1,720,984 research outputs found
Updated Steel Weight Estimation for Cruise Ship Concept Design
No full textEstimating the steel weight of ships during the early conceptual stages is of the utmost importance since it represents about 50% of the lightship weight of the ship. From a technical standpoint, it significantly affects cargo capacity, design speed, stability, and ship safety, thus requiring an accurate estimation. The steel weight is usually evaluated using simple empirical formulations during the concept design, mainly based on the ship's main particulars. Those formulas are derived by statistical analysis of past projects and can be applied only for the specific ship type (or types) included in the considered database. In the literature, many formulas are present mainly related to cargo ships. Currently, no empirical formulation is available for cruise ships that are applicable in the very early conceptual stages. The present study aims to identify an empirical formulation for estimating the steel weight of a luxury cruise ship based on calibrating a set of existing empirical formulas
Bulkheads’ Position Optimisation in the Concept Design of Ships under Deterministic Rules
Full text linkThe position of the transverse bulkheads is the most important aspect in determining the internal subdivision of the ship and has a strong impact on the general arrangement, weight distribution and capacity of the ship. Nowadays, deterministic rules still apply to various types of ships such as gas carriers, naval ships, icebreakers, etc. For these vessels a new floodable length can be defined as the extent of the ship that can be flooded, still assuring compliance with the damage stability criteria. The main objective of this paper is using the floodable lengths to optimize the position of bulkheads. The proposed methodology maximises the margin between the floodable length and the actual flooded length, which consists of two lost contiguous compartments. This method, applicable in the framework of multi-attribute decision-making techniques for ship concept design, allows identification of the minimum number of bulkheads a ship requires, quantification, and maximisation of the safety margin for compliance with deterministic damage stability criteria. This margin ensures maximum flexibility for changes that may be required in the next design phases. The proposed method, based on a multi-stage optimization, is tested on a compressed natural gas carrier to define the minimum number and position of the transverse bulkheads dividing the cargo holds
Effect of Database Generation on Damage Consequences’ Assessment Based on Random Forests
Full text linkRecently, the application of machine learning has been explored to assess the main damage consequences without employing flooding sensors. This method can be the base of a new generation of onboard decision support systems to help the master during the progressive flooding of the ship. In particular, the application of random forests has been found suitable to assess the final fate of the ship and the damaged compartments’ set and estimate the time-to-flood. Random forests have to be trained using a database of precalculated progressive flooding simulations. In the present work, multiple options for database generation were tested and compared: three based on Monte Carlo (MC) sampling based on different probability distributions of the damage parameters and a parametric one. The methods were tested on a barge geometry to highlight the main effects on the damage consequences’ assessment in order to ease the further development of flooding-sensor-agnostic decision support systems for flooding emergencies
A model for intact and damage stability evaluation of CNG ships during the concept design stage
Full text linkTo face the design of a new ship concept, the evaluation of multiple feasible solutions concerning several aspects of naval architecture and marine engineering is necessary. Compressed natural gas technologies are in continuous development; therefore, there are no available databases for existing ships to use as a basis for the design process of a new unit. In this sense, the adoption of a modern multi-attribute decision-based method can help the designer for the study of a completely new ship prototype. A database of compressed natural gas ships was generated starting from a baseline hull, varying six hull-form parameters by means of the design of experiment technique. Between the attributes involved in the concept design process, stability is for sure one of the most relevant topics, both for intact and damaged cases. This work describes two approaches to identify the compliance of a ship with the intact stability regulations based on the ship main geometrical quantities. Moreover, a metamodel based on the maximum floodable length concept (damage stability) allows determining the main internal subdivision of the ship. The metamodel outcomes were compared with results from direct calculations on a ship external to the database, highlighting the adequate accuracy given by the developed methods
A fast algorithm for onboard progressive flooding simulation
Full text linkThe need for decision support after a flooding casualty requires the development of fast and accurate progressive flooding simulation procedures. Here, a new quasi-static technique is presented, proposing a differential algebraic formulation capable to consider independently the flooding process in the internal rooms. The proposed method is efficient while simulating long flooding chains along rooms connected by similar size openings, a condition that likely occurs on large passenger ships. Moreover, the computational performances of the simulation procedure have been enhanced by adapting the time step to the progressive flooding pace. The adoption of an adaptive time step algorithm reduces significantly the calculation time. The novel procedure has been tested on the recommended benchmark cases for flooding simulations, highlighting the accuracy and flexibility of the proposed method
A fast simulation method for the probabilistic assessment of emissions in cruise ship's itinerary planning
Full text linkThis study employs a probabilistic methodology to forecast cruise ship emissions during the itinerary planning phase, considering environmental factors (current, waves, wind), fouling, shallow water, loading conditions, and Fresh Water (FW) production effects. Probability distributions of environmental parameters are established based on statistical data and utilized for generating deterministic scenarios through Monte Carlo sampling. The resulting scenarios are simulated to define probability distributions for carbon dioxide emissions, carbon intensity indicators, and other pertinent quantities. The simulation model is validated using data from an existing ship. To demonstrate the effectiveness of the proposed methodology in strategic itinerary planning, multiple alternatives for an existing itinerary are simulated. Specifically, a Mediterranean cruise is simulated in both the original sequence and in reverse, with and without FW production. The reverse sequence without FW production demonstrates a potential reduction of approximately 190 tCO2e/week emissions. Furthermore, in this scenario, a comparison is made between a standard Power Management System (PMS) with an equal load on all engines and an optimized PMS with optimized engine loads, resulting in an additional average reduction of 86 tCO2e. In the latter itinerary, the most probable rating according to Carbon Intensity Indicator is reduced from original E to C
