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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.

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 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.

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.

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...

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.

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.

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.

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.

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.

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.

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.

The study aimed to verify whether it is possible to diagnose the coking of a marine diesel engine injector nozzle by performing a spectral analysis of the crankshaft&rsquo, s torsional vibrations. The measurements were taken using laser heads, clocked at 16 MHz. The reasons for selecting this type of optical sensors are described as well. The tests were carried out under laboratory conditions, using a test stand with a Sulzer 3AL 25/3 engine, operating under a load created by a Domel GD8 500&ndash, 50/3 electric generator. A unique method is presented in the paper, which enables the measuring and calculation of torsional vibrations of engine crankshafts. The method was developed at the Chair of Marine Power Plants at the Maritime University of Gdynia. It has been proven that the distribution of differences in the values of individual harmonic components depends on the location of a defective injector nozzle in the cylinder.

A shift towards electric and hybrid propulsion within the marine sector create new challenges for conventional water jet units manoeuvred by hydraulic systems. The high efficiency in high speed water jet crafts benefit from being powered by electricity but will be compromised by constantly running hydraulic pumps, draining available electric capacity on-board. Wear and tear on hydraulic components are also an environmental contamination hazard, due to high pressure oil and exposed cylinder rods. However, conventional hydraulic power packs with subsystems to manoeuvre water jet unit is a well proven and reliable marine application.Steer-by-wire is not an uncommon subject, as it is frequently used in several industries such as aviation, automotive and offshore. The purpose of the study is to prepare a concept design proposal with CAD-models and drawings of electrically powered manoeuvring system for Marine Jet Powers DRB 750 steering units. The study did a literature study on the topic and qualitative research to fulfil the purpose. A generic product and concept development is conducted and computer aided design is done to present proposed prototype design.Results from the research gave 4 commercially available electrical actuators, all with significantly different functionality from each other resulting in 4 different concepts and thereof 1 prototype proposal integrated in the waterjet unit according to DNV standards.The selected concept in the study will need some further manufacturing configuration and optimisation for a full installation and working prototype. Ett skifte mot elektisk och hybriddrift inom marina fartyg och framdrivningssystem skapar nya utmaningar och möjligheter, även så för höghastighetsfartyg där vattenjet har en fördel i sin karaktäristiska höga effektivitet. Idag manövreras vattenjetsaggregat med hjälp av hydraulik, som många gånger drivs med framdrivningsmaskineriet och/eller med en elektisk pump. Dessa system blir en energitjuv i en elektrisk eller hybridlösning för framdrivningen och så saknar det en naturlig lösning på hur en hydraulisk pump ska drivas. Slitage och skador på hydrauliska system kan även leda till miljöfarliga utsläpp av hydraulolja. Framför allt då det handlar om höga hydrauliska tryck och bland annat kolvstänger som är utsatta för påfrestningar från fartygens yttre miljö. Dock är hydrauliska system väl beprövade och pålitliga i marina miljöer.Styrning med hjälp av elkraft är inget som är nytt, även kallat Steer-by-wire, det har gjorts och används inom många områden så som flygplans-, bil- och offshoreindustrin. Syftet med studien är att skapa ett prototypförslag för elektisk manövrering av Marine Jet Powers vattenjetaggregat DRB 750. För att uppnå detta har en litteraturstudie genomförts och kvalitativ forskning för att samla information och få förståelse för ämnet. En generisk product- och konceptutveckling har använts med hjälp av datorstödd konstruktion för att presentera ett prototypförslag.Det har resulterat i 4 koncept med integrerade lösningar från olika tillverkare, som alla skiljer från varandra i funktionalitet och skulle kunna användas på ett sätt för att uppnå målet. Varav ett koncept som valdes, det vidareutvecklades till ett prototypförslag med skruvförband i vattenjetaggregatet och som även sågs till att uppfylla DNV:s standarder och regler. Det valda konceptet behöver vidare utveckling, integrering och optimering för att kunna installeras och testas i fungerande prototyp.

In this study, the effect of the channel dimensions on the performance of a marine MHD thruster is investigated using a fully three-dimensional numerical model. In this model, all electric,...

