Search Results (50)

Seagoing marine propulsion analysis in terms of main engine performance and fixed-pitch propeller hydrodynamics is an engineering problem that has not been exactly defined to date. This study utilizes an original and comprehensive mathematical approach—involving the approximate representation of one function by another—to define this problem in mathematical terms and solve it. This is achieved by imperatively applying an original and sophisticated hybrid combination of an existing, formidable and ingenious, mathematical methodology with different original comprehensive functional systems. These original functional systems approximately represent the operations of vessels under seagoing conditions, including the thermo-fluid and frictional processes of vessels’ main engines in terms of fuel oil consumption, as well as the hydrodynamic performance of the respective vessels in terms of the shaft propulsion power and the rotational speed of the fixed-pitch propellers driven by these engines. Based on the least-squares criterion, this original and sophisticated hybrid combination systematically attains remarkably close approximate representations under seagoing conditions. Apart from this novel exact definition in mathematical terms and the significance of the above original representations, this combination is also applicable for the approximation of the baselines demarcating the standard engineering context representing the ideal reference (sea trials) conditions, from the seagoing conditions. Full article

Phytoplankton are essential indicators of aquatic ecosystem health. Traditional phytoplankton detection methods using microscopy struggle to identify species with small particle sizes or unclear morphological characteristics. In contrast, molecular methods have high accuracy but struggle to simultaneously detect prokaryotic and eukaryotic organisms due to primer specificity. As algal blooms can be caused by both prokaryotes and eukaryotes, methods that can detect both are required. This study used both microscopic detection and high-throughput sequencing methods to analyze phytoplankton in seagoing waters in eastern coastal China. Two high-throughput sequencing primers targeting 16S rDNA for prokaryotes and 18S rDNA for eukaryotes were used, and the results were compared with those of microscopic analysis. Microscopy identified 230 phytoplankton species across 73 genera, mainly belonging to Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Dinophyta, and Chrysophyta. Twenty-four species across 16 sampling stations exceeded 1 million cells/L. High-throughput sequencing yielded 8642 prokaryotic and 7375 eukaryotic operational taxonomic units, with 432 identified as phytoplankton. Chlorophyta and Bacillariophyta had the highest species richness, accounting for 34% and 17%, respectively. High-throughput sequencing detected more species than microscopic detection but relied on gene reference databases and provided only the relative abundance of species based on operational taxonomic unit counts. Full article

Limiting the fuel sulphur content (FSC) of ships can significantly reduce the harm caused by ship emissions, and analyzing ship exhaust gas to estimate FSC is a rapid, efficient, and low-cost monitoring method. To solve the difficulty in measuring FSC using sniffer equipment in a complex port area, a ship emission monitoring option for FSC measurement in complex environments is proposed here. First, the exhaust gas measurement data of a time series collected using the sniffer equipment were examined to determine the dataset that could be used to estimate FSC. Second, the background value of polluted gases in the environment was dynamically calculated to suppress the interference of various pollution sources. The gas-measured value series was then converted into a mean value series, and the peak points in the mean value series were automatically selected for the calculation of FSC. Finally, the wind speed, wind direction, automatic identification system information, plume diffusion model, and FSC results of ship targets around the equipment were correlated. Between June and August 2023, we conducted a field observation campaign at Ningbo Port, China, where 2624 ships were monitored. A comparison of the real and measured FSC values of eight ships showed that the system could accurately measure FSC at 0.10% (m/m) and 0.50% (m/m) levels despite measurement uncertainty that may be greater at a 0.01% (m/m) FSC level. The FSC statistics of 2624 ships showed that the FSC of small seagoing ships was relatively higher than that of other types of ships. This study proposes a monitoring option for ship emissions, designs and develops an associated system, and collects data to validate the effectiveness and accuracy of this option. This approach has been integrated into daily business operations within the maritime sector, significantly enhancing the efficiency of supervision in this field. Full article

This paper aims to consider the issue of increasing the environmental friendliness of shipping by using alternative fuels in marine diesel engines. It has been determined that marine diesel engines are not only the main heat engines used on ships of sea and inland waterway transport, but are also sources of emissions of toxic components with exhaust gases. The main compounds whose emissions are controlled and regulated by international organizations are sulfur oxides (SO_X) and nitrogen oxides (NO_X), as well as carbon dioxide (CO₂). Reducing NO_X and CO₂ emissions while simultaneously increasing the environmental friendliness of shipping is possible by using fuel mixtures in marine diesel engines that include biodiesel fuel. During the research carried out on Wartsila 6L32 marine diesel engines (Shanghai Wartsila Qiyao Diesel Co. Ltd., Shanghai, China), RMG500 and DMA10 petroleum fuels were used, as well as their mixtures with biodiesel fuel FAME. It was found that when using mixtures containing 10–30% of FAME biodiesel, NO_X emissions are reduced by 11.20–27.10%; under the same conditions, CO₂ emissions are reduced by 5.31–19.47%. The use of alternative fuels in marine diesel engines (one of which is biodiesel and fuel mixtures containing it) is one of the ways to increase the level of environmental sustainability of seagoing vessels and promote ecological shipping. This is of particular relevance when operating vessels in special ecological areas of the World Ocean. The relatively low energy intensity of the method of creating and using such fuel mixtures contributes to the spread of its use on many means of maritime transport. Full article

