Knocking prediction in internal combustion engines via thermodynamic modeling: preliminary results and comparison with experimental data

In this work, we present a method based on a zero-dimensional thermodynamic model for estimating the onset of the knocking phenomena in a flex-fuel engine using gasohol (gasoline blended with anhydrous ethanol) and blends of gasohol with hydrous ethanol. The contents of the combustion chamber are assumed homogeneous and the energy release is modeled by the well-known Wiebe's equations. Heat loss through the walls of the cylinder is modeled by the Woschni's equations. The fuel ignition delay is based on an improved empirical Arrhenius model found in the literature, which depends only on the pressure, temperature, fuel-air equivalence ratio, octane number and percentage of ethanol or methanol present in the fuel. A proper scheme for coupling these models is presented, allowing for knocking occurrence estimation. Simulated results are compared with experimental data, showing agreement compatible with the modeling adopted.