Marine Propulsion System Research Articles

Dynamic Modeling of a Hybrid Propulsion System for Tourist Boat

Interest in designing more efficient and versatile ships comes from increasingly stringent regulations on emissions. In this context, a possible solution to overcome these limits may be the replacement of marine propulsion systems based on diesel engines with hybrid architectures. This paper provides a dynamic analysis of a hybrid marine propulsion system (HPS) consisting of an internal combustion engine and an electric engine coupled with a battery pack. A dynamic simulation of a daily working cycle was carried out based on a real load demand. The instantaneous behavior of each component was evaluated. A brief summary of the HPS performance, varying the battery pack capacity, was provided together with an estimation of its impact on the system efficiency. Referring to this last point, the adoption of a hybrid system has permitted a decrease in the specific consumption, on a given route, of about 2% with respect to the case where the propulsion is entrusted only to the diesel engine.

Methods for determining mechanical losses of marine diesel engines

Abstract The paper presents based on literature critical evaluation of commonly known methods for determining the mechanical losses of a piston engine. Their advantages and disadvantages were pointed out also the possibility of their use in a marine propulsion system was assessed.

Modeling and simulation of a two-shaft gas turbine propulsion system containing a frictional plate–type clutch

A marine propulsion system is composed of several sub-systems that operate in a variety of energy fields. The propulsion power of a ship can be provided from a two-shaft gas turbine. In this article, the modeling of a two-shaft gas turbine and its associated sub-systems including gears, flexible couplings and clutch is considered. These components are connected in the form of a virtual marine propulsion system, which is based on the bond-graph approach. When a clutch is used in a propulsion system, discontinuities occur in the describing model, which leads to some challenging problems when performing computer simulations. The two main difficulties are the numerical stiffness and the variable model structure. In this research, the bond-graph method is adapted as the modeling framework in order to allow a constant system structure model that minimizes the stiffness problem. Next, simulation results of a two-shaft gas turbine are presented in the off-design condition and verified with experimental tests. These results demonstrate the acceptable accuracy of computer simulations. Also, the effects of clutch performance on the dynamics of the marine propulsion system are discussed.

A Novel Type-2 Fuzzy Logic for Improved Risk Analysis of Proton Exchange Membrane Fuel Cells in Marine Power Systems Application

A marine energy system, which is fundamentally not paired with electric grids, should work for an extended period with high reliability. To put it in another way, by employing electrical utilities on a ship, the electrical power demand has been increasing in recent years. Besides, fuel cells in marine power generation may reduce the loss of energy and weight in long cables and provide a platform such that each piece of marine equipment is supplied with its own isolated wire connection. Hence, fuel cells can be promising power generation equipment in the marine industry. Besides, failure modes and effects analysis (FMEA) is widely accepted throughout the industry as a valuable tool for identifying, ranking, and mitigating risks. The FMEA process can help to design safe hydrogen fueling stations. In this paper, a robust FMEA has been developed to identify the potentially hazardous conditions of the marine propulsion system by considering a general type-2 fuzzy logic set. The general type-2 fuzzy system is decomposed of several interval type-2 fuzzy logic systems to reduce the inherent highly computational burden of the general type-2 fuzzy systems. Linguistic rules are directly incorporated into the fuzzy system. Finally, the results demonstrate the success and effectiveness of the proposed approach in computing the risk priority number as compared to state-of-the-art methods.

An effective framework for life cycle and cost assessment for marine vessels aiming to select optimal propulsion systems

By adopting the concept of modularity, this paper introduced an optimal framework which facilitates life cycle assessment and life cycle cost assessment, thereby supporting rapid and reliable decision-making in the marine industry. The benefits of the proposed framework were discussed through two case studies where the optimal configurations of marine propulsion systems were determined from the economic and environmental perspectives. First, the performance of a short-route ferry using the hybrid system was compared with those of equivalent ships using diesel-electric and diesel-mechanical propulsion systems respectively. Research findings revealed the excellence of the hybrid system in both economic and environmental aspects. Second, the same method was applied to an offshore tug vessel to determine an optimal engine configuration. Results of analysis emphasised that the selection of multiple small-sized engines is more effective than two medium-sized engines. Both studies have proven that the proposed framework would be useful and practical for accelerating the life cycle analysis which allows ship designers and owners to obtain the long-term view of economic and environmental impacts for particular products or systems without demanding process. The paper also opened up the possibility of extending the application of the proposed framework to the areas where proper decision-making is essential but under-used.

