Numerical Calculation of the Ignition Limit on Lean-Burn SI Engines

Abstract

A model predicting the ignition probability of the lean-burn SI engine in the vicinity of the lean-burn limit was constructed using the percolation model in continuous space. Calculated percolation probabilities reproduced the experimental results when the following conditions were applied, considering the actual ignition on SI engine. First, the heat generation of the spark plug should be larger (15 to 20 times) than that of the exothermic reaction of the fuel particle. Second, the scale of the percolation should be more than the twice of the range of the heat generation of the spark plug. This result suggested that the size of the flame core would have about the twice size as the effective range of heating by the spark plug.