Cyclic Variability Patterns in a Spark Ignition Engine Fueled With LPG

Cycle-to-cycle combustion variations in a spark ignition engine, lean operated, were approached with symbolic sequence statistics and return maps. The engine was operated with a gaseous fuel (LPG) and with a strong swirl induction generated, to give relatively advanced mixture homogeneity. A transition to nonlinear deterministic behavior was identified when the equivalence ratio was decreased to very lean conditions. It was thus found that the effect of residual gas fraction on communication between successive combustion events is weaker with an improved mixing. The deterministic effects, which are not controllable, can thus be removed to lower equivalence ratios and higher levels of residuals by an improved mixing within the cylinder.