This thesis follows the study and development of the CFD model of H2 engines using a previous CNG engine model. To do our research, a CFD commercial code CONVERGE was used, which has allowed us to reduce the time for the model pre-processing, thanks to the independent meshing tools its sophisticated algorithms that can refine the mesh locally. All our study was conducted on the Fiat FIRE 1400 16V engine, which is installed in the test bench of DENERG laboratories. In this thesis, the models ECFM and ISSIM were used, which allowed the combustion described by splitting the chemical parameters from the physical one, reducing the numerical cost, and avoiding reproducing all the combustion kinematics.