디지털 트윈 구축을 위한 선박 추진체계 디지털 모델링 연구

Abstract

In this manuscript, a mathematical model on the propulsion system of a ship for the development of digital-twin ship platforms that are key technology for operating ships in digital space is proposed. Real-time continuous and variable data such as pressure variations of the engine and the crank angles, and the temperatures obtained from the actual ship were used for the proposed mathematical model. In order to simulate accurately the combustion process occurring in the marine diesel engine of the propulsion system, the conventional four-stroke engine cycles consisting of suction, compression, explosion, and exhaust, were considered as 5 processing cycles in this study, such as suction, compression, explosion, expansion and exhaust. That is, the expansion process has been considered additionally. The MATLAB Simulink has been used to construct the proposed digital model considering the time scale. operating conditions of the fuel injection system and the load of the propulsion system were also simplified. The process of the fuel injection was considered as time-dependent mass changes during fuel boosting in which the opening of the injection valve was operated at a certain preset pressure, eventually completing the combustion physics in the engine cylinder. The calculated data that show the relations between the pressure and the crank angle, and the temperature and the crank angle, showed good similarity with those obtained from the actual engine running, though there was a slight discrepance. It seems that the discrepance can be largely reduced if more time consecutive data can be obtained from long period of engine operations. It was confirmed that real-time data processing was possible by changing the amount of angular acceleration in real time by the time-dependant digital data. It has been verified that the comparison error between the actual ship test data and the digital model was measured as 0.8% ~ 4.2% under low speed and no-load conditions.