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Detalles de la revista
Formato
Revista
eISSN
2083-7429
Publicado por primera vez
20 Jul 2007
Periodo de publicación
4 veces al año
Idiomas
Inglés

Buscar

Volumen 28 (2021): Edición 2 (June 2021)

Detalles de la revista
Formato
Revista
eISSN
2083-7429
Publicado por primera vez
20 Jul 2007
Periodo de publicación
4 veces al año
Idiomas
Inglés

Buscar

14 Artículos
Acceso abierto

Numerical Study of the Effect of Wing Position on the Dynamic Motion Characteristics of an Underwater Glider

Publicado en línea: 15 Jul 2021
Páginas: 4 - 17

Resumen

Abstract

Underwater gliders are winged, autonomous underwater vehicles that are broadly applied in physical and biological oceanography. The position of the wing has an important effect on the movement performance of the underwater glider. In this paper, the dynamic motion of a series of underwater glider models with different longitudinal wing positions are simulated, which provides guidance for the design of underwater gliders. The results show that when the net buoyancy is constant, the wing position affects the gliding angle, but does not affect the relationship between the gliding angle and the gliding speed. In addition, the farther the wing position of the glider is from the buoyancy centre, the longer it takes for the attitude of a glider to change, whether the wing is in front of, or behind, the buoyancy centre.

Palabras clave

  • underwater glider
  • motion simulation
  • wing position
Acceso abierto

Control of Unmanned Surface Vehicle Along the Desired Trajectory Using Improved Line of Sight and Estimated Sideslip Angle

Publicado en línea: 15 Jul 2021
Páginas: 18 - 26

Resumen

Abstract

In order to improve the accuracy and robustness of path following control for an Unmanned Surface Vehicle (USV) suffering from unknown and complex disturbances, a variable speed curve path following a control method based on an extended state observer was proposed. Firstly, the effect of the environmental disturbances on the USV is equivalent to an unknown and time-varying sideslip angle, and the sideslip angle is estimated by using the extended state observer (ESO) and compensated in the Line of Sight (LOS) guidance law. Secondly, based on the traditional LOS guidance law, the design of the surge velocity guidance law is added to enable the USV to self-adjust the surge velocity according to the curvature of the curve path, thus further improving the tracking accuracy. Finally, the heading and speed controller of the USV is designed by using a sliding mode control to track the desired heading and speed accurately, and then the path following control of the USV’s curve path is realised. Simulation results verify the effectiveness of the proposed method.

Palabras clave

  • USV
  • curve path following control
  • surge velocity guidance law
  • extended state observer
  • sliding mode control
Acceso abierto

A Multi-Case-Based Assembly Management Method for the Shipbuilding Industry

Publicado en línea: 15 Jul 2021
Páginas: 27 - 35

Resumen

Abstract

This article describes a method for planning the assembly of ship hulls that focuses on a welding sequence, takes into account subassembly processes and makes use of a previously built database of structures. Different degrees of similarity between structures are taken into account. The described research led to the development of an intelligent hybrid sequencing method for structure assembly that uses fuzzy clustering, case-based reasoning and evolutionary optimization. The method is called ‘Multi-case-Based Assembly Planning (MBAP)’. The method is developed to provide satisfactory solutions with low user effort. The analyses carried out show that the calculations are highly time-efficient. The developed evolutionary algorithm converges on sub-optimal solutions. The MBAP method can be directly implemented by any shipbuilder that assembles hulls. Apart from this, fuzzy clustering integrated with case-based reasoning can be applied in practice. The integration of fuzzy clustering and case-based reasoning has been taken to a level higher than previously described in the literature.

Palabras clave

  • assembly management
  • shipbuilding
  • case-based reasoning
  • fuzzy classification
Acceso abierto

Application of an Artificial Neural Network and Multiple Nonlinear Regression to Estimate Container Ship Length Between Perpendiculars

Publicado en línea: 15 Jul 2021
Páginas: 36 - 45

Resumen

Abstract

Container ship length was estimated using artificial neural networks (ANN), as well as a random search based on Multiple Nonlinear Regression (MNLR). Two alternative equations were developed to estimate the length between perpendiculars based on container number and ship velocity using the aforementioned methods and an up-to-date container ship database. These equations could have practical applications during the preliminary design stage of a container ship. The application of heuristic techniques for the development of a MNLR model by variable and function randomisation leads to the automatic discovery of equation sets. It has been shown that an equation elaborated using this method, based on a random search, is more accurate and has a simpler mathematical form than an equation derived using ANN.

