force is generated by rotation of a circular disk with a number of lifting blades fitted on the periphery of the disk, so that the propeller axis of rotation is perpendicular to the direction of thrust force. Each blade pitches about its own axis, and the thrust magnitude and direction can be adjusted by controlling the pitching angle of the blades. Therefore, the propulsion and maneuvering units are combined together and no separate rudder is needed to maneuver the ship. Two configurations of marine cycloidal propeller have been studied and developed based on propeller pitch: low-pitch propeller (designed for advance coefficient less than one, means λ 1). Low-pitch marine cycloidal propellers are used in applications with low-speed maneuvering requirements, such as tugboats and minesweepers. In this study, the effects of blade number on hydrodynamic performance of low-pitch marine cycloidal propeller with pure cycloidal motion of the blades are investigated. The turbulent flow around marine cycloidal propeller is solved using a 2.5D numerical method based on unsteady Reynolds-averaged Navier–Stokes equations with shear-stress transport k–ω turbulent model. The presented numerical method was validated against experimental data and showed good agreement. The results showed that the thrust coefficient of marine cycloidal propeller generally decreases by increasing the blade number, whereas the torque coefficient increases. Consequently, the hydrodynamic efficiency of marine cycloidal propeller drops as the blade number increases.

Journal bearings are known to be intrinsic components in different marine applications. They are regarded as the most instrumental means by which large loads could be transmitted at mean speed of rotation. Hydrodynamic journal bearings, based on hydrodynamic lubrication, have undoubtedly proved to be among the most effective types of journal bearings designs, commonly used in marine applications. In hydrodynamic lubrication, metal-to-metal contact could be prevented via a separation between the load carrying surfaces of the bearing, that could be attained by means of a relatively thick film of lubricant. Extending bearing life in marine propulsion systems, auxiliary equipment and diesel engines, reducing friction energy losses and wear, minimizing maintenance expenses and downtime of machinery due to frequent bearing failure are the most important objectives being born in mind on launching the bearing design procedures.In the study at hand, an attempt has been made to perform a study of pressure distribution within hydrodynamic journal bearing on experimental bases. The experimental study has entailed the use of versatile lubrication oils, among of which comprised SEA 20W50, SEA 10W40 and SEA 5W30, for the sake of identifying their individual role in determining the condition of lubrication “hydrodynamic or hydrostatic”. Besides, the study has been extended to cover the pressure behaviour of different lubricants within the hydrodynamic journal bearing, at different speeds ranging from 50 to 400 RPM at constant loads. For accurately testing the 105 mm internal diameter, 58 mm bearing length and “l/d = 0.5” made of white metal, a use has been made of the universal journal bearing test rig “UJBTR”. Pressure distribution is further circumferentially investigated under constant loading, with operating at different journal rotational speeds.

Full-film hydrodynamic lubrication of marine propulsion shafting journal bearings in running condition is discussed. Considerable computational difficulties in non-linear determining the quasi-static equilibrium of the shafting are highlighted. To overcome this problem the approach using two optimization methods (the particle swarm method and the interior point method) in combination with the specially developed relaxation technique is proposed. The developed algorithm allows to calculate marine propulsion shafting bending with taking into account lubrication in all journal bearings and exact form of journal inside bearings, compared to results of most of the publications which consider lubrication only in the aft most stern tube bearing and assume rest of bearings to be represented by points. The calculation results of typical shafting design with four bearings are provided. The significance of taking into account lubrication in all bearings is shown, specifically more exact values of bearings’ reactions, shafting deflections, minimum film thickness and maximum hydrodynamic pressure in the stern tube bearing in case of considering lubrication in all bearings.

Electric propulsion has become the solution for large marine vessels over conventional combustion engine propulsion. An azimuth thruster is the primary propulsion unit in such electrified ships, and it has become prevalent recently. However, the mechanical failures among bevel gear, coupling, and bearing in the thruster are reported commonly, and it may be attributed to the dynamic mismatch and torsional oscillations between the motor drive and mechanical drivetrain systems. One main advantage of using electric propulsion is its flexible and instant torque control that can reduce the torsional stress in the drivetrain. In this paper, a new speed difference-based active torque compensating method is proposed. A detailed model for the azimuth propulsion system is developed, and a power electronics-based controller is used to manage the excessive drivetrain torque caused by a sudden load change. The proposed controller can change the damping ratio by introducing virtual material damping in the system, which decreases the resonant torque amplitude in the driveline. The resonant torque attenuating effects are validated both by simulation and experiment with a multi-inertia model operating at rapid ventilation.

