Wyniki wyszukiwania - BazTech

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Application of fuel cold energy in CO2 BOG reliquefaction system on ammonia-powered CO2 carrier

Lin Yiqun, Lu Jie, Li Boyang, Li Yajing, Yang Qingyong

Polish Maritime Research

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2023

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nr 3

22--34

EN

A CO2 boiled off gas (CO2 BOG) reliquefaction system using liquid ammonia cold energy is designed to solve the problems of fuel cold energy waste and the large power consumption of the compressor in the process of CO2 BOG reliquefaction on an ammonia-powered CO2 carrier. Aspen HYSYS is used to simulate the calculation, and it is found that the system has lower power consumption than the existing reliquefaction method. The temperature of the heat exchanger heater-1 heat flow outlet node (node C-4) is optimised, and it is found that, with the increase of the node C-4 temperature, the power consumption of the compressor gradually increases, and the liquefaction fraction of CO2 BOG gradually decreases. Under 85% conditions, when the ambient temperature is 0°C and the temperature of node C-4 is -9°C, the liquid fraction of CO2 BOG reaches the maximum, which is 74.46%, and the power of Compressor-1 is the minimum, which is 40.90 kW. According to this, the optimum temperature of node C-4 under various working conditions is determined. The exergy efficiency model is established, in an 85% ship working condition with the ambient temperature of 40°C, and the exergy efficiency of the system is the maximum, reaching 59.58%. Therefore, the CO2 BOG reliquefaction system proposed in this study could realise effective utilisation of liquid ammonia cold energy.

2

Study of a new type of Flettner rotor in merchant ships

Li Boyang, Zhang Rui, Li Yajing, Zhang Baoshou, Guo Chao

Polish Maritime Research

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2021

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nr 1

28--41

EN

Wind energy is a clean and renewable source of energy. This study seeks to explore the potential for utilising wind power for merchant ships. A new type of Flettner rotor (rotating cylinder) mounted on the superstructure of a ship is proposed and numerically simulated. The construction and installation of the rotating cylinder is designed and a numerical simulation of the ship-mounted cylinder is carried out, using the commercially available CFD code Ansys Fluent to obtain parameters such as lift and drag coefficient of the cylinder in different conditions. Specifically, it is found that the cylinder type superstructure can play a certain role in reducing the effect of friction by comparing traditional and cylindrical superstructures; the rotating cylinder can generate auxiliary thrust for the ship. After analysis, the wind speed around the cylinder and spin ratio will have a direct influence on its thrust effect; there is an inflection point in the lift coefficient with the increase of α; the thrust coefficient (8.63) reaches the maximum environmental wind speed at 10 m/s and spin ratio is 2.5. For the rotating cylinder, the greater the environmental wind, the greater the thrust contribution generated under the same spin ratio conditions. The maximum thrust can reach 750,000 N; the cylinder’s auxiliary propulsion contribution shows a better advantage in α = 2.0. The effective power generated by the cylinder reaches a maximum of 2,240 kW for environmental wind speed = 20 m/s and α = 1.0.

3

Research on the application of cold energy of largescale LNG-powered container ships to refrigerated containers

Li Yajing, Li Boyang, Deng Fang, Yang Qianqian, Zhang Baoshou

Polish Maritime Research

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2021

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nr 4

107--121

EN

With the aim of considering the problem of excess fuel cold energy and excessive power consumption of refrigerated containers on large LNG-powered container ships, a new utilisation method using LNG-fuelled cold energy to cool refrigerated containers in cargo holds is proposed in this study, and the main structure of the cold storage in the method is modelled in three dimensions. Then, combined with the different conditions, 15 different combination schemes of high temperature cold storage and low temperature cold storage are designed to utilise the cold energy of LNG fuel, the exergy efficiency and cold energy utilisation rate calculation model of the system is established. The simulation tool ‘Aspen HYSYS’ is used to simulate and calculate the exergy efficiency and cold energy utilisation rate of the system under 15 combinations, verifying the feasibility of the scheme. According to the characteristics of such a ship’s cross-seasonal navigation routes and the number of refrigerated containers loaded in different ports, the combination schemes of the number of low-temperature cold storage and high-temperature cold storage are selected. Thus, the average exergy efficiency and cold energy utilisation rate of the whole line is obtained, which proves that LNG-powered container ships could effectively utilise the cold energy of LNG. By calculating the total electric energy consumed by refrigerated containers on the whole sailing route, before and after the adoption of the LNG cold energy method, it is found that the adoption of this new method can promote the realisation of energy saving and emission reduction of ships.