Propulsion Plant Research Articles

Optimization of Fuel Consumption by Controlling the Load Distribution between Engines in an LNG Ship Electric Propulsion Plant

Due to growing environmental concerns and stringent emissions regulations, optimizing the fuel consumption of marine propulsion systems is crucial. This work deals with the potential in an LNG ship propulsion system to reduce fuel consumption through controlled load distribution between engines in Dual-Fuel Diesel Electric (DFDE) plant. Based on cyclical data acquisition measured onboard and using an optimization model, this study evaluates different load distribution strategies between setups according to the optimization model results and automatic (equal) operation to determine their effectiveness in improving fuel efficiency. The analysis includes scenarios with different fuel types, including LNG, MDO and HFO, at different engine loads. The results indicate that load distribution adjustment based on the optimization model results significantly improves fuel efficiency compared to conventional methods of uniform load distribution controlled by power management systems in almost all load intervals. This research contributes to the maritime industry by demonstrating that strategic load management can achieve significant fuel savings and reduce environmental impact, which is in line with global sustainability goals. This work not only provides a framework for the implementation of more efficient energy management systems on LNG vessels, but also sets a benchmark for future innovations in maritime energy optimization as well as in the view of exhaust emission reduction.

Modeling a Zero-Emissions Hydrogen-Powered Catamaran Ferry Using AVL Cruise-M Software

This work focuses on the modeling of a zero-emissions, high-speed catamaran ferry employing a full-electric propulsion system. It addresses the global emphasis on full-electric vessels to align with IMO regulations regarding ship emissions and energy efficiency improvement. Using the AVL Cruise-M software, this research verified the implementation of an onboard fuel cell power-generating system integrated with a propulsion plant, aiming to assess its dynamic performance under load variations. The catamaran was 30 m long and 10 m wide with a cruise speed of 20 knots. The power system consisted of a proton-exchange membrane fuel cell (PEM) system, with a nominal power of 1600 kWe, a battery pack with a capacity of 2 kWh, two 777 kW electric motors, and their relative balance of the plant (BoP) subsystems. The simulation results show that the battery effectively supported the PEM during the maneuvering phase, enhancing its overall performance and energy economy.

WR21 marine gas turbine thermodynamic simulator for ship propulsion studies

An original modular mathematical model, based on physical laws, for steady state and dynamics performance simulation of the WR21 gas turbine is presented in the paper. The model, developed in Matlab-Simulink language, is organized in modular form. Each gas turbine component (i.e. compressor, turbine, combustor, heat exchanger) is modelled in a specific simulator block, that simulates the performance of its pertinent component by means of steady state performance maps and/or correlations, time dependent momentum, energy and mass equations, nonlinear algebraic equations. The great application flexibility of the component simulator modules, allows to modelling any gas turbine layout (i.e. axial or radial flow compressor and turbine, rotating shafts number, heat exchangers). The WR21gas turbine, developed mainly for marine propulsion application, is a three shafts gas turbine with thermal regeneration. It is characterized by a high thermodynamic efficiency, which remains high up to 30% of the design power. The WR21 simulator results are validated by comparison with manufacturer or literature data. The WR21 gas turbine main performances are compared to those of the LM 2500 gas turbine, obtained by a previously author paper. The LM 2500 is the gas turbine currently most used in naval propulsion plants. In the article, a comparison between the steady state working data of the two gas turbines is reported in tabular and graphical form and commented.

Studying influence of the mathematical model error on the results of calculating freedom torsional vibration for marine diesel propulsion system

The Freedom Torsional Vibrations (FTV) Calculation (FTVC) for the marine main propulsion plant (MPP) to determine the freedom frequencies and the FTV formations of the mechanical system. Normally, the MPP is dynamically modeled as a finite n concentrated masses with the parameters of: Mass moment of inertia Jk (kgm2, k = 1÷ n) and the torsional stiffness Ck,k+1 (Nm/rad) between the k and k+1 concentrated masses. This paper studies the influence of the number of concentrated masses n as well as the accuracy of determining Jp (Moment of inertia of the propeller) on the solution of the MPP's FTVC. The research verifies to the MMP on the Korean ship XXX-XXX-XXX, using the MDE 6G70MEC. Keywords: Freedom Torsional Vibration (FTV); Mathematic model of the FTV; Exactness of the FTV calculation.

