Analysis of the flame thickness of turbulent flamelets in the thin reaction zones regime

The thickness of the instantaneous flamelets in a turbulent flame brush on a weak-swirl burner burning in the thin reaction zones regime was analyzed experimentally, theoretically, and numerically. The experimental flame thickness was measured correlating two simultaneous Rayleigh images and one OH-image from two closely spaced cross sections in the flame. The low temperature edge of the flame was thickened by turbulent eddies but these structures could not penetrate far enough into the flame front to distort the inner layer for the moderate Karlovitz numbers used. The flame front based on the temperature gradient at the inner layer became thinner for lean flames and thicker for rich methane-air flames.