Evaluation of fluid motion in an engine cylinder during the intake stroke

The performances of a new Scania swirl-generating inlet port geometry have been evaluated by means of Time-Resolved Stereo PIV in a water-analogue engine setup mimicking the intake stroke. Two con figurations have been inspected: a fi xed valve lift case and a more realistic situation where the valves move according to a typical lift pro file. A three-dimensional reconstruction of the mean flow has been made from a number of different measured vertical planes intersecting in the cylinder axis. A coherent swirling pattern develops in the three-dimensional flow, where the azimuthal component is predominant over the vertical and radial one. The organization of such large-scale flow structure increases with time during the stroke and with the distance from the cylinder deck. The influence of the valve motion on the swirling magnitude has been found to be negligible, whereas it affects signifi cantly turbulence levels and the tumbling pattern. Phase Invariant POD has been used to detect major cyclic variations in planar data: unusual cyclic variability has been found in some of the planes. Finally, PIV data have been compared with RANS CFD results. A good agreement has been found in planar (radial and vertical) data, whereas RANS simulations seem to underestimate signi ficantly the magnitude of the azimuthal component and therefore the swirl intensity.