Department of Marine Technology, Amirkabir University of Technology, Tehran, Iran
Advanced models of spray breakup and droplet collision are implemented in OpenFOAM code for comparing the flat-wall impinging and free fuel sprays under ultra-high pressure direct injection diesel engines. The non-evaporating spray and ambient gas flow characteristics are analyzed by a combination of Eulerian and Lagrangian methods for continuous and dispersed phase, respectively. Various injection pressures and two different impinging distances are used. Reynolds Averaged Navier Stokes (RANS) equations are solved using standard k-ε turbulence model. Computational domain and grid size are determined based on a mesh study. Numerical results are validated by published experimental data for free and wall-impinging sprays. The robustness and accuracy of the proposed scheme are confirmed by comparing the main characteristics of spray and surrounding gas against published experimental data. To accomplish this, spray shape, penetration and gas velocity vectors are compared with experimental data and insightful understanding of the spray characteristics are provided. In comparison with free spray, tip penetration has been limited in impinging sprays. Turbulent flow in impinging sprays leads to more induced air motion. Also, impinging spray leads to more pushed-out gas velocity. The obtained results indicate that the numerical findings are generally in good agreement with experimental data in case of ultra-high injection pressures and micro-hole injectors.