A marine propulsion system is composed of several sub-systems that operate in a variety of energy fields. The propulsion power of a ship can be provided from a two-shaft gas turbine. In this article, the modeling of a two-shaft gas turbine and its associated sub-systems including gears, flexible couplings and clutch is considered. These components are connected in the form of a virtual marine propulsion system, which is based on the bond-graph approach. When a clutch is used in a propulsion system, discontinuities occur in the describing model, which leads to some challenging problems when performing computer simulations. The two main difficulties are the numerical stiffness and the variable model structure. In this research, the bond-graph method is adapted as the modeling framework in order to allow a constant system structure model that minimizes the stiffness problem. Next, simulation results of a two-shaft gas turbine are presented in the off-design condition and verified with experimental tests. These results demonstrate the acceptable accuracy of computer simulations. Also, the effects of clutch performance on the dynamics of the marine propulsion system are discussed.

The aim of this article is to provide a theoretical basis upon which to advance and deploy novel tandem flapping foil systems for efficient marine propulsion. We put forth three key insights into tandem flapping foil hydrodynamics related to their choreography, propulsive efficiency, and unsteady loading. In particular, we propose that the performance of the aft foil depends on a new nondimensional number, s/Uτ, which is the interfoil separation s normalized by the distance that the freestream U advects in one flapping period, τ. Additionally, we show how unsteady loading can be mitigated through choice of phase lag. 1. Introduction Marine propulsion has been an important engineering problem since the time of Archimedes (287–212 BC) (Carlton 1994). The evolution of propulsor design from the classic Archimedes screw to the modern screw propeller has primarily been driven by considerations of efficiency. A hydrodynamically efficient propulsor has low friction losses, low turbulent losses, an ability to manipulate incident vorticity, and a stable and persistent jet-type wake. it is composed of lifting surfaces with high aspect ratio and large lift-to-drag ratio. Although screw propellers offer advantages with regard to mechanical simplicity (just need to turn the shaft!), they have practical limitations that place upper bounds on the overall hydrodynamic efficiency, such as the limitations of aspect ratio due to cavitation at high tip speeds. Research with isolated flapping foils has demonstrated up to 87% propulsive efficiency (Anderson et al. 1998), nearly achieving the ideal efficiency of an actuator disk. However, single-foil propulsion is not practical due to shortcomings, such as large oscillations in thrust, large unsteady side forces, and no mechanical redundancy. Many other nontraditional propulsors also suffer these flaws or are simply inefficient. Biomimetic concept designs and trade-offs have recently been reviewed by Fish (2013). One promising nontraditional propulsor concept involves in-line tandem flapping foils (two hydrofoils, one aft of the other). Recent research indicates that the high efficiency of a single flapping foil may be possible with a tandem foil arrangement (Akhtar et al. 2007; Boschitsch et al. 2014). Tandem flapping foils may also solve the operational problems associated with a single foil, such as inconsistent thrust and side force.

The calculation of natural frequencies is very significant at the design phase of marine propulsion shafts. And added mass of propellers has high effect on natural frequencies. At present, the effect of wake shedding from the propeller’s trailing edge on added mass is unclear. Then their influence on propulsion shafts natural frequencies is also vague. So in this study, the influence of wake shedding on propellers added mass and propulsion shafts natural frequencies is evaluated. Our results show that first, for the first lateral natural frequency, the max relative error reaches up to 6.52 % if the wake shedding is ignored. So for the lateral vibration, the wake should be considered. Second for the first torsion natural frequency, the max relative error amounts to 5.10 % when the skew angle is 108 degrees. So for the torsion vibration, the wake should also be considered when the skew angle is large. Third, for the axial vibration, the influence of wake is little and may be ignored.

The influences of bearing support performance which would be affected by the quality of shafting alignment apparently on the lateral vibration natural frequencies of marine propulsion shafting are analyzed in this paper. A three dimensional finite element model representing the entire propulsion shafting, including the bearings, shaft and propeller, has been developed using finite element software for lateral vibration analyses. The effects of the number of bearings, the stiffness and effective contact length of the bearings on the natural frequencies of the shaft are studied respectively. The simulation analysis show that the bearing of a certain position often only has a significant impact on the frequencies of a certain order or a few orders, and the natural frequencies of the shaft can be transferred to avoid the resonance speeds through the reasonable arrangement and performance design of the shaft bearings. In addition, the curve alignment technology is also presented to improve the current shafting alignment quality and misalignment angle error, so as to ensure the design performance of radial bearings. Experimental results show that the curve alignment technology is an effective method to reduce the uneven load and eccentric wear of the bearings, which are beneficial to avoid the resonance vibration and improve the life and stability of shaft system.

