Ship Propulsion Research Articles

Dynamic Failure Analysis of Ship Energy Systems Using an Adaptive Machine Learning Formalism

The criticality of shipping operations in global trade requires a comprehensive understanding of its sustainability. This depends on the integrity/performance of the ship structure and vital systems, such as the ship propulsion engine. The current research paper presents the application of an adaptive machine learning formalism, the Bayesian network, for failure assessment of a ship propulsion engine considering nonlinear and nonsequential failure interactions. The model captures critical failure influencing factors and their complex interactions to predict the failure probability of the ship energy system. Sensitivity and uncertainty analysis was carried out to establish the degree of influence of vital failure influencing factors as they affect the ship propulsion engine’s reliability and the associated uncertainty in the prior data processing. The model is tested on the propulsion engine of an ocean going vessel to forecast the likelihood of failure based on the logical dependencies among failure causative factors. Two scenarios were analyzed based on canonical probabilistic algorithms, and the results show that upon evidence on the three critical failure modes, the ship propulsion engine failure likelihood increased by 11.8%, 8.2%, and 9.4%, respectively. The model shows an adaptive/dynamic capability to capture new failure information and update the system’s failure probability. The proposed approach provides a condition monitoring tool and early warning guide for integrity management of critical ship energy systems.

Exploring the Green-Oriented Transition Process of Ship Power Systems: A Patent-Based Overview on Innovation Trends and Patterns

The shipping industry has accelerated the transformation of its carbon emission reduction and decarbonization, and relevant patents are rapidly increasing, but the industry still lacks consensus on the low-carbon development route of ship propulsion technology. We used the Derwent Innovation Index to collect the global patent information on ship power systems between 1965 and 2022 and proposed a new patent information mining framework. It is used for the dynamic tracking and analysis of global technology correlation characteristics, hot technology topics, and competitive situations. The findings indicate that: (1) the innovation of ship power systems is more radical and concentrated in the fuel field represented by LNG technology, whereas technical innovation in the field of pure electric propulsion is more scattered. Small tonnage ships, underwater operations, and recreation technology are among its innovation hotspots. (2) Pure electric propulsion technology is dominated by combined innovation with other propulsion methods (hybrid propulsion technology) and Chinese universities have recently begun to lead this technology. (3) Fuel cells and remote control have become innovation hotspots. Fuel cell technology, which combines electric, fuel, and hybrid power technology, is now on the cutting edge of innovation and has the potential for disruptive innovation.

Research on MDO of Ship Propulsion Shafting Dynamics Considering the Coupling Effect of a Propeller-Shafting-Hull System

Abstract Dynamic designs for ship propulsion shafting can be categorised as complex multi-disciplinary coupling systems. The traditional single disciplinary optimisation design method has become a bottleneck, restricting the further improvement of shafting design. In this paper, taking a complex propulsion shafting as the object, a dynamic analysis model of the propeller-shafting-hull system was established. In order to analyse the coupling effect of propeller hydrodynamics on shafting dynamics, the propeller’s hydrodynamic force in the wake flow field was calculated as the input for shafting alignment and vibration analysis. On this basis, the discipline decomposition and analysis of the subdisciplines in design of shafting dynamics were carried out. The coupling relationships between design variables in the subdisciplines were studied and the Multi-disciplinary Design Optimisation (MDO) framework of shafting dynamics was established. Finally, taking the hollowness of the shaft segments and the vertical displacement of bearings as design variables, combined with the optimal algorithm, the MDO of shafting dynamics, considering the coupling effect of the propeller-shafting-hull system, was realised. The results presented in this paper can provide a beneficial reference for improving the design quality of ship shafting.

