Measurement and analysis of flame surface density for turbulent premixed combustion on a nozzle-type burner

The flame surface density for turbulent premixed combustion on a nozzle- type burner is measured by planar laser-induced fluorescence (PLIF) and image processing techniques. The maximum flame surface density tends to show linear dependence on the K-factor given as a function of the integral length scale and u'₀/S(L). The flame surface density shows an asymmetric profile in c space with the peak location correlated in terms of the dimensionless parameter, N(B), which represents the degree of gradient or countergradient diffusion by turbulence. At values of N(B) close to unity the peak occurs at a value of c of about 0.7. As N(B) increases above unity, the peak moves to a lower value in c space, approaching a symmetric profile. The thickness of a turbulent flame brush nondimensionalized by the integral length scale tends to show linear dependence on the H-factor which is obtained by integrating the first moment equation of the reaction progress variable. The flame surface density increases at a higher ambient pressure due to decrease in the laminar burning velocity and the length scales of flame wrinkling. (C) 2000 by The Combustion Institute.