The study of ship underwater radiated noise is nowadays a topic of great and largely recognized importance. This is due to the fact that in the last decades, the problem of the impact of anthropogenic noise on marine life has been addressed with higher emphasis, giving rise to different efforts aimed to the analysis of its effects on different organisms and, in parallel, to means for the reduction of shipping noise. In this context, attention is focused on the propeller noise, which, in cavitating conditions, may represent the most important noise source of the ship. The propeller noise has been studied for long time with different approaches. One of the most effective approaches is represented by model scale testing in cavitation tunnels or similar facilities. Despite having been adopted for several years, radiated noise experiments in model scale are usually affected by significant scale effects and technical issues. One of these aspects is represented by the correct modelling of the propeller inflow; different techniques are adopted, depending on the facility, in order to reproduce a certain target wake. One of the main problems is to define this target wake, which should in principle coincide with the ship wake; as it is well known, it is usually derived from model scale towing tank measurements, with the necessity for the prediction of the full-scale wake field. Starting from the outcomes of a previous work on the influence of different approaches for the prediction of the full-scale wake field for a single screw ship, in this work, attention is focused on the case of a fast twin screw vessel, analysing the different issues which may be connected to this hull form.

The fault-tolerant permanent magnet motor (FTPMM) drives are desired in electric ship propulsion systems. The winding inductance, the sinusoidal degree of the back electromotive force (back-EMF) waveform, and the total harmonic distortion (THD) of the cogging torque are the important factors that affect the operating performance of FTPMM drive. A performance optimization of a three-phase FTPMM by varying motor structural parameters is presented in this article. By analyzing mathematical formulas, notch parameters and permanent magnet size are designed optimally to obtain large winding self-inductance, good sinusoidal degree of back-EMF, and low THD of cogging torque. The finite element verification in Ansoft proves selected parameters reasonable. Finally, an experimental prototype motor is specifically built according to determined parameters; and good performances, magnetic isolation, and fault-tolerant capacity can be guaranteed.

Using the controllable pitch propeller (CPP) in marine propulsion system makes it possible to have maximum ship speed and low fuel consumption at different engine rpm. Good maneuverability is another advantage of such propeller. This feature has persuaded designers to use CPP in ships with various mission profiles like tugs or ferries. The hub boss is of great importance in CP Propellers because it provides housing for blade actuation mechanism. On the other hand, hub boss geometry should be selected as small as possible since it has negative effect on hydrodynamic performance of propeller, specially its thrust and efficiency. In this article, a 3D potential flow-based solver is developed to predict the hydrodynamic characteristic of marine propellers for preliminary and basic design purposes. Through applying the time stepping scheme, it is possible to generate the rollup wake pattern at each time step. As a result, the interaction of vortex wake-lifting/non-lifting bodies are correctly taken into consideration. Validation of the proposed numerical model is carried out with two standard marine propellers (DTMB4119 and KP505) and a high skewed B-series Controllable Pitch Propeller (CPP). Subsequently, a series of parametric simulations are performed on different non-dimensional hub diameters of a CP propeller to find an appropriate hub diameter (big enough to provide CPP mechanism) with highest propeller performance. Ultimately, the suitable hub diameter is determined for an appropriate design of a CP propeller. Rollup pattern for the RV propeller with different hub diameters.

Turbomachinery is one of the most complex machinery that we have today. They have a variety of applications ranging from aircraft engines to huge industrial machines like power generators and marine propulsion. In this study, dynamic stability aspects are evaluated based on Campbell’s criteria. Campbell introduced the concept of traveling waves in his investigations on turbine disk failures. The same concepts are extended to the dynamic stability of Labyrinth seals, which have cylindrical shell-type vibrations. Evaluation of Campbell’s criteria involves three main areas—evaluation of frequency versus the nodal diameter (f/N), evaluation of intersection of each frequency line with the per revolution line and evaluation of interaction points for each frequency line with respect to other stationary or rotating component. All these criteria were studied, and it was felt necessary that the process of evaluating by plotting the above graphs needs to be automated to save post-processing time and also to standardize the procedure. The user has to extract the frequencies from a standard FEA package like ANSYS and input them in the marked cells in the Excel-based tool. Standard color-coding like yellow for input fields, blue color for operating speeds, and red color for design margin is used in the tool. Also, a set of clear instructions is provided in one of the worksheets.

