Dynamic simulation to analyze the influence of VVT strategies on the fuel spray and flow characteristics in an internal combustion engine

A CFD three-dimensional analysis of an internal combustion engine was carried out to evaluate the gasoline-ethanol E27 fuel spray and flow characteristics using variable valve timing (VVT) technology. In this study, the fuel injection has been made using port fuel injection (PFI) and the simulations modeled two conditions of valve timing: baseline and retarding the intake valve opening (IVO) 40°. The dynamic performance of this numerical model was validated comparing simulation results of cylinder pressure, mass burned fraction, cylinder temperature, and heat release with experimental data. The effects of in-cylinder fluid flow patterns, such as tumble and swirl, on combustion were numerically investigated for the two studied conditions and it was verified an extreme reduction of swirl when IVO is retarded, besides differences in tumble and cross-tumble. It was also observed major alterations on spray behavior using a retarded IVO, mostly in velocities, atomization, and remaining fuel in the admission port. Effects of exhaust gas recirculation (EGR) were also evaluated and proved to be more significant in the baseline condition.