Data from a two-stage axial vapor cryogenic compressor on the dual-fuel diesel-electric (DFDE) liquefied natural gas (LNG) carrier were measured and analyzed to investigate compressor energy and ...exergy efficiency in real exploitation conditions. The running parameters of the two-stage compressor were collected while changing the main propeller shafts rpm. As the compressor supply of vaporized gas to the main engines increases, so does the load and rpm in propulsion electric motors, and vice versa. The results show that when the main engine load varied from 46 to 56 rpm at main propulsion shafts increased mass flow rate of vaporized LNG at a two-stage compressor has an influence on compressor performance. Compressor average energy efficiency is around 50%, while the exergy efficiency of the compressor is significantly lower in all measured ranges and on average is around 34%. The change in the ambient temperature from 0 to 50 °C also influences the compressor's exergy efficiency. Higher exergy efficiency is achieved at lower ambient temperatures. As temperature increases, overall compressor exergy efficiency decreases by about 7% on average over the whole analyzed range. The proposed new concept of energy-saving and increasing the compressor efficiency based on pre-cooling of the compressor second stage is also analyzed. The temperature at the second stage was varied in the range from 0 to -50 °C, which results in power savings up to 26 kW for optimal running regimes.
Air pollution from ships is increasing due to higher global demand of goods, and with them, global emission standards as well. These standards are prescribed by MARPOL Annex VI and the introduction ...of emission control areas (ECA). Ships built before 1990. do not have to comply with these rules, but ships built after the early 2000. must follow “NOx Emission Tier I”, which allows 17g/kWh NOx (for the slow speed diesel engines with <130 rpm), and selective catalytic reactors (SCR) are not necessary. Tier III NOx Emission standard was enforced in 2016 and it requires an 80% reduction in NOx emission compared to the Tier I, specifically 3.4 g/kWh, which can not be achieved without SCR or without using some other types of fuels. The focus of this paper is to do analysis how the ammonia dosage to SCR affects to the NOx formation in exhaust gasses on various engine speed (loads), as well as how it affects to some important engine parameters and specific fuel oil consumption (SFOC). The analysis was performed on Kongsberg engine room simulator (ERS), MC 90-V Model, as well as on MATLAB by using mathematical models. All external influences are excluded from the analysis like wind or rough sea. All data on different scenarios has been recorded after prolonged period to avoid inconsistencies. The results are shown graphically, and conclusions are presented.
A common way of measuring heavy fuel oil consumption on board a vessel is to use volumetric fuel flow meters installed at fuel systems inlets for each of the major fuel consumers. At each stage of ...the fuel processing cycle, certain mass fuel losses or deviations and calculation errors occur that are not counted accurately into fuel consumption figures. The goal of this paper is to identify those fuel mass losses and measuring/calculating errors and perform their quantitative numerical analysis based on actual data. Fuel mass losses defined as deviations identified during the fuel preparation process are evaporation of volatile organic compounds, water drainage, fuel separation, and leakages while errors identified are flow meter accuracy and volumetric/mass flow conversion accuracy. By utilizing statistical analysis of obtained data from engine logbook extracts from three different ships numerical models were generated for each fuel mass loss point. Measuring errors and volumetric/mass conversion errors are numerically analyzed based on actual equipment and models used onboard example vessels. By computational analysis of the obtained models, approximate percentage losses and errors are presented as a fraction of fuel quantity on board or as a fraction of fuel consumed. Those losses and errors present between 0,001% and 5% of fuel stock or fuel consumption figures for each identified loss/error point. This paper presents a contribution for more accurate heavy fuel oil consumption calculation and consequently accurate declaration of remaining fuel stock onboard. It also presents a base for possible further research on the possible influence of fuel grade, fuel water content on the accuracy of consumption calculation.
Firefighting and evacuation training are important tasks in maritime education and training, especially for crews working on large passenger ships, to ensure the safety of the vessel, cargo and ...passengers. With the evolution of virtual reality (VR) technology and the introduction of wearable hardware, a change in paradigm has happened in firefighting and evacuation training where these new technologies are being introduced. This paper serves as a review on the use of VR technology in maritime firefighting and evacuation training, trying to answer the following questions: what is the current state of using VR technology, and what are the research gaps that need to be addressed to further accelerate the implementation of VR? Research shows that other industries have adopted the use of VR technology relatively quickly, but the maritime industry still seems reluctant. As for the research gaps, the physics-based modelling of fire spread is discussed along with two other topics: the lack of immersive solutions for evacuation and the potential for developing search and rescue scenarios onboard a ship.
Ship systems for natural gas liquefaction Vorkapić, Aleksandar; Kralj, Predrag; Bernečić, Dean
Pomorstvo (Rijeka : 1999),
12/2016, Letnik:
30, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This review describes the current liquefaction systems on ships for natural gas transportation in liquid form (Liquefied Natural Gas – LNG). Since in the construction of a gas carrier an essential ...requirement is the selection of a liquefaction system, this paper describes the principles of operation, thermal and technological processes, as well as the advantages of each system.
The Regulations for Preventing Collisions at Sea (COLREG) is a collection of international legal standards adopted in order to avoid collisions at sea. Comprehensive knowledge of these rules is ...required for all who sail on the sea. The ACTs project (Avoiding Collisions at Sea) investigates the current problems in applying these Rules and intends to develop a new online course making it simpler and easier to understand them. A COLREG questionnaire has been drawn up for research purposes. The purpose of the questionnaire is checking which rules are more difficult to understand. In this paper, the authors analyse the level of understanding of the Rules in a group of secondary maritime school students. The survey results indicate that many of the basic principles of COLREG are neither understood nor applied.
