Numerical analysis of the hydrogen-air mixture formation process in a direct-injection engine for off-road applications

Among the different hydrogen premixed combustion concepts, direct injection (DI) is one of the most promising for internal combustion engine (ICE) applications. However, to fully exploit the benefits of this solution, the optimization of the mixture preparation process is a crucial factor. In the present work, a study of the hydrogenair mixture formation process in a DI H2-ICE for off-road applications was performed through 3D-CFD simulations. First, a sensitivity analysis on the injection timing was carried out to select the optimal injection operating window, capable of maximizing mixture homogeneity, without a significant volumetric efficiency reduction. Then, different spray injector guiding caps were tested to assess their effect on in-cylinder dynamics and mixture characteristics consequently. Finally, the impact of swirl intensity on hydrogen distribution has been assessed. The optimization of the combustion chamber geometry has allowed the achievement of significant improvements in terms of mixture homogeneity.