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In today’s environment of increasing pressure to reduce fuel consumption and emissions of carbon dioxide (CO2) and nitrogen oxides (NOx), the LNG (Liquefied Natural Gas) transportation industry is growing in size and influence. In this context, further efforts are needed to improve the energy efficiency of LNG marine energy power plant. The LNG vessels and their equipment considered in this study have different power consumption requirements depending on the vessel’s mode of operation (loading/unloading, maneuvering, anchoring, at sea, etc.). For each ship mode, where the power plant requirements are the same, the specific fuel consumption (SFOC) and exhaust emissions, NOx and CO2, are compared with a different number of engines in the network to find the optimal number of engines in the network, considering both the safety aspect and the port requirements. An analysis was performed showing the efficiency of the on-board power management system (PMS) in terms of manual load sharing between engines. A comprehensive analysis of the data and its comparison led to the conclusion that the manual distribution of power among the engines is the slightly better solution. The obtained results show that further analysis of the number of engines for a given load with minimum fuel consumption and CO2 and NOx emissions is required.

The development of new technologies and their application in marine systems has increased the complexity of propulsion systems. The increase in the number of ships within the merchant fleets has resulted in difficult monitoring of the condition of ships and the need for expertise in electronically controlled propulsion systems. The introduction of diagnostic systems enables easier analysis of operating parameters, and thus improves the efficiency of the marine energy system. The paper examines new diagnostic systems, one of which is a remote monitoring system applied to a marine engine during its operation. During the research, the most influential parameters of the tested engine were identified and its operation was analyzed. Conclusions were drawn on the advantages and disadvantages of the application of remote monitoring systems for marine engines and provided guidelines for determining the remote monitoring system of marine energy systems that should be installed in ships to increase energy efficiency.

A certain amount of spare parts is required for any maintenance operation. The organization and the implementation of proper maintenance requires appropriate amount of spare parts. Safety and reliability of the ship depends upon proper maintenance, requiring appropriate amount of spare parts as well. The ship is a vehicle that is in constant motion with a limited amount of useful space in general, this fact is also applied to spare parts storage. Spare parts in stock represent not only "dead capital”, but also a significant annual cost. Therefore, more attention should be given to optimization of spare parts. Determination of the optimal amount of spare parts can be presented as a compromise that should meet the requirements for proper and timely maintenance, as well as decrease of the costs for spare parts. The Planned Maintenance System is used for planning, documentation and implementation of surveys and maintenance, as well as for monitoring of spare parts stock and consumption. Systematically and continuously collected data from a computerized Planned Maintenance System can be used for the optimization of spare parts. This paper shows how to implement the optimization of spare parts on board using analysis of the data obtained from the ship's computerized Planned Maintenance System.

This paper discusses an onboard compressed air supplied system. The system is described by differential equations of its components by which the model is developed. The simulation of the system has been made for different operating conditions (different initial conditions of the air and stepped regulation of air flow through compressor). Furthermore, simulation of the system under heat exchanger failure is also considered. The results of the simulation show the changes in pressure and temperature over time and the energy consumption for different operating conditions. In addition, the simulation results show that the energy consumption is the lowest in case of normal operation of the system with air flow regulation through compressor.

This paper discusses the influence of the poppet geometry of the direct spring operated pressure relief valve on the dynamics of its motions. Using derived differential equations, a mathematical model in Matlab –Simulink has been obtained. The results obtained by a computer simulation describe dynamic properties of the poppet and its influence on the system dynamic with respect to the poppet geometry.