Energetska optimizacija serijskog hibridnog električnog brodskog porivnog sustava

The electric ship propulsion system due to its economic advantages and, first of all, better mechanical properties than internal combustion engines (influence on ship manoeuvrability) have gained popularity in recent years. This paper presents an investigation of a series hybrid electric propulsion system where two sources of power are used: a permanent magnet synchronous generator and energy storage battery to supply electric propulsion system, which is a permanent magnet synchronous motor. Controlling the power flow from multiple power sources in a series hybrid mechatronic system is important to increase the energy efficiency of the propulsion system. Developing a suitable power flow control method is difficult due to the nonlinear nature of the power sources in the series system. In this paper a method of energy optimization of the system has been verified which allows to improve energy efficiency by reducing reactive power in the system. In this paper, an analytical study of the mechatronic system of a serial hybrid electric ship propulsion system is carried out based on the analysis of the steady-state electromagnetic and energy relations. The proposed control with energy optimization was compared with the commonly used FOC control. The analytical studies have been confirmed by performing simulation studies in Matlab-Simulink program. The proposed optimization method allows its use not only in ship electric drives but also in other autonomous electric drives using the series topology of the hybrid system.

Testing the Inclination of an Industrial Diesel Engine Under Static Conditions According to the International Convention for the Safety of Life at Sea (SOLAS) Regulations

many industrial diesel engines are used as the main engine of the ship. Apart from being relatively cheaper, the availability of industrial engine is also very abundant, and the repair process is also not too complicated. However, when viewed from the SOLAS regulations related to the main requirements for a ship propulsion engine, it must also be considered, because it operates at sea, so that ship engines must be tougher than industrial engines, especially related to engine performance when experiencing rolling and trim. The purpose of this research is to test the feasibility of industrial diesel engines being operated on ships. By using a water-cooled single-cylinder diesel engine which is commonly used in small ships. The experimental method was used in this research to obtain optimal results according to the conditions in the field, the engine was made in three variations, namely the normal condition (without inclination angle), the rolling condition of 15 0 , and the trim condition of 5 0 which complies with SOLAS regulations related to the inclination angle. The results of the research obtained torque, Specific Fuel Consumption (SFC), and engine thermal efficiency in various engine variations. The highest torque is in the condition of the 15 0 rolling engine, which is 13.87 N.m. The lowest SFC is in the condition of the 15 0 rolling engine, which is 194 gr/kW.h. and the highest thermal efficiency was also obtained at the condition of the 15 0 rolling engine, namely 44.9%. The higher the engine speed, the higher the engine performance value in rolling 15 0 conditions, and the 5 0 trim conditions experience an increasing trend, but in low rotation conditions (750 Rpm) the performance decreases. Seeing the results obtained, a water-cooled single-cylinder diesel engine can be used as a small boat propulsion engine.

Detection of ice using ship propulsion and navigation measurements

The presence of sea-ice influences the operation of ships in polar waters. Ice navigation leads to increased rates of damage accumulation in propulsion machinery. Methods and algorithms used to monitor the condition of the propulsion machinery can benefit from indicators that detect either operation in ice-infested waters or direct detection of propeller–ice interaction. This paper explores existing methods that inform the novel application of automatically detecting sea-ice based on high frequency shaft response measurements, low frequency propulsion control measurements, and navigation data. These methods include rule-based approaches, machine learning based classification, and statistical change detection. Methods are evaluated based on misclassification errors during cross-validation. It is shown that detection using the selected data is possible and able to give satisfactory prediction accuracy based on a case-study vessel. The results also show that machine learning approaches provide a solution that balances prediction accuracy and the rate of false negative predictions. The recommended method is to use support vector machine classifiers with a radial basis function kernel.

