Reference Ship Research Articles

Ship-based carbon capture onboard of diesel or LNG-fuelled ships

Total shipping carbon emissions were approximately 938 million tonnes CO2 in 2012. Zero emission shipping options rely on the use of electricity or alternative fuels, such as blue hydrogen or ammonia. However, that requires major modifications to the ships and the logistics of fuel distribution. As a transition solution, which can be implemented on much shorter term; this study presents the technical and economic evaluation for ship-based carbon capture (SBCC) on diesel or LNG-fuelled vessels. Two reference ship engines of 1280 kW and 3000 kW were chosen. The process is simulated using Aspen Plus®, with 30 wt% aqueous monoethanolamine (MEA) and 30 wt% aqueous piperazine (PZ) as solvents. CAPEX and OPEX were reduced by integrating the thermal energy of the exhaust gas with the stripper reboiler for the diesel and LNG powered ships. For the LNG ships, the cooling capacity from evaporation of LNG was used for liquefying the captured CO2. By using piperazine, which allows CO2 to be desorbed at higher pressure than MEA, the minimal cost of CO2 captured achieved was 98 €/tonne CO2 with a corresponding 1.8 million euros equipment cost for the 3000 kW engine ship. Additionally, the feasibility of SBCC is investigated by adapting an existing cargo ship design (powered by the reference 3000 kW engine) for including the carbon capture process equipment. The capture, compression and storage units are fitted onboard, and the design is modified so that the transport capacity remains the same, while maintaining the ship stability.

Conditional reliability of bulk carriers damaged by ship collisions

Time-variant reliability analysis of a bulk carrier in damage conditions, after a collision event, is performed by Monte Carlo simulation. Two different collision models are applied, the former based on the deterministic format actually embodied in the Harmonized Common Structural Rules for Oil Tankers and Bulk Carriers, the latter based on a probabilistic format, derived by the recently developed GOALDS database statistics for collision and grounding events. A modified incremental-iterative method is applied, to account for instantaneous neutral axis rotation, due to asymmetrically damaged cross-sections, as for collision events. Time-variant residual strength statistical properties are preliminarily determined by Monte Carlo simulation, up to 25-year ship lifetime, accounting for corrosion wastages of all structural members contributing to hull girder strength, welding residual stresses and material properties randomness. Finally, time-variant reliability analysis is performed, to investigate the incidence of the applied collision damage models on hull girder annual failure probabilities in sagging and hogging conditions. Reliability analysis is performed for the Capesize single side bulk carrier, benchmarked in the 2012 ISSC report and assumed as reference ship in current analysis. Obtained results are fully investigated and discussed.

Incidence of load combination methods on time-variant oil tanker reliability in intact conditions

Reliability analysis of an oil tanker in intact conditions is performed to investigate the incidence of load combination methods on hull girder sagging/hogging time-variant failure probability. Particularly, Turkstra rule, Ferry Borges and Castanheta method and Poisson square wave model are applied to evaluate the statistical distribution of bending moment, with reference to both one voyage and 1-year period. Statistical properties of time-variant ultimate strength are determined by Monte Carlo simulation, up to 25-year ship lifetime; bending capacity is determined by means of a modified incremental-iterative method, to account for corrosion wastage of structural members contributing to hull girder strength, welding residual stresses and material properties randomness. After determining the still water load combination factors, based on statistical properties of still water, wave and total vertical bending moments, with reference to 1-year time interval, reliability analysis is performed by Monte Carlo simulation, based on limit state formulations relative to different load combination methods. Finally, the VLCC double hull oil tanker, benchmarked in the 2012 ISSC report, is assumed as a reference ship and obtained results are fully discussed.