An appropriate assessment of the dynamic behavior of marine propulsion shaft in ships is essential to enable optional delivery of power to the propeller and to minimize unnecessary vibration. Various vibrations coupling with each other can significantly influence the dynamical behavior of the shaft and threaten the reliability of ships. This paper presents a finite element analysis model with multiple constraint conditions to analyze the coupled transverse and longitudinal vibrations of a marine propulsion shaft. Based on this model, in addition to the coupled natural frequencies of each direction, the maximum acceleration are also determined. Furthermore, the simulation of an idling and loading vibration analysis is discussed and validated against experimental results, over a range of rotational speeds. The output of numerical simulation is found to agree with the corresponding results from experimental tests. Finally, an accurate and applicative FEA model for coupled transverse-longitudinal vibration of shaft has been obtained.

Tilting pad thrust bearings are a key component of marine propulsion shaft systems. The dynamic performance of thrust bearings has a significant influence on the propeller vibration. To investigate the axial oil film stiffness of tilting pad thrust bearings, a two-dimensional thermohydrodynamic model incorporating the vibration frequency is developed. The test apparatus and experimental identification model are also constructed. The axial oil film stiffness is experimentally identified at different speeds, loads, and temperature employing the hammer impulse excitation. The axial oil film stiffness between theoretical and experimental results is compared. The discrepancies are not more than 7% for 30 kN operation cases but increase with axial static load. This is partially because the influence of the pivot stiffness becomes obvious with the axial static load increase and cannot be ignored. The results indicate that axial oil film stiffness is at a magnitude of 109 N·m−1. Compared to foundation sti...

A single shaft dual turbine drive, for a marine propulsion system, is considered. Distributed-lumped analysis is used in the dynamic response prediction. This enables the relatively concentrated assemblies to be included as lumped, point-wise representations. The propulsion shaft is incorporated as a dispersed inertia and stiffness model. Multivariable, least effort regulation is employed to achieve the control required. The performance of the closed-loop system following reference input and load disturbance changes is evaluated and the drive shaft speed and twist angle response transients are computed.

The recovery of high temperature thermal energy released by propulsion engines in order to cover thermal loads is commonplace in contemporary ships. However, the medium- and low-temperature thermal energy is only partially exploited or not exploited at all. In the present work, an organic Rankine cycle system driving an electric generator is considered, in addition to the exhaust gas boiler, in order to recover available heat and produce electrical energy. The specifications of the system are determined by an optimization procedure taking economic criteria into consideration, apart from the technical criteria usually used in this kind of studies. More specifically, with the net present value as the objective function and by application of optimization algorithms, the optimal synthesis, design and operation of the organic Rankine cycle system are determined. For the particular vessel considered, the installation of the organic Rankine cycle is technically feasible and economically profitable, with a dynamic payback period of 4 years. The solution of the optimization problem is supplemented with a sensitivity analysis with respect to important parameters.

Stern bearing is a key component of marine propulsion plant. Its environment is diverse, working condition changeable, and condition severe, so that stern bearing load is of strong time variability, which directly affects the safety and reliability of the system and the normal navigation of ships. In this paper, three affecting factors of the stern bearing load such as hull deformation, propeller hydrodynamic vertical force and bearing wear are calculated and characterized by random theory. The uncertainty mathematical model of stern bearing load is established to research the relationships between factors and uncertainty load of stern bearing. The validity of calculation mathematical model and results is verified by examples and experiment yet. Therefore, the research on the uncertainty load of stern bearing has important theoretical significance and engineering practical value.

The energies produced by the diesel engines of strong power are largely used in marine propulsion because of their favorable reliability and their significant output. However, the increasingly constraining legislations, aimed at limiting the pollutant emissions from the exhaust gas produced by these engines, tend to call into question their supremacy. The analysis of the pollutant emissions and their reduction in the exhaust gas of the slow turbocharged marine diesel engine using ANSYS 15 constitutes the principal objective of this study. To address problems of global air pollution due to the pollutant emission from fuel oil engine combustion, it is necessary to understand the mechanisms by which pollutants are produced in combustion processes. In the present work, an experimental and numerical study is carried out on a unit of real use aboard a car ferry ship. A numerical model based on a detailed chemical kinetics scheme is used to calculate the emissions of NOx, SOx and Sooth in an internal combustion engine model for the same characteristics of the real unit. The combustion process parameters based on the numerical model might now be optimized in order to decrease the pollutant emissions in order to meet the IMO regulations.

