This study aims at developing an integrated model that combines detailed engine thermodynamic modelling and the control system functional modelling paving the way towards the development of high-fidelity digital twins. To sufficiently represent the combustion process, a multi-Wiebe function approach was employed, whereas a database for storing the combustion model parameters was developed. The developed model was employed for the systematic investigation of a marine four-stroke dual fuel engine response during demanding transient operation with mode switching and load changes. The derived results were analysed to identify the critical engine components and their effect on the engine operational limitations. The results demonstrate that the developed model can sufficiently represent the engine and its subsystems/components behaviour and effectively capture the engine control system’s functionality. The appropriate turbocharger matching along with the sufficient design of the exhaust gas waste gate valve and fuel control systems are crucial for ensuring the smooth engine operation of dual fuel engines.

As the environmental regulations have become more stringent, the shipping industry has been focusing on more efficient and environmentally friendly means of propulsion and electric power generation. In this respect, dual fuel engines, which operate either in diesel mode or dual fuel (DF) mode by burning diesel fuel or natural gas and pilot diesel fuel to initiate ignition respectively, has become one of the most promising solutions as their dual fuel operation leads to reduced nitrogen oxide (NOx), carbon dioxide (CO2), as well as almost elimination of particulate matter (PM) and sulphur oxide (SOx) emissions. The present study focuses on the comprehensive investigation of a large marine two-stroke dual fuel engine of the low gas pressure concept by using the GT-Power™ software. Appropriate combustion, scavenging, heat transfer and friction models were used to fully represent the engine performance and emissions characteristics whereas a knocking model was employed to characterise the engine abnormal combustion. The simulation results were initially validated against the manufacturer data and subsequently, the entire engine envelope in both operating modes was simulated. The derived results were used for analysing and discussing the engine operation, performance and emissions as well as for comparing the two operating modes in terms of the turbocharger matching. In addition, a parametric investigation was performed in the dual fuel mode and the results were used for identifying the settings that can further optimize the engine operation in terms of CO2 and NOx emissions trade-off. The results indicate that the CO2 and NOx emissions can be simultaneously reduced; however, the engine optimisation in the high load region is challenging due to the permissible cylinder pressure constraint