Pri prvim razmatranjima zraka kao objekta primjene u solarnim dimnjačkim elektranama zrak se pretpostavljao kao sušti zrak, bez sadržaja vlage. Ovim se pojednostavnilo razmatranje promjena stanja zraka u procesima u solarnim dimnjačkim elektranama. Time su uklonjene mogućnosti kondenzacije ili kristalizacije vodene pare i zaleđivanje kondenzata vlažnog zraka te utjecaj navedenih na radnu sposobnost zraka i njegovu tehničku iskoristivost u turbinama. Predložene metode proračuna uzdizanja vlažnog zraka kroz atmosferu i računanja njegove tehnički radne sposobnosti u gravitacijskom polju – visinskog potencijala od Petele i Michauda ne daje potpun uvid kako u njegov tehnički iskoristivi dio eksergije tako i u uplivu pojave kondenzacije i kristalizacije na sam proces uzdizanja. U radu je dan novi, alternativni proračun uzdizanja vlažnog zraka kroz atmosferu u gravitacijskom polju. Primjenom novog načina proračuna dobivaju se rezultati kojima su jasno određena stanja vlažnog zraka tijekom uzdizanja, pojava te utjecaj kondenzacije odnosno kristalizacije vodene pare na visinski potencijal. Temeljem izvedenih izraza izrađen je matematički model uzdizanja vlažnog zraka kroz atmosferu u programskom jeziku MATLAB. Rezultati dobiveni numeričkom simulacijom daju jasan prikaz utjecaja temperature, relativne vlažnosti i izdvojene količine kondenzata odnosno kristala na visinski potencijal vlažnog zraka. Novi numerički model uzdizanja vlažnog zraka i njime dobiveni rezultati predstavljaju osnovu za teoretsku analizu procesa velikih rashladnih tornjeva, solarnih dimnjačkih elektrana te osnovu za koncipiranje elektrana s gravitacijskim vrtložnim stupom.

Raspoloživost propulzijskoga dizelskog motora u pogledu snage ili bilo koje druge značajke, pri raznim eksploatacijskim uvjetima utvrđuje se proračunima, a potvrđuje empirijskim metodama. Računalno-simulacijski modeli veoma su važni za takve analize. Računalno-simulacijski model brodskoga propulzijskog dizelskog motora osnovan na matematičkom modelu, prikazan je u ovom radu [1]. Model je upotrijebljen za analizu stacionarnih i dinamičkih uvjeta rada sporohodnoga propulzijskog dizelskog motora s prednabijanjem i brodskoga vijčanog propulzora s nepomičnim krilima. Model je izrađen uz uporabu računalne aplikacije MATLAB 7.0.4.- SIMULINK, na osnovi detaljnoga matematičkog nultodimenzionalnog modela. U ovome radu navedeni model je poslužio za raščlambu utjecaja promjene snage u pojedinim cilindrima na radne značajke motora. Promjena snage simulirana je prekidanjem dobave goriva jednome cilindru pri različitim opterećenjima motora i različitim ograničenjima poluge goriva. Analizom rezultata simulacije utvrđene su granice radnih značajka motora i sigurna pogonska stanja., Availability of propulsion diesel engine such as power or any other characteristics, under different exploitation conditions is determined by calculations, and is confirmed by empirical methods. Computer simulation models are very important for such analyses. The computer-simulation model of ship propulsion diesel engine based on mathematical model has been presented in the work [1]. The model is applied in the analysis of the static and dynamic operating conditions of the turbo-charged slowspeed diesel propulsion engine and the fixed blade propeller. The model was created by applying computer program MATLAB 7.0.4.-SIMULINK, and according the detailed mathematical zero-dimensional model. In this paper, the aimed model is used for analyzing the influence of the power changing of one of the cylinder on the engine performance. The power changing has been simulated by cutting of fuel delivery to one cylinder under different loading conditions and by the different limit of fuel rack. By analyzing the results of the simulation, the limits of engine working parameters and safety boundary conditions have been determined.

Maritime electrical systems are autonomous systems. The prime movers including diesel engines, gas/steam turbines, are integral parts of the systems. The power consumers are large compared with the total capacity of the system, as for example thrusters and propulsion systems for dynamic positition operated vessels, drilling systems etc. The complexity of vessels such as cruise vessels, ice breakers or vessels where much manoeuvring is required (frequent change in propulsion load) requires dependable electrical power for operation, integrity of the well and safety – of both the installation and its personnel. With the increasing use of +450 V with onboard equipment the special course (High Voltage)/lecture or simulator is aimed at engineers/personnel (electrical or non-electrical) required to carry out restricted switching duties and includes preparation procedures for using HV systems safely. The simulator/course was identified as the best choice to create the competent ship operators within shortest time. Specific training objectives include the overall training objective of specific model is: − To understand the total plant operation, familiarisation with electric plant, understand the need for high voltage levels in a large power system etc. − To reduce the risk of human error in the operation and maintenance of marine equipment.