This paper discusses the themes of optimal design and management strategies of hybrid energy storage system (HESS) for marine applications. This design and related strategy are aimed to improve battery pack durability, ensuring a smooth profile of the required current, through the complementary action of super-capacitors. A DC/DC bidirectional power converter allows for the integration of these devices and control of on-board power fluxes. The proposed methodology is based upon the solution of a constrained optimization problem. In order to overcome computational issues, proper formulation of the mathematical problem is based upon the Ritz method, which is one of the direct methods for solving problems related to calculus of variations. The solution of the optimization procedure, which is the key finding in this paper, permits to obtain battery voltage and current profile, which enables the designer to determine battery and super-capacitor sizes and also provides battery/super-capacitor reference current profiles to be tracked by the DC/DC bidirectional power converter. The procedure is evaluated with reference to the case study of a water-bus operating in the Venetian lagoon, whose operative cycle has been acquired during proper measurement campaigns. Then, the performance of energy management strategies are verified by means of laboratory experimentations on the hybrid energy storage system, which have been carried out by scaling operative cycles at single storage cell level. The obtained results show the potential advantages of proper design and energy management obtained through this new methodology, in terms of investment and maintenance costs for sustainable maritime transport.

Nowadays, more than in the past, marine industries are paying increasing attention to the environmental impact of ships and vessels. Several solutions have been studied and adopted with the final aim of reducing the exhaust gas emissions, mainly acting on the fuel consumption reduction. Within this scenario, the aim of this article is to investigate the energy performance and the fuel saving potential when employing a magnetic continuously variable transmission in a marine propulsion system. Such magnetic continuously variable transmission, considered among other possible continuously variable transmission designs since its torque capabilities are perfectly suitable for the application at hand, is employed in order to optimize the overall propulsion efficiency through an appropriate optimal variation of the reduction ratio as a function of the propeller loads. A secondary benefit, although not less important, is that the magnetic continuously variable transmission is an oil-free transmission that consequently offers a lower environmental impact as compared to traditional lubricated gearboxes. Owing to these considerations, in the article, the magnetic continuously variable transmission size is first selected on the basis of a simplified static model of the vessel. Subsequently, a dynamic mathematical model representing the overall drivetrain dynamic of the propulsion plant is developed, with the purpose of simulating the transmission behaviour during fast ship manoeuvres. Then, in order to test the effectiveness of the proposed design, a trawler is selected as a case study. This particular ship type has been chosen as it provides a variegated operative profile in terms of speed and required thrust, thus being a representative case of those ships in which a continuously variable transmission installation could effectively provide practical benefits. A quantitative analysis of the plant efficiency is finally provided and critically discussed.

The paper presents exergy analysis of main propulsion steam turbine from LNG carrier steam propulsion plant. Measurement data required for turbine exergy analysis were obtained during the LNG carrier exploitation at three different turbine loads. Turbine cumulative exergy destruction and exergy efficiency are directly proportional - they increase during the increase in propulsion propeller speed (steam turbine load). Cumulative exergy destruction and exergy efficiency amounts 2041 kW and 66.01 % at the lowest (41.78 rpm), up to the 5923 kW and 80.72 % at the highest (83.00 rpm) propulsion propeller speed. Increase in propulsion propeller speed resulted with an increase in analyzed turbine developed power from 3964 kW at 41.78 rpm to 24805 kW at 83.00 rpm. Analyzed turbine lost power at the highest propulsion propeller speed is the highest and amounts 3339 kW. Steam content at the main propulsion turbine outlet decreases during the increase in propulsion propeller speed. Exergy flow streams can vary considerably, even for a small difference in propulsion propeller speed. Steam turbine in land-based power plant (high power steam turbine) or in marine steam plant (low power steam turbine) is not the component which exergy destruction or exergy efficiency is significantly influenced by the ambient temperature change. A detail analysis of main propulsion steam turbine from the marine steam power plant at several loads is hard to find in the scientific and professional literature.

Reactivity Controlled Compression Ignition (RCCI) is commonly mentioned as a potential efficient and clean combustion concept. This study makes the first evaluation of natural gas-diesel RCCI combustion for mid-speed marine engines. A state-of-the-art dual-fuel engine with 350 mm bore diameter is the basis for numerical simulations. GT-Power is used to create a one-dimensional air-path model. RCCI is simulated using TNO's multi-zone combustion model incorporating detailed chemical kinetics. The simulations aim to optimize engine efficiency, with peak in-cylinder pressure and emissions as constraints. The study shows best-point Indicated Efficiency of 47.8% is achievable (@75% load) using RCCI mode on stock engine hardware, while meeting IMO Tier III's NOx limit. This performance is similar to the best contemporary marine gas engines, but RCCI also provides additional methane and CO emission reductions. Thus, RCCI combustion can meet Europe's new rigorous Stage V limits, offering significant improvements in a marine engine's GHG footprint. Crucially, the study indicates an engine using hardware optimized for RCCI could deliver outstanding indicated efficiencies of 52%, with emissions of below 1 g/kWh for all legislative species. This combination of high efficiency and ultra-low emissions would make RCCI combustion an attractive proposition for future marine propulsion and gen-set applications.