Ultimate limit state-based multi-objective optimum design technology for hull structural scantlings of merchant cargo ships

As the ultimate limit state is now a primary criterion for ship structural design, multi-objective optimization techniques for both minimizing weight and maximizing safety are routine practices in the structural design of naval ships as such techniques are critical for determining the structural weight needed to meet the functional requirements associated with naval armaments. However, a comparative approach is still used in the structural design of merchant cargo ships, based on measurements from existing as-built reference ships. This comparative approach obviously needs to be upgraded, because it requires more man-hours and causes more design errors than a fully automated design procedure. The comparative approach may also lead to inadequate design results, in which some structural members are too strong, and others barely satisfy the strength criteria, which can lead to catastrophic failures in some cases. The aim of this paper is to develop a fully automated methodology for the optimum design of hull structural scantlings for merchant cargo ships that are modelled by plate-shell finite elements. A full optimization technique with multi-objectives is applied for minimizing structural weight and maximizing structural safety, as per design constraints associated with the ultimate limit states of the plate panels, support members and hull girders. The developed procedure is applied to the hull structural scantlings of a very large crude oil carrier (VLCC), and this test demonstrates the procedure's capacity to meet the strength requirements of common structural rules. A comparison between the new design and an as-built reference ship is made, confirming that the proposed procedure reduces the number of man-hours required by about 20%, lightens the structural weight by 3% and improves the safety factors for the critical members.

Impacts of the rudder profile on manoeuvring performance of ships

The profile of a ship rudder influences the forces it generates, which in turn influence the manoeuvring performance of a ship. Thus, rudder forces and moments should be calculated considering the profile. Instead of an empirical estimation of the rudder normal force coefficient, this paper applies a RANS method to determine the hydrodynamic characteristics of various profiles, i.e. lift and drag coefficients. The RANS method is validated with a classic NACA 0012 profile and applied to 9 profiles from the NACA series, the wedge-tail series, and the IFS series. Furthermore, the 2D open-water RANS results are corrected for the effects of the propeller slipstream and the rudder aspect ratio. New regression formulas of the normal force coefficients are proposed for the tested profiles. These formulas are then integrated into a standard MMG model. Taking the KVLCC2 tanker as a reference ship, the manoeuvring model is validated with free-running tests executed by MARIN. Finally, the manoeuvring performance of the reference ship with various rudder profiles are quantified with turning and zigzag manoeuvres. The simulation results confirm that the wedge-tail series is most effective (largest manoeuvring forces) while the NACA series is most efficient (highest lift to drag ratio) among the tested profiles. The IFS series achieves a balance of effectiveness and efficiency.

Experimental investigation of Steel–Concrete–Polymer composite barrier for the ship internal tank construction

Transportation of dangerous cargo by ships demands ensuring an appropriate protection level in case of an accident. Two of the most dangerous accident types resulting in an oil spill are grounding and ship to ship collision. The article presents results of research on a new composite construction for a ship hull that increases structural safety during collision. The concept of semi-elastic Steel–Concrete–Polymer structure is presented. The most important results of the research are discussed. The resistance to collision and grounding of the new sandwich solution is investigated by means of two independent large scale experiments. The first collision experiment was conducted on a reference ship section representative for a double bottom or a double side of a ship. The second test was performed on a construction similar to the first one, but with an additional semi-elastic protective barrier. Both ship sections were loaded in the same manner by a sphere-shaped intender simulating the assumed collision scenario. On the basis of large-scale collision experiments the new solution of semi-elastic protective barrier was proven to significantly increase resistance to collision and grounding.

Reference ship selection for the on-time performance benchmarking of ships

The on-time performance of a ship is one of the major aspects of a ship’s operational reliability. The establishment of proper benchmarking for it would help the ship’s stakeholders to a considerable extent with respect to enhancement of the performance. This paper investigates and suggests a methodology for selection of a ship as a point of reference, so that improvement in the on-time performance of other ships could be achieved. The issue is addressed through comparative studies of ships, exclusively from an on-time performance viewpoint. The paper proposes a structure that would guide the development of a support system for improvement in the operational reliability of a ship. The on-time performance of a ship is expressed in terms of 12 primary attributes signifying the diverse aspects of its operational reliability. Four ships of like characteristics voyaging between Singapore and Japan are considered for the study and an assessor’s objective and subjective responses to the attributes are collected for these ships. The fuzzy analytical hierarchy process is used to allot priority weights to all the attributes, and then an evidential reasoning procedure is applied to obtain the utility values of the ships. Based on the utility values, comparison is carried out and the best of the four ships is selected as the reference ship for the marine sector under investigation. The proposed framework would be useful for enhancement of the ship’s operational efficiency, reliability and performance. It would also help the ship’s stakeholders in terms of better scheduling and proper management of the ship’s arrival at the destination harbour.