Sensor Set Decomposition for Enhanced Distributed Sensor Fault Isolability of Marine Propulsion Systems

This paper proposes a greedy stochastic optimization algorithm for the sensor set decomposition used in the sensor fault monitoring of marine propulsion systems, based on fault isolability criteria. These criteria are expressed mathematically in terms of the number of unique columns in the theoretical fault signature matrices (FSMs) used during the sensor fault isolation process. Due to the large scale and complexity of marine propulsion plants, the diagnostic layer follows a distributed architecture with a combinatorial logic used for fault isolation in two cyber levels; the local and global decision logic. As a result, the FSMs of both levels are formulated as an integrated optimization problem. Each solution regarding the sensor set decomposition is then used to generate the respective distributed monitoring architecture, using semantic (qualitative) knowledge for the propulsion plant. Thus, the need for an analytical model of the plant is removed. Moreover, based on the design of the distributed monitoring architecture, the respective theoretical FSMs (quantitative) are Automatically generated and used for the evaluation of the objective function. Finally, simulation results are used to illustrate the application of the greedy stochastic optimization algorithm and its efficiency.

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.

Explainable Prognostics Method through Differential Evolved RVR Ensemble of Relevance Vector Machines

Operating experience from various mechanical components indicates that their operating performance depends on non-well known physical mechanisms, while it is likely that various unexpected factors will act as catalysts for reaching the failure point. Therefore, one way to overcome the partially knowledge of physical mechanisms is the use of data-driven methods that estimate the degradation patterns and predict the failure point. Thus, there is a growing need to design and develop new and more sophisticated prognostic technologies that can estimate the remaining useful life of a mechanical component. In this work, a new method for prognostics is proposed that not only provides a prediction over the failure point but also provides an explanation over the rationale behind that prediction. The proposed method utilized tools from artificial intelligence and more specifically relevance vector machines (RVM) and differential evolution (DE). The cornerstone of the method is the assembly of an ensemble comprised of multiple RVM equipped with different kernels, and the subsequent evolution of the ensemble using the differential evolution. DE will provide a set of values for the coefficients of the ensemble. Then based on the coefficients together with their associated RVMs are used to provide an explanation over the prediction. The explanation stems from the kernels themselves as each kernel models different set of properties. The presented method is tested on a set of real-world degradation data taken from a Gas Turbine (GT) propulsion plant.

Modelling of the availability for the ship integrated control system sensors

Innovative control systems regulate and adjust a lot of operational conditions of the modern ship’s functions. A comprehensive Ship Integrated Control System (SICS), for the operation of the propulsion plant, the power management of the auxiliary engines, the operation of the auxiliary machinery, the loading and unloading of cargo, the navigation, the management of maintenance and the purchase of spare parts is implemented in the paper. A strategy where preventive maintenance is carried out and different repair actions can be considered is proposed. The SICS is subjected to various levels of degradation, and if so, a repair process will be undertaken to restore the system to its full working state. The aim of the paper is to optimize the best strategy for the different sensors of the SICS where only maintenance actions are performed or only repair actions need to be carried out. The model is developed and applied to the sensors of a ship and the objective is to determine the optimal asymptotic availability, and in particular in the main propulsion plant of a Liquefied Natural Gas (LNG) carrier. The model is illustrated by a numerical example based on empirical data.

