Evaluation of spatial distribution and cycle-to-cycle variation in two-stroke engine combustion using the multiple-ion probe method

This study explores flame propagation behavior in a two-stroke gasoline engine using a multiple-ion-probe measurement technique. Ion probes were installed on the combustion chamber wall to detect the timing of local flame arrival with high temporal resolution. The recorded arrival times were spatially interpolated to reconstruct the evolving flame front as a series of contour lines. From these data, burned area and flame front length were calculated at each time step. Their time histories were analyzed across multiple engine cycles to evaluate the dynamic characteristics of combustion. The results revealed clear cycle-to-cycle variations in both propagation speed and flame geometry, including differences in front deformation and growth patterns. Additionally, comparisons based on equivalent flame radius provided spatial insight into the development of flame structure. This approach demonstrates the potential of ion-probe-based diagnostics for capturing detailed, cycle-resolved information on flame dynamics in spark-ignition engines.