Experimental and Computational Investigation of Subcritical Near-Nozzle Spray Structure and Primary Atomization in the Engine Combustion Network Spray D

Abstract

In order to improve understanding of the primary atomization process for diesel-like sprays, a collaborative experimental and computational study was focused on the near-nozzle spray structure for the Engine Combustion Network Spray D single-hole injector. These results were presented at the 5th Workshop of the Engine Combustion Network in Detroit, Michigan. Application of x-ray diagnostics to the Spray D standard cold condition enabled quantification of distributions of mass, phase interfacial area, and droplet size in the near-nozzle region from 0.1 to 14 mm from the nozzle exit. Using these data, several modeling frameworks, from Lagrangian-Eulerian to Eulerian-Eulerian and from Reynolds-Averaged Navier Stokes (RANS) to Direct Numerical Simulation (DNS), were assessed in their ability to capture and explain experimentally observed spray details. Due to its computational efficiency, the Lagrangian-Eulerian approach was able to provide spray predictions across a broad range of conditions. In general, this "engineering-level" simulation was able to reproduce the details of the droplet size distribution throughout the spray after calibration of the spray breakup model constants against the experimental data. Complementary to this approach, higher fidelity modeling techniques were able to provide detailed insight into the experimental trends. For example, interface-capturing multiphase simulations were able to capture the experimentally observed bi-modal behavior in the transverse interfacial area distributions in the near-nozzle region. Further analysis of the spray predictions suggests that peaks in the interfacial area distribution may coincide with regions of finely atomized droplets, whereas local minima may coincide with regions of continuous liquid structures. The results from this study highlight the potential of x-ray diagnostics to reveal salient details of the near-nozzle spray structure, and to guide improvements to existing primary atomization modeling approaches.

Examination of diesel spray combustion in supercritical ambient fluid using large-eddy simulations

“…Various experiments have been performed under Engine Combustion Network 1 (ECN) Spray A [2][3][4][5][6][7][8] and Spray D [9][10][11][12][13][14][15][16][17][18] target conditions in order to contribute to the understanding of diesel combustion. In addition, Reynolds-Averaged Navier-Stokes (RANS) and largeeddy simulations (LES) have been used to simulate Spray A [19][20][21][22][23][24][25][26][27][28][29][30][31] and Spray D 15,[32][33][34] in computational investigations.…”

Visual experimental investigations of string cavitation and residual bubbles in the diesel nozzle and effects on initial spray structures

“…With the development of X-ray technology, the real flow conditions and detailed spray characteristics were obtained. 51–53 Swantek et al 54 captured the bubble formation and air ingestion after the end of injection in the single-hole diesel injector based on the X-ray phase-contrast imaging technique. Moon et al 55 also found the air ingestion inside the diesel nozzle using the X-ray phase-contrast imaging technique.…”

Development of a CFD Solver for Primary Diesel Jet Atomization in FOAM-Extend

“…The mean droplet diameter slightly increases from 6.5 µm to 6.7 µm at the end, which is not intuitive. Furthermore, compared to experimentally measured results, the droplet diameter of approximately d ≈ 6.7 µm is significantly higher than the experimentally measured Sauter Mean Diameter (SMD) of approximately d 32 ≈ 1.8 µm [7,25]. The reason for such a discrepancy could lie either in the droplet detection algorithm used for post processing of the results or the computational set-up.…”

“…The simulations also proved to be quite informative on the structures of separated fuel: approximately two thirds of the structures had a nearly spherical shapre, while the remaining one third had a more elongated shape (ligaments), which would have probably undergone a secondary break-up eventually. Another state-of-the-art primary break-up simulation has been presented as a part of the Battistoni et al's review paper [7]. The simulation concerns ECN's Spray D injector and it required 188 000 core hours of computational time to perform, providing insightful physics happening during the atomization.…”