Study on proposed respectively method for marine propulsion plant system: a case study on passenger ship

Study on proposed respectively method for marine propulsion plant system: a case study on passenger ship

Identification of waste heat energy sources of a conventional steam propulsion plant of an LNG carrier

Identification of waste heat energy sources of a conventional steam propulsion plant of an LNG carrier

Significant Development Potential of the Solid Oxide Fuel Cell for the Technical Progress of the Marine Main Propulsion Plant in the Context of Energy Conservation and Emission Reduction

The International Maritime Organization (IMO) has proposed a series of strict pollutant emission regulations and carbon emission reduction targets, and the shipping industry is seeking new types of the marine main propulsion plant with advantages of high-efficiency and low-emission. Among the possible alternatives, the marine electric propulsion technology whose electric power source is fuel cell has gained sufficient attentions. At present, the worldwide research of the marine applications for fuel cell supplying propulsion power focuses more on the proton exchange membrane fuel cell (PEMFC) with low power instead of other types of fuel cell, and a series of research projects have achieved concrete results such as the industrialized marine fuel cell system or practical demonstration application. But the development trends of the application of the marine fuel cell supplying propulsion power are from the small boat to the great ship, from the navigating zone with low environmental complexity such as coastal water, inland waters to the ocean with complex navigation conditions. Thus, the power demand of the marine fuel cell in the future will show steady growth, which will create more development opportunities for the solid oxide fuel cell (SOFC) with the advantages of higher power, greater efficiency, long life span and fuel diversity. Although some challenges exist, the solid oxide fuel cell with significant development potential can certainly lead the technical progress of the marine main propulsion plant in the context of energy conservation and emission reduction.

Simulation-Driven Robust Optimization of the Design of Zero Emission Vessels

The International Maritime Organization (IMO) Decarbonization Roadmap for curbing and eliminating Greenhouse Gas (GHG) emissions by 2030 and 2050, respectively, is a “herculean” task in its own respect. If it is now combined with fundamental changes in trade dynamics, volatile market conditions, tighter shipping financing platforms with sustainability-linked interest rates and international safety regulations setup, a completely new framework for commercial ship design characterized by strict and often contradicting requirements emerge In parallel, zero carbon fuels available (readily or in the future) require extensive technological modifications and technical leaps in the current arrangements ship propulsion plants (with little to no existing reference) characterized by elevated consumption figures due to low energy density leading to an overshoot in voyage expense costs and the Total Cost of Ownership (TCO), respectively. Considering such a tight design space, holistic approaches with lifecycle considerations aiming at robust designs are deemed necessary. Pursuant to this roadmap, the authors have developed a design methodology fully integrated within the CAE software CAESES™ that encompass all aspects of ship design (stability, strength, powering and propulsion, safety, economics) and has an inherent dynamic voyage simulation module, enabling the user to simulate the response in variations of the geometrical, design variables of the vessel under uncertainty. The methodology has been extended to model the design and propulsion plant of an Ammonia powered Large Bulk carrier and deployed in global ship design optimization studies and utility-based ranking and selection process.

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

The paper reports the comparison between diesel-electric and mechanical propulsion plants, employed to a small cruise ship propulsion. The plants prime movers are the Rolls-Royce Bergen marine diesel engines. Both engine versions, characterized by similar rated power but different power lint curve and specific fuel contours trend in the power-speed plan, are tested in all the considered propulsion plant types by simulation. In addition, the diesel-electric propulsion plants are simulated considering the diesel generators working in both constant or variable speed. The comparison between all the considered ship propulsion plants are presented in tabular and graphical form and commented.

Wind-Assisted Ship Propulsion: Matching Flettner Rotors with Diesel Engines and Controllable Pitch Propellers

The harvesting of wind energy and its transformation into a thrust force for ship propulsion are gaining in popularity due to the expected benefit in fuel consumption and emission reductions. To exploit these benefits, a proper matching between the conventional diesel engine-screw propeller propulsion plant and the wind-assisted plant is key. This paper aims to present a method and a code for the preliminary sizing of a ship propulsion plant based on a diesel engine, a controllable pitch propeller, and one or more Flettner rotors. A mathematical model describing the behaviour of the rotor in terms of propulsive thrust and power is proposed. The rotor model has been integrated into an existing diesel propulsion model in order to evaluate the ship’s fuel consumption. The ship’s propulsion model is written in a parametric form with respect to the following design parameters: ship dimensions and resistance-speed curve, propeller diameter, engine power, rotor geometry, and true wind conditions. The methodology helps in evaluating the engine–propeller working points and eventually the total ship propulsive power, including the power required to spin the rotor. It provides a way to compare wind-assisted propulsive solutions in terms of fuel consumption and CO2 emissions. A 3000-ton Ro-Ro/Pax ferry has been selected as a case study. Results on the parametric analysis of rotor dimensions and propeller pitch optimization are presented.

