Distribution of Temperature and Characteristics of Soot Volume Fraction in MILD-OCC Flame

Coal and methane were burnt in the MILD-OCC combustion flame under different combustion conditions to study the temperature distribution and characteristics of soot volume fraction. In this experiment, the flame temperature distribution is measured by thermocouple and the volume fraction (fv) of soot at each sampling point is calculated, then combining with the mass concentration of soot by the filter weighing method to obtain the distribution characteristics of soot in the flame. The results of thermocouple particle densitometry (TPD) show that the formation and oxidation of soot at every point in the flame is related closely to its position and temperature in the flame. The fv of soot in the center of the flame is negatively correlated with the temperature of the flame during the MILD-OCC combustion. The lower temperature region of the flame is conducive to the growth of soot, which leads to higher value of fv. The higher temperature in the center of the flame is beneficial to the oxidation of the soot particles, resulting to lower value of fv. The results of the filter membrane weighing method show that the formation of soot mainly occurs in the central region of the flame. When the radial distance increases, the flame temperature rises, and the soot concentration decreases due to oxidation. On the whole, the distribution of soot measured by the filter membrane weighing method is roughly consistent with that calculated by the TPD, which provides a reference for further research on the MILD-OCC combustion.