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Computational fluid dynamics of gas-fueled large-bore spark ignition engines with pre-chamber ignition can speed up the design process of these engines provided that 1) the reliability of the results is not affected by poor meshing and 2) the time cost of the meshing process does not negatively compensate for the advantages of running a computer simulation. In this work a flame propagation model that runs with arbitrary hybrid meshes was developed and coupled with the KIVA4-MHI CFD solver, in order to address these aims. The solver follows the G-Equation level-set method for turbulent flame propagation by Tan and Reitz, and employs improved numerics to handle meshes featuring different cell types such as hexahedra, tetrahedra, square pyramids and triangular prisms. Detailed reaction kinetics from the SpeedCHEM solver are used to compute the non-equilibrium composition evolution downstream and upstream of the flame surface, where chemical equilibrium is instead assumed.

The present work aims to determine the gas pressure acting in the ring pack area in a medium-speed four stroke diesel engine. The experimental part of the study was carried out as firing engine tests, with an instrumented piston, with telemetric data transmission, and an instrumented cylinder liner in a 6-cylinder test engine. The results, in terms of inter-ring gas pressure are compared with the results of computer simulations. Moreover, the computer simulations were carried out to predict and compare the effects of the piston running clearance and the ring face wear on the inter-ring pressures. The study comprises aspects on inter-ring pressures under a set of loads. The measured inter-ring gas pressures indicate steady ring operation. The simulation results show good agreement with measurement results.

Recent advancements in internal combustion engine due to stricter emission regulations require the turbocharger to function with a higher efficiency over the entire operation range. Furthermore, the need for higher boosting pressure requires the extension of rotation speed margin forcing the inclusion of resonance speeds for high order vibration modes, posing a threat on the reliability of the turbine. This paper introduces new variable geometry nozzle vanes and turbine rotor designed based on the understanding and control of tip leakage flows, utilizing both low and high fidelity CFD simulations. Low fidelity single passage steady state simulations were used for vane profile tuning and high fidelity full-scale unsteady simulations for evaluating stator-rotor interactions respectively. The new vane design is comprised of a three-dimensional stacking in the span wise direction which has been found effective in reducing the nozzle tip leakage loss.