U radu je prikazana analiza promjene stanja fluida u pneumatskom sustavu klipnog kompresora, promatranog kao vlažni zrak (smjesa idealnih plinova, zraka i vodene pare). Uspostavljene su diferencijalne jednadžbe kojima je opisan kontinuirani dinamički model, a pomoću MATLAB-a izvedena je simulacija promjena stanja fluida. Kao rezultati simulacija prikazane su promjene stanja fluida, te napravljena usporedba pri istoj početnoj temperaturi i različitim vlažnostima vlažnog zraka.

In this paper movement of the one direct acting spring relief valve used in ship pneumatic system is analyzed. Using differential equations, for dynamic and thermodynamic subsystems, a continuous dynamic model is described in MATLAB Simulink. As simulation results, piston valve movement and control volume pressure changing, relevant for construction and exploitation of spring relief valve, is showed and analyzed.

A higher professional level is quite essential these days for marine engineers to operate safely and properly a merchant vessel equipped with advanced automation systems. Educational and technical training using a simulator is one of most effective skill-up methods. This paper presents overview of part of the possibility provides by ship’ s engine room simulator Kongsberg ERS-L11 MAN B&W-5L90MC– VLCC Version MC90-IV in students and seafarers education and practical training in conditions nearby realistic circumstances at sea.

The inevitable computerisation and automation of the shipboard propulsion system have given rise to an increasing number of possibilities of improvements in its operation. This is the area in which the expert system has made an enormous impact upon the further employment of computers aboard the ship. By eliminating the camshaft and replacing it with a high-pressure variable injection timing pump (VIT) an optimum injection time in a variety of operating modes has been achieved. A further advantage of the VIT pump is that various parameters can be easily adjusted during engine operation, e.g. time of injection, gradual injection, etc., seeking thereby an optimum injection mode. The paper deals with a conceptual solution concerning the VIT pump operation by means of the expert system, aimed at determining an optimum angle of fuel injection. The results of simulation hereby presented clearly justify the employment of such a system aboard the ship. The fuel injection control sub-system makes a part of the entire shipboard propulsion system. It can significantly contribute towards a better understanding of the functioning of other operating systems, which makes it particularly suitable to be included in the marine engineering teaching curriculum, primarily the courses dealing with marine engines.

This article presents a mathematical model of a complete diesel-electric propulsion system, including components as diesel generators, distribution network: variable speed thruster-drives, and conventional motor loads. The model is split into two parts: One power generating part where the load is specified with an aggregated active and reactive power load demand. Secondly, a power consumption part where the effects of the different load types as thruster drives, motors and other loads are modeled. The paper discusses and analyses The problem of load regulation and regulation of shaft generator within the ship's electric power system, the final goal being an optimisation of expenses.

This paper presents problem of finding coefficients of the approximate function and the application of the search method, called Genetic Algorithm (GA) for finding an optimal solution. GA is based on Darwin's evolution theory and it simulates natural evaluation of the chromosome. By using some genetic operators as for example selection, crossover and mutation, the goal of the GA is to produce better items. Set of points like T={; ; (x1, y1), (x2, y2), ... , (xp, yp)}; ; and the function g(x) with the following coefficients: a0, a1, a2, where ai  [lb, ub] are considered. The paper examines the feasibility of using genetic algorithm in determining coefficients so that the above men tied curve g(x) yields the solution best suited to the measurements conducted beforehand. For the solution discussed in this paper the function g(x) approximates operation costs of diesel generator pertaining to the ship board electrical power system.

U radu je analizirano gibanje jednog sigurnosnog ventila koji se koristi za ograničenje tlaka u brodskim hidrauličnim sustavima. Uspostavljen je dinamički model ventila, a njegovo je gibanje opisano izvedenom diferencijalnom jednadžbom. Pri računalnoj simulaciji, korišten je kontinuirani matematički model u Dynamo simulacijskom jeziku. Kao rezultat, dobivene su dinamičke veličine stanja ventila za njegovo puno i smanjeno opterećenje u radnim uvjetima.

