Showing papers in "Brodogradnja in 2015"
Journal Article•
TL;DR: In this paper, the authors considered the possibility of the use of hydrogen fuel for marine applications and discussed different stages of hydrogen gas cycle beginning with hydrogen generation process from clean energy until using it as fuel for internal combustion engines on-board one RO/RO ship, named Taba, operating in the Mediterranean Sea.
Abstract: Summary Modern marine power plants have been designed to improve the overall ship’s efficiency. This pushed the designers of marine machinery to search for unconventional fuels for these plants. During the previous years, diesel oil has been extensively used on-board ships. Due to the high price of light diesel oil and the environmental problems resulting from the use of heavy fuel oil, it has become necessary to search for an alternative to traditional fuels. As a result, natural gas fuel has been used on-board some types of ships, especially short-voyage cruise ships. Unfortunately, there are still some technical and logistic problems related to the use of natural gas as a fuel, especially as it is considered a non-renewable energy source. The use of hydrogen fuel on-board ships, particularly in modern power plants may contribute to overcoming the above problems. The present paper considers the possibility of the use of hydrogen fuel for marine applications and discusses different stages of hydrogen gas cycle beginning with hydrogen generation process from clean energy until using it as fuel for internal combustion engines on-board one RO/RO ship, named Taba, operating in the Mediterranean Sea. Compared to the diesel engine, the hydrogen fuelled engine is found to be lower in thermal efficiency and fuel consumption, however, some adjustments are needed.
36 citations
Journal Article•
TL;DR: In this article, the SWATH hull form is used for small working craft and pleasure boat design in rough sea at zero and low speed, where the main dimensions allow enough static stability.
Abstract: The good seakeeping characteristics of SWATH hull form are very interesting for small working craft and pleasure boats. Intrinsic limitations as the low values of weight per inch of immersion and transversal and longitudinal instability, can be acceptable and successfully managed when the mission profile does not ask for significant load variation and shift. The exploitation of SWATH concept is limited by the craft size, but if main dimensions allow enough static stability, this configuration appears very promising. SWATH behaviour in rough sea at zero and low speed have led to consider this hull form within the small craft design research program in progress at University of Naples Federico II.
30 citations
Journal Article•
TL;DR: In this article, steam and SOFC based reforming options of natural gas for PEM fuel cells are proposed as an attractive option to limit the environmental impact of the marine sector, which can be assessed using computer predictions incorporating chemical flow sheeting software.
Abstract: UDC 629.5.5.026:629.5.03(62-81, 62-622) Original scientific paper Summary The need for green energy sources without or with low emissions in addition to improve the using efficiency of current fossil fuels in the marine field makes it important to replace or improve current fossil-fuelled engines. The replacement process should work on narrowing the gap between the most scientific innovative clean energy technologies and the concepts of feasibility and cost-effective solutions. Early expectations of very low emissions and relatively high efficiencies have been met in marine power plants using fuel cell. In this study, steam and SOFC based reforming options of natural gas for PEM fuel cells are proposed as an attractive option to limit the environmental impact of the marine sector. The benefits of these two different reforming options can be assessed using computer predictions incorporating chemical flow sheeting software. It is found that a high overall efficiency approaching 60% may be achieved using SOFC based reforming systems which are significantly better than a reformed PEM system or an SOFC only system.
17 citations
Journal Article•
TL;DR: In this article, the hydrodynamics and noise prediction of a five blade marine propeller were analyzed through numerical and experimental methods under variety operational conditions, and good agreement were observed between numerical and test results, qualitatively and quantitatively.
