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The air entrainment in a transient non-evaporating diesel spray was studied using laser Doppler velocimetry, to provide information on the mixing properties in the near-field region extending to 160 nozzle diameters (40 mm). The spray was injected into confined quiescent air at ambient pressure and temperature. The air velocity component normal to a cylindrical surface surrounding the spray was measured during the entire injection period, allowing the instantaneous air mass flow rate and the entrainment rates to be evaluated as a function of time. Two injection conditions were examined and their influence on the entrainment quantified. In the near field zone investigated, the air entrainment in transient liquid jets appears to be lower than that in steady gaseous jets, but larger than that in steady liquid jets.

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.