Investigation of the Effects of the Pre-Duct in a Ship on Propeller–Hull Interactions Using the CFD Method

The power requirement of a ship propulsion system is directly proportional to the fuel consumption and the emissions released. By reducing the engine power, the fuel consumption and emissions can be reduced. One of the energy saving devices (ESDs) that is positioned in a region between the stern hull and propeller is the pre-duct. The ESD can improve the propulsive coefficient of the propulsion system. This research explains the effect of a circular pre-duct on the hull-propeller interaction. A numerical simulation uses the Japan bulk carrier (JBC) standard model for the hull and propeller. A circular pre-duct was applied to the ship with different diameters, stands, and lengths of the chord. The simulation has already been validated with the result of the resistance and self-propulsion test in the towing tank. The results show that the diameter of the pre-duct affects the water flow to the propeller. The model with 1Dp can make the positive value of the propulsive coefficient be about 1.72%. The size of the foil chord of the pre-duct can improve the performance until 2.88% at 1D 2S NS model. The stand of the pre-duct has a bad effect on the propulsive coefficient. The enlarged shape of the foil pre-duct can increase the water flow on the suction side. Also, making the diameter larger than the propeller diameter and eliminating the stand on the pre-duct make the incoming flow has no resistance or damages the rotary flow before the propeller. So that, the rampant flow to the propeller becomes larger and there are no significant obstacles until the propulsive coefficient value increases significantly.

Life Cycle Cost Analysis for Scotland Short-Sea Ferries

The pathway to zero carbon emissions passing through carbon emissions reduction is mandatory in the shipping industry. Regarding the various methodologies and technologies reviewed for this purpose, Life Cycle Cost Analysis (LCCA) has been used as an excellent tool to determine economic feasibility and sustainability and to present directions. However, insufficient commercial applications cause a conflict of opinion on which fuel is the key to decarbonisation. Many LCCA comparison studies about eco-friendly ship propulsion claim different results. In order to overcome this and discover the key factors that affect the overall comparative analysis and results in the maritime field, it is necessary to conduct the comparative analysis considering more diverse case ships, case routes, and various types that combine each system. This study aims to analyse which greener fuels are most economically beneficial for the shipping sector and prove the factors influencing different results in LCCA. This study was conducted on hydrogen, ammonia, and electric energy, which are carbon-free fuels among various alternative fuels that are currently in the limelight. As the power source, a PEMFC and battery were used as the main power source, and a solar PV system was installed as an auxiliary power source to compare economic feasibility. Several cost data for LCCA were selected from various feasible case studies. As the difficulty caused by the storage and transportation of hydrogen and ammonia should not be underestimated, in this study, the LCCA considers not only the CapEx and OpEx but also fuel transport costs. As a result, fuel cell propulsion systems with hydrogen as fuel proved financial effectiveness for short-distance ferries as they are more inexpensive than ammonia-fuelled PEMFCs and batteries. The fuel cost takes around half of the total life-cycle cost during the life span.

Solid oxide fuel cells for shipping: A machine learning model for early detection of hazardous system deviations

With rising concerns about the amount of pollutant emissions generated by shipping and the consequent pressure to curb the environmental impact of shipping activities, fuel cells are expected to take an important role in ship propulsion. In particular, Solid Oxide Fuel Cells (SOFCs) are envisaged to provide high electrical efficiency and offer the opportunity of combining heat and power production. This work deals with the safety issues related to the safety implications of the use of Fuel Cells in maritime applications. A machine-learning model for identifying and intercepting critical events, based on the early detection of the system weak signals, is developed and applied to a Solid Oxide Fuel Cell (SOFC) system. The model relies on a hybrid approach: a data-driven model based on gradient-boosted decision trees and a computational model of the SOFC system are integrated to enhance the data-driven approach by implementing physics-based knowledge to boost the resulting predictive capabilities. The outlined approach even if it requires further validation at the full scale may be considered a step forward in enabling the prediction of the conditions that may lead to an accident with remarkable accuracy.

