Local Flame Front Structure in the Vicinity of the Piston in a Transparent SI Engine 2001-01-1957

We present an experimental investigation of the local flame front characteristics as function of the distance between the flame front and the piston. The objective of this paper is to provide some experimental data about the flame characteristics at the approach of the piston. The transparent engine speed is fixed at 2000 rpm and air-methane mixture was used with an equivalence ratio equal to 0.9. PLIF acetone imaging was acquired to estimate first the curvature, the curvature radius and the normal direction orientation of the local contours as function of the flame-piston distance. A discontinuity in these parameters appears when the distance is less than 1 mm. Secondly we apply local roughness analysis system to estimate the local fractal dimension of the flame front. We conclude that fractal dimension changes rapidly at 2.5 mm from the piston. A logarithm law was found to define the fractal dimension as function of flame-piston distance.