Алгоритм управления движением колесного судна при ветровом воздействии

The article highlights the study of the influence of wind parameters and operating modes of the propulsion plant on the quality indicators of motion control of the vessel with a paddle type propulsion and steering system. The dynamics of the vessel motion is considered on the basis of a mathematical model of a paddle vessel. Wind action has a significant impact on the dynamic characteristics of the vessel due to its design features: flat bottom, shallow draft, large windage. The effect of apparent and true wind with both constant and variable wind parameters and operating modes of the propulsion plant is analyzed. Conclusions are drawn about the limits of the vessel controllability for various parameters of motion and wind action. The operability area of the vessel control system is constructed depending on the direction and speed of the wind. It is noted that a change in the speed of the vessel leads to a change in the parameters of the apparent wind, which in turn affects the dynamics of the vessel. To compensate for the effect of wind changes there is proposed an algorithm for changing the speed of the vessel while keeping a given optimal trajectory under wind impact. The algorithm is designed subject to the control of the ratio of the rotational speed of the propeller wheels, without taking into account the impact of the thruster. A computer simulation of the ship’s movement was performed with a changing speed of movement and different parameters of the wind effect, taking into account the proposed algorithm. The proposed control algorithm makes it possible to compensate for the effect of apparent wind in transient operating modes of the propulsion plant, to ensure movement along a given trajectory and to improve the accuracy of ship control.

A study on interaction among hull, diesel engine and propellers of a twin-screw ship during turning circle maneuver

A marine propulsion plant will experience power fluctuations during ship maneuvers. In the turning circle maneuver, the propulsive load increases significantly, and the power required by the two shafts of a twin-screw ship may be completely inconsistent. To protect the propulsion plant, the interaction between the engine and the propellers should be studied in depth. In this paper, the twin-screw ONRT ship and the 16PA6-STC diesel engine are selected as the study objects. A series of captive model tests are simulated by using CFD method to obtain the hydrodynamic derivatives and hull-propeller-rudder interaction coefficients in the MMG model. The effective wake fraction is computed under the maneuvering conditions. Turning circle maneuver of the ship is predicted by using the established MMG model, and the predicted ship maneuvering characteristics show good agreement with the available experimental results, which verifies the CFD-based modeling method. Finally, a dynamic model of hull-engine-propeller system is established on the simulation platform for evaluating the operating characteristics of propulsion plant. The propeller loads are predicted and the interaction among hull, engine and propellers is investigated. This study helps to provide a deeper insight into the engine operation behaviors during turning circle maneuver of a ship.

Preliminary Design and Simulation of a Thermal Management System with Integrated Secondary Power Generation Capability for a Mach 8 Aircraft Concept Exploiting Liquid Hydrogen

This paper introduces the concept of a thermal management system (TMS) with integrated on-board power generation capabilities for a Mach 8 hypersonic aircraft powered by liquid hydrogen (LH2). This work, developed within the EU-funded STRATOFLY Project, aims to demonstrate an opportunity for facing the challenges of hypersonic flight for civil applications, mainly dealing with thermal and environmental control, as well as propellant distribution and on-board power generation, adopting a highly integrated plant characterized by a multi-functional architecture. The TMS concept described in this paper makes benefit of the connection between the propellant storage and distribution subsystems of the aircraft to exploit hydrogen vapors and liquid flow as the means to drive a thermodynamic cycle able, on one hand, to ensure engine feed and thermal control of the cabin environment, while providing, on the other hand, the necessary power for other on-board systems and utilities, especially during the operation of high-speed propulsion plants, which cannot host traditional generators. The system layout, inspired by concepts studied within precursor EU-funded projects, is detailed and modified in order to suggest an operable solution that can be installed on-board the reference aircraft, with focus on those interfaces impacting its performance requirements and integration features as part of the overall systems architecture of the plane. Analysis and modeling of the system is performed, and the main results in terms of performance along the reference mission profile are discussed.