The process of designing a marine propeller for under water applications involves various complex analyses. Analysis is of iterative in nature which makes it cumbersome and inefficient to understand. A part of the research work entitled in this paper is concerned with the material effect and stress behavioural characteristics of a marine propeller blade subjected to cantilever condition. Designing and analysing the behaviour of an anisotropic composite material is one of the most important technologies in the area of marine propulsion. Based on FEM the conventional and composite material marine propeller blades are analysed. To simulate the blade layup and to determine the stress characteristics, ANSYS software with shell 181 elements is taken for reference. A study has also been carried out for determining the stress and deformation pattern arising due to varying ply layup and material. The obtained numerical results are then compared and summarised in. Computational efficiency and integrity of the presently adapted method in this work are determined by several case studies.

Naval propulsion systems are characterized by a high degree of complexity within a single system and a large variation between the solutions applied to individual vessels. In this situation, issues relating to the comprehensive diagnostic is a serious problem. Diagnostics models are useful to made the this problem easier. It should be emphasized that it is impossible to develop a universal model correct for all types of vessels. The paper presents general guidelines for the creation of diagnostic models. The results of first stage of studies on diagnostic model covers unit equipped with a twin-engine twin-shaft drive system had been presented.Introduction Changes of technical state of the machine occur as a result of its response to changes in the energy emitted by them. If qualitative and quantitative parameters of this energy are known diagnostician after proper analysis is able to determine the technical condition of the machine. It can be concluded that the technical diagnostics is a test of object response to the impact of energy causing change of its technical condition [9]. As far as the destruction of the object model is concerned we find that the degree of wear of the machine is proportional to the energy dissipated from it.

Complexity of modern and large ships poses a challenge to effective and comprehensive reliability and safety assessment of the propeller operations. The marine propulsion system forms the fundamental of ships' operations. The propeller reliability and safety directly affects the safe operation of the ship including its cost performance. Therefore, focusing this research on examination of safety and reliability of the propeller operations is paramount. In view of this, propeller operations are analysed to facilitate identification of their various failure modes and associated risk implications under uncertainty. Furthermore, advanced algorithms, such as fuzzy logic, evidential reasoning (ER), analytical hierarchical process (AHP) and expected utility theory, are used to develop a robust methodology that can be employed in assessment of safety and reliability of the propeller operations. Application of the developed methodology shows that the safety and reliability of ship propeller operations are not at op...

Transport depends on crude oil as a source of fuel for trucks, trains and ships and bitumen for roads. Europe has shown that even with a strong commitment to emission reduction, transport Green House Gas emissions will continue to rise relative to other sectors. As Australia’s freight task increases and as fuel supply risks increase, the need for change is also increasing. Investment will be required in transport fleet expansion and replacement, meaning that now is an opportune time to review our transport paradigm. Sea transport is no different to road, rail and air in its ability to leverage improvements in engine efficiency, materials, logistics management, control systems, renewable fuels, hybrid, solar and energy storage technologies. However, sea transport has two unique advantages over other transport modes: a low cost of infrastructure and the capability of harnessing wind by direct conversion of kinetic energy. The development of high-efficiency vessels and market drivers are close to a t...

Applications for low-speed high-torque machines include marine propulsion and wind power generation. Since electric machinery size is more directly related to required torque than to required power, high required torque leads to large machines. Mechanical gears increase the speed and lower the required torque of the machine to reduce size. This, however, results in increased noise and maintenance, and decreased reliability. Magnetic gears offer the advantages of mechanical gears without the disadvantages created by physical contact. Integrating magnetic gears into the machine structure offers additional mass savings. This study proposes a novel machine architecture, which integrates magnetic gearing and a permanent magnet synchronous machine to create an inner rotor flux-modulated permanent magnet synchronous machine. Unlike previous arrangements, the proposed machine utilizes a more desirable inner rotor configuration and avoids multiple magnet arrays. This study presents a finite–element-based design model of the proposed machine to be utilized in an optimization-based design environment. A multiobjective design study is presented for a laboratory scale application. The resulting tradeoff between mass and loss is compared with that of a permanent magnet synchronous machine for the same application.

