Cycle-Resolved Two-Dimensional Flame Visualization in a Spark-Ignition Engine

A cycle-resolved two-dimensional flame visualization technique using Mie-scattering from submicron sized smoke particles added to the homogeneous charge mixture of a spark-ignition engine has been developed. This diagnostic technique was applied to a square piston engine with four windows. Pulsed laser sheets were generated by a copper vapor laser at a frequencies of 6 kHz. The light scattered by the smoke particles was collected by a drum camera on high sensitivity photographic film.

The flame contours were analyzed using fractal analysis and complex Fourier transform procedures. Radii of curvature, wrinkling factors and turbulent burning velocities have been determined at different engine speeds and equivalence ratios.