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Towards a digital-twin of a mid-speed marine engine: From detailed 1D engine model to real-time implementation on a target platform

Thriving to meet the increasingly stringent emission targets, system complexity becomes a limiting factor for the development of marine mid-speed engines. Control-oriented modelling comes as a solution, cutting down calibration time and enabling robust control strategies. At the same time, real-time, physics-based engine models (digital twins) are gaining significance as they excel in predictive capability and scalability over widely used mean-value, data-driven approaches. The present work explores the route towards building a control-oriented digital twin of a Wärtsilä 4L20 marine engine. Starting from a detailed 1-dimensional model (GT-Suite), we explore reduction strategies towards a Fast Running Model (FRM), balancing the tradeoff between calculation speed and target accuracy. Finally, the FRM is tested for real-time implementation on a target machine. The state of the art experimental data from the 4L20 platform in the VEBIC Engine Laboratory serves as the baseline for model calibration. Calibration and validation of the modelling procedure, at different stages, covers four representative operating points and involves correlation of crank-angle resolved in-cylinder pressures, thermal state at several locations of the engine air-path and relevant performance indicators. The results allow answering several relevant research questions, specific to the application of digital twins in the marine domain. (i) How to discretize large volumes specific to marine engines to capture system dynamics (including pulsations) with high calculation speed requirements; (ii) what mechanisms are responsible for accuracy loss when transferring the code to FRM and further towards a real-time license, (iii) what are the enablers and limiting factors of the developed model in typical engine control applications.
Topic: Engine testing and modelling
Author: Saana Hautala
Co-authors: Maciej Mikulski, Emma Söderäng, Xiaoguo Storm, Seppo Niemi