Abstract: In this study, the hydrodynamics and noise prediction of a five blade marine propeller were analyzed through numerical and experimental methods under variety operational conditions The hydrodynamics of the propeller was studied and the characteristic curves were presented in both numerical and experimental methods Inception and development of sheet cavitation conditions are obtained in both numerical and experimental methods The cavitation was started and developed by either increasing the propeller rotational speed in constant pressure or decreasing pressure, while the velocity was kept constant Good agreements are observed between numerical and experimental results, qualitatively and quantitatively The noise of the propeller was analyzed through Computational fluid dynamics (CFD) method, based on the formulation of Ffowcs Williams and Hawkings (FW-H) Similarly, the experimental results collected from hydrophones were compared with numerical simulations Finally, the effects of reflection in cavitation tunnel were obtained by considering overall sound pressure levels in numerical and experimental results
12 citations
Journal Article•
TL;DR: In this paper, the authors describe a near-time computational solver as the main piece of a decision support system (DSS) which analyses and monitors the behaviour of sails and rigging.
Abstract: The operational complexity and performance requirements of modern racing yachts demand the use of advanced applications, such as a decision support system (DSS) able to assist crew members during navigation. In this article, the authors describe a near-time computational solver as the main piece of a DSS which analyses and monitors the behaviour of sails and rigging. The solver is made up of two different interconnected tools: an iterative Fluid-Structure Interaction algorithm and an advanced Wireless Sensor Network to monitor rigging. The real-time DSS quantifies crew manoeuvres in physical terms, which are reproduced by a simulation program. It can be used in the design phase of sailing yachts and as an aid for real-time boat performance optimisation and accident prevention. This novel DSS is a useful tool for navigation, especially in races.
9 citations
Journal Article•
TL;DR: In this paper, an incremental-iterative progressive collapse analysis method prescribed by the IACS Harmonized Common Structural Rules (H-CSR) is used for determination of the ultimate vertical bending moment and collapse sequence of the considered structures.
Abstract: Within the scope of the presented work a hull girder ultimate strength analyses of the double hull oil tanker structures damaged by the collision or grounding is performed. An incremental-iterative progressive collapse analysis method prescribed by the forthcoming IACS Harmonized Common Structural Rules (H-CSR) is used for determination of the ultimate vertical bending moment and collapse sequence of the considered structures. Three characteristic variants of the oil tanker main frame cross sections of a different geometry and size (Aframax, Suezmax and VLCC) are considered. The position of a ship’s side and/or bottom damage is defined in accordance with the IACS H-CSR. Proposed analytical formulations of the relationship between reduction of the hull girder ultimate vertical bending moment (with respect to the undamaged state) and damage size are based on the results of a systematic variation of a ship’s side or bottom damage size. Finally, comparison of the collapse sequences determined for the undamaged and damaged state in upright position (defined by IACS H-CSR) of the considered structure of the Aframax ship example is performed.
5 citations
Journal Article•
TL;DR: In this paper, a statistical formula for dynamic excitation of propeller was developed and superimposition of local effects has been performed with the use of an analytical formula, where transversal beams, longitudinal girders, stiffeners and pillars as supported structural elements are considered in the vibration local response.
Abstract: This approach is based on the assumption that the ship hull can be represented as a non uniform section beam. The propeller excitations in terms of pressure pulses and shaft line moments and forces are introduced. To take into account this exciting source in the early design stage a statistical formula for dynamic excitation of propeller was developed. Furthermore the superimposition of local effects has been performed with the use of an analytical formula. The local effect due to the different space topologies such as cabins, public spaces, technical and machinery areas has been taken into account. The transversal beams, longitudinal girders, stiffeners and pillars as supported structural elements are considered in the vibration local response.
2 citations
Journal Article•
TL;DR: Using data on pirate attacks recently occurring in High Risk Areas, this article analyses the design and use of the citadel as a self-protection measure against piracy and various requirements for these structures are recommended.
Abstract: As piracy continues to pose a threat to the shipping industry, a number of measures for protecting ships, cargo and crew will need to be implemented. Along with other steps, such as deploying military rescue teams, securing the crew within a ship’s citadel has proved to be a highly effective form of self-protection against hostage-taking by pirates. From a design standpoint, aspects that should be considered include the location and dimensions of the citadel, the maximum time crew can stay within it and the specific requirements for various elements of the ship or citadel equipment. Exploiting data on pirate attacks recently occurring in High Risk Areas, this article analyses the design and use of the citadel as a self-protection measure against piracy. As a conclusion, various requirements for these structures are recommended.
1 citations