An Experimental and Simulation Study of Early Flame Development in a Homogeneous-charge Spark-Ignition Engine

An integrated experimental and Large-Eddy Simulation (LES) study is presented for homogeneous premixed combustion in a spark-ignition engine, called the Transparent Combustion Chamber engine. The emphasis has been on developing strategies for making quantitative comparisons between high-speed/high-resolution optical diagnostics and LES using common metrics for both the experiments and the simulations, and focusing on the important early flame development period. Results from two different LES turbulent combustion models are presented, using the same numerical methods and computational mesh. Both models yield Cycle-to-Cycle Variations in combustion that are higher than what is observed in the experiments. The results revealed strengths and limitations of the experimental diagnostics and the LES models, and suggest directions for future diagnostic and simulation efforts. Particularly, flame development between the times corresponding to the laminar-to-turbulent transition was observed and 1% mass-burned fraction are especially important in establishing the subsequent combustion event for each cycle.