FKFS Veranstaltungen

2025 Stuttgart International Symposium
on Automotive and Engine Technology

3. - 4. Juli 2025

Session: Hydrogen I | | 12:30 - 13:00

Numerical Investigation of Injection and Mixture Formation in Hydrogen Combustion Engines by Means of Different 3D-CFD Simulation Approaches

Robin Schmelcher, IFS, University of Stuttgart

Increasingly stringent regulations relating to the emissions of passenger cars and commercial vehicles demand alternative powertrain technologies in order to effectively achieve the climate targets. Hydrogen can play a crucial role as alternative energy carrier regarding the EU targets for CO2-neutral mobility towards 2050. Therefore, it represents a reasonable choice not only for fuel cell powered vehicles, but also for fueling internal combustion engines (ICE). This paper focuses on the numerical investigation of high-pressure hydrogen injection and the mixture formation inside a high-tumble ICE with a conventional liquid fuel injector for passenger cars. Since the traditional 3D-CFD approach of simulating the inner flow of an injector requires a very high spatial and temporal resolution, the enormous computational effort, especially for full engine simulations, is a big challenge for an effective virtual development of modern ICEs. An alternative and more pragmatic lagrangian 3D-CFD approach offers opportunities for a significant reduction in computational effort without sacrificing reliable results. The detailed and the lagrangian approach are both validated against optical measurements inside a spray chamber, provided by Robert Bosch GmbH, for various injection pressures, chamber pressures and injector positions to ensure an accurate reproduction of the injection process in the simulation. The effects on jet propagation and mixture formation are examined in a virtual 3D-CFD single-cylinder engine test bench under the consideration of a boosted high tumble engine concept and direct injection up to 220 bar. Due to the high tendency of hydrogen to generate knocking and backfiring phenomena, it is crucial to investigate the homogenization of the mixture and possible back flows into the intake manifold. Therefore, different injection and operating strategies are tested in the simulation to evaluate and optimize performance, efficiency and reliability of the engine.