Techno-economic model-based design space exploration of ‘combined’ ship propulsion systems

The architecture of a ship propulsion system, developed during early stages of the overall ship design process, has a very large impact on the overall design and performance of the ship. The design space exploration to arrive at the final ship propulsion architecture can be a rather complex process for high-performance 'combined' ship propulsion systems designed to achieve multiple, often conflicting, design objectives. This paper proposes a novel process for the process of design space exploration based on a model-based ‘Techno-economic & Environmental Risk Assessment’ (TERA) approach, executed using a hybrid ‘Multiple-Criteria Decision-Making’ (MCDM) procedure, to select a compromise solution from competing propulsion system architectures populating the design space. The process utilizes a combination of performance data generated from performance simulation of developed models, as well as comparative expert opinions-based metrics for information not available early in the ship design process for selection of a 'compromise solution'. The paper includes an illustrative example of application of the proposed process for design space exploration for a combined propulsion system architecture for a notional destroyer.

Using Nuclear Energy for Maritime Decarbonization and Related Environmental Challenges: Existing Regulatory Shortcomings and Improvements.

In recent years, the use of nuclear energy as propulsion for merchant ships has been proposed as a means of promoting the transition toward maritime decarbonization and environmentally sustainable shipping. However, there are concerns that nuclear-powered merchant ships could pose risks to the marine environment in the event of accidents, such as collisions, machinery failure or damage, fire, or explosions. The current international regulatory framework for nuclear-powered merchant ships is insufficient to address these risks. This research aims to address this gap by conducting a policy analysis of the existing regulations and a critical examination of their effectiveness in addressing the environmental risks of nuclear-powered merchant ships. Through this analysis, the study identifies the shortcomings and insufficiencies in the current framework and explores potential solutions to improve it, with the goal of enhancing the international community's ability to mitigate the potential impacts of radioactive marine pollution from nuclear-propelled ships in an era of maritime decarbonization.

Computational fluid dynamics for naval hydrodynamics

This article describes key issues which have to be addressed to apply Computational Fluid Dynamics to Naval Hydrodynamics. The specific aspects of Naval Hydrodynamics are discussed and illustrated by recent simulations and comparisons with available experiments. Free-surface flows with or without waves and even violent phenomena such as ventilation or cavitation can be modelled with mixture-fluid surface capturing. Turbulence modelling of thick boundary layers and vortical flows requires anisotropic RANS models or hybrid RANS/LES in case of strongly separated flows. Moreover, fluid–structure interaction in the form of rigid or flexible body motion and multi-body systems is crucial to represent ship manoeuvring and propulsion. Finally, the paper underlines the central role played by anisotropic adaptive grid refinement in the accurate simulation of marine flows.

Sensorless Control of Dual Three-Phase Permanent Magnet Synchronous Machines—A Review

This paper presents an overview of various sensorless control methods, with a focus on dual three-phase permanent magnet synchronous machines (DTP-PMSM). Owing to the important role that DTP-PMSMs play in motion-control applications in industry, most academic researchers and industry activists seek to reduce costs and size while increasing the capability and efficiency of motion applications. This has led to an increase in the number of publications about multiphase machines in recent years. The purpose of this article is to review the most important sensorless control techniques, which are divided into two main categories, namely saliency-based control method for low-speed range and model-based control method for high-speed range. Both methods are subdivided into other categories, with a focus on DTP-PMSMs. The methods are compared with each other for the purpose of selecting the most suitable control technique for implementation in applications such as ship propulsion, wind turbines, and aerospace.

Economic Feasibility of Retrofitting an Ageing Ship to Improve the Environmental Footprint

Natural gas is cheaper than fuel on an energy basis, making it an alternative ship fuel which leads to a reduced operating cost and clean gas environmental conditions. The current study analyses the retrofit of an ageing multi-purpose ship to use liquefied natural gas as a primary ship fuel in the context of a short-ship sea operation. The objective is to transform an existing commercial ageing ship propulsion system into a green energy propulsion one and to analyse the economic feasibility considering the high volatility and increased LNG price. Four scenarios were analysed based on the net present value representing Denying, Disinterested, Good and Acceptable financial cash outflow. It was concluded that in the present economic instability and price of LNG fuel and CO2 taxes, the ship owner needs to rely on the long-term contract of buying LNG fuel to implement measures to reduce greenhouse gas emissions and keep good benefits in shipping.

