Soot Particle Inception and Growth Processes in Combustion

A study of soot particle inception and growth has been completed which considered fuel molecular structure, fuel concentration, temperature and operating pressure effects. These studies indicated