Ship Classification in Single-Pol SAR Images Based on Fuzzy Logic

This paper presents a new ship classification methodology that uses single-pol synthetic aperture radar (SAR) images to categorize targets based on a fuzzy logic (FL) decision rule. As such, the method tries to overcome the lack of an operational solution that is able to reliably classify ships with one SAR channel. The method has the following three main stages: (1) radar signature isolation; (2) parametric vector ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> ) estimation; and (3) decision rule. The first part analyzes the reflectivity histogram of the ship signature to iteratively cluster the pixels of interest. Then, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> is calculated by estimating the values of some macroscale features such as length, breadth, and radar cross section profile along the ship signature. Finally, the decision rule is evaluated with FL so that the measured vector <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> is correlated with the vectors associated with a set of reference categories. These categories have been defined based on user feedback and have been characterized with accurate simulation studies. Specifically, the values of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> for each reference ship have been derived with the SAR simulator GRECOSAR. The classification method has been tested with several ENVISAT images acquired for the surroundings of the Strait of Gibraltar. Ground truth has been retrieved via transponder polls, which reveals a preliminary ratio of positive classifications close to 70%. Although this value is not definitive and more tests are needed, it is a good starting point.

LNG運搬船の事故による環境影響

Natural gas produces less carbon dioxide, nitrogen oxides and sulfur oxides per unit heat released than other fossil fuels such as oil and coal. In line with efforts to preserve global environment and to promote sustainable development of world economy, the demand for natural gas has steadily increased. This study was conducted to analyze the risk of GHG (greenhouse gas) release caused by accidents involving natural gas carriers. LNG, which stands for Liquefied Natural Gas, is composed mainly of CH4, so the composition of LNG was assumed to be 100% CH4. Also, the other components of natural gas are not recognized as GHG. To estimate the maximum environmental impact, “Q-Max” which is currently the largest LNG carrier was used as the reference ship. For comparison, CO2 emissions from the propulsion engine were calculated. The environmental impact due to accidents was insignificant compared with the impact of CO2 emissions from the propulsion engine.

Ship selection using a multiple-criteria synthesis approach

A method is presented for selecting a preferred ship from a group of candidates as a reference ship for a new design. The method is based on a recently developed approach for multiple-criteria decision analysis under uncertainty, the evidential reasoning approach. Using this method, both quantitative and qualitative attributes of a complicated nature can be considered in the selection process. The method consists of three phases: identifying suitable candidate ships, evaluating them in terms of both conventional techno-economical and qualitative attributes, and aggregating all the attributes using the evidential reasoning approach. This three-phase procedure is illustrated by means of an oil tanker selection example. The results of this study show that the evidential reasoning approach can support multiple-criteria ship selection processes when both qualitative and quantitative information with or without uncertainties have to be taken into account. The outcomes generated by the method include the ranking of the candidate ships and indications of their strengths and weaknesses in the format of performance distributions over different assessment grades. Such information is vital in helping decision makers to make an informed selection and be aware of any risk implication associated with the selection.

