Hydrogen is widely recognized as a key energy carrier for future sustainable powertrain systems in long-distance transportation and marine applications, due to its potential for carbon-free energy conversion. In propulsion systems such as heavy-duty engines and gas turbines, hydrogen can provide high thermal efficiency while eliminating CO2 emissions. However, hydrogen has unique physical and chemical properties, including high diffusivity, wide flammability limits, and high flame speed, which lead to combustion characteristics that differ significantly from those of conventional hydrocarbon fuels. These properties introduce challenges related to mixture formation, ignition control, flame stabilization, and NOx formation. This project aims to improve the fundamental understanding of hydrogen–air turbulent mixing and combustion under engine-relevant conditions using high-fidelity numerical combustion simulations. The work focuses on the interaction between direct-injected hydrogen jets and turbulent flow fields, as well as their effects on hydrogen combustion in high-pressure environments. This is directly relevant for future hydrogen direct-injection combustion concepts of hydrogen-engine design. LES simulations will be performed using CONVERGE 4.1 with its advanced Adaptive Mesh Refinement (AMR) technology, allowing efficient resolution of transient flow structures and reacting regions while maintaining manageable computational costs. Subsequently, advanced combustion models will be developed on openfoam platform. Typical simulations employ computational domains of approximately 120 × 120 × 120 mm with effective mesh sizes approaching 20 ~ 50 million cells. The numerical campaign will investigate local flow–chemistry mechanisms that control hydrogen mixing and combustion, enabling more accurate prediction of transient hydrogen jet behavior and turbulence–chemistry interactions. Previous hydrogen studies from literature, have demonstrated that scalar-dissipation effects and shock/flow/flame interaction can be decisive for flame stabilization. LES turbulence model with advanced turbulence–chemistry interaction models coupled with, such as transported probability density function (PDF) methods, offer improved predictive capability for turbulent reacting flows by representing unresolved thermochemical fluctuations and nonlinear finite-rate chemistry effects. This H₂ simulation research is also closely connected to ongoing optical experiments at Chalmers University of Technology, where the laser-diagnostics will provide high-accuracy data for combustion-model validation and improvement of predictive capabilities. The resulting datasets will support the development and validation of advanced combustion models for the following implementation in OpenFOAM frameworks. The expected outcomes include an improved understanding of hydrogen–air mixing and combustion, and validation of LES methodologies for hydrogen combustion. Finally, the research results will be consolidated into a high-quality publication to the leading journal "Combustion and Flame", together with dissemination of results at the leading international conferences “International Symposium on Combustion” Supervisor and Co-Investigator: Prof. Andrei Lipatnikov Affiliation: Department of Mechanical Engineering, Chalmers University of Technology, Gothenburg, Sweden.