Diesel Spray Characterization and Numerical Simulation Using Eulerian-Lagrangian Model

Fulfill emission restrictions is the most challenging task of future engines development. In this context, improvements with regard to the spray and mixture formation in internal combustion engines are necessary. Experimental investigation and numerical simulation have been used to predict and analyze complex in cylinder processes. In this paper, a diesel spray characterization using optical diagnostics was made in order to provide input data and boundary conditions for a diesel spray computational fluid dynamics simulation (CFD), using the Eulerian-Lagrangian model. Combining the advantages of Eulerian and Lagrangian approaches, this model is able to predict continuously the whole spray evolution. The main difficulty of numerical spray simulation is the correct representation of the two characteristic spray zones: dense near the nozzle and dilute downstream. In the dense zone, the spray and its gaseous environment are presented as an effective single-phase fluid with a highly variable density. To describe the liquid dispersion, the transport equations for the liquid mass fraction and for the liquid/gas interface density are solved. The transition to the Lagrangian calculation is applied when the spray is considered to be diluted enough. Spray characteristics such as cone angle, velocity field, and tip penetration were determined. Simulations were carried out at the CTM - UFMG (Technology Center of Mobility - UFMG).