Comparative analysis of the thermodynamic performances of solid oxide fuel cell–gas turbine integrated systems for marine vessels using ammonia and hydrogen as fuels

To mitigate environmental issues and implement energy management strategies, hydrogen is emerging as the most promising and sustainable energy source to help achieve decarbonization targets and meet world energy demands. However, hydrogen poses significant storage and transportation challenges due to its low volumetric and gravimetric density. Hence, ammonia is a potential candidate for a hydrogen storage medium because it contains 17.65% hydrogen by weight, and its volumetric hydrogen density is 45% higher than that of liquid hydrogen. In the maritime sector, these available fuels of ammonia and hydrogen are utilized via internal combustion engines, fuel cells, and gas turbines, which are employed on board ships. This study investigates the possibility of using ammonia and hydrogen as fuels for Solid Oxide Fuel Cells (SOFCs). A combined SOFC-Gas Turbine (GT) system was proposed to generate power for marine propulsion plants. This system was designed and modeled with support from Aspen HYSYS V.12.1. Thermodynamics performances of the proposed system were analyzed using the first and second laws of thermodynamics. The energy efficiencies of direct ammonia and hydrogen SOFCs were 60.96 and 64.46%, respectively. The energy efficiencies of the combined systems increased by 12.37 and 13.97% when using ammonia and hydrogen as fuels, respectively, compared with that of single SOFC systems. The exergy destruction of the primary components with each fuel was examined. Furthermore, a parametric study was performed to select the most suitable fuel utilization factor for the system. This analysis proved that ammonia has the potential as a hydrogen carrier and that waste heat recovery is an effective method to improve the thermodynamic performance of an SOFC system.

Smartenance DC-DC On-Board Power Converters

Traditional marine power grids, using diesel motors/generators, pollute the atmosphere with their CO2 emissions and adverse particles. Nowadays, green energy supplies like solar systems and fuel cells play significant roles in the electrification of marine propulsion plants. In general, marine power systems with green energy units are often considered as a kind of mobile DC microgrids under constant power loads (CPLs). However, since the CPLs impose nonlinearity and negative impedance instability on marine power systems, traditional linear controllers no longer stabilize the system under various disturbances. This motivated this brief to develop a non-integer model predictive control for the accurate control of DC/DC converters with CPLs to stabilize the main bus voltage and current in the full-electric ferry ship. In practice, the stability of ship systems is highly threatened due to the negative-independence effect of CPLs. To address the adverse challenges of CPLs, the deep deterministic policy gradient (DDPG) with actor and critic neural networks (NNs) is applied to effectively design the coefficients embedded in the non-integer MPC. In this approach, the actor NN provides the regulatory signals to adjust the non-integer MPC controller while the critic NN is trained to evaluate the quality of actions of actor NN. The experimental results with comparative analysis are carried out to validate the accuracy of the non-integer MPC under the change in the CPL’s power. The results demonstrated that the proposed controller offers a higher level of robustness than the state-of-art-schemes.

Influence of the marine engine load diagram characteristics on the ship propulsion system performance

In this study two four-stroke marine diesel engines, characterized by very similar nominal power and speed, but with very different trend of the power lint curve and specific fuel consumption contours in the engine load diagram, are compared by simulation, using each of them as an alternative to the other engine, for the motorization of a conventional (mechanical) propulsion plant for a small cruise ship. It is thus possible to determine and compare the efficiencies of the two engines and the vessel propulsion system overall performance for different ship speeds. The results of the comparisons are presented and discussed in the paper.