Detection and Isolation of Interturn Faults in Inductors of LCL Filter for Marine Electric Propulsion System

This paper presents an online technique to detect and isolate the interturn fault in the inductors of the LCL filter integrated with the active front-end rectifier used for electric propulsion of marine vessels. The proposed online technique is based on the fundamental component of the core-leakage flux measured at the yoke center of the inductor. A comparative study of the grid currents and the core-leakage fluxes under interturn faults is carried out using the proposed analytical models which reveal high sensitivity of the core-leakage flux at the yoke center when compared to the grid currents. The theoretical analysis is validated experimentally on a laboratory-based 11.3-kW marine propulsion system test rig for 1-turn, 2-turn, and 4-turn faults under various loading and supply voltage unbalance conditions. An online fault notification and isolation framework has also been proposed and validated experimentally with two different techniques to increase the reliability for 1-turn fault detection. The methodology requires just a single, low-bandwidth, and inexpensive magnetic flux sensor in addition to the existing current sensors to detect as low as 1-turn fault out of 63 turns.

Degradation Detection and Diagnosis of Inductors in LCL Filter Integrated With Active Front End Rectifier

This paper presents an online methodology to detect and diagnose the inductor degradation in LCL filter integrated with Active Front End Rectifier (AFER) for electric drives in marine propulsion system (MPS). The proposed methodology monitors the leakage fluxes of converter-side inductor and compares it with the same under healthy condition to detect and diagnose the inductance degradation. The magnitude of leakage flux's fundamental component is extracted using the Fast Fourier Transform (FFT) and is used for detection of inductance degradation. Hence, inexpensive and low bandwidth magnetic flux sensors along with a simple FFT algorithm are used to detect and diagnose the inductance degradation. The leakage fluxes of the inductor during degradation are analyzed using the developed analytical model and validated on a laboratory prototype of 11.3-kW MPS test-rig. The validation was carried out for different degrees of converter-side inductor degradation from 3% to 19% under 33%, 73%, and 100% of full-load capacity of the MPS test-rig. Both estimated results using the analytical model and experimental results obtained are found to be in good agreement. The proposed online technique can detect and estimate the degraded inductance as low as 3% and is superior to the technique using grid currents in detecting the inductor abnormality.

Vibration of diesel-electric hybrid propulsion system with nonlinear component

The lumped parameter method is used to model the components of a marine diesel-electric hybrid propulsion system. Modular modeling and five basic models of torsional vibration are used to establish the torsion of the diesel-electric hybrid propulsion system with a nonlinear components vibration mathematical model. In order to include the nonlinear parts of the marine diesel-hybrid propulsion shafting torsional vibration system characteristics, by combining the perturbation method with the advantages and disadvantages of the harmonic method, a perturbation-harmonic method is presented to solve the diesel-electric hybrid propulsion shafting free vibration characteristics. At the same time, the nonlinear vibration characteristics of the hybrid propulsion shaft system are calculated and analyzed using the incremental harmonic balance method. In order to verify the correctness of the theoretical method of hybrid propulsion system, the correctness of the vibration model and method is verified by carrying out actual tests on a 10,000-ton marine surveillance ship. In order to verify the mathematical model of the ship diesel-hybrid propulsion system and the correctness of the theoretical calculation method, the torsional vibration test is carried out by a strain gauge method for a 10,000-ton marine propulsion shaft. The correctness of the torsional vibration mathematical model and the calculation method is verified by comparing the torsional vibration test data and the theoretical calculation data of the ship propulsion shaft system, which provides the theoretical significance for the calculation and analysis of the torsional vibration of the ship propulsion shaft system.

Transient load share management of a diesel electric hybrid powertrain for ship propulsion

In this paper, a transient load share methodology for a hybrid diesel electric marine propulsion system is presented. The aim of the system is the performance enhancement and reduction of gaseous emissions during low-load transient operation. The controlled variable is λ while the manipulated variable is the torque from the electric motor regulated by a frequency inverter. The model for the λ behaviour is based on experimental identification while λ values in feedback loop come from an actual and a virtual sensor, the later based on first principles modelling. A nominal model is used for the synthesis of a robust H∞ controller for the controlled variable regulation. Experimental results in a full scale hybrid diesel electric powertrain under realistic loading scenarios verified the successful hybridisation.

Common failures of ship propulsion shafts

This article aims to provide a critical review of the most common failures of ship propulsion systems as a crucial ship system, with emphasis on fatigue failure. The accent is given on the shaft of marine propulsion systems as a most common point of failures in the entire propulsion system. A general description of failure causes and failure analysis methodology is presented. Several representative case studies summaries for fatigue failure on critical points of the propulsion shaft are described. Torsional vibrations and geometric stress concentrations of the shaft are identified as the most common cause of fatigue failure. The importance of constant monitoring, measurement and data collection of fatigue indicators and indicative events that have influence on fatigue development is emphasized. Methods used in failure analysis are discussed and propositions for improvement are given, especially in terms of using numerical routines in failure prediction.