Improvement and Optimization Configuration of Inland Ship Power and Propulsion System

Advances in power and propulsion and energy management improvements can significantly contribute to reducing emissions. The International Maritime Organization (IMO) Marpol regulations impose increasingly stringent restrictions on ship’s emission. According to the measured data of the target ship in typical working profiles, the power fluctuation, fuel consumption and emission data are analyzed, and the result represented that there are serious fuel consumption and pollution problems in the diesel engine power system. Based on the ship-engine propeller matching design theory, the ship-engine propeller model was built, and the new propulsion system power of the target ship was obtained by simulation. From the perspectives of power, economy and green, the performance and emission indexes of diesel engine and LNG engine are compared and analyzed, and the fuel cost advantage, green advantage and power performance disadvantage of LNG engine compared with diesel engine are determined. By comparing the topological structures of different hybrid propulsion forms, the new propulsion form of the ship is improved to be the gas-electric hybrid propulsion system based on the ESS (Energy Storage System), and the selection of the supercapacitors and lithium batteries is compared. Based on the low-pass filter strategy, the power distribution of the ultracapacitor and lithium battery is distributed. In order to determine the optimal ESS configuration, a capacity configuration model with investment cost, fuel cost and energy storage life as objective functions was established. NGSA-II algorithm was used to calculate the model and scheme selection was completed based on the scheme decision model. In this case, the optimal scheme significantly reduces pollutant emissions, it also reduces daily fuel costs by 38% and the result shows that we can complete the cost recovery in 1.28 years.

Retrofitting WASP to a RoPax Vessel—Design, Performance and Uncertainties

Wind-assisted propulsion (WASP) is one of the most promising ship propulsion alternatives that radically reduce greenhouse gas emissions and are available today. Using the example of a RoPax ferry, this study presents the performance potential of WASP systems under realistic weather conditions. Different design alternatives and system layouts are discussed. Further, uncertainties in the performance prediction of WASP systems are analyzed. Included in the analysis are the sail forces as well as the aero- and hydrodynamic interaction effects, i.e., the sail–sail and sail–deck interaction as well as the drift and yaw of the ship. As a result, this study provides guidelines on the most important parameters when designing and modeling a WASP ship. Finally, the study presents an analysis of the expected accuracy of the employed empirical/analytical performance prediction model ShipCLEAN.

Wind-Assisted Ship Propulsion of a Series 60 Ship Using a Static Kite Sail

Following the International Maritime Organization’s goal to reduce greenhouse gas emissions, the interest in the application of wind-assisted ship propulsion (WASP) in maritime transportation is on the rise. Although a variety of WASP systems exist, the application in maritime shipping is still limited, especially in the case of kite sails. This paper presents a numerical model to carry out a theoretical assessment of the influence of the kite planform area and wind speed on the aerodynamic performance of a kite sail providing propulsive assistance to a 75 m long ship having a Series 60 hull. A static kite sail is assumed, on which a tail wind generates a thrust force to pull the vessel via a tether. While the mass of the kite is neglected, that of the tether is accounted for. A model is implemented for the tensioned tether having a catenary profile. The results generally show a positive correlation between the aerodynamic forces and the kite parameters. As expected, the output parameter values corresponding to the optimal angle of attack for a range of vessel speeds are also found to increase with an increasing relative wind speed. It is concluded that a static 320 m2 kite sail would be sufficient to meet the entire propulsion requirements of the vessel under consideration under appropriate wind conditions.

