Three - Zone Model of Combustion and Chemical Non-Equilibrium Ionization in the SI Engine 2004-01-0622
During last four years the authors were involved in the simulation and investigation of combustion and ionization in the cylinder of gasoline and natural gas Spark Ignition (SI) engine. Two-zone model of combustion and chemical non-equilibrium ionization and results of the numerous numerical investigation were presented by the authors at SAE 2002 and SAE 2003 World Congresses. This model and numerical results provided an important insight into combustion products behavior and gave the chance to find correlation between chemical and thermal ionization of combustion products and SI engine performances.
In order to provide better correspondence of the numerical data to the experimental results in the wide range of operational parameters for different geometry of engines a new three-zone model was developed and successfully tested. In comparison with previous one new model includes the additional third zone, which simulates the processes in the small volume of flame kernel inside the gap between spark plug electrodes.
Following processes in the flame kernel are taken into account:
detailed mechanism of chemical interaction including chemical and thermal ionization;
heat exchange between combustion products and electrodes;
mass exchange between third zone and combustion products in the cylinder.
The comparison of numerical and experimental results showed more accurate correlation between measured and calculated values of pressure and ion current. The concentration of electrons in the gap between spark plug electrodes corresponds better to the experimental data for gasoline engines in comparison with two-zone model. Three-zone model became a new generation among the models for the investigation of in-cylinder combustion products ionization and simulation of operational and ecological performances of SI engine.