Thermal interaction between main engine body and ship hull

The paper presents analysis of displacement of a propulsion system shaft line and a crankshaft axis caused by temperature of marine, slow-speed main engine. Detailed information of thermal displacement of a power transmission system axis is significant during a shaft line alignment and a crankshaft springing analysis and during designing of structural health monitoring (SHM) system. A warmed-up main engine is a source of deformations of an engine body as well as a ship hull in the area of an engine room and hence axis of a crankshaft and a shaft line. Engines' producers recommend the model of parallel displacement of the crankshaft axis under the influence of an engine heat. This model may be too simple in some cases (especially for SHM systems).The paper presents computations of MAN B&W K98MC type engine mounted on 3000 TEU container ship. The engine body is much stiffer than its foundation pads and ship hull (double bottom) - boundary conditions of the engine. Especially for the high power marine engines correct model of the boundary conditions plays a key role during the analyses. Presented numerical analyses are based on temperature measurements of the main engine body and the ship hull during a sea voyage. Numerical analyses were performed using Nastran software based on Finite Element Method. The FEM model of the engine body comprised over 800 thousand degree of freedom (dof); the model of the ship hull contains over 200 thousand dof. Both models are analysed separately; the mutually interaction between them is taken into account by heat transfer and special model of boundary conditions. The specialized SHM system dedicated to marine propulsion systems working in very bad environmental conditions is the future aim of the research.

The Hunt for Red October II: A magnetohydrodynamic boat demonstration for introductory physics

The 1990 film “The Hunt for Red October” (based on Tom Clancy’s 1984 debut novel of the same name) featured actors like Sean Connery and Alec Baldwin, but the star of the movie for physicists was a revolutionary new magnetohydrodynamic (MHD) marine propulsion system. The so-called “caterpillar drive” worked with no moving parts, allowing a nuclear missile-armed Soviet submarine to approach the U.S. coast undetected. As the submarine captain (played by Connery) said, “Once the world trembled at the sound of our rockets … now they will tremble again—at the sound of our silence.

Model Predictive Control for Hybrid Diesel-Electric Marine Propulsion

In this work, the problem of energy management strategies in hybrid diesel-electric marine propulsion systems is investigated with the implementation of two types of Model Predictive Controllers. The system behavior is described by models based on system identification as well as on first-principles. These models were used for the design of linear and adaptive predictive controllers respectively. The controllers were successfully tested at HIPPO-1 testbed, at the Laboratory of Marine Engineering, evaluating diverse strategies for disturbance rejection, system stability, and operation of the plant within desirable limits.

A Review of the Surface Drives Employed for High Speed Planing Craft

Marine propulsion systems are the core of high speed planing craft (HSPC), a major factor in creating acceleration, and speed retaining therein. HSPC have used many surface drives to drive the craft. The propulsion systems installed on these vessels are always an important factor for buyers and users, This article reviews and compares the several different of surface drives system been designed for planing boat and the important factors to evaluate a surface drive system have later been investigated, The overall results show that the best propulsion system have higher safety and reasonable price and lower maintenance cost per year and can provide more speed for boats. Hence, the articulated surface drives while having high hydrodynamic efficiency will be a priority for installed on most new planing craft.

Effects of different grain sized sands on wear behaviours of NBR/casting copper alloys

Nitrile Butadience Rubber (NBR) is widely used in marine water-lubricated stern tube bearings. The sand in water, especially in a river (e.g., Yangtze River), is a key factor affecting the tribological properties and lubrication performance of the rubber stern tube bearings. Studying the wear performance of rubber stern tube bearings under different grain sized sands will provide a guide for rational design of the rubber stern tube bearings to reduce wear and prolong service life. In this study, a CBZ-1 tribo-tester was used to conduct sliding wear tests under the sand water with different grain sizes (i.e., 4.5µm, 23µm, 48µm, 75µm), distilled water-lubricated conditions and the same mass concentration of 1.1%. The comparison analyses of friction coefficient, wear volumes and the worn surface morphologies were conducted. The results showed that the grain size of sands, sliding velocity and applied load had significant effects on the wear performance of NBR/ZCuSn10Zn2 cast copper. The friction coefficient, wear volumes and worn surface morphologies of most samples increased as the applied load and grain size increased. The sand particles destroyed the water-film to reduce the properties of NBR/ZCuSn10Zn2 cast copper. Meanwhile, the higher the sliding velocity, the easier the water-film formed between the NBR/ZCuSn10Zn2 cast copper. The friction coefficient, wear volumes and worn surface morphologies of rubbing pairs decreased as the sliding velocity increased. It is believed that the knowledge obtained in this study provides the real practical basis for running condition selection of water-lubricated rubbing stern tube bearings in marine propulsion systems.

