Ignition and Combustion Simulations of Spray-Guided SIDI Engine using Arrhenius Combustion with Spark-Energy Deposition Model

An Arrhenius combustion model (chemically controlled model) with a spark-energy deposition model having a moving spherical ignition source in the Converge CFD code is validated with a single-cylinder spray-guided SIDI engine at idle-like lean-burn operating conditions with both single- and double-pulse fuel injection. It was found that a fine mesh is required for accurate solving of "laminar-flame" like reaction front propagation. A reduced chemistry mechanism for iso-octane is used as gasoline surrogate. The effects of spark advance were studied by the simulation and experiment. The results show that this modeling approach can provide reasonable predictions for the spray-guided SIDI engine with single- and double-pulse injections.

The analysis of combustion regimes of the spray-guided SIDI engine-operating conditions indicates that the Damköhler number varies from 0.02 to 0.08 (Da≺≺1) and the Karlovitz number varies from 25 to 800 (Ka≻≻1), implying that ignition and combustion occur predominantly in thickened flame regimes where the chemical reactions dominate the combustion due to a slow reaction rate. Therefore, the assumption of a well-stirred reactor is valid for the combustion simulation of the spray-guided SIDI engine, permitting the use of the Arrhenius-type combustion model which neglects the interaction between reaction and turbulence in each computational cell.