The purpose of this study is to explore the potentiality of wind propulsion on semi-submersible ships. A new type of Flettner rotor (two rotating cylinders) system installed on a semi-submersible ship is proposed. The structure and installation of two cylinders with a height of 20 m and a diameter of 14 m are introduced. The numerical simulation of the cylinder is carried out in Fluent software. The influence of apparent wind angle and spin ratio on the two cylinders are analysed, when the distance between two cylinders is 3D-13D (D is cylinder diameter). When the distance between two cylinders is 3D, the performance of the system increases with an increase in spin ratio. Moreover, the apparent wind angle also has an effect on the system performance. Specifically, the thrust contribution of the system at the apparent wind angle of 120° is the largest at the spin ratio of 3.0. The maximum thrust reaches 500 kN. When the spin ratio is 2.5 and the apparent wind angle is 120°, the maximum effective power of the system is 1734 kW. In addition, the influence of the two cylinders distance on system performance cannot be ignored. When the distance between the two cylinders is 7D and the spin ratio is 2.5, the effective power of the system reaches a maximum, which is 1932 kW.
Aiming at the problems that the fuel releases a lot of cold energy and the refrigerated containers consume a lot of electricity on large LNG powered container ships, a set of cold energy cascade utilization scheme that mainly uses LNG cold energy for refrigerated containers is designed. The simulation software Aspen HYSYS is used to establish and simulate the process of the ship’s cold energy cascade utilization system under five different working conditions, and the main parameters of the key nodes are obtained, according to the established exergy efficiency model, the exergy efficiency of the main equipment and the whole system is solved. Under the five working conditions, the maximum exergy efficiency of the refrigerated container system before optimization is 24.54%, at this time, the exergy efficiency of the entire cold energy utilization system is 24.86%. With the goal of improving the exergy efficiency of the entire system, using a hierarchical optimization method, the key parameters affecting the exergy efficiency of each cold energy utilization module are analyzed and optimized respectively, and the optimal operating parameters of different cold energy utilization module were determined. So as to realize the optimization of the whole cold energy cascade utilization system. The results show that the exergy efficiency of the optimized LNG cold energy cascade utilization system for ships under five working conditions is improved, under the 65% working condition, the exergy efficiency of the optimized refrigerated container system is 27.69%, and the exergy efficiency of the whole cold energy utilization system is 28.04%, which are increased by 3.15% and 3.18% respectively. Which proves that the LNG cold energy cascade utilization system can realize the effective utilization of LNG cold energy.
In order to solve the problems of excess cold energy of the fuel and large power load required for refrigeration of refrigerated containers on LNG powered container ships, this study proposes a scheme to use the fuel cold energy of LNG powered container ships for refrigerated containers, the process simulation software Aspen HYSYS is used to simulate the cold energy utilization scheme, with the help of MATLAB, the multivariable optimization research on the cold energy utilization scheme of LNG powered container ship is carried out, taking the cold energy utilization rate of LNG cold energy scheme as the objective function, the LNG cold energy utilization scheme is optimized.
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