Palabras clave

  • ship design
  • ANN
  • regression
  • container ship
  • length
Acceso abierto

Numerical Estimation of Hull Hydrodynamic Derivatives in Ship Maneuvering Prediction

Publicado en línea: 15 Jul 2021
Páginas: 46 - 53

Resumen

Abstract

Prediction of the maneuvering characteristics of a ship at the design stage can be done by means of model tests, computational simulations or a combination of both. The model tests can be realized as a direct simulation of the standard maneuvers with the free running model, which gives the most accurate results but is also the least affordable, as it requires a very large tank or natural lake, as well as the complex equipment of the model. Alternatively, a captive model test can be used to identify the hydrodynamic characteristics of the hull, which can be used to simulate the standard maneuvers with the use of dedicated software. Two types of captive model tests are distinguished: circular motion tests (CMT) and planar motion mechanism tests (PMM). The paper presents an attempt to develop a computational method for ship maneuverability prediction in which the hydrodynamic characteristics of the hull are identified by means of computational fluid dynamics (CFD). The CFD analyses presented here directly simulate the circular motion test. The resulting hull characteristics are verified against the available literature data, and the results of the simulations are verified against the results of free running model tests. Reasonable agreement shows the large potential of the proposed method.

Palabras clave

  • Captive model tests
  • CFD tools in maneuvering prediction
  • MOERI Container ship (KCS)
  • Hull hydrodynamic derivatives
  • Mathematical model of ship motion
Acceso abierto

Blade Cup Method for Cavitation Reduction in Marine Propellers

Publicado en línea: 15 Jul 2021
Páginas: 54 - 62

Resumen

Abstract

Energy efficiency has become more important in every industry and daily life. Designing and building a more efficient marine vehicle can lead to lower fuel consumption and a longer lifetime for the components of the vehicle.

Erosion caused by cavitation reduces the service life of the propeller and the related components in the propulsion and maneuvering system. Reducing cavitation leads to a longer life for these components. This paper aims to explain and investigate propeller blade cup as a cavitation reduction method for marine propellers. A cavitating no-cup propeller is created and analyzed then the cupped version of this propeller is generated and analyzed to compare with the no-cup propeller. Cavitation results of these propellers are investigated. In addition, the thrust, torque, and efficiency of the propellers are compared.

Palabras clave

  • Marine Propeller
  • Computational Fluid Dynamics
  • Propeller Cup
  • Cupping
  • Cavitation
  • Propeller Efficiency
  • Vibration
  • Noise
  • Erosion
Acceso abierto

Implementing Simulationx in the Modelling of Marine Shafting Steady State Torsional Vibrations

Publicado en línea: 15 Jul 2021
Páginas: 63 - 71

Resumen

Abstract

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.

Palabras clave

  • mechanical dynamic system
  • critical speeds
  • torsional stress amplitudes
  • two-stroke marine Diesel engine
  • normal firing
Acceso abierto

Energy Analysis of the Propulsion Shaft Fatigue Process in a Rotating Mechanical System Part III Dimensional Analysis

Publicado en línea: 15 Jul 2021
Páginas: 72 - 77

Resumen

Abstract

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.

Palabras clave

  • ship propulsion shaft
  • dimensional analysis
  • Buckingham theorems
  • similarity criteria
Acceso abierto

Optimisation of the Topping-Up Process of Lubricating Oil in Medium-Speed Marine Engines

Publicado en línea: 15 Jul 2021
Páginas: 78 - 84

Resumen

Abstract

In this paper, we examine the problem of optimising the process of topping up lubricating oil in medium-speed marine engines. This process is one of the methods that can be applied to improve the properties of lubricating oil. The amount of fresh oil added to lubricating oil system always balances its consumption, but the method used to top up depends on the marine engineer. Small amounts of fresh oil can be added at short intervals, or large ones at long intervals, and the element of randomness often plays a significant role here. It would therefore be valuable to find a method that can help the mechanical engineer to choose the right strategy. We apply a multi-criteria optimisation method for this purpose, and assume that the criterion functions depend on the concentration of solid impurities and the alkalinity, which are among the most important aspects of the quality and properties of lubricating oil. These criterion functions form the basis for multi-objective optimisation carried out with the use of the MATLAB computer program.

