Mathematical Modeling of Detonation in Spark Ignition Engines

This article presents the feasibility of mathematical modeling of detonation based on the analysis of a computational model of the thermodynamic cycle of a spark-ignition piston engine. This model approximates the actual cycle and allows for the time-dependent determination of the current cycle pressure and the temperature of the unburned propellant with sufficient accuracy. The model takes into account heat exchange between the combustion zones of the propellant and the combustion chamber walls. The onset of detonation is associated with the moment of self-ignition of the unburned propellant, determined based on the thermodynamic parameters of the unburned propellant and the kinetic mechanism of pre-flame chemical processes in the fuel–air mixture. It is shown that mathematical modeling of the self-ignition mechanism of the unburned portion of the charge in spark-ignition piston internal combustion engines can be performed in the same way as modeling the self-ignition mechanism of the fuel–air mixture under continuous compression in free-flying piston engines. The accuracy of the self-ignition calculation using the cycle model was verified experimentally by indexing at various speeds, with different excess-air (α) and filling (ηv) ratios, and at various mixture temperatures in the intake manifold. The modeling results were verified experimentally using isooctane ON100, a ON60 mixture, and commercial gasolines.