Numerical study of a marine dual-fuel four-stroke engine

Continuously increasing environmental demands in conjunction with the planned strong penetration of the LNG, render the use of LNG as an attractive alternative marine fuel. In this framework, the traditional ship propulsion plants based on Diesel engines running with HFO, should be revisited and compared to the more efficient and environmentally friendly propulsion systems that use dual fuel engines. The present study deals with the computational investigation of a marine four-stroke dual fuel (DF) engine, in both diesel and DF mode operation. The engine model was set up in a commercial software and used to compare the performance and emissions of the investigated engine operation at steady state conditions. The engine diesel mode was initially set up and the model was calibrated to adequately represent the engine operation. Subsequently, the engine dual fuel model was set up by considering the injection of two different fuels; methane and pilot diesel fuel. The derived results were analysed for revealing the differences of the engine performance and emissions at each engine mode. In addition, the turbocharger matching at each mode is investigated revealing the challenges due to the completely different air-fuel ratio strategies used in diesel and dual fuel modes, re-spectively

Ship machinery condition monitoring using performance data through supervised learning

This paper aims to present a methodology for intelligent monitoring of marine machinery using performance data. Monitoring of machinery condition is a crucial aspect of maintenance optimisation that is required for the vessel operation to remain sustainable and profitable. The proposed methodology will train models pertinent to specific machinery components using pre-classified performance data and then classify new data points using the models developed. For this, measurements are suitably analysed and processed to retain most of the information (variance) of the original dataset while minimising number of required dimensions. Finally, new data are compared against the models developed to evaluate their condition. The above will provide a flexible but robust framework for the early detection of emerging machinery faults. This will lead to minimisation of ship downtime and increase of the ship’s operability and income through operational enhancement. Case studies that show initial results obtained through main engine data are included

Computational investigation of ship propulsion performance in rough seas

In this paper, the performance of a merchant vessel propulsion system during acceleration is evaluated under different sea state conditions. The various parts of the main propulsion system have been modelled by using a mean value approach for the engine model with differential equations to calculate the engine crankshaft and turbocharger shaft speeds. Ship propulsion system has been modelled by using differential equations to calculate vessel speed and speed of advance. The output of the engine model has been validated under steady conditions according to the main engine shop test performance data. The calm water resistance is calculated following the ship sea trials results, whilst Wageningen polynomials have been used to simulate the propeller performance for the given hull resistance and speed. In order to estimate the added resistance for different weather conditions, the recommended procedures by International Standards have been followed. Then, the propulsion system performance is evaluated, both in calm water and waves, to investigate the main engine response during acceleration. Based on the simulation results, the propulsion system performance is discussed in respect for the engine response and vessel hydrodynamic performance, predicting the maximum vessel speed for the available engine power and speed

Predictive maintenance decision support system for enhanced energy efficiency of ship machinery

A decision support system (DSS) is an application that analyses data and presents results to users. DSS rapidly shift through huge amount of available data and thus allowing for faster analysis of condition monitoring data early detection of faults and improved allocation of resources. DSS can also predict and plan for future ship operators’ needs in order to optimize ship machinery operations. Such a system can provide substantial benefits to the maritime industry in terms of energy efficiency as the operation of the vessel can be optimised towards this end. As part of the INCASS (Inspection Capabilities for Enhanced Ship Safety) EU FP7 project, this paper presents a novel DSS solution which interrogates data from dynamic condition monitoring and compares them with historic data to present decision support information onboard a ship. To provide for Condition Based inspection and criticality based maintenance for ship machinery, data is acquired and stored for analysis through the DSS. Moreover surveys involving off-line and real time on-line measurement approaches are combined to provide a more complete monitoring method. The result is a reliable user friendly graphical interface (GUI) developed in Java language that can be employed onboard any vessel and can provide relevant and on-time information. The proposed actions from the DSS target energy efficient operation and reduction of fuel consumption and ship emissions. Moreover, a major factor taken into account through the prediction mechanism of the DSS is to assist in better spare parts scheduling and prioritizing ship inspection, maintenance and repairs towards enhanced and efficient ship operations

A modelling approach for predicting marine engines shaft dynamics

For making decisions on maintenance and operations of ship systems in a timely and cost effective way, intelligent approaches for continuously assessing the critical ship systems condition are required. This study aims to provide a framework for large marine two-stroke diesel engines performance assessment, by mapping the relationship of specific malfunctioning engine conditions on the Instantaneous Crankshaft Torque (ICT). This is accomplished by the development of a thermodynamics model, which is coupled with a lumped mass crankshaft dynamics model, in order to predict the engine shaft dynamics and torsional response. Subsequently, by employing the coupled engine models, a number of case studies are simulated for investigating the influence on the engine ICT, which include: (a) change in the Start of Injection (SOI), (b) change in the Rate of Heat Release (RHR), (c) change in the scavenge air pressure, and (d) leaking exhaust valve. By investigating the predicted ICT from the coupled model in both the time and frequency domains, distinct frequencies are identified, which correspond to specific engine malfunctioning conditions. Based on the derived results, these engine malfunctioning conditions are mapped with the frequencies most affected in the engine’s instantaneous torque, which demonstrate the usefulness of implementing the the ICT measurement for diagnostic purposes