Palabras clave

  • multi-objective optimisation
  • medium-speed marine engine
  • lubricating oil
  • soild impurities
  • alkalinity
  • topping-up process
Acceso abierto

Investigations of the Emission Characteristics of a Dual-Fuel Gas Turbine Combustion Chamber Operating Simultaneously on Liquid and Gaseous Fuels

Publicado en línea: 15 Jul 2021
Páginas: 85 - 95

Resumen

Abstract

This study is dedicated to investigations of the working process in a dual-fuel low-emission combustion chamber for a floating vessel’s gas turbine. As the object of the research, a low-emission gas turbine combustion chamber with partial premixing of fuel and air inside the outer and inner radial-axial swirls was chosen. The method of the research is based on the numerical solution of the system of differential equations which represent the physical process of mass and energy conservation and transformations and species transport for a multi-component chemically reactive turbulent system, considering nitrogen oxides formation and a discrete ordinates model of radiation. The chemistry kinetics is presented by the 6-step mechanism of combustion. Seven fuel supply operating modes, varying from 100% gaseous fuel to 100% liquid fuel, have been analysed. This analysis has revealed the possibility of the application of computational fluid dynamics for problems of dual-fuel combustion chambers for the design of a floating vessel’s gas turbine. Moreover, the study has shown the possibility of working in different transitional gaseous and liquid fuel supply modes, as they satisfy modern ecological requirements. The dependencies of the averaged temperature, NO, and CO concentrations along the length of the low-emission gas turbine combustion chamber for different cases of fuel supply are presented. Depending on the different operating modes, the calculated emission of nitrogen oxides NO and carbon monoxide CO at the outlet cross-section of a flame tube are different, but, they lie in the ranges of 31‒50 and 23‒24 mg/nm3 on the peak of 100% liquid fuel supply mode. At operating modes where a gaseous fuel supply prevails, nitrogen oxide NO and carbon monoxide CO emissions lie in the ranges of 1.2‒4.0 and 0.04‒18 mg/nm3 respectively.

Palabras clave

  • gas turbine engine
  • dual-fuel combustion
  • combustion chamber
  • liquid and gaseous fuels
Acceso abierto

Minimizing Greenhouse Gas Emissions From Ships Using a Pareto Multi-Objective Optimization Approach

Publicado en línea: 15 Jul 2021
Páginas: 96 - 101

Resumen

Abstract

To confront climate change, decarbonization strategies must change the global economy. According to statements made as part of the European Green Deal, maritime transport should also become drastically less polluting. As a result, the price of transport must reflect the impact it has on the environment and on health.

In such a framework, the purpose of this paper is to suggest a novel method for minimizing emissions from ships, based on so-called Pareto multi-objective optimization. For a given voyage by a ship, the problem is to minimize emissions on the one hand and minimize fuel consumption or passage time on the other. Minimizing emissions is considered as the preferred objective. Therefore, the objective of minimizing fuel consumption or passage time needs to be reformulated as a constraint. Solving such a problem consists of finding most favourable path and speed for the ship and satisfying the optimization criteria.

Relatively new systems such as hybrid diesel–electric systems have the potential to offer significant emissions benefits. A hybrid power supply utilizes the maximum efficiency of the direct mechanical drive and the flexibility of a combination of combustion power from the prime mover and stored power from energy storage from an electrical supply, at part load and overload.

A new report by the American Bureau of Shipping suggests that maritime transport is likely to meet the International Maritime Organization’s target by 2030, solely by using current technology and operational measures. However, this would not be enough to attain the target of reducing CO2 emissions by 2050 by at least 50% compared to 2008. New technologies and operational methods must be applied.

Palabras clave

  • Minimizing emissions from ships
  • Pareto multi-objective optimization
  • Minimizing emissions as preference objective
  • Ship routing optimization
  • Hybrid power to lower emissions
Acceso abierto

Review of Research Results Concerning the Modelling of Shipping Noise

Publicado en línea: 15 Jul 2021
Páginas: 102 - 115

Resumen

Abstract

The effect of underwater radiated noise (URN) pollution (produced by merchant ships) on marine ecology has become a topic of extreme concern for both the academic community and the general public. This paper summarises some research results and modelling about shipping noise published over several decades, which comprises the research significance of low-frequency ambient noise and shipping noise, shipping noise source levels (SL), empirical models and the measurement standards of shipping noise. In short, we try to present an overall outline of shipping noise and ocean ambient noise for related research.

