Ship Propulsion Research Articles

Wave-assisted propulsion: An experimental study on traveling ships

A submerged hydrofoil interacting with incoming waves produces combined heaving and pitching motion, facilitating the conversion of wave energy into thrust. When the foil is attached to the ship hull, the generated “green” power from wave energy could assist the ship's propulsion system and significantly reduce fuel costs. This study experimentally assesses thrust generation from a fixed mid-hull foil by comparing towing force at different wave and traveling speeds. The optimal mid-hull foil demonstrates a fuel cost reduction ranging from 10.3% to 20.4% at diverse traveling speeds and wave parameters. Thrust generation increases at higher traveling speeds. Additionally, this study mathematically describes the hydrofoil motion with an outer pivot, which better suits the ship–foil model. This study then introduces a Strouhal number (StA,S) specifically for the ship–foil model, considering ship travel, ship response, and the hydrofoil's rotation around its outer pivot.

Characteristic Analysis of the Magnetic Variable Speed Diesel–Electric Hybrid Motor With Auxiliary Teeth for Ship Propulsion

Characteristic Analysis of the Magnetic Variable Speed Diesel–Electric Hybrid Motor With Auxiliary Teeth for Ship Propulsion

Comparative analysis among different alternative fuels for ship propulsion in a well-to-wake perspective

The shipping sector is required to give a significant contribution to the reduction of Green House Gas (GHG) emissions, according to the ambitious goals fixed by the International Maritime Organization (IMO). To achieve these targets, new technologies and measures are required, related to logistics, digitalization, hydrodynamics, machinery, energy, and aftertreatment. A large potential to reduce GHG emissions is offered by alternative fuels. In this perspective a Well-to-Wake (WtW) approach is due for a comprehensive analysis. The paper is focused on the evaluation of WtW CO2 equivalent emission factors for LNG, methanol, and ammonia. The extensive bibliographic research on this topic outlines the large differences occurring when considering grey or green fuel production pathways. A case study based on a cruise ship allows to compare alternative fuels produced from fossil or renewable sources, considering two typical cruise profiles. Results in terms of Carbon Intensity Indicator confirms that the WtW approach points out the great potential of alternative green fuels for GHG emissions reduction.

Flettner Rotor Implication on Ship Ferry The Kalianget-Kagean Route Using Computational Fluid Dynamics

Ship's Ferries are a sea crossing that continues to operate around the time. The consequence related to shipping activities is an increase in ship exhaust emissions. One alternative for ship propulsion that is environmentally friendly is the Flettner rotor. The working principle of the tool follows the theory of the Magnus effect, where the force arises due to the difference in pressure between the two sides of the Flettner rotor. This study implicates the Flettner rotor on the Kalianget-Kangean ferry route with variations in wind speeds of 10, 15 and 20 knots and variations in dimensions of 3x1, 5x1 and 7x1 meters with a rotational speed of 500 rpm. Optimal results through computational fluid dynamics (CFD) simulations show a coefficient of lift (CL) of 3.647 and a lift force (Fl) of 2,980,631.2 kilonewton with dimensions of 5x1 meters and a wind speed of 15 knots. While the implicit percentage of Flettner rotors in KMP. DBS I of 18.11%, KMP. DBS III of 11.27%, and KMP. NS 92 of 5.45%.

Empowering 6G maritime communications with distributed intelligence and over-the-air model sharing

