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TY - THES AU - Wegmann, Tim TI - Multiphase flow in internal combustion engines on high-performance computers PB - Rheinisch-Westfälische Technische Hochschule Aachen VL - Dissertation CY - Aachen M1 - RWTH-2025-00617 SP - 1 Online-Ressource : Illustrationen PY - 2024 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2025 N1 - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2024 AB - Multiphase flow in internal combustion engines is among the most challenging technical computational fluid dynamics application. The interaction of the compressible, unsteady and turbulent flow with numerous tiny spray droplets requires complex physical models including phase transition. Scale resolving direct injection simulations are rarely found in the literature due to these complex models and high computational costs. This work aims to close this gap by presenting numerical methods which enable efficient spray injection simulations for moving boundary applications. Simulation results with high spatial and temporal resolution are presented. A non-blocking interleaved time step procedure is introduced for an efficient Eulerian-Lagrangian phase coupling on Cartesian meshes. A fine-grained domain decompositioning approach and a load balancing strategy with dynamic workload estimators has shown to increase the parallel performance significantly. The numerical framework has been validated by experimental measurements both, for in-cylinder cold flow and spray chamber injection cases. Particle image velocimetry measurements in the tumble plane of an optical test engine show a good agreement with the simulated velocity field throughout the intake and compression stroke. Liquid and vapor penetration measurements in constant pressure chambers coincide with numerical predictions for different injector geometries and fuel properties. A novel scale separation of the turbulent in-cylinder flow by means of empirical mode decomposition is presented. The approach enables the analysis of the instantaneous large scale coherent motion of individual cycles and the estimation of the ensemble mean from a limited number of cycles. The direct injection simulations reveal different influencing parameters on the fuel vapor distribution at the ignition timing, e.g., the start of injection, the injector geometry and fuel properties. The analysis shows that the spatial fuel vapor distribution is prone to cycle-to-cycle variation. As initial improvements an optimal start of injection is investigated and a modified injector geometry is introduced. A correlation is found between a sustained tumble motion and improved fuel-air mixing towards the end of the compression stroke. The fuel entrainment of the main chamber injection into the pre-chamber is investigated for stoichiometric and a lean condition. The simulation results serve as benchmark and data set for further analysis of the turbulent fuel-air mixing process. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2025-00617 UR - https://publications.rwth-aachen.de/record/1002672 ER -