Palabras clave

  • shipping noise
  • noise source level model
  • measurement standard
  • ocean ambient noise
Acceso abierto

Design Criteria for Scantling of Longitudinal and Transverse Connections in the Torsion Box Under Fatigue Loading

Publicado en línea: 15 Jul 2021
Páginas: 116 - 127

Resumen

Abstract

Fatigue is one of the main failure modes in marine structures, and it is caused by the strong cyclic characteristics of the loads they support. This failure mode is amplified in areas of high stress concentration, such as at the intersection of primary and secondary elements. In this paper, a two-phase study is proposed that compares numerical and experimental results using a digital image correlation technique. The described procedure establishes selection, design, and scantling criteria and provides recommendations for the design of the transverse structure using specimens with different geometries. These geometries correspond to different designs for the transverse primary structure that use a longitudinal secondary stiffener with variable thickness and longitudinal spacing to transverse in a dynamic and quasi-static regime. The stress state for this regime is calculated based on the biaxiality indication concept, which uses the fatigue phenomenon (safety factor and sensitivity curves) and fracture mechanics (parameters of the Paris crack propagation law, correlation value, and law of variation of the stress intensity factor).

Palabras clave

  • Fatigue life
  • ship structures
  • crack growth
  • fracture
Acceso abierto

Joints Of Steel Sandwich Structures

Publicado en línea: 15 Jul 2021
Páginas: 128 - 135

Resumen

Abstract

Steel sandwich structures are perceived as alternatives to single-skin welded structures in the shipbuilding industry due its advantages like significant reduction of mass in relation to typical single skin structure. However, beside problems with their strength properties itself, applications in real structures requires of solving the problem of joining, both for connection sandwich to sandwich as well as sandwiches to single-shell structures. Proper design of joints is connected with some factors like lack of attempt to interior of panel, introduction of additional parts and welds with completely different stiffness. In the paper the results of laboratory fatigue tests of selected joints as well as numerical calculation of stressed for different kind of joints of sandwich structures are presented. As result of calculations optimisation of geometry for selected joints is performed.

Palabras clave

  • steel sandwich
  • joints
  • strength
  • laboratory test
14 Artículos
Acceso abierto

Numerical Study of the Effect of Wing Position on the Dynamic Motion Characteristics of an Underwater Glider

Publicado en línea: 15 Jul 2021
Páginas: 4 - 17

Resumen

Abstract

Underwater gliders are winged, autonomous underwater vehicles that are broadly applied in physical and biological oceanography. The position of the wing has an important effect on the movement performance of the underwater glider. In this paper, the dynamic motion of a series of underwater glider models with different longitudinal wing positions are simulated, which provides guidance for the design of underwater gliders. The results show that when the net buoyancy is constant, the wing position affects the gliding angle, but does not affect the relationship between the gliding angle and the gliding speed. In addition, the farther the wing position of the glider is from the buoyancy centre, the longer it takes for the attitude of a glider to change, whether the wing is in front of, or behind, the buoyancy centre.

Palabras clave

  • underwater glider
  • motion simulation
  • wing position
Acceso abierto

Control of Unmanned Surface Vehicle Along the Desired Trajectory Using Improved Line of Sight and Estimated Sideslip Angle

Publicado en línea: 15 Jul 2021
Páginas: 18 - 26

Resumen

Abstract

In order to improve the accuracy and robustness of path following control for an Unmanned Surface Vehicle (USV) suffering from unknown and complex disturbances, a variable speed curve path following a control method based on an extended state observer was proposed. Firstly, the effect of the environmental disturbances on the USV is equivalent to an unknown and time-varying sideslip angle, and the sideslip angle is estimated by using the extended state observer (ESO) and compensated in the Line of Sight (LOS) guidance law. Secondly, based on the traditional LOS guidance law, the design of the surge velocity guidance law is added to enable the USV to self-adjust the surge velocity according to the curvature of the curve path, thus further improving the tracking accuracy. Finally, the heading and speed controller of the USV is designed by using a sliding mode control to track the desired heading and speed accurately, and then the path following control of the USV’s curve path is realised. Simulation results verify the effectiveness of the proposed method.

