Application of a New Turbulent Flame Speed Combustion Model on Burn Rate Simulation of Spark Ignition Engines

This work presents turbulent premixed combustion modeling in spark ignition engines using G-equation based turbulent combustion model. In present study, a turbulent flame speed expression proposed and validated in recent years by two co-authors of this paper is applied to the combustion simulation of spark ignition engines. This turbulent flame speed expression has no adjustable parameters and its constants are closely tied to the physics of scalar mixing at small scales. Based on this flame speed expression, a minor modification is introduced in this paper considering the fact that the turbulent flame speed changes to laminar flame speed if there is no turbulence. This modified turbulent flame speed expression is implemented into Ford in-house CFD code MESIM (multi-dimensional engine simulation), and is validated extensively. The predictions of the modified turbulent flame speed expression are compared to a wide range of experimental data of turbulent flame speed from various flame configurations and conditions, with the same values of the model constants. The quantitative comparisons are found to be very good with experimental data beyond the usually restricted range for existing turbulent flame speed models. Finally, applications of the new turbulent flame speed combustion model to the burn rate simulation of several spark ignition engines/operating conditions have been carried out. The simulated incylinder pressures and burn rates are compared with experimental data and good agreements are found for low tumble ratio engine operating conditions.