Studies of the Control of In-cylinder Inhomogeneities in a 4VVAS Gasoline Engine 2008-01-0052
In this research, numerical simulation using Star-CD is performed to investigate the mixing process of a single-cylinder experimental gasoline engine equipped with 4VVAS (4 Variable Valve System). Different engine operating conditions are studied with respect to valve parameters, including EVC (Exhaust Valve Closing), IVO (Intake Valve Opening), and IVL (Intake Valve Lift). The definitions of RGF (Residual Gas Fraction)/temperature statistical distribution and inhomogeneity are proposed and quantified, on which the influences of the aforementioned valve parameters are analyzed.
Results reveal that, the distribution of in-cylinder residuals varies with valve parameter combinations. Intake valve timing has a greater effect on the in-cylinder distribution and inhomogeneity of residuals than intake valve lift. Earlier IVO leads to lower RGF inhomogeneity around TDC. Different combinations of valve management parameters can result in distinct stratification patterns of residuals in the position and shape of the local high-RGF region. Exhaust valve timing greatly affects the intake process. Late EVC can Intensify the real intake duration and reduce the RGF inhomogeneity. The distribution and inhomogeneity of temperature are jointly decided by RGF and the temperature differential between the charge and the cylinder wall.