Exhaust gas scrubber is one of the options to comply with the new regulations for sulphur emissions in the shipping industry. This article presents a model-based approach to assess the energy and environmental performance effects from the installation of a seawater flue gas desulphurisation scrubber on a marine two-stroke diesel engine propulsion plant. A mathematical model was built that describes the governing physical and chemical behaviour of the integrated machinery system. The model was used to examine the impact of main scrubber design characteristics on the engine fuel consumption under different engine loads. The results indicate that the desulphurisation system causes an increase in the engine fuel consumption, for constant power output. This is due to the increased back-pressure to the turbocharging system caused by the pressure drops in the desulphurisation system. This effect can be partly mitigated by the installation of forced-draft fans after the desulphurisation system limiting the negative impact on the overall system efficiency to half of its initial value.

The paper analyses legal requirements for the composition of exhaust gas emitted by ships, marine engines including. The background for this paper is the increasingly stricter limits set for the emission of the toxic exhaust gas components by marine engines. Legal requirements force designers to search for new constructions of marine propulsion systems and constantly improve the existing ones. One of the solutions is supplying water into the combustion chambers of diesel engines—the solution widely known for many years n ow wins favour and, according to the authors, has a chance to gain competitive advantage over alternative constructions. A special attention has been paid to the allowed amount of nitrogen oxides and sulphur oxides in exhaust gas resulting from the International Convention for the Prevention of Pollution from Ships. So far, one, global evaluation of brand new and retrofitted marine propulsion system designs presenting this issue thoroughly has not been done. The authors’ interest in the issue derives from this fact and has been confirmed by many papers. We showed the mechanism of decreasing nitrogen oxides in exhaust gas by means of water supply into the combustion chambers of diesel engines. We presented an overview of designs which might be used to retrofit vessels already in operation or introduced at the stage of vessel construction in the shipyard. The paper also contains an evaluation of the described designs. The following systems have been discussed: continuous water injection into the scavenging air, humid air motor, direct water injection with the use of combined nozzles, water-cooled residual gas system and fuel–water emulsion supply system using emulsifiers or devices of high-pressure water injection into fuel. We have made a comparison of the effectiveness of different methods used to reduce the emission of nitrogen oxides. Advantages and disadvantages of supplying water into the combustion chambers of diesel engines have been shown together with the comparison of the range of changes in their construction. The authors have indicated potential opportunities derived from injecting Brown’s gas into the combustion chamber in order to change the composition of the exhaust gas. As a consequence, it will also affect the natural environment where vessels operate.

Four permanent magnet machine topologies — a traditional surface mounted permanent magnet machine (SMPM), a heterogeneous pole permanent magnet machine (HPM), an asymmetric salient surface mounted permanent magnet machine (APM), and an interior permanent magnet machine (IPM) — are compared for use in an electric ship propulsion application. Using a multi-objective design approach coupled with analytical and hybrid magnetic equivalent circuit (MEC) models and a highly consistent set of design constraints, Pareto fronts demonstrating the trade-off between loss and volume for each machine topology are presented and compared.

Marine propulsion unit (MPU) is one of the dominant vibration and noise sources onboard ship. Its vibration can be attenuated effectively by isolating MPU with low-frequency mounting system. But this is difficult to implement due to the stringent requirement of MPU alignment with the propulsion shafting. In this paper a novel air spring mounting system (ASMS) for propulsion system is proposed consisting of air spring subsystem, alignment control subsystem and safety protection subsystem. The load distribution optimization method and dynamic model of ASMS are presented. The factors that affect system stability and natural frequencies are analyzed, as well as the design measures to enhance system performance. A theoretical model is presented to estimate the isolation effect of ASMS. The monitoring model of alignment between MPU and propulsion shafting is established, followed by the alignment control algorithm and converge rule which assures the fast and uniform convergence of both air springs׳ load distribution and alignment control process. Safety protection mechanism is designed to ensure that the MPU can operate safely in case of ASMS failure or other extreme circumstances. A scaled ASMS prototype is manufactured and tested on a special experimental setup. Experimental results validate the effectiveness of theoretical models and show that the performance of ASMS satisfies the operation requirements of MPU.

