Interaction between a diesel-fuel spray and entrained air with single- and double-injection strategies using large eddy simulations

Abstract

Interaction between fuel and air in a combustion chamber is one of the main drivers of the mixing process. Experimentally, flow visualizations are limited by high droplet density in the spray. Numerically, the ability of large eddy simulations (LES) to resolve large scales of flow offers good perspectives on capturing flow structures issued from the interaction between the Lagrangian (fuel droplets) and Eulerian (ambient gas) phases. This study examined these interactions first during a single injection using 3D and 2D criteria for both phases. As for the 3D criteria, the spray shape was analyzed in parallel to the Q-criteria applied to the Eulerian phase, making it possible to relate the spray deformations to some specific Eulerian structures. Secondly, 2D criteria were the fuel mass-fraction field and Eulerian streamlines, both taken in the mid-plane of the spray. This last analysis allows for identifying certain mechanisms involved in the Eulerian phase's structure generation and relates it to high fuel-concentration areas in the fuel mass-fraction visualizations. Keywords: Diesel fuel spray, Large eddy simulation, Multiple injection, Coherent structures, Lagrangian-Eulerian interaction, Air-spray interactions