Neizbježnom upotrebom računala i same automatizacije brodskoga propulzijskog sustava, došlo se do velikog broja mogućih poboljšanja njegova rada. Ekspertni sustavi u ovom području imaju veliki utjecaj na daljnji razvoj upotrebe računala na brodovima. Izbacivanjem bregaste osovine i njezinom zamjenom visokotlačnom pumpom promjenjiva vremena dobave (VIT) postiže se optimalno vrijeme ubrizgavanja goriva u cilindar u različitim režimima rada. Daljnja prednost VIT-pumpe je ta što se tijekom rada motora nesmetano mogu ugađati raznovrsni parametri (vrijeme ubrizgavanja, stupnjevano ubrizgavanje goriva u cilindar… ) i tako optimizirati ubrizgavanje goriva u cilindar. U radu je prikazano idejno rješenje upravljanja VIT-pumpom s pomoću ekspertnog sustava radi određivanja optimalnog kuta pri ubrizgavanju goriva. Rezultati simulacije pokazuju opravdanost upotrebe ovakva sustava na brodovima.

The motion of a back pressure spring valve used in ships hydraulic system is presented in this paper. Dynamical model of valve is made, and its motion is described with performed differential equation. Mathematical model in MatLab-Simulink simulation language is used for computer simulation. As a result, dynamical quantities of valves state are obtained for his full and reduced load in working conditions.

Conventional databases represent the state of an enterprise at a single moment of time. They support modification operations which facilitate the transition from one consistent database state to another. For queries, they assume that all facts stored in the database are valid at the time instant a query is evaluated. There exist many application domains where it is needed to reconstruct earlier database states or even store future database states in parallel. The different database states are stored as temporal data. This paper shows one approach to managing temporal data, along with the corresponding prototype implementations.

The motion of a back pressure spring valve used in ships hydraulic system is presented in this paper. Dynamical model of valve is made, and its motion is described with performed differential equation. Mathematical model in MatLab-Simulink simulation language is used for computer simulation. As a result, dynamical quantities of valves state are obtained for his full and reduced load in working conditions.

This paper discusses and analyses the problem of load regulation within the ship's electric power system, the final goal being an optimisation of expenses. Determining an adequate distribution of load with regard to the primary electric power sources in order to achieve optimum effects constitutes an extremely difficult optimisation problem in the solving of which the application of genetic algorithm has proved to be particularly effective. The modulus of power calculations yields the data concerning voltages and losses which, together with other criteria, are used in the GA subsystem in order to conduct the optimisation, resulting in a set of solutions containing the appertaining quality evaluation. Our motivation for applying a genetic algorithm to the unit commitment problem is that it can completely replace mathematical programming methods and is easy to implement as a search procedure.

Electric drive is increasingly gaining in importance within the general ship propulsion system. Contemporary electric propulsion mainly contains a fixed propeller, a synchronous or asynchronous propulsion engine and PWM frequency converter with an adequate drive. During recent years the azimuth system has become the most popular concept within the shipboard electric propulsion system. Ship’ s maneuverability has been significantly improved and the hull’ s vibration reduced. The employment of an external propulsion unit gives additional space for cargo or passengers. Dynamics of operation of the marine permanent magnet synchronous machine has been analyzed during operation in case of sudden increase of loading at propeller by application of mathematical model Matlab.

In the past decade, the increasing demand for safety, efficiency and lower environmental impact from shipping has dominated the development of the industry. This paper summarizes technical and marketing information of the « ; near-term» ; fuel cell technology.

Computer analysis and simulation is of vital importance to ensure the successful design and development of marine engineering systems. In many areas, conventional modelling methods have produced system representations which are inaccurate and (or computationally) expensive in terms of processing power and memory requirements. In this paper Matlab-Simulink was chosen as the modelling tool and Power System Block set (PSB) was also used. Initially it was intended to use PSB to build a reasonably detailed model of the system and the system to use this single model to examine all electrical response.

