<div class="section abstract"><div class="htmlview paragraph">To meet emission targets, alternative fuels are increasingly vital in reducing exhaust emissions. One effective and cost-efficient method to achieve sustainable emission reductions is through hydrogen (H<sub>2</sub>) operated modern combustion engines. In line with the energy transformation, similar to Germany’s “Energiewende”, industries need CO<sub>2</sub>-neutral solutions, with special importance in the mobility sector. Hydrogen, as a carbon-free fuel, presents a viable alternative to conventional options and has been subject to extensive scientific research.</div><div class="htmlview paragraph">The development of hydrogen combustion engines is still in the conceptualization phase. This study focuses on a direct-injection (DI) combustion engine from a commercial vehicle converted from diesel DI-compression ignition (CI) to hydrogen DI-spark ignition (SI) operation. The main objectives were to validate simulation models using 1D and 3D simulation software and to conduct a comprehensive analysis of engine operation. The 1D simulation utilized a predictive combustion model, offering the advantage of analyzing operating points not covered by available measurements. The 3D simulation employed a chemical mechanism describing the reaction kinetics of hydrogen combustion in air.</div><div class="htmlview paragraph">GT-Power, a commercial software, was used for preliminary 1D analysis, forming the foundation for subsequent 3D CFD simulations in AVL FIRE®. The study aimed to analyze mixture formation, temperature distribution, and emissions formation. The paper presents the outcomes of this initial investigation, focusing on essential findings and derived conclusions while addressing potential difficulties and barriers. The study aims to provide a robust groundwork for future projects in this domain.</div></div>
