Abstract
Structure and propagation characteristics of spark-ignited flames are observed using high-speed schlieren photograph and tomography. The spark-ignited flame is initiated in a quasi-turbulent wake, which is formed behind a rod-array in the propane-air stoichiometric mixture stream and consist of a series of Karman vortex streets having an almost single turbulence length scale. The scale and intensity of vortices are adjusted in the ranges of l=0.2〜1.5 mm and u'= 0.9〜7.7 m/s. It is confirmed that eddies having scales larger than the laminar flame thickness enhance the burning velocity due to lesser cooling, while those having smaller scales suppress it because of intense cooling. It is also shown that the spark-ignited flame in the intense and fine quasi-turbulent wake, which is established behind a rod-array of 0.3 mm diameter in the high-speed mixture streams of 20〜50 m/s, exhibits a nature inherent in the wrinkled flame with pockets.
