Large Eddy Simulation of the Intake Flow in a Realistic Single Cylinder Configuration

The present paper focuses on gaining a deeper understanding about the turbulent flow inside an engine cylinder using large eddy simulation. While the main motivation of the current study is to gain a deeper understanding of the flow patterns and especially about the swirl, the background motivation of this study is the development and testing of suitable methods for the large eddy simulation of combustion engines and the validation of the used simulation methodology. In particular, we study the swirl and other flow features generated by the intake jets inside the cylinder. The simulated geometry is the Sisu Diesel 84 engine cylinder where the exhaust valves are closed and the intake valves have constant valve lifts. Furthermore, the piston has been removed so that the flow is able to exit from the opposite end of the cylinder. Special attention is paid on the generation of the computational grid so that the wall and the intake jet regions are made sufficiently fine for wall-resolved large eddy simulation. The Reynolds number, as referred to the diameter and velocity of the intake channels, is evaluated to be of the order of 80 000. The time development and the mixing capabilities of the flow are studied using passive scalars and in-cylinder flow fields of the simulation are compared with previously published results on Reynolds-Averaged Navier-Stokes simulations, particle image velocimetry measurement data and paddlewheel measurement data of the same engine cylinder configuration. The simulations reveal detailed information about the development of the flow and about the generation of the swirl. Especially it was noticed that the fill port seems to have a larger role in the generation of the swirl than the swirl port. The simulations were carried out using OpenFOAM, open source CFD software.