Vibration Diagnostics of the Naval Propulsion Systems

Abstract The paper presents examples of vibration performances of the naval propulsion systems. It describes the methodology of preparation for measurement, used gauges and their restrictions. The necessity of synchronous measurements had been justified. The work contains also samples of analysis, to facilitate the reader with the components of amplitude-frequency spectra of naval propulsion systems. An overview of the existing normative documents had been presented. At the same time limitations of applying of them during technical monitoring of marine propulsion systems had been presented.

Energy and exergy analysis of the turbo-generators and steam turbine for the main feed water pump drive on LNG carrier

Nowadays, marine propulsion systems are mainly based on internal combustion diesel engines. Despite this fact, a number of LNG carriers have steam propulsion plants. In such plants, steam turbines are used not only for ship propulsion, but also for electrical power generation and main feed water pump drive. Marine turbo-generators and steam turbine for the main feed water pump drive were investigated on the analyzed LNG carrier with steam propulsion plant. The measurements of various operating parameters were performed and obtained data were used for energy and exergy analysis. All the measurements and calculations were performed during the ship acceleration. The analysis shows that the energy and exergy efficiencies of both analyzed low-power turbines vary between 46% and 62% what is significantly lower in comparison with the high-power steam turbines. The ambient temperature has a low impact on exergy efficiency of analyzed turbines (change in ambient temperature for 10°C causes less than 1% change in exergy efficiency). The highest exergy efficiencies were achieved at the lowest observed ambient temperature. Also, the highest efficiencies were achieved at 71.5% of maximum developed turbo-generator power while the highest efficiencies of steam turbine for the main feed water pump drive were achieved at maximum turbine developed power. Replacing the existing steam turbine for the main feed water pump drive with an electric motor would increase the turbo-generator energy and exergy efficiencies for at least 1–3% in all analyzed operating points.

Marine Duty Harmonic Mitigation on DC Propulsion Saves Oil Service Vessel Program

An offshore oil and gas service vessel equipped with dc propulsion drives retrofitted with revenue generating equipment, such as remote operated vehicles (ROV) and cranes, could not pass sea trials due to multiple failures (including loss of navigation) caused by harmonic distortion. Marine propulsion systems represent a dominant load on most vessels and dynamically positioned (DP) offshore installations. These propulsion systems are typically nonlinear in nature with very high harmonic injection, which can have a significant impact on vessel wide systems and subsystems. AC adjustable speed drive (ASD) propulsion systems characteristically inject current harmonics into the generator system impedance creating voltage distortion. DC ASDs produce even higher voltage distortion levels due to voltage notching caused by the thyristor firing which makes their harmonic mitigation requirement much more challenging. In order to eliminate the numerous harmonic problems, the dc propulsion system of the oil service vessel was retrofitted with harmonic mitigation equipment. The case study discusses: 1) operational issues including component failures in crane controls and ROV equipment while operating in DP mode; 2) field testing to document the harmonic distortion conditions created by the propulsion and thruster dc ASDs prior to treatment; 3) computer simulation of the dc drive propulsion system to determine a harmonic mitigation strategy; and 4) extensive sea trial testing of the power system with harmonic mitigation to demonstrate compliance with ABS harmonic limits, compatibility of the harmonic mitigation with the ASD equipment, and resolution of all connected equipment failures and operational problems.

Thermomechanical analysis of porous solid oxide fuel cell by using peridynamics

Solid oxide fuel cell (SOFC) is widely used in hybrid marine propulsion systems due to its high power output, excellent emission control and wide fuel suitability. However, the operating temperature in SOFC will rise up to 800–1000 ℃ due to redox reaction among hydrogen and oxygen ions. This provides a suitable environment for ions transporting through ceramic materials. Under such operation temperatures, degradation may occur in the electrodes and electrolyte. As a result, unstable voltage, low capacity and cell failure may eventually occur. This study presents thermomechanical analysis of a porous SOFC cell plate which contains electrodes, electrolytes and pores. A microscale specimen in the shape of a plate is considered in order to maintain uniform temperature loading and increase the accuracy of estimation. A new computational technique, peridynamics, is utilized to calculate the deformations and stresses of the cell plate. Moreover, the crack formation and propagation are also obtained by using peridynamics. According to the numerical results, damage evolution depends on the electrolyte/electrode interface strength during the charging process. For weak interface strength case, damage emerges at the electrode/electrolyte interface. On the other hand, for stronger interface cases, damage emerges on pore boundaries especially with sharp corner.

Marine Propulsion System Reliability Assesment by Fault Tree Analysis

Research on reliability to ensure that the operation of transport facilities is safe. This issue is always concerned by transportation operators. This article presents a number of research using Fault Tree Analysis method (FTA) to model the analysis, reliability assessment of marine propulsion system.