Search Results

The purpose of this paper is to characterise barrel swirl behaviour in a production four-valve engine with pentroof chamber. Steady flow analysis showed that the insertion of tubes into the cylinder head's induction tracts increased the tumbling ratio of the in-cylinder flow field at intake valve closure. A comparison of LDA measurements, conducted along the spark plug axis, for tubes and no tubes inserted yielded the following conclusions. The results indicated that the barrel swirl generated was not efficiently breaking down into turbulence but forming two counter-rotating vortices in the horizontal cylinder plane. The turbulence levels and cycle-to-cycle flow variations towards the end of the compression stroke increased with tumbling ratio. The former suggested faster combustion rates if applied to a lean burn engine, however, the latter suggested greater cyclic combustion instability and may limit lean burn capability.

The purpose of this paper is to characterise the flow field through the inlet valves, and tumble to swirl conversion tube of a steady state flow rig using HWA. LDA and CFD techniques. Three cylinder head configurations were developed which were found to produce three levels of barrel swirl motion. The swirl precesses around the central core of the conversion tube at all degrees of swirl. Varying degrees of swirl produced differing axial velocity profiles, and flow reversal occurred in the central core of the conversion tube for the high swirling case. The results obtained for this study indicate that care must be exercised when deducing the barrel swirl ratio for real engines from steady flow rig analysis.