Use of electrical energy on board ship has been defined by a set of requirements which differ from those under stationary conditions. Since testing and checking of the electric power system is difficult to be carried out under operating conditions, relevant mathematical model shall be applied. Dynamics of parallel operation of the marine synchronous generators has been analyzed during operation in case of sudden increase or decrease of loading in electric power system by application of mathematical model MatLab.

This atricle deals with the application of personal computer in preventive maintenance of the ship(s) propelling system. Preventive maintenance is very extensive and responsible work and thus it is to be specially considered. Application of computers for making decisions, planning and reporting on preventive maintenance activities reduces human errors, negligence, disregards and omissions to the minimum extent.

Električna propulzija zauzima sve značajnije mjesto u brodskom porivnom sustavu. Suvremeni sustavi električne propulzije uglavnom sadrže propeler s fiksnim krilcima, sinkroni ili asinkroni propulzijski motor, pretvarač frekvencije i srednjohodne dizel-generatorske a.c. jedinice. U zadnjih nekoliko godina najpopularniji koncept u sustavu brodske električne propulzije jest azimutni sustav. Manevarske brodske sposobnosti znatno su poboljšane, a vibracije trupa umanjene. Korištenjem vanjske propulzijske jedinice dobiva se dodatni raspoloživi prostor za teret ili putnike.

Konstruktal (AlMg4, 5Mg1 - 7020) is wrought thermally hardened aluminium alloy, which when in hardened condition reaches the strength of low carbon steel. Due to proper mechanical properties and low density, it is mostly used in aircraft industry and in bearing structures. The literature conceptions about the problems that accur during the process of welding this alloy are given in this article. The results of the mechanical and metallographical testing of welded experimental specimens are given as well. With weldability investigation of alloy konstruktal for different welding processes, authors wish to give contribution to weldability knowledge base of wrought thermally hardened aluminium alloys.

Organski Rankineov ciklus (ORC) je posebna vrsta Rankineovog ciklusa u kojem se kao radni medij umjesto vode koristi neki organski fluid niže temperature vrelišta. Princip rada između klasičnog i organskog Rankineovog ciklusa se ne razlikuje, a glavna razlika je upotreba fluida drugačijih svojstava. Prema tome, izmijenjena toplina te ostali termodinamički parametri su drugačiji u ovom tipu procesa te će biti prikazani u ovom radu. Prikazano je kako radni fluid igra ključnu ulogu u radu ORC sustava te je obrađen način odabira organskog fluida. Primjenom ORC sustava moguće je dobiti toplinsku i električnu energiju iz jednog izvora topline. Organic Rankine cycle is a special type of cycle which is using organic fluid with lower boiling temperature instead of water as working fluid. Working principle of classic Rankine and organic Rankine cycle are the same, main difference is in usage of different working fluid. By that, exchanged heat and other thermodynamical properties are different in this type of cycle and this will be shown in the paper. It is also shown how working fluid is the key in this type of cycle and how to choose the organic fluid. By using organic Rankine cycle, it is possible to get both heat and electrical energy from one source of heat.

U radu su opisani izmjenjivači topline te njihovu podjelu i pojedine karakteristike. Koncepcija rada temelji se na pet osnovnih cjelina i uvodom. U drugoj cjelini objašnjeni su sami izmjenjivači topline. U trećoj cjelini navedeni su zahtjevi Klasifikacijskog društva u pogledu konstrukcije, armature i kontrolnih mjernih instrumenata te navedene su vrste zavara. Četvrta cjelina odnosi se na proračun brodskih rashladnih uređaja. Cjelina obrađuje proračun kondenzatora i proračun isparivača. U petoj cjelini prikazani su dosadašnja razmatranja proračuna učinkovitosti izmjenjivača topline, uključujući i eksergijsku učinkovitost izmjenjivača topline. This paper describes a heat exchanger in marine refrigeration equipment and marine steam generators and their categorization and individual characteristics. The concept of work is based on five basic units and introduction. In the second part are explained heat exchangers alone. In a third part are mentioned Classification Society requirements in terms of structure, armature and measuring instruments, The fourth part is dedicated to calculation of marine refrigeration equipment. In a fifth chapter efficiency calculation principle are shown, including exergy efficiency of heat exchangers.