Retrofitting a Diesel baseline to a fully H2 spark ignition engine by comining experiments and CFD simulation

Authors

G. Maio, R. Kumar, M. Andre, L. Rouleau, B. Walter, O. Ladget, F. Duffour - IFP Energies Nouvelles, G. Dober, C. Lesieur, J. Shi, L. Doradoux - BorgWarner Inc.

Summary

The hydrogen spark ignition engine is one of the possible promising alternatives to fossil fuel driven mobility in order to reduce the carbon footprint of the ground transport sector. Diesel engine conversion to H2 operation is a valuable technological solution, as it combines the advantages of the existing and proven ICE technology with a carbon free fuel. The present work shows the methodology followed to retrofit an existing base-line diesel engine to a full hydrogen spark ignition configuration, dedicated to light commercial vehicles. The proposed workflow relies on the combination of experiments and simulations to optimize the injector design and its interaction with the in-cylinder aero-dynamic field. In the first step of this study, the numerical CFD injection model is calibrated versus experimental data from an optically accessible, closed and constant volume vessel. Different injection operating conditions (vessel pressure and temperature) and injector configurations (without cap and with cap) are investigated using the Schlieren technique. Jet contours and penetration values, obtained from numerical simulation, are compared to experiments to validate the approach. In the second step, the validated CFD injection model is integrated into a full engine 3D computation in order to define the optimal injector configurations for the final benchmark test through a parametric study. A parallel parametric study investigated different piston designs to maximize turbulence level generation. Engine combustion results are compared to identify the best compromise in terms of mixture formation, turbulence generation, efficiency, NOx emissions and abnormal combustion occurrence. Finally, the optimized design is implemented in hardware to an all-metal single cylinder engine, allowing to assess the retrofit approach and to validate the numerical simulations on a selected matrix of operating points.