1D/3D simulation procedure to investigate the potential of a lean burn hydrogen fuelled engine

In recent years hydrogen, especially the one generated by renewable energy, is gaining increasing attention as a clean fuel to support the future mobility towards efficient and low emission solutions for propulsion systems. In this scenario, the present work deals with the virtual conversion of a single-cylinder Diesel engine, conceived for marine applications, into a hydrogen Spark Ignition (SI) unit. A simulation methodology is adopted, combining 1D and 3D Computational Fluid Dynamics (CFD) methods. First, experiments are realized on the original Diesel engine mounted on a test bench, collecting main performance indicators and emissions. A complete 1D engine model (GT-PowerTM) is developed and validated against measurements. Then, a 3D model of the cylinder (STAR-CD) is set-up and the related combustion outcomes are compared both with 1D and experimental results, showing an overall good agreement. In a second stage, the Diesel unit is converted into a port-injected hydrogen SI engine; the 3D model is re-arranged and utilized to reproduce pre-mixed hydrogen combustions under ultra-lean air/fuel (A/F) mixtures. Also, the 1D model is partly modified and coupled to an advanced combustion sub-model integrated with fast tabulated chemical kinetics to predict the knock. In particular, 1D combustion evolution is calibrated against the results of 3D CFD hydrogen combustion simulation. Finally, the calibrated 1D model is applied to investigate the advantages of ultra-lean hydrogen combustion in terms of efficiency, NO, and unburned H2 formation at medium/high loads.