Introduction: Shipping and maritime transportation have gradually gained a key role in worldwide economical strategies and modern business models. The realization of Smart Shipping (SMS) powered by advanced 6G communication networks, as well as innovative Machine Learning (ML) solutions, has recently become the focal point in the maritime sector. However, conventional centralized learning schemes are unsuitable in the maritime domain, due to considerable data communication overhead, stringent energy constraints, increased transmission failures in the harsh propagation environment, as well as data privacy concerns.Methods: To overcome these challenges, we propose the joint adoption of Federated Learning (FL) principles and the utilization of the Over-the-Air computation (AirComp) wireless transmission framework. Thus, this paper initially describes the mathematical considerations of a 6G maritime communication system, focusing on the heterogeneity of the relevant nodes and the channel models, including an Unmanned Aerial Vehicle (UAV)-aided relaying model that is usually required in maritime communications. The communication network, enhanced with the AirComp technique for efficiency purposes, forms the technical basis for the collaborative learning across multiple Internet of Maritime Things (IoMT) nodes in FL tasks. The workflow of the FL/AirComp scheme is illustrated and proposed as a communication-efficient and privacy-aware SMS framework, considering spectrum and energy efficiency aspects under a sum transmitting power constraint.Results: Then, the performance of the proposed methodology is assessed in an important ML task, related to intelligent maritime transportation systems, namely, the prediction of the Cargo Ship Propulsion Power using real data originating from six cargo ships and utilizing long-short-term-memory (LSTM) neural networks. Upon extensive experimentation, FL showed higher prediction accuracy relative to the typical Ensemble Learning technique by a factor of 3.04. The AirComp system performance was evaluated under varying noise conditions and number of IoMT nodes, using simulation data for the channel state information by regulating the power of the transmitting IoMT entities and the scaling factor at the shore base station.Discussion: The results clearly indicate the efficiency of the proposed FL/AirComp scheme in achieving low computation error, collaborative learning, spectrum efficiency and privacy protection in wireless maritime communications, while providing adequate accuracy levels with respect to the optimization objective.

New approaches to assess and improve ship operating performance

The deterioration in the technical conditions of the main engine, hull, and propeller over time in service is natural and causes adverse effects on ship operating performance, so determining and overcoming this phenomenon is necessary. However, effectively solving this problem is not simple because it is affected by many complex and random factors such as engine deterioration, increased roughness of hull and propeller surfaces, changes in sea state and ship load, etc. In this study, our new approach based on the black-box method and detailed propeller diagrams provides an effective way to assess and improve ship performance both under specific operating conditions and after a period of service. This method was verified and validated with the test data of the Glory Star oil tanker and applied to the Duong River dry cargo ship in Vietnam to determine its performance degradation and provide solutions to overcome this problem. The results showed that after 5 years out of dry dock, the study ship's performance or propulsion efficiency was reduced by about 8.6%, resulting in an increase in fuel consumption of about 6.5% and a decrease in ship speed of about 14.7%. By applying technical solutions such as tuning the engine operating mode and choosing a practical propeller design point, the performance of this ship was greatly improved and brought about high economic and technical efficiency. Especially, the cutting of the propeller edges not only solved the torque-rich phenomena occurring on the study ship's main engine after 5 service years, but also saved 5.1% and 4.9% in hourly fuel consumption, and increased 3.9% and 4.9% in ship speed, calculated for ballast and full load sea trials, respectively.

Multiphysics Modeling and Co-Simulation of Ship Electric Power and Propulsion Systems for Virtual Testing and Verification

Multiphysics Modeling and Co-Simulation of Ship Electric Power and Propulsion Systems for Virtual Testing and Verification

Dynamic Performance of a Decoupled Dual Wound Synchronous Generator for Electric Propulsion of Ships

Dynamic Performance of a Decoupled Dual Wound Synchronous Generator for Electric Propulsion of Ships

Analiza uticaja različitih vrsta goriva na potrošnju i izduvne emisije brodskog dvotaktnog dizel motora

Two-stroke diesel engines are a vital component of merchant ship propulsion, but their use of heavy fuel oil contributes significantly to environmental pollution. This paper explores the impact of different fuel types on the fuel consumption and exhaust emissions of a two-stroke diesel engine used in maritime transport. In an effort to reduce these negative impacts, alternatives in the form of high-quality diesel fuels and their blends with biodiesel have been investigated. An experimental method was applied to analyse the performance of the two-stroke diesel engine, commonly used in commercial maritime traffic. Pure Euro diesel and various blends of Euro diesel with biodiesel obtained from waste sunflower oil were used in different proportions (7%, 20%, 25%). Exhaust emissions, including CO, CO 2, NO x , SO 2, and O 2 , were monitored during four different engine operating regimes. The experiment was conducted on the training ship Jadran, part of the Navy of Montenegro, while the ship was docked in the homeport. The engine load during moored ship operations represents a specific propulsion characteristic known as the heavy propeller loading, as referred to in the literature. The results of this research provide insights into the efficiency of different fuel types on the performance and ecological aspects of the two-stroke diesel engine under real operational conditions in maritime traffic.