In the field of vessel motion control system design, it is of essential importance to consider the environmental disturbances which affect a ship’s hull, including wind, waves and currents. The conventional modelling techniques for wind disturbance simulation are designed to represent the behaviour of winds over open sea areas. However, before being implemented on a real seagoing vessel, its motion control systems are often tested on scale models built for a ship. Such tests are usually carried out on small bodies of water, where wind and wave models built for the open sea cannot be used. Therefore, a wind and wave model for a small body of water is required so that the effects of external disturbances on the motion of the scale model can be properly considered in the early stages of control system design. This paper presents the construction of a wind speed and direction simulator for a small lake, which was used as a test area for a free-floating, manned training vessel built at a 1:24 scale. This paper describes modifications made to the model, employing a von Karman spectrum to characterise the wind. These modifications were designed to align the model with the observed phenomena in a lake test area. The resulting model exhibits a clear structure and can be readily implemented both in software and on a microprocessor-based hardware platform. Full article

The squirrel cage induction generator or SCIG (Squirrel Cage Induction Generator) belongs to the family of induction machines, which are currently used as the most common electrical machines. The use of power electronic converter systems along with advanced control vector algorithms allows for the implementation of the effective operation of squirrel cage generators in various conditions. Up to now, there are a few practical realizations of squirrel cage generators, which are installed on board the vessels; mostly, these generators act as shaft generators, and it originates from the rules that require self-excitement of main electrical generators, acting as an immediate ready-to-use voltage source. In this article, we present a solution that utilizes an SCIG that operates with varying rotational speed as a shaft generator but can also act as an emergency propeller drive in case of main combustion engine failure. The main achievement of the presented work was the creation of a control table prepared for real-time software of the machine-side inverter. The data for the table were collected during the experimental research, and such a setup allowed us to use a DTC-controlled SCIG as a generator that rotated with variable speed and under changing load. Full article

Tide dikes play a key role in preventing seawater intrusion in coastal regions; however, their effects on trace metal distribution and accumulation remain unclear. This study explored the distribution and enrichment of trace metals (As, Cr, Cu, Ni, Pb, and Zn) inside and outside tide dikes in Laizhou Bay. The accumulative risk of these metals in the two habitats was analyzed by combining their sources. The results show that the average enrichment factor, geological accumulation index, and potential ecological risk index of As in the outside habitat are significantly higher than those in the inside habitat (p < 0.001), which indicates that the tide dike effectively reduces the migration of As from outside to inside habitats. For other trace metals, no statistical differences were found between the two habitats. Based on principal component analysis and redundancy analysis of trace metals and their correlations with soil physicochemical properties, we speculated that Cr and Zn may derive from soil parent material and rock weathering. Cu, Pb, and Ni may be related to atmospheric nitrogen deposition resulting from nearby agricultural activities, and As may come from industrial wastewater or transport through seagoing rivers. The findings suggest that tide dikes effectively block exogenous trace metals but not those from natural sources. Full article

Based on 40 years of routine water quality monitoring data from Shenzhen Bay and special intensive monitoring since 2021, we analysed the spatiotemporal variations in nitrogen and phosphorus pollution. The results indicate serious levels of nitrogen and phosphorus pollution in Shenzhen Bay. Although recent trends show a decline in concentrations of inorganic nitrogen and reactive phosphate—with the annual average concentration of inorganic nitrogen dropping below 1.0 mg/L since 2020 and reactive phosphate levels near the bay mouth decreasing to approximately 0.020 mg/L—the overall water quality still does not meet China’s Class IV seawater quality standards. Additionally, water quality is poorer during the rainy season, with the average summer concentration of inorganic nitrogen being over 25% higher than in spring and autumn. The water quality is primarily influenced by land-sourced pollutants and tidal effects, generally, with the concentration of DIN and DIP decreased from the estuary of the Shenzhen River, the main seagoing river, to the bay mouth. Near the river’s mouth, concentrations of inorganic nitrogen and reactive phosphate are approximately six and four times higher, respectively, than those near the bay mouth. Due to current emission standards and sewage disposal methods, the proportion of nitrate nitrogen in DIN has significantly increased, exceeding 80% since 2020. To improve the water quality of Shenzhen Bay and to reduce pollution inputs, coordinated land and marine development activities are recommended. Full article

