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The influence of spray-wall interaction on air entrainment in an unsteady non-evaporating diesel spray was studied using laser Doppler anemometry. The spray was injected into confined quiescent air at ambient pressure and temperature and made to impact on a flat wall. The air velocity component normal to a cylindrical surface surrounding the spray was measured during the entire injection period, allowing to evaluate the time history of the entrained air mass flow rate. The influence of wall distance and spray impingement angle on air entrainment characteristics has been investigated and the results indicate that the presence of a wall increases the entrained mass flow rate in the region close to the surface, during the main injection period. Normal impingement appears to produce stronger effects than oblique incidence at 30 and 45 deg. A qualitative explanation of the results is also proposed, based on the drop-gas momentum exchange mechanism.

A laser Doppler velocimeter (LDV) has been used to investigate the in-cylinder flow pattern produced in a steady state flow rig by the helical inlet port of a model cylinder head, typical of those used in internal combustion engines. Measurements were taken of the axial and tangential velocity components on four radial axes, at a one bore distance from the cylinder head. The LDV results showed that the axial vortex formed behind the inlet port extends to more than one bore from the cylinder head and the tangential velocity profile is never that of a pure forced vortex. At lower lifts of the valve a smaller contra-rotating swirl was found together with the main swirl pattern, whereas at higher lifts a single swirl was established at the one bore position. Both the tangential and axial fluctuating velocity components were found more uniform than the mean values, with zones of higher turbulence around the flow reversal points corresponding to regions of steep mean velocity gradients.

The effects of two types of intake ports on the in-cylinder bulk flow and turbulence structure were investigated in steady flow tests by using laser doppler anemometry. The results, obtained at constant mass flow-rate in a plane 15 mm or 0.19 bore diameters from the cylinder head, confirmed the expected differences in the tangential flow pattern, but revealed similarity in the axial velocity distribution characterized by a large recirculation zone (RZ) attached to the inlet valve. In both cases the turbulence was found higher, more inhomogeneous and more non-isotropic in the regions of positive axial flow than in the RZ. Localized highly turbulent conditions have been identified and characterized as a consequence of bi-modal probability distribution functions (pdf) of velocity and aperiodic oscillations from one velocity regime to another.