Palabras clave

  • USV
  • curve path following control
  • surge velocity guidance law
  • extended state observer
  • sliding mode control
Acceso abierto

A Multi-Case-Based Assembly Management Method for the Shipbuilding Industry

Publicado en línea: 15 Jul 2021
Páginas: 27 - 35

Resumen

Abstract

This article describes a method for planning the assembly of ship hulls that focuses on a welding sequence, takes into account subassembly processes and makes use of a previously built database of structures. Different degrees of similarity between structures are taken into account. The described research led to the development of an intelligent hybrid sequencing method for structure assembly that uses fuzzy clustering, case-based reasoning and evolutionary optimization. The method is called ‘Multi-case-Based Assembly Planning (MBAP)’. The method is developed to provide satisfactory solutions with low user effort. The analyses carried out show that the calculations are highly time-efficient. The developed evolutionary algorithm converges on sub-optimal solutions. The MBAP method can be directly implemented by any shipbuilder that assembles hulls. Apart from this, fuzzy clustering integrated with case-based reasoning can be applied in practice. The integration of fuzzy clustering and case-based reasoning has been taken to a level higher than previously described in the literature.

Palabras clave

  • assembly management
  • shipbuilding
  • case-based reasoning
  • fuzzy classification
Acceso abierto

Application of an Artificial Neural Network and Multiple Nonlinear Regression to Estimate Container Ship Length Between Perpendiculars

Publicado en línea: 15 Jul 2021
Páginas: 36 - 45

Resumen

Abstract

Container ship length was estimated using artificial neural networks (ANN), as well as a random search based on Multiple Nonlinear Regression (MNLR). Two alternative equations were developed to estimate the length between perpendiculars based on container number and ship velocity using the aforementioned methods and an up-to-date container ship database. These equations could have practical applications during the preliminary design stage of a container ship. The application of heuristic techniques for the development of a MNLR model by variable and function randomisation leads to the automatic discovery of equation sets. It has been shown that an equation elaborated using this method, based on a random search, is more accurate and has a simpler mathematical form than an equation derived using ANN.

Palabras clave

  • ship design
  • ANN
  • regression
  • container ship
  • length
Acceso abierto

Numerical Estimation of Hull Hydrodynamic Derivatives in Ship Maneuvering Prediction

Publicado en línea: 15 Jul 2021
Páginas: 46 - 53

Resumen

Abstract

Prediction of the maneuvering characteristics of a ship at the design stage can be done by means of model tests, computational simulations or a combination of both. The model tests can be realized as a direct simulation of the standard maneuvers with the free running model, which gives the most accurate results but is also the least affordable, as it requires a very large tank or natural lake, as well as the complex equipment of the model. Alternatively, a captive model test can be used to identify the hydrodynamic characteristics of the hull, which can be used to simulate the standard maneuvers with the use of dedicated software. Two types of captive model tests are distinguished: circular motion tests (CMT) and planar motion mechanism tests (PMM). The paper presents an attempt to develop a computational method for ship maneuverability prediction in which the hydrodynamic characteristics of the hull are identified by means of computational fluid dynamics (CFD). The CFD analyses presented here directly simulate the circular motion test. The resulting hull characteristics are verified against the available literature data, and the results of the simulations are verified against the results of free running model tests. Reasonable agreement shows the large potential of the proposed method.

Palabras clave

  • Captive model tests
  • CFD tools in maneuvering prediction
  • MOERI Container ship (KCS)
  • Hull hydrodynamic derivatives
  • Mathematical model of ship motion
Acceso abierto

Blade Cup Method for Cavitation Reduction in Marine Propellers

Publicado en línea: 15 Jul 2021
Páginas: 54 - 62

Resumen

Abstract

Energy efficiency has become more important in every industry and daily life. Designing and building a more efficient marine vehicle can lead to lower fuel consumption and a longer lifetime for the components of the vehicle.

Erosion caused by cavitation reduces the service life of the propeller and the related components in the propulsion and maneuvering system. Reducing cavitation leads to a longer life for these components. This paper aims to explain and investigate propeller blade cup as a cavitation reduction method for marine propellers. A cavitating no-cup propeller is created and analyzed then the cupped version of this propeller is generated and analyzed to compare with the no-cup propeller. Cavitation results of these propellers are investigated. In addition, the thrust, torque, and efficiency of the propellers are compared.