Wave-induced vertical bending moment estimation by onboard tiltmeters units on container ship

Full-scale measurements in oceangoing ships have shown that the relationship between bending moment with the curvature curve of hull girder. As part of the INCASS (Inspection Capabilities for Enhanced Ship Safety) EU FP7 project, this paper carried out an estimation of wave-induced vertical bending moment for cargo hold of the 4250 TEU container ship, based on the data of pitch angles processing from the Tiltmeter units placed on board. The results are enable to be processed to the Decision Support System (DSS), in order to assist to monitoring and risk analysis for ship structure and machinery the towards enhanced and efficient ship operations (Konstantinos, et al., 2015). The prediction values also provide a reference for the trend analy-sis of the past record signals (Ulrik Dam et al, 2015) for evaluation of longitudinal strength of container ship. The advance in different pitch angle response (deformation curvature) of hull girder can be as a development of modern decision support systems for guidance to the ship's master (Lloyd's Register, 2016

Tanker ship structural analysis for intact and damage cases

This paper presents the work carried out to assess the structural calculation of a tanker ship in intact and damage conditions, in order to know the areas of the central cargo ship exposed to greater stresses. Analysing the results obtained from the intact condition and damage conditions due to grounding. The method selected to simulate the damage conditions has been done applying a change in the mechanical properties of the material; reductions of 40, 60 and 80 % of Young Modules were applied. The validation of the results was made following the guidelines "Common Structural Rules for Bulk Carriers and Oil Tankers" from IACS. The finite element method and finite element analysis software (Ansys®) were used to analyse intact and ground-ing cases. For intact case only one scenario was done, full load condition. For grounding, three scenarios were done. The results presented correspond to the validation of the finite element model, and the results concern-ing the maximum value of Von Mises Stress for each load condition, verifying if the permissible stress has been exceeded in each of the conditions analysed

Analysis of the wave-induced vertical bending moment and comparison with the class imposed design loads for 4250 TEU container ship

The long-term predictions of vertical wave bending moment are made for the extreme design values on ship. As part of the INCASS (Inspection Capabilities for Enhanced Ship Safety), this paper carried out a short-term estimation of wave loads for 4250 TEU container ship by the hydrodynamic analysis software of ANSYS-Aqwa based on three-dimensional linear potential flow theories. Based on the short-term predic-tion and the wave statistic of the North Atlantic Ocean, a long-term prediction of vertical wave bending mo-ment is obtained. The results are required and processed to the Decision Support System (DSS), in order to assist to monitoring and risk analysis for ship structure and machinery the towards enhanced and efficient ship operations (Konstantinos, et al., 2015). The prediction values also provide a reference for the trend analysis of the past record signals (Ulrik Dam et al, 2015) for evaluation of longitudinal strength of container ship

Comparison of diesel-electric with hybrid-electric propulsion system safety using system-theoretic process analysis

Cruise ship industry is rapidly developing, with both the vessels size and number constantly growing up, which renders ensuring passengers, crew and ship safety a paramount necessity. Collision, grounding and fire are among the most frequent accidents on cruise ships with high consequences. In this study, a hazard analysis of diesel-electric and hybrid-electric propulsion system is undertaken using System-Theoretic Process Analysis (STPA). The results demonstrate significant increase in potential hazardous scenarios due to failures in automation and control systems, leading to fire and a higher number of scenarios leading to propulsion and power loss in hybrid-electric propulsion systems than on a conventional cruise-ship propulsion system. Results also demonstrate that STPA enhancement is required to compare the risk of two propulsion systems

An intelligent system for vessels structural reliability evaluation

An intelligent system is proposed within INCASS (Inspection Capabilities for Enhanced Ship Safety) project for evaluating ship structural reliability and assisting in fatigue damage and structure response assessment. The system combines hydrodynamic, finite element and structural reliability models.. The hydrodynamic analysis model is not discussed in this paper. The finite element model input is a mesh for the mid-ship part of the vessel. Finally, the in-house structural reliability model input is the calculated output of the previous model as well as models for estimating crack development and propagation, corrosion growth and fatigue loading. The output includes the probability of failure for all the investigated components versus time which can be used to assess safe operation through the developed decision support software. The database can receive information from various sources including inspection and robotic systems data. The case study of a capsize bulk carrier the presents structural evaluation process