An Examination of Spray Stochastics in Single-Hole Diesel Injectors

Recent advances in x-ray spray diagnostics at Argonne National Laboratory's Advanced Photon Source have made absorption measurements of individual spray events possible. A focused x-ray beam (5×6 μm) enables collection of data along a single line of sight in the flow field and these measurements have allowed the calculation of quantitative, shot-to-shot statistics for the projected mass of fuel sprays. Raster scanning though the spray generates a two-dimensional field of data, which is a path integrated representation of a three-dimensional flow. In a previous work, we investigated the shot-to-shot variation over 32 events by visualizing the ensemble standard deviations throughout a two dimensional mapping of the spray. In the current work, provide further analysis of the time to steady-state and steady-state spatial location of the fluctuating field via the transverse integrated fluctuations (TIF). We then utilize newly acquired data with a much larger number of spray events (between 200 and 400), to assess the statistical convergence of the ensemble mean and standard deviation. The spatial domain has been extended to out to 24.0 mm downstream of the nozzle. A 180 μm nozzle has been used for this portion of the study, at two rail pressures (500 and 1500 bar), and two ambient pressures (1 and 20 bar).