Size Distribution of Soot Particles in Premixed n-Heptane and Methylcyclohexane Flames

The size distributions of soot particles from premixed n-heptane and methylcyclohexane flames were measured and compared at different particle residence times. The micro-orifice probe sampling technique and the scanning mobility particle sizer were used for the particle size measurement in the burner-stabilized stagnation flame configuration. For both flame series, the mixture C/O mole ratio was 0.6 and the maximum flame temperature was controlled around 1835 K to investigate the fuel structure effects on soot propensity. It was observed that, with the increased particle residence time, the particle size distribution function of both flames evolved from the unimodal (only the nucleation mode) to the bimodal (both the nucleation and coagulation modes) distribution. The particle nucleation strength and particle growth rate of the methylcyclohexane flame were quantitatively lower than those of the n-heptane flame. Considering the equivalence ratio difference between the two flames, the sooting propensity dis...