The Temporal Rate of Fractal Dimension Growth in Flame Front Wrinkles during the Early Phase of Flame Propagation in an SI Engine.

Abstract

Turbulent premixed flame fronts during the early phase of flame propagation were visualized by a laser-light sheet technique in an optically accessible spark ignition engine. Time-resolved continuous images of wrinkling flame fronts were captured by a high-speed video camera. The test engine was operated at various engine speeds and compression ratios. The image data were processed to measure the fractal dimension in a time series for each cycle and to investigate the nature of fractal dimension growth in the early phase of flame development. The results show that the temporal rate of fractal dimension growth increases as the engine speed and the compression ratio increase. The empirical correlation was derived for the temporal rate of fractal dimension growth as a function of turbulence intensity and pressure.