International Shipbuilding Progress - Volume 57, issue 1-2

Authors: Zhan, Yiting | Liu, Yujun | Deng, Yanping

Article Type: Research Article

Abstract: The concept and framework of a ship knowledge library that supports quick design and modeling were put forward based on research on the knowledge representation of hull structure components and the organizational mechanism, combined with the digital design technology and the RPD development approach. The knowledge framework could be used to encapsulate the digital design functionality for the hull structure and manage correlation information using a distributed database. Then a prototype software system was developed, achieving the quick design and alteration of the 3D structure model, which was demonstrated with a fact ship model.

Keywords: Hull structural model, rapid product development, digitalized design, ship design

DOI: 10.3233/ISP-2010-0060

Citation: International Shipbuilding Progress, vol. 57, no. 1-2, pp. 1-13, 2010

Authors: Bi, J.Y. | Zong, Z. | Fu, G.N.

Article Type: Research Article

Abstract: A series of model self-propulsion tests are designed by orthogonal optimization method in order to discuss the propulsive performance of a four-propeller model. The research on propulsive performance includes propulsive efficiency, axial thrust and shaft torque. Axial thrust and shaft torque are got from self-propulsion experiments, and propulsive efficiency of every propeller is calculated based on five parameters measured in self-propulsion tests and resistance tests, respectively. After testing and calculating, the percentages of propulsive performance are obtained to analyze four-propeller arrangement. Five factors with different levels are confirmed in the orthogonal experimental design. By changing transverse positions and longitudinal positions …with three levels and rotation directions of four propellers with two levels, propulsive performance of each propeller would change obviously. Three ways are performed to analyze experimental results and discuss the influencing factors. The optimum combination of five factors with different levels is obtained by analyzing the effect of four-propeller arrangement. And the major factor is found according to the order of magnitude of five factors. Depending on all analyses, the optimum arrangement of propeller positions and rotation directions is acquired to distribute four propellers in the wake of the model hull. Show more

Keywords: Propulsive performance, self-propulsion test, orthogonal analysis, propulsive efficiency, axial thrust, shaft torque

DOI: 10.3233/ISP-2010-0061

Citation: International Shipbuilding Progress, vol. 57, no. 1-2, pp. 15-34, 2010

Authors: Shi, W. | Grimmelius, H.T. | Stapersma, D.

Article Type: Research Article

Abstract: From fuel to ship moving, the overall energy conversion efficiency consists of three parts: the engine efficiency, the transmission efficiency and the propulsive efficiency. In off-design conditions, there are three factors, namely the engine speed, the propeller pitch ratio and the rudder activity, and an additional disturbance, ship loading factor that can impact the behaviour of ship propulsion system and influence the overall energy conversion efficiency. In this study, by means of computer simulation, four elementary types of off-design conditions, each of which is relevant to one of the impact factors, and entire voyage simulations which combines the off-design and …design operation conditions, are investigated to reveal the behaviour of the ship propulsion system. The results demonstrate that, in terms of fuel consumption, the power specific fuel consumption is mainly determined by engine efficiency while ship speed plays the most important role in calculation of ton-mile specific fuel consumption. On the voyage basis, high percentage of manoeuvering stage and intensive rudder activity result in large ton-mile specific fuel consumption, while low cruising speed could improve the fuel economy on ton-mile basis. Show more

Keywords: Propulsion system, simulation fuel consumption, off-design condition

DOI: 10.3233/ISP-2010-0062

Citation: International Shipbuilding Progress, vol. 57, no. 1-2, pp. 35-64, 2010

Authors: Senjanović, Ivo | Vladimir, Nikola | Tomić, Marko

Article Type: Research Article

Abstract: Very large container ships are rather flexible due to their large deck openings. Hydroelastic stress analysis is therefore required as a base for reliable structural design. In the early design stage, the coupling of the beam model with a 3D hydrodynamic model is rational and preferable. The calculation is performed utilizing the modal superposition method, so natural hull modes have to be determined in an appropriate way. Consequently, the advanced thin-walled girder theory, which takes the influence of shear on both bending and torsion into account, is applied to calculate the hull flexural and torsional stiffness properties. A characteristic of …very large container ships is the quite short engine room, whose closed structure behaves as an open hold structure with a shear centre outside the cross-section, very close to that of the open section. As a result, torsionally induced horizontal bending is negligible, while the distortion of the cross-sections appears as a new problem. The task is solved by an energy balance approach that enables the use of effective stiffness. Hence, the effect of interior decks is taken into account by increasing the torsional stiffness of the open cross-section within the engine room domain. The procedure is checked by the 3D FEM analysis of a ship-like pontoon. Such a modified beam model of the engine room structure can be included in the general beam model of a ship hull for the need of hydroelastic analysis, where only a few first dry natural frequencies and mode shapes are required. For practical use in the preliminary design of ship structures, the simplicity of the beam model presents an advantage over 3D FEM models. Show more

Keywords: Container ship, engine room structure, torsion, thin-walled girder, analytical solution, FEM, hydroelasticity

DOI: 10.3233/ISP-2010-0063

Citation: International Shipbuilding Progress, vol. 57, no. 1-2, pp. 65-85, 2010