Water jet mixed-flow pumps have been widely used in the field of marine propulsion. To ensure that the pumps work at stable conditions, flow instabilities were analyzed under low flow-rate conditions, where unstable flow most likely occurs. A numerical simulation was performed with the realizable k-epsilon turbulence model. This model exhibits better agreement with the experimental data of the performance curve compared with the standard k-epsilon turbulence model. Performance and internal flow analyses in the diffuser and impeller channels were conducted separately. Results show that the performance curve of the pump model with and without guide vane presents a positive slope at 28–59 % of the designed flow rate where stall occurs. Furthermore, the stalled flow in the impeller channels, rather than the reverse flow in the diffuser channels, causes the positive slope of performance. The stalled flow is located at the leading edge of the blade tip. It develops from the suction side to the pressure side of the blade. In addition, the stall zone extends gradually from three to five impeller passages with decreasing flow rate. The results can serve as references to improve the performance instabilities of water jet mixed-flow pumps.

The author would like to thank S. Djebarri from the Research Institute of Naval Academy for his help with computing the machines with FEA program FEMM and F. Byrne from the French Naval Academy for her English proofreading; International audience; Five-phase Surface-Mounted Permanent Magnet (SMPM) machines can inherently produce a smooth electromagnetic torque which can be increased when using third harmonic current injection. To really take advantage of these characteristics, the rotor magnets can be shaped in order to obtain a back-emf with large third harmonic term. This is the scope of the paper. For the design specifications of a low speed marine propulsion machine, the following objective must be achieved: to significantly mitigate the pulsating torque without reducing the average torque bearing in mind the solution where the rotor is made with full pole-pitch magnets. An analytical field computation, called equivalent coil method, is developed in order to quicly explore the magnet geometries. Thus a procedure to optimize small trapezoid notches at the surface of the pole magnets is performed. Referring to the classical fully pole-pitch magnet shape, the solution found allows a substantial reduction of the pulsating torque without reducing the torque density. Furthermore, with regard to an equivalent three-phase machine, for the same copper losses, the average torque of the optimized five-phase machine can be potentially higher if the third harmonic current injection is implemented.

This research presents analysis, experiment, and prediction of the performance of a unique marine propulsion concept, the air-augmented waterjet, having a revolutionary potential for significant thrust augmentation and boost capability of waterjet systems. So far, this concept has not been realized in any operational vessel. The air-augmented waterjet propulsion concept is similar to an after-burner in the aeronautical turbojet engine. The thrust augmentation results from the injection of air bubbles into the water flow, converting their expansion work òpdV into additional kinetic energy of the exhaust jet without affecting the pump operation. It can enable substantially augmenting boost capability, overcoming hump resistance, and increasing maximum attainable vessel speed while avoiding cavitation problems. Static tests at the Technion's water tank, using a jetski waterjet engine of a nominal power of 50 kW, have been conducted with and without air injection over a range of motor revolutions per minute (rpm). The addition of air increased the thrust by 20% to 50% depending on the airflow rate and engine rpm. Air expansion work increased the exhaust jet kinetic energy at an efficiency of 70% approximately. Based on the static experiments, prediction of the system behavior for different vessel speeds and engine power levels has been made, revealing a higher relative thrust augmentation for the same pump power and airflow rate at higher vessel speeds. The air-augmented waterjet concept may add a new dimension to marine propulsion as well as upgrade existing vessels.

This work is part of a research project conceived at the Federal University of Rio Grande. The project aims to create and develop mechanical devices that use the Coanda effect to enhance their overall efficiency. The focus herein is analyzing the physical phenomenon occurring in a conceptual water-jet propulsor. In the proposed concept, a water-jet propulsor has its impeller replaced by injectors that produce the so-called Coanda effect, increasing thereby the mass flow rate. In order to simulate the flow through the propulsor, a numerical model was developed. In this model the time-averaged conservation equations of mass and momentum were solved numerically by the finite volume method, more precisely with the commercial package ANSYS FLUENT (version 14.0). For the closure of the constitutive equations, the k-ω URANS turbulence model was employed. The simulation was performed for a transient state with a timestep of ∆t = 1×10-3 s and a total physical time of t = 6.0 s. Static pressure fields, streamlines and speed profiles are used to analyze the equipment performance and the phenomenon occurrence. The results show that the Coanda Effect is able to generate thrust in a waterjet propulsion device without impeller. The study suggests that the employment of this principle has promising applicability in marine propulsion and deserves attention on future works.