Seafarers Involvement in Implementing Energy Efficiency Operational Measures in Maritime Industry

The Fourth GHG Study 2020 of the International Maritime Organization (IMO) reported that 2.89% of total global anthropogenic CO2 emissions had been emitted by international shipping. IMO's initial strategy is to set carbon intensity goals of at least a 40% reduction in CO2 emissions per transport work by 2030, and a 70% reduction by 2050 must be met. This has led IMO to introduce guidelines for calculating energy efficiency in both the design and operation phases using the Energy Efficiency Design Index (EEDI), the Ship Energy Efficiency Management Plan (SEEMP), the Energy Efficiency Existing Ship Index (EEXI), and the Carbon Intensity Indicator (CII). In the decade between 2008 and 2018, the energy efficiency of international shipping operations advanced by one-third. By adopting energy efficiency design and operational measures and introducing innovative technologies, many shipping companies worldwide reported remarkable financial and environmental benefits by saving fuel on every voyage. Ships are operated by ashore technical managers and aboard crewmembers; thus, they are directly involved in implementing energy efficiency operational measures. Therefore, the scope of this study is only limited to ashore technical managers and aboard ship crews only. This study has found that Master and Deck Crews are directly involved in implementing the ship's navigation and port operation-related EE measures. In contrast, the Chief Engineer and Engine Crews are directly involved in all ships’ propulsion, power generation, and management-related operational EE measures to implement onboard ships. Since the ashore managers supervise the ship's Master and Chief Engineer, they have reasonable control in every aspect of the fleet's energy efficiency operations, from navigation to port operations and ship's propulsion to power generation and management.

The GATERS Project – An innovative way of retrofitting ships for greener and safer operations

This paper presents the first-year activities of the H2020 Innovation Action project GATERS for greener propulsion of ships using an innovative retrofit energy-saving and steering device, the Gate Rudder System (GRS). One of the project's main aims is to retrofit a target coastal vessel with a GRS for the first time and demonstrate its effectiveness. The target vessel is the existing 6400 DWT general cargo ship (MV Erge), currently fitted with a high-lift conventional rudder system (CRS), which a retrofit GRS will replace in GATERS as one of the project aims. This paper provides a background of GRS technology and the project motivation, including a brief project overview. The details of the retrofit task involving the design of the main GRS components and estimated power-saving are also reported in the paper. The vessel is scheduled to be retrofitted in December 2022 for demonstration and further performance monitoring.

A new validated open-source numerical tool for the evaluation of the performance of wind-assisted ship propulsion systems

Wind propulsion is envisioned as one of the solutions for the decarbonisation of maritime transport, as it offers high efficiency in terms of primary energy comsumption. Many wind propulsion systems already exist at various development stages, but the uncertainties over their performance is a strong obstacle to their adoption by ship owners. This paper presents a general method for the assessment of steady and unsteady performances of wind- propelled ships with 6 degrees of freedom, as implemented in the open-source program xWASP_CN. Inspired by system-based modelling, the method consists in the independent modelling of the forces acting on the ship, as functions of the ship’s 6 degrees of freedom and environmental conditions. An original root-finding algorithm that leverages the specifics of the physical problem to find the steady equilibrium is presented. The method works either like a Power Prediction Program (PPP) or like a Velocity Prediction Program (VPP). As a PPP, the forward speed and course are fixed while the required propulsive power, leeway angle, heel, trim and sinkage are solved. As a VPP, only the course is fixed and the attained forward speed, leeway angle, heel, trim and sinkage are solved. This makes the method suitable for both hybrid propulsion and pure wind propulsion. The force models can be semi-empirical (usually requiring very little input data), based on preliminary experimental or numerical results (such as forward resistance curves, lift/drag coefficients and frequency-domain sea-keeping coefficients), or full-fledged flow solvers (e.g. potential theory, CFD). Thus the method is suitable for all design stages as each force can be modelled with several levels of accuracy depending on the input data available. Comparisons of an intermediate-level model with experiments on a 18-ft catamaran fitted with a Flettner rotor and a water turbine show good agreement for steady-state results.