A generalized kinetic model with variable octane number for engine knock prediction

Abstract

A generalized research octane number (GRON) model, including 22 species and 21 reactions, has been developed to simulate the hydrocarbon oxidation with the goal of predicting engine knock. The simplicity of the model enables to represent gasoline with different octane numbers by adjusting the global low-temperature reaction rate. The model was validated against shock tube experimental data obtained over a wide range of conditions, including equivalence ratios from 0.5 to 2.0, initial pressures from 13 to 55bar, and initial temperatures from 700 to 1250K. Both gasoline engine knock and normal combustion were investigated using Computational Fluid Dynamics (CFD) couple with the present GRON. The numerical results proved to be in good agreement with the experimental data. Both the cylinder pressure traces and the distribution of important radical species (CHO and OH) during knocking combustion can be predicted reasonably well. Compared to the CFD calculations using detailed mechanisms, the generalized kinetic model enables a reduction of the computational time by more than 90%.