A Hybrid-Electric Passenger Vessel for Inland Waterway
Full text linkThe problem of air pollution is one of the biggest issues discussed worldwide: due to this reason, various measures to reduce global pollution, especially CO2 emissions, are being taken by Governments. One of the main causes of pollution is represented by the transport sector, which includes also maritime transport. Therefore, it is necessary to study and find new types of propulsion that ensure a reduction of pollutant emissions. A way to achieve this aim is represented by hybrid-electric propulsion systems, capable of ensuring a good range in ZEM - Zero Emission Mode - navigation. In this paper, the application of hybrid-electric propulsion on a small boat for passenger transport in inland waters has been analysed. Based on the results of preliminary studies, a prototype of the vessel was built; the boat has been a useful and remarkable test bench to validate such a technology, in terms of eco-friendliness, energy efficiency, and reliability. Here, the theoretical estimates carried out in the early stage of design have been compared with the experimental data obtained on the prototype during a sea trials campaign carried out in a real operative environment
A Rational Approach to the Ecological Transition in the Cruise Market: Technologies and Design Compromises for the Fuel Switch
Full text linkSupporting policies to achieve a green revolution and ecological transition is a global trend. Although the maritime transport of goods and people can rightly be counted among the least polluting sectors, much can be done to further reduce its environmental footprint. Moreover, to boost the ecological transition of vessels, a whole series of international regulations and national laws have been promulgated. Among these, the most impactful on both design and operational management of ships concern the containment of air-polluting emissions in terms of GHG, NOx, SOx and PM. To address this challenge, it might seem that many technologies already successfully used in other transport sectors could be applied. However, the peculiar characteristics of ships make this statement not entirely true. In fact, technological solutions recently adopted, for example, in the automotive sector must deal with the large size of vessels and the consequent large amount of energy necessary for their operation. In this paper, with reference to the case study of a medium/large-sized passenger cruise ship, the use of different fuels (LNG, ammonia, hydrogen) and technologies (internal combustion engines, fuel cells) for propulsion and energy generation on board will be compared. By imposing the design constraint of not modifying the payload and the speed of the ship, the criticalities linked to the use of one fuel rather than another will be highlighted. The current limits of application of some fuels will be made evident, with reference to the state of maturity of the relevant technologies. Furthermore, the operational consequences in terms of autonomy reduction will be presented. The obtained results underline the necessity for shipowners and shipbuilders to reflect on the compromises required by the challenges of the ecological transition, which will force them to choose between reducing payload or reducing performance
Refitting a Cruise Ship with More Electric Power & Energy Systems: A Methodology to Evaluate the Impact on Fuel Efficiency
No full textIn today's tourism landscape, cruise ships play a crucial role in the recreational maritime transport market. However, the sector is facing a crucial challenge in finding novel solutions to limit their environmental impact. While new ships can be easily designed and built considering modern environmentally friendly solutions, there still remain a huge number of vessels that are still far from the end of their useful life, which may benefit from modern technologies' introduction during mid-life refitting operations. However, spending effort on refitting a ship to improve its fuel efficiency may be futile if the resulting impact is not capable of repaying itself in terms of reduced operating costs. In this context, cruise ships are endowed with a full-electric architecture, which eases electrification and introduction of energy storage systems. Thus, in this paper, a methodology is proposed to evaluate the impact on fuel efficiency of refitting a cruise ship with more electric power & energy systems. A case study is proposed, taking an old-fashioned cruise ship, and introducing energy storage systems and frequency converters for chillers' high power induction motors. The results provide useful insights on the opportunity of applying such modern technologies to ships that have not been designed taking them into account
Towards CO2 emissions reduction of shipping: Ca(OH)2 based carbon capture system for safeguarding the marine environment
Full text linkClimate change poses a global challenge related to the reduction of pollutant atmospheric emissions and the maritime transportation sector is directly involved, due to its significant impact on the production of Greenhouse Gases and other substances. While established technologies have effectively targeted emissions like Nitrogen Oxides (NOX) and Sulfur Oxides (SOX), the persistence of Carbon dioxide (CO2) emissions represents an ongoing and significant concern. Novel technologies targeting CO2 reduction have been lately studied and proposed for inland applications, and are now being developed for maritime applications. With this regard, the present study explores the potential of Carbon Capture Systems (CCS) to mitigate CO2 emissions produced by cargo ships. While the implementation of CCS faces challenges, including space limitations and logistical complexities, its possible integration onboard marks a significant step in the fight against climate change. The authors propose an innovative approach using a Calcium Hydroxide Ca(OH)2 based CCS, offering the dual benefit of CO2 reduction and the potential resolution of ocean acidification through Calcium carbonate (CaCO3), the final product resulting from the CO2 capture process. Additionally, the study examines the feasibility of the generated product for reuse in industry, promoting a circular economy and addressing environmental issues. This innovative solution underscores the urgent need for transformative measures to reduce maritime emissions, in line with efforts to safeguarding the marine environment and combat climate change
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