Measurements of Wave Induced Hull Girder Vibrations of an Ore Carrier in Different Trades

Currently, the conventional wave loading is the only effect considered in fatigue assessment of ships. Det Norske Veritas (DNV) has recently confirmed that fatigue damage from wave induced vibrations may be of similar magnitude as from the conventional wave loading (Moe et al., 2005, RINA, International Conference, Design and Operation of Bulk Carriers, London, Oct. 18–19, pp. 57–85). A 40% contribution to the total fatigue damage in deck amidships is documented through extensive measurements onboard an ore carrier (the reference ship) trading in the North Atlantic. The effect of strengthening the vessel, i.e., increasing the natural frequency by 10%, is ineffective in reducing the relative magnitude of the vibration damage. The wave induced vibration, often referred to as whipping and/or springing, also contributes to fatigue damage for other ship types and trades (Moe et al.). This paper considers the effect of trade. It indicates when the wave induced vibrations should be accounted for in the design phase with respect to fatigue damage. A second ore carrier (the target ship) is monitored with respect to the wave induced hull vibrations and their fatigue effect. Stress records from strain sensors located in the midship deck region are supplemented by wave radar and wind records. Based on the measurements, the vibration stress response and associated vibration induced fatigue damage are determined for varying wind and wave forces and relative headings. While the reference ship operates in the Canada to Europe ore trade, the target ship trades between Canada and Europe, Brazil and Europe, and South Africa and Europe. A procedure is suggested by Moe et al. to estimate the long term fatigue damage for different trades by utilizing the measured data from the reference ship. The vibration and wave damage are considered separately. By comparing the measured wave environment and the DNV North Atlantic scatter diagram, the effect of routing indicated a reduction of the fatigue damage by one-third. A slightly revised procedure is applied to estimate the effect of trade for the second ore carrier, comparing the long term predicted fatigue damage with the measured fatigue damage. The importance of trade is confirmed. However, the relative contribution of the vibration damage is shown to increase in less harsh environments. The target ship vibrates more than the reference ship for the same trade and Beaufort strength. The vibration damage of the target ship constitutes 56% of the total measured damage, and the high natural frequency is observed to have no significant effect.

Calculation of the collision resistance of ships and its assessment for classification purposes

Within the framework of a research programme “Tanker Safety”, Germanischer Lloyd has developed a program system for the evaluation of the absorbed plastic deformation energy in a ship-ship collision. The ultimate load capacities of the ship structures in the areas affected by the collision are evaluated stepwise. The total collision energy absorbed by plastic deformations of the ship structures is evaluated on the basis of the minima of the ultimate load capacities and the corresponding penetration depths. By means of the collision energy absorbed, the collision speed necessary to cause damage can be determined. It is now possible to classify ships with regard to their resistance against collisions and to assign relevant class notations. The resistance of a ship against collision impacts is expressed by the class notation COLL with index numbers ranging from 1 to 6. The index numbers indicate that—as compared with a non-strengthened single hull reference ship—a critical situation is likely to occur only if the deformation energy absorbed in the collision exceeds that of the non-strengthened reference ship by specified values. A “critical situation” is defined by, for example, rupture of cargo tanks with subsequent spillage of cargo or water ingress into dry cargo holds.

Calculation of the collision resistance of ships and its assessment for classification purposes

Within the framework of a research programme ‘Tanker Safety’ Germanischer Lloyd has developed a program system for the evaluation of the absorbed plastic deformation energy in a ship-ship collision. The ultimate load capacities of the ship structures in the areas affected by the collision are evaluated stepwise. The total collision energy absorbed by plastic deformations of the ship structures is evaluated on the basis of the minima of the ultimate load capacities and the corresponding penetration depths. By means of the collision energy absorbed, the collision speed necessary to cause damage can be determined. It is now possible to classify ships with regard to their resistance against collisions and to assign relevant class notations. The resistance of a ship against collision impacts is expressed by the class notation COLL with index numbers 1/2/3, etc. The index numbers indicate that — as compared with a non-strengthened single hull reference ship — a critical situation is likely to occur only if the deformation energy absorbed in the collision exceeds that of the non-strengthened reference ship by more than 100%/200%/300%, etc. A ‘critical situation’ is defined by, for example, rupture of cargo tanks with subsequent spillage of cargo or water ingress into dry cargo holds.