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The air entrainment in a transient diesel spray was studied using laser Doppler anemometry to provide information on the effect of gas density and temperature. The spray was injected vertically into a confined quiescent atmosphere and the entrained mass flow rate was evaluated by measuring the air velocity component normal to a cylindrical geometric surface surrounding the spray, and extending to about 200 nozzle diameters (50 mm). The experimental results, relative to a density range from 0.84 to 7.02 kg/m3 and a temperature range from 293 to 473 K, indicate that the non dimensional entrainment rate, averaged in time over the main injection period, depends on the distance from the nozzle and both gas density and temperature. A first analysis, based on the available data, allowed to quantify the dependence and provided a correlation with such variables.

Different laser based techniques were applied to investigate the effect of gas density on the penetration of a Diesel Spray and the entrainment of the surrounding air. The experiments were conducted in a constant volume chamber under quiescent conditions. Gas density was varied in a wide range (from 1.17 kg/m3 to 40 kg/m3) while keeping temperature constant at ambient conditions. Spray penetration was measured by different techniques: Laser Doppler Velocimetry (LDV), Laser Beam Extinction (LBE) and Laser Sheet Visualisation (LSV). The results were compared to estimate the level of agreement among the techniques. A comparison with existing penetration models was also performed and an empirical law is proposed to better correlate the results. The two-dimensional gas velocity field generated by the spray was measured by LDV and compared to PIV results evidencing different peculiarities of the two techniques in describing the structure of the flow field.

The paper reports on an experimental investigation of the aero-thermal flow field configuration at the exit of a vented automotive brake disc. The main goal is to obtain a deeper insight of the aero-thermal phenomena upon which brake efficiency strongly depends; a second goal is to generate a complete data set for CFD code validation. A multiple pin disc geometry was tested at two disc rotational speeds and at four moderate braking conditions. The experiments were mainly focused on a coupled thermal and fluid dynamics survey. Local mean temperature and velocity measurements at disc exit were carried out in the relative frame; global parameters, as the vented mass flow rate, the heat power released to the vented air and the internal convective heat transfer coefficient were then evaluated. It was found that the flow structure does not really change, varying the rotational speed and the braking conditions.

The paper reports on an experimental investigation of the mean and turbulent flow structure at the exit of vented automotive brake discs. The main goal is to obtain a deeper insight of the aero-thermal phenomena upon which the brake efficiency strongly depends; a second important result is the generation of a comprehensive data set for CFD code validation. Two disc geometries were tested: a backward curved blade and a multiple pin configuration. The experiments were mainly focused on the evaluation of local and global fluid dynamic features, as vented mass flow rate and turbulence characteristics at the disc exit. Results in terms of mean and turbulence velocity component distributions and vented mass flow rate through the brake disc passages allow a comprehensive description of the flow behavior, together with a comparison between the two disc geometries.