Analysis of Data-Driven Modeling of Cycloconverters for Efficient Electromagnetic Transient Simulations of Electrified Ship Propulsion Systems

Simulation studies of modern electrified ship propulsion systems using the discrete switching models of cycloconverters are very time-consuming and require expertise and accuracy in modeling all the details of the ship’s electric power system. Alternatively, data-driven models of cycloconverter-based Variable-Frequency-Drive (VFD) systems are proposed, which may simplify the modeling and improve simulation efficiency and speed. The data-driven models can be established based on several measurements or a few runs of the detailed simulations, but their subsequent use enables very fast and efficient systemlevel studies. In this paper, the data-driven models of cycloconverter-based VFDs are analyzed in terms of their accuracy and numerical efficiency with respect to their detailed switching model counterparts for harmonic studies of an example ship propulsion system. The advantages and drawbacks of both modeling techniques are demonstrated through time-domain and frequency-domain electromagnetic transient simulations conducted in MATLAB/Simulink using the Simscape Electrical toolbox.

Ship Propulsion Experimental Teaching System Based on Virtual Reality

Ship Propulsion Experimental Teaching System Based on Virtual Reality

Modeling ship-wind turbine dynamics for optimal energy generation and navigation

This paper deals with modeling the dynamics of the ship-wind turbine system in order to optimize power generation and ensure safe navigation. The focus is on developing mathematical models describing the interaction of wind forces, turbine performance and ship dynamics. Numerical simulations are used to investigate the effects of varying wind conditions, turbine design and navigation parameters on energy efficiency. Control strategies are also developed to maximize the energy output of wind turbines while maintaining stability and safety of ship navigation. Model validation is performed through comparative analysis with experimental data or cases from existing wind-assisted ship propulsion systems. The aim of the study is to provide valuable practical recommendations for the implementation of wind energy technologies in maritime operations, contributing to sustainable development and environmental standards in shipping.

Zeroth-Order Vibration Analysis and Mitigation in Integral-Slot IPMSMs by Rotor Static Modulation Theory for Electrified Ship Propulsion

Zeroth-Order Vibration Analysis and Mitigation in Integral-Slot IPMSMs by Rotor Static Modulation Theory for Electrified Ship Propulsion

A suggestion for space harmonic injection into motor current to reduce propeller vibration

Propellers produce fluctuating thrust and torque as they rotate in a non-uniform wake field. They contribute most of the vibration and noise generated by the propeller and can lead to mechanical damage to shafts and bearings. Recently, the demand for electric propulsion ships has increased. As the torque and speed fluctuations are generated in marine propellers, harmonic components in the current and voltage of the propulsion motor occur and lead to increased losses, device degradation, and torque pulsations. In this study, a harmonic injection method is proposed to reduce the impact of motor and mechanical vibration caused by the fluctuating load torque of the propeller. A harmonic component is applied to the current of the motor to generate a motor torque with a different phase of the same magnitude as the variation of the load torque of the motor. In this study, a computational fluid dynamics simulation was performed to obtain the torque of the target vessel, medium range tanker, and a MATLAB Simulink was used to model the motor simulation. It was found that the harmonic injection method can reduce the mechanical torque fluctuation of the motor by 87%.

Power Control Strategy Optimization to Improve Energy Efficiency of the Hybrid Electric Propulsion Ship

Power Control Strategy Optimization to Improve Energy Efficiency of the Hybrid Electric Propulsion Ship

Study on the seawater cooled PRHRS of a nuclear propulsion ship with the upper heat exchanger for driving force and the seawater heat exchanger as an ultimate heat sink