This article presents the issues related to the operation and modelling of a ship’s main propulsion steam boiler. Such objects are used widely in seagoing ships, especially very large crude oil carriers, as a main propulsion turbine feed. The advantages, along with the simple construction, thus greatly improve reliability making oil feed boilers an excellent source of power for the chosen types of large ships. It is worth mentioning that a vast part of the research work was performed in previous years regarding automatic control of boiler automation, but, since then, this technology has not been the focus of the researchers. Due to the fact that there is little information available on algorithms for controlling ship boilers, in the presented article, the authors created a unique solution for the control system of a propulsion boiler. The proposed control algorithm takes into account the operating parameters of the ship and allows for quick implementation in a simulation system working in a hardware loop, which can be used for quick testing of solutions for boiler systems fed with alternative fuels. In the future, fossil fuels will become less important than they are now, but the control techniques of boilers will eventually change due to different fuel parameters and, therefore, the development of such boilers is necessary. This article presents the results of research collected in real ship boilers during their operation and, based on the results, a digital model of such an object along with the necessary controls was created. This model was implemented into Hardware-In-Loop, which is the initial step for preparing the full model (including sensors, etc.) of a steam-heated boiler. The theoretical background, along with the chosen simulation and experimental results of control implemented into HIL, are presented to validate assumptions. Full article

This study was aimed at improving the energy efficiency of the distribution of liquefied natural gas (LNG) as shipping fuel in the southern Baltic Sea. The objective of this study was to determine the demand for LNG for maritime shipping by analyzing the distribution of the resource from the water side (ship-to-ship). LNG was chosen due to the location of the LNG terminal in Świnoujście within the analyzed water area, where a problem has arisen in the southern part of the Baltic Sea regarding fuel supply for vessels due to the lack of developed infrastructure along the coast. An analysis was conducted to optimize the size of the LNG fleet and infrastructure facilities. Seeking compliance with Annex VI to the MARPOL 73/78 Convention, adopted by the International Maritime Organization (IMO), shipowners see potential in the switch from conventional fuels to LNG. As one of the alternative solutions, it will contribute to reducing harmful emissions. Determination of the LNG distribution volume requires the identification of LNG storage facility locations, specifying the number of LNG-powered ships (broken down by type) and the number of LNG bunkering ships. The first part of this study contains a detailed analysis of the number of sea-going ships that provide services in the southern part of the Baltic Sea and the world’s number of LNG bunkering ships. The database contains a set of the characteristics required to determine the optimal demand for LNG, where LNG bunkering vessels are capable of supplying fuel within the shortest possible time and covering the shortest possible distance to LNG-powered ships. The characteristics include the type of ship, requested LNG volume, the speed of LNG bunkering ships, the distance between LNG facilities, and the loading rate (the volume of fuel received per time unit). Based on the collected data, the volume of LNG distribution was determined using MATLAB R2019a software. The remainder of this study contains a description of the conducted research and results of an analysis of the traffic density in the Baltic Sea. The results were obtained on the basis of data from the Statistical Yearbook of Maritime Economy and IALA IWRAP Mk2 2020 software. The number of LNG-powered ships and number of LNG bunkering ships were specified, and the demand for LNG for the area under analysis was determined. Full article

Efficient coordinated scheduling has long been a focal point in port research, complicated by the diverse optimization goals dictated by different port characteristics. This study focuses on Yangtze River ports, exploring coordinated scheduling amidst river–sea intermodal transportation. Our research aims to reduce berth deviation costs and shorten the total scheduling time for ships, while maximizing berth utilization rates for ports. Initially, we analyzed the operational realities of Yangtze River ports and waterways. Subsequently, we innovatively introduced three key factors influencing scheduling: berth preferences, seagoing ship inspections, and planning cycles. Finally we proposed the optimized Non-dominated Sorting Genetic Algorithm III (NSGA-III). Evaluating the model using a seven-day dataset of vessel activities at Yangtze River ports revealed significant improvements: the optimized NSGA-III enhanced objective values by 30.81%, 13.73%, and 12.11% compared to the original scheduling approach, surpassing both conventional NSGA-III and NSGA-II algorithms. This study underscores the model’s efficacy in not only reducing operational costs through optimized ship and berth sequencing but also in enhancing clearance efficiency for relevant authorities. Full article