Reliability of the marine propulsion system is closely correlated with the safety of navigation at sea. Typical ship’s powertrain has a lot of advantages (mainly efficiency) but is the source of high vibration level. What is more, rough sea conditions can be a source of additional ship vibration, especially for big container ships. Vibrations may have a dangerous influence on ship equipment’s strength and consequently on the ship’s safety. Torsional vibrations of the marine power transmission system are usually the most dangerous for the shaft line and the crankshaft. The power of propulsion system is quite often measured by commercial measuring device based on instantaneous angular speed (IAS). The angular speed measurements are performed using two optical sensors for reading the IAS, mounted at shaft line. The authors try to use existing apparatus for torsional vibrations’ continuous monitoring. Designing monitoring methodology consists several analytical methods. Simplified method of torsional vibration calculation is a first one. Simplified calculation method gives us a determination possibility of torsional vibrations in typical and emergency working conditions. Natural frequency value (resonance location) as well as vibration amplitudes can be estimated on the base of the method. The presented calculation method was verified by comparison with the detailed finite element method calculation and measurements on real ships. The second part of the monitoring system contains methodology of monitoring of piston engine’s crankshaft torsional vibrations by measurement of IAS at free and power output ends of the engine’s crankshaft. It is assumed that calculation of differential value between both ends shall give the picture of torsion angle magnitudes and phases of the peak values. Analysis method of recorded signals (e.g., recalculation of angular distance sampling into constants time function and frequency base by FFT analysis) is also developed. Description of the measurements of the crankshaft torsional vibration for marine engine with some simulated malfunction (a leak of fuel injection pump, and relayed on mounting of sets of injection valves with different nozzles characteristics—spraying nozzle angle) is presented. Presented results of experiment derive from test cycle carried out using laboratory stand of Gdynia Maritime University equipped with 3-cylinder self-ignition engine, powering electric generator. The planned monitoring system should have detecting possibility of torsional vibration changes (propulsion system malfunction), the ability to assess the degree of danger of failure and eventually determination of the risk of damage and the causes of propulsion system’s threat failure.

Over the last few decades, oil tankers and bulk carriers, which preferably adopting the concept of a single stern tube bearing, have been subjected to the mechanical damages on propulsion shaft bearings since such a concept overly requires a single bearing to support the full load of the propulsion shaft. This paper was to fundamentally address the problem of current practices of aligning a single stern tube bearing for commercial ships by determining the effective supporting point to balance the load of the propulsion shaft properly. Since selecting a case ship subjected to the damage on the stern tube bearing, it investigated the actual cause of the damage, thereby finding a practical way to enhance the sustainability of the propulsion shaft system using the single stern tube bearing. Computer-aided simulations using the finite element analysis as well as on-site measurements were carried out. Research findings revealed that the ignorance of the relative slope angle between the propulsion shaft and the aft stern tube bearing had led to misalignment, which resulted in adverse effects on the stability of the shaft system, and consequently damaged the stern tube bearing. Results of the analysis suggested that the degree of slope be taken into account when estimating the effective supporting point of the bearing. Finally, this paper pointed out that the establishment of a shaft installation guideline considering the effect of the shaft slope, thereby preventing wiping damage of the aft stern tube bearing would be an urgent task.

The modern development of marine propulsion drives leads to more and more frequent requirements of the electric motor as the main propulsion element, and its control is carried out by frequent converters. The conversion of electrical energy AC-DC-AC leads to certain power losses and problems in the operation of generators. This paper presents a study of a synchronous generator in different operating states using the space vector theory and the instantaneous power theory to determine the processes of the co-operation of a synchronous generator and a load.

The All-Electric Ship platform requires significantly higher torque density and payload efficiency for marine propulsion and electrical power generation. We have developed a nanostructured groundwall insulation for high torque density medium voltage propulsion motors. Our 2D nanoclay composite exhibits 2X combined improvement in electrical, dielectric, and thermal performance over the state-of-the-art micaceous insulation, achieved via a high thermal conductivity of >0.8 W/(m·K)., high breakdown strength of >40 kV/mm, and low loss factor of

The present work deals with environmental sustainability and specific engineering solutions able to cope with such a global issue. Attention is focused on renewable energy and innovative fuels as effective strategies in contributing valuable techniques in order to face the need of mitigating environmental problems concerning climate change and global warming. The research study is targeted on optimized design and management of fluid machinery, and extensively on optimized energy conversion systems, conceptualized in accordance with current standards and regulations, governing the reference sector. The analysis investigates small energy supply from renewables (wind power) and innovative marine propulsion (alternative fuels and unconventional propulsion systems). Regulations and technical design are constantly focused for the study. The work proposes case solutions for energy design and management actions dealing with the theme of environmental sustainability: engineering analyses (design, technical-economical evaluation, performance results) for hybrid wind powered plants empowering SWRO (Sea Water Reverse Osmosis) desalination processes; engineering analyses (design, technical evaluation, performance results) for wind turbine rotors operating in sites characterized by a small wind resource; engineering analyses (design, technical evaluation, performance results) for marine ship propulsion empowered by LNG as an alternative sustainable fuel and by gas turbines as prime movers coupled to combined cycles as an innovative propulsion system (COGES configuration).