Palabras clave

  • Marine Propeller
  • Computational Fluid Dynamics
  • Propeller Cup
  • Cupping
  • Cavitation
  • Propeller Efficiency
  • Vibration
  • Noise
  • Erosion
Acceso abierto

Implementing Simulationx in the Modelling of Marine Shafting Steady State Torsional Vibrations

Publicado en línea: 15 Jul 2021
Páginas: 63 - 71

Resumen

Abstract

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.

Palabras clave

  • mechanical dynamic system
  • critical speeds
  • torsional stress amplitudes
  • two-stroke marine Diesel engine
  • normal firing
Acceso abierto

Energy Analysis of the Propulsion Shaft Fatigue Process in a Rotating Mechanical System Part III Dimensional Analysis

Publicado en línea: 15 Jul 2021
Páginas: 72 - 77

Resumen

Abstract

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.

Palabras clave

  • ship propulsion shaft
  • dimensional analysis
  • Buckingham theorems
  • similarity criteria
Acceso abierto

Optimisation of the Topping-Up Process of Lubricating Oil in Medium-Speed Marine Engines

Publicado en línea: 15 Jul 2021
Páginas: 78 - 84

Resumen

Abstract

In this paper, we examine the problem of optimising the process of topping up lubricating oil in medium-speed marine engines. This process is one of the methods that can be applied to improve the properties of lubricating oil. The amount of fresh oil added to lubricating oil system always balances its consumption, but the method used to top up depends on the marine engineer. Small amounts of fresh oil can be added at short intervals, or large ones at long intervals, and the element of randomness often plays a significant role here. It would therefore be valuable to find a method that can help the mechanical engineer to choose the right strategy. We apply a multi-criteria optimisation method for this purpose, and assume that the criterion functions depend on the concentration of solid impurities and the alkalinity, which are among the most important aspects of the quality and properties of lubricating oil. These criterion functions form the basis for multi-objective optimisation carried out with the use of the MATLAB computer program.

Palabras clave

  • multi-objective optimisation
  • medium-speed marine engine
  • lubricating oil
  • soild impurities
  • alkalinity
  • topping-up process
Acceso abierto

Investigations of the Emission Characteristics of a Dual-Fuel Gas Turbine Combustion Chamber Operating Simultaneously on Liquid and Gaseous Fuels

Publicado en línea: 15 Jul 2021
Páginas: 85 - 95

Resumen

Abstract

This study is dedicated to investigations of the working process in a dual-fuel low-emission combustion chamber for a floating vessel’s gas turbine. As the object of the research, a low-emission gas turbine combustion chamber with partial premixing of fuel and air inside the outer and inner radial-axial swirls was chosen. The method of the research is based on the numerical solution of the system of differential equations which represent the physical process of mass and energy conservation and transformations and species transport for a multi-component chemically reactive turbulent system, considering nitrogen oxides formation and a discrete ordinates model of radiation. The chemistry kinetics is presented by the 6-step mechanism of combustion. Seven fuel supply operating modes, varying from 100% gaseous fuel to 100% liquid fuel, have been analysed. This analysis has revealed the possibility of the application of computational fluid dynamics for problems of dual-fuel combustion chambers for the design of a floating vessel’s gas turbine. Moreover, the study has shown the possibility of working in different transitional gaseous and liquid fuel supply modes, as they satisfy modern ecological requirements. The dependencies of the averaged temperature, NO, and CO concentrations along the length of the low-emission gas turbine combustion chamber for different cases of fuel supply are presented. Depending on the different operating modes, the calculated emission of nitrogen oxides NO and carbon monoxide CO at the outlet cross-section of a flame tube are different, but, they lie in the ranges of 31‒50 and 23‒24 mg/nm3 on the peak of 100% liquid fuel supply mode. At operating modes where a gaseous fuel supply prevails, nitrogen oxide NO and carbon monoxide CO emissions lie in the ranges of 1.2‒4.0 and 0.04‒18 mg/nm3 respectively.

