Soot Concentration and Absorption Coefficient in a Low-Pressure Flame.

摘要

Soot concentrations at different positions through the carbon formation zone of a premixed acetylene/oxygen flat flame at 20mm Hg were evaluated by measuring the attenuation of a laser beam passed through the flame. The required soot absorption coefficients were measured in the same optical system by replacing the flame with standard soot samples deposited on glass slides in a molecular beam sampling instrument. In comparison with soot particle concentrations measured previously under the same flame conditions using molecular beam sampling and electron microscope analysis of beam deposits,the concentrations observed here are substantially larger in the regions of particle nucleation and rapid surface growth. The difference is attributed to absorption by large hydrocarbon species whose sizes range up to that of the smallest soot particles observed under the electron microscope (about 15 A diameter or 2130atomic mass units). (Modified author abstract)