The main purpose of a vessel is to transport goods and passengers at minimum cost. Out of the analysis of relevant global databases on ship machinery failures, it is obvious that the most frequent ...failures occur precisely on the generator-running diesel engines. Any failure in the electrical system can leave the ship without propulsion, even if the main engine is working properly. In that case, the consequences could be devastating: higher running expenses, damage to the ship, oil spill or substantial marine pollution. These are the reasons why solutions that will prevent the ship being unable to manoeuvre during her exploitation should be implemented. Therefore, it is necessary to define a propulsion restoration model which would not depend on the primary electrical energy. The paper provides a model of the marine auxiliary system for more reliable propulsion. This includes starting, reversing and stopping of the propulsion engine. The proposed solution of reliable propulsion model based on the use of a shaft generator and an excitation engine enables the restoration of propulsion following total failure of the electrical energy primary production system, and the self-propelled ship navigation. A ship is an important factor in the Technology of Transport, and the implementation of this model increases safety, reduces downtime, and significantly decreases hazards of pollution damage.KEYWORDSreliable propulsion, failure, ship auxiliary system, control, propulsion restoration
This paper presents and explains the results obtained in a study on multiple injections in slow-speed two-stroke marine diesel engines. The study included a simulation model of engine operation ...processes. The validity of the model was verified by comparing the obtained values with the measured values on three types of engines, Wartsila 7 RT Flex 50, MAN B&W MC 50 and ME 60. Pressure and temperature values in the engine cylinder were obtained for every degree within a single full crankshaft revolution for two types of fuel injection: conventional and multiple fuel injections. Even though the experiments were carried out with five, six and seven injections, the study has been restricted to three injections for practical purposes. Pressure and temperature parameters are processed in tables and charts. First and second time derivatives of pressure and temperature were calculated, i.e. the rate of change of pressure and temperature and the acceleration of the rate of change in pressure and in temperature were calculated.
Provider: - Institution: - Data provided by Europeana Collections- U radu je opisan nuldimenzionalni matematički model za simulaciju
radnog procesa sporookretnog dvotaktnog brodskog dizelskog motora, ...na
osnovu kojeg je napravljen računalni program u FORTRANU i Matlabu.
Temelj rada čini modeliranje izgaranja korištenjem Vibe funkcije te
Fourrierove funkcije 8. reda koja još točnije prezentira zakon izgaranja.
Izvršen je veliki broj simulacija kako bi se pronašli odgovarajući parametri
Vibe funkcije, koeficijenti Fourrierovog reda, kao i uvidjele pojedine zakonitosti.
Provjera modela je napravljena usporedbom sa stvarnim izmjerenim
vrijednostima na tri sporookretna brodska dizelska motora na probnom stolu,
probnoj vožnji i eksploataciji, na raznim režimima rada. Simulirani su režimi
rada motora s ranijim i kasnijim ubrizgavanjima, kao i rad s manjim i većim
pretičcima zraka te raznim parametrima forme i stupnja iskoristivosti izgaranja
Vibe funkcije. Simulirane su i razne kombinacije trostrukog višestrukog
ubrizgavanja te prezentirani oblici krivulje izgaranja i ostali dijagrami važni za
usporedbu. Rezultati simulacija su prezentirani grafički i opisani tekstualno, te
su izneseni najvažniji zaključci.
Simulacijski model primijenjen u ovom radu može biti korišten u
optimiranju motora, kao alat za učenje studenata te kao pomoć pri obrazovanju
kako novog tako i iskusnog strojarskog časničkog kadra.- In this paper the two stroke slow speed diesel engine nuldimensional
model has been described and presented as the base for a new computer
program made in FORTRAN and the language of technical computing Matlab.
The base of this dissertation is diesel engine combustion modeling, which
is done using well known Vibe function, but also applying new Fourier’s
function found by investigation in this paper. To determine a suitable parameters
of Vibe function, coefficients of Fourier’s functions, and to realize the particular
rules, a huge number of simulations has been done.
The results obtained by numerical simulation are confirmed by
comparison with the values that were measured during engine test bed and ship
trial. The three slow speed diesel engines on different working points have been
researched. The simulations of advanced and late injection have been done, as
well as different air-fuel ratio and different form parameters and combustion
efficiencies. The sequential (multi) combustion in three phases is also simulated
and presented heat release rate. The simulation's results has been presented
graphically and described textually as well as main conclusions.
The simulation model presented in this paper can be used for optimization
and final engine tuning as well as education tool for new and experienced
marine engineers.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
U priloženom radu je analiziran utjecaj koeficijenta prijelaza topline na tlak izgaranja u cilindru. Analiza je izvršena primjenom simulacijskog modela koji se koristio za potrebe istraživanja ...utjecaja višestrukog ubrizgavanja na procese i produkte izgaranja u cilindru sporookretnog brodskog dizelskog motora. U svrhu analize primijenjen je nuldimenzionalni matematički model izgaranja, koji je vrednovan usporedbom stvarnih podataka s broda i rezultata dobivenih simulacijama. U radu je napravljena komparacija utjecaja prijelaza topline primjenjujući izraze za prijelaz topline po Annandu, Eichelbergu i Woschniju. Rezultati su analizirani i prezentirani grafički te statistički obrađeni. Objašnjen je i predložen najbolji izbor.
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