Two-Dimensional Droplet Size and Volume Fraction Distributions From the Near-Injector Region of High-Pressure Diesel Sprays

Abstract

Droplet diameter and volume fraction measurements are reported as a function of radial and axial position near the injector orifice within a high-pressure spray typical of diesel systems. Injection system parameters were peak pressures of ~ 80 MPa and a single orifice injector with a 0.16 mm diameter and an L/D ratio of ~ 4. Two cases are presented and discussed in detail; injection into room ambient conditions and injection with combustion (initial conditions: 873 K, 12.5 atm). Scattered light at two infrared wavelengths was collected from a spatially resolved probe volume and, through scattering theory, both Sauter mean diameter and liquid volume fraction were produced. Spray properties were determined as a function of time at a number of points, and these points form a grid based on multiple axial and radial positions within the spray. Results from multiple, yet identical, events were used to construct twodimensional contour plots of the Sauter mean diameter and volume fraction within the spray.

Measurements of droplet size in shear-driven atomization using ultra-small angle x-ray scattering

“…The current data provide a quantitative method to directly validate computational models of spray breakup, which have heretofore relied only on measurements of droplet size in the far-field region. That said, it is encouraging that the far-field droplet sizes found in this work are similar to those found in other recent measurements of diesel sprays using optical diagnostics [9,42].…”

“…It is useful to compare the droplet sizes seen in these measurements with those from other studies. Optical far-field measurements of droplet size give similar droplet sizes to those seen in this study [9,42]. Moreover, recent LES simulations of diesel injection at similar injection pressures [13] have shown the formation of large populations of ~ 2 micron droplets starting within 1 nozzle diameter of the injector exit, consistent with the results of this study.…”

“…The nearnozzle region of diesel sprays (within roughly 50-100 nozzle diameters, depending on ambient density) is optically dense, which severely hampers optical diagnostics of these sprays. Some studies of diesel spray droplet size and velocity have been performed, using PDPA [3][4][5], light extinction [6,7], laser diffraction [8], scattering [9], and imaging [10,11], though generally in the spray far-field. Droplet size measurements close to the nozzle of a diesel spray are limited to a very thin region at the periphery of the plume where the optical density is modest, and the size distribution may be filtered by entrainment [11].…”

Optical Arrangements for Time-Gated Ballistic Imaging

“…The scattering environment was simulated with a monodisperse suspension of varying sizes and concentrations of polystyrene (PS) spheres in distilled water. Typical Diesel spray droplet sizes, depending on conditions, fall in the range of 5-20 µm [5]. Thus, our measurements are analogous to 5, 10, 15, and 20 µm Diesel droplets in varying concentrations.…”

Infrared thermography-based visualization of droplet transport in liquid sprays

“…The main advantage of the thermographic method over photographic method is as a result of the fact that the infrared wavelengths are attenuated less than the visible wavelengths by the spray [19,20]. This is because the attenuation of the electromagnetic wave within a scattering and an absorbing medium like a liquid spray with the same size distribution will decrease with increasing wavelength within the electromagnetic spectrum.…”