Effects of relative port orientation on the in-cylinder flow patterns in a small unit displacement HSDI Diesel Engine

The paper aims at providing information about the in-cylinder flow structure and its evolution of a high speed direct injection (HSD1) four valve per cylinder engine for off-highway applications. Fully transient CFD analyses by means of state-of-the-art tools and methodologies are carried out for the whole intake and compression strokes, in order to evaluate port effects on both engine permability and in-cylinder flow field evolution. Organized mean motions (i.e., swirl, tumble and squish) are investigated, trying to establish general rules in the port design optimization process, addressing relationships between the relative port orientation and the in-cylinder flow structure. Different port configurations are compared, each deriving from the rotation of the BASE port configuration on two different planes, the former being perpendicular to the cylinder axis, while the latter being parallel to the cylinder axis. Relative intake port orientation proves to strongly influence the flow field evolution within the combustion chamber, and is therefore expected to play a non negligible role on the subsequent spray evolution and fuel combustion.