Based on a prototype presented in a prior publication, this research investigates the operational characteristics of a methane-fueled solid oxide fuel cell (SOFC) system with anode off-gas recirculation (AOGR) for electrical energy supply on sea-going vessels. The proposed first-principle system model utilizes a spatially segmented SOFC stack and lumped balance of plant components validated on the component level to accurately depict the steady-state and transient operating behavior. Five operational limitations are chosen to highlight permissible operating conditions with regard to stack and pre-reformer degradation. Steady-state operating maps are presented, emphasizing efficient operating conditions at maximum stack fuel utilization and minimal permissible oxygen-to-carbon ratio. Exemplary transient load changes illustrate increasing system control complexity caused by gas flow delays due to the spatially distributed plant layout. Actuation strategies are presented and underline the need for a top-level model predictive system controller to assure a dynamic and efficient operation within the defined constraints. Full article

In the operation of internal combustion engines, despite technical state monitoring, some cracks that develop in metal components go undetected, leading to secondary, critical, or degradation damage. The diagnostic systems used in floating objects mainly use quasi-static thermodynamic signals, which alert operators too late about emerging damage. Although various methods have been developed to detect cracks in internal combustion engine components, the effectiveness and implementation of the proposed methods are not satisfactory. Therefore, this article presents the use of selected vibration and in-cylinder pressure signals to diagnose the development of damage in some components of marine diesel engines. The investigations were conducted under the natural conditions of the operation of sea-going vessels during port-handling operations. During these investigations, it was possible to observe clear changes in the values of diagnostic symptoms, which corresponded to the development of damage. The developing damage detected in the study involved cracks in injector nozzles manufactured from alloy steel. Despite advances in design, materials, and manufacturing technology, injector nozzle cracks still occur. The diagnostic symptoms used to detect damage development were the amplitude and spectral and wavelet measurements of vibration acceleration signals. This work aimed to search for crack-oriented methods of signal analysis, for example, computer visualization and the recording of diagnostic parameters in various domains. Decimation, windowed, time, amplitude, and time-frequency domain analyses; wavelet statistics; color analysis; and machine learning were used for classification using artificial neural networks. Experimental investigations showed the possibility of diagnosing the development processes of damage to marine diesel engines. The advanced signal processing methods used made it possible to obtain many signal measurements, from which the most useful diagnostic symptoms were selected. The new symptoms found with decimation, time-domain windowed analysis, and Haar wavelet statistics were more useful than the existing ones. Full article

Weight reduction remains a relevant topic for various ship structures, as it can improve their seagoing capacity, especially for high-speed and light-craft vessels, and make deck equipment more efficient. The introduction of new lightweight composite materials and the development of new processing technologies and computer modeling tools open up new opportunities in equipment design, but also require new design approaches, including those based on optimization techniques. This article presents an engineering technique for optimizing the design of a ship’s crane manipulator boom based on modern computer simulation tools and numerical optimization methods. The loads on the crane arising due to the ship’s motion were obtained and specified, and the requirements for the finite element model for strength and stability analysis were derived. Constructive, technological, and resource constraints were then derived to reduce the number of independent optimization parameters. The mass reduction problem was set and solved by combining the screening method and the Jaya algorithm. Applying this developed technique for optimizing the crane boom structure using 465 parameters, an 18% reduction in mass was achieved. Full article

As the primary consumers in aquatic organisms, zooplankton play an important role in aquatic ecosystems. It is valuable for management and researchers to have an insight into the responses of zooplankton community patterns to environmental factors. In this study, RDA and variation partitioning analysis were adopted to determine the important environmental factors affecting zooplankton abundance and biomass, as well as the relative importance of different environmental factors. The findings reveal that TN (total nitrogen), WD (water depth), pH, and SAL (salinity) were all important abiotic factors shaping the zooplankton community pattern in the study area. TN affected protozoa by influencing Stentor amethystinus, while the effects of WD on copepods may have been mainly induced by the responses of Calanus sinicus and Paracyclopina nana. By inhibiting Stentor amethystinus and Vorticella lutea, pH significantly affected protozoa. In addition, Rotifera and copepods were affected by SAL mainly through the responses of Brachionus calyciflorus, Calanus sinicus, and Ectocyclops phaleratus. Importantly, fundamental alternations in the variation trends of zooplankton abundance and biomass along the salinity gradient were found when the salinity was approximately 4–5. By combining these results with the findings on phytoplankton responses to salinity in previous studies, it can be concluded that salinity may influence the river ecosystem by influencing zooplankton abundance and biomass rather than phytoplankton. Full article