During the conceptual and preliminary design stage of a ship, designers need to ensure that the selected principal dimensions and parameters are good enough to deliver a stable ship (statically and dynamically) besides deadweight and speed. To support this, the initial intact stability of the proposed ship is required to be calculated, and in doing so, the lightship weight and its detailed breakdown are necessary to be known. After hull steel weight, machinery weight, mainly, marine propulsion and power generation machinery, play a vital role in the lightship weight estimate of a ship due to its robustness. The correct estimation of respective weights improves the accuracy of calculating a ship's initial stability typically to be designed and built. Hence, it would be advantageous for the designer to convince the ship owner. A total of 3006 marine propulsion (main marine diesel) engines and 348 power generation (auxiliary marine diesel) engines/generators of various power output (generators output for auxiliary engines), engine RPM and cylinder number of different engine makers are collected. These are analyzed and presented in both tabular and graphical forms to demonstrate the possible relationship between marine propulsion engine weight and power generation engine weight, and their respective power output, RPM, cylinder number, power-RPM ratio and power-RPM ratio per cylinder.In this article, the authors have attempted to investigate the behavior of marine propulsion engine weight and power generation engine/generator weight regarding engine power output, generator power output, engine RPM and cylinder number (independent variables). Further attempts have been made to identify those independent variables that influence the weight of the marine propulsion engine and power generation engine/generator (dependent variables), and their interrelationships. A mathematical model has thus been developed and proposed, as a guiding tool, for the designer to estimate the weight of main and auxiliary engines more accurately during the conceptual and preliminary design stage.

Requirements on ships are rapidly increasing. In particular, safety and environmental impact are under increasing scrutiny. At the same time, cost and profitability remain as important as they have ever been. These increasingly stringent constraints are beginning to pose problems during the design process. For example, the energy efficiency design index (EEDI) aims to reduce emissions of carbon dioxide by progressively limiting engine power installed on board. However, these reductions in propulsive power raise concerns about the ship's manoeuvrability in rough seas. Moreover, the expected introduction of novel power and propulsion systems based on, for example, fuel cell technology, further raises uncertainty regarding the performance of future ships and propulsion systems in dynamic environments. Considering these developments, detailed predictions of manoeuvrability and propulsion plant behaviour are becoming increasingly important in the ship design process. Yet, present prediction methods are insu_cient to evaluate manoeuvrability and behaviour of ship propulsion systems in complex, dynamic environments such as heavy seas. Fully numerical methods based on computational fluid dynamics (CFD) and first principles are inherently uncertain and compute-intensive. As such, these methods are presently unsuitable to assess the dynamic interaction between machinery and hydrodynamics over prolonged periods of time. As an alternative to numerical methods, experiments with scale model ships can be conducted. However, such experiments are subject to hydrodynamic scale effects: viscous friction, spray formation and propeller cavitation are not the same as at full scale. Moreover, these model ships are powered by considerably simplified propulsion systems, causing entirely different propulsion plant dynamics than at full scale. Ideally, scale model experiments would be conducted with, for example, a perfectly downscaled diesel engine, gearbox and propeller; in practice, however, this is generally not feasible. As such, existing prediction methods leave great uncertainty how future ship designs can simultaneously meet all requirements regarding operational performance, safety and compliance with environmental regulations. A possible way to bridge this knowledge gap is by conducting hardware in the loop (HIL) experiments in the ship model basin. Such experiments combine numerical simulations with a physical test setup. During HIL experiments with free sailing ship models, the propulsion engine and other machinery are simulated by a computer. These simulations are then used to control an electric motor, powering the propeller of a physical scale model ship. As such, the complex interaction between engine, propeller, hull and environment can be physically reproduced, allowing to assess design choices early on in the ship design process.

Longitudinal vibration reduction of marine propulsion shafting has drawn great attention of research. In this paper, a low-frequency mounting system (LFMS) is designed. LFMS consists of three sub-systems: floatable self-alignment thrust bearing, floating raft, and air spring mounting system. Floatable self-alignment thrust bearing is a new type of thrust bearing, which can provide small displacement compensation for shafting. In order to maximize the overall vibration behavior of the control system, thrust bearing and marine propulsion unit are integrated on the floating raft air spring mounting system can adjust the floating raft attitude to meet the shafting alignment requirements. A theoretical model is presented to estimate the isolation effect of LFMS. The first-order longitudinal vibration frequency of shafting is 9.8 Hz. Experiments are carried out to verify the isolation effect of LFMS. Experiments show that LFMS has an obvious vibration isolation effect above 10 Hz.