As international maritime trade among countries increases, great efforts are being made to reduce the amount of greenhouse gases emitted from ships using conventional fossil fuels. A variety of environment-friendly power sources for ships are being considered, and nuclear energy is one of them. The research described in this paper focuses on elemental technologies related to nuclear-powered ships rather than the nuclear reactor technology itself. Among those technologies, the Passive Residual Heat Removal System (PRHRS) of a nuclear-powered ship is studied to remove residual heat by using seawater as an alternative heat sink. New concept of PRHRS is proposed and it is named as SWC-PRHRS. SWC-PRHRS has two heat exchangers: one is for driving force and another is for dumping the most of residual heat to the sea. Numerical analysis and experimental studies are conducted to improve the performance of SWC-PRHRS. The numerical results show that most of the residual heat comes from a reactor core is eliminated by sea water cooling proving the concept of SWC-PRHRS is working properly without any operator intervention and additional water supply. Experimental studies are conducted based on the numerical analysis results. From the experimental results, it is found that the mass flow rate of SWC-PRHRS is very sensitive to the filling ratio of SWC-PRHRS and there are three distinctive filling ratio ranges. Through the experiment, it is confirmed that SWC-PRHRS is working efficiently with the lower mass flow rate and the smaller upper heat exchanger without any operator intervention. SWC-PRHRS could remove a large amount of residual decay heat from the ship's reactor and release it to the sea. Considering the size, weight, and exceptional heat removal capability of SWC-PRHRS, it is clear that SWC-PRHRS is well suited for marine application usage.

Point Cloud-Based Spatial Environment Development for Near Real-Time Erection Simulation in Shipyards

<i>Interference and collisions often occur in the loading process at shipyards. Existing simulation methods focus primarily on resource processes and schedules, and there is a lack of real-time reflection in the complex and highly variable loading process. This study aims to develop a spatial environment incorporating real-time product data, such as hulls, and confirms its effectiveness by simulating various construction scenarios. As a method, a near real-time spatial environment based on broadband laser scanning was established, with the situation of loading heavy cargo assumed when converting an existing ship into an LNG dual-fuel propulsion ship. A case study simulation of near-real-time cargo loading processes was then conducted using Unity 3D to confirm the interference and collision risks within the spatial environment. The results indicated that interference occurred in structures previously not identified in the design data, and a collision occurred during the loading object erection phase. The simulation confirmed that the identification of interference and collision risks during the erection phase highlights the need for a relocation or removal process of potential hazards before erection takes place. An improved erection simulation that integrates near real-time data could effectively prevent interference and collision risks.</i>

Economic and environmental comparison between diesel-electric and mechanical propulsion plants for a small cruise ship

The paper reports an economic and environmental comparison between diesel-electric and mechanical propulsion plants, employed as an alternative to the other one, to the propulsion of a small cruise ship, also described in a previously authors article. The plants prime mover are two versions of the Rolls-Royce Bergen marine diesel engines, employed one as an alternative to the other in all the considered propulsion plants. The engines are characterized by similar rated power but with different power lint curves and specific fuel contours trend in the operating diagram. The diesel-electric propulsion plants are simulated considering the diesel generators working in both constant and variable speed. The economic and environmental (by EEDI and CII index) comparison results, between the considered ship propulsion plants, are presented in tabular and graphical form and commented.

Supercritical CO2-cooled fast reactor and cold shutdown system for ship propulsion

A neutronics study of a supercritical CO2-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO2 fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO2-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

Addressing the Training Gap for Ammonia-Fuelled Propulsion Systems: A Literature Review and Proposal for a New Job Training Program

The maritime industry is increasingly turning to ammonia as a promising alternative marine fuel to achieve sustainable and environmentally friendly shipping practices. However, this transition presents operational challenges and safety concerns that necessitate specialized training for marine engineers. This literature review examines the existing research on ammonia's operational challenges and identifies a critical research gap - the lack of comprehensive training programs for marine engineers to handle ammonia-fuelled propulsion systems effectively. The review highlights the importance of theoretical knowledge and practical training in such programs to ensure safe and efficient operations. Additionally, the study analyzes current training initiatives provided by leading maritime education institutions, Det Norske Veritas (DNV) Energy Academy, Lloyd's Maritime Academy, and Maritime Training Academy, to derive insights for developing a new job training program on ammonia-fuelled propulsion ships. The proposed program encompasses theoretical lectures and practical hands-on experiences, empowering marine engineers to navigate ammonia as a fuel source proficiently. By addressing this research gap and providing specialized training, the maritime industry can facilitate a smooth transition to ammonia as a marine fuel, promoting reduced environmental impacts and enhanced operational efficiency in the shipping sector. This literature review and proposal aim to contribute to the ongoing efforts in achieving sustainable and responsible maritime practices in the context of ammonia as a promising alternative marine fuel.