Palabras clave

  • gas turbine engine
  • dual-fuel combustion
  • combustion chamber
  • liquid and gaseous fuels
Acceso abierto

Minimizing Greenhouse Gas Emissions From Ships Using a Pareto Multi-Objective Optimization Approach

Publicado en línea: 15 Jul 2021
Páginas: 96 - 101

Resumen

Abstract

To confront climate change, decarbonization strategies must change the global economy. According to statements made as part of the European Green Deal, maritime transport should also become drastically less polluting. As a result, the price of transport must reflect the impact it has on the environment and on health.

In such a framework, the purpose of this paper is to suggest a novel method for minimizing emissions from ships, based on so-called Pareto multi-objective optimization. For a given voyage by a ship, the problem is to minimize emissions on the one hand and minimize fuel consumption or passage time on the other. Minimizing emissions is considered as the preferred objective. Therefore, the objective of minimizing fuel consumption or passage time needs to be reformulated as a constraint. Solving such a problem consists of finding most favourable path and speed for the ship and satisfying the optimization criteria.

Relatively new systems such as hybrid diesel–electric systems have the potential to offer significant emissions benefits. A hybrid power supply utilizes the maximum efficiency of the direct mechanical drive and the flexibility of a combination of combustion power from the prime mover and stored power from energy storage from an electrical supply, at part load and overload.

A new report by the American Bureau of Shipping suggests that maritime transport is likely to meet the International Maritime Organization’s target by 2030, solely by using current technology and operational measures. However, this would not be enough to attain the target of reducing CO2 emissions by 2050 by at least 50% compared to 2008. New technologies and operational methods must be applied.

Palabras clave

  • Minimizing emissions from ships
  • Pareto multi-objective optimization
  • Minimizing emissions as preference objective
  • Ship routing optimization
  • Hybrid power to lower emissions
Acceso abierto

Review of Research Results Concerning the Modelling of Shipping Noise

Publicado en línea: 15 Jul 2021
Páginas: 102 - 115

Resumen

Abstract

The effect of underwater radiated noise (URN) pollution (produced by merchant ships) on marine ecology has become a topic of extreme concern for both the academic community and the general public. This paper summarises some research results and modelling about shipping noise published over several decades, which comprises the research significance of low-frequency ambient noise and shipping noise, shipping noise source levels (SL), empirical models and the measurement standards of shipping noise. In short, we try to present an overall outline of shipping noise and ocean ambient noise for related research.

Palabras clave

  • shipping noise
  • noise source level model
  • measurement standard
  • ocean ambient noise
Acceso abierto

Design Criteria for Scantling of Longitudinal and Transverse Connections in the Torsion Box Under Fatigue Loading

Publicado en línea: 15 Jul 2021
Páginas: 116 - 127

Resumen

Abstract

Fatigue is one of the main failure modes in marine structures, and it is caused by the strong cyclic characteristics of the loads they support. This failure mode is amplified in areas of high stress concentration, such as at the intersection of primary and secondary elements. In this paper, a two-phase study is proposed that compares numerical and experimental results using a digital image correlation technique. The described procedure establishes selection, design, and scantling criteria and provides recommendations for the design of the transverse structure using specimens with different geometries. These geometries correspond to different designs for the transverse primary structure that use a longitudinal secondary stiffener with variable thickness and longitudinal spacing to transverse in a dynamic and quasi-static regime. The stress state for this regime is calculated based on the biaxiality indication concept, which uses the fatigue phenomenon (safety factor and sensitivity curves) and fracture mechanics (parameters of the Paris crack propagation law, correlation value, and law of variation of the stress intensity factor).

Palabras clave

  • Fatigue life
  • ship structures
  • crack growth
  • fracture
Acceso abierto

Joints Of Steel Sandwich Structures

Publicado en línea: 15 Jul 2021
Páginas: 128 - 135

Resumen

Abstract

Steel sandwich structures are perceived as alternatives to single-skin welded structures in the shipbuilding industry due its advantages like significant reduction of mass in relation to typical single skin structure. However, beside problems with their strength properties itself, applications in real structures requires of solving the problem of joining, both for connection sandwich to sandwich as well as sandwiches to single-shell structures. Proper design of joints is connected with some factors like lack of attempt to interior of panel, introduction of additional parts and welds with completely different stiffness. In the paper the results of laboratory fatigue tests of selected joints as well as numerical calculation of stressed for different kind of joints of sandwich structures are presented. As result of calculations optimisation of geometry for selected joints is performed.

Palabras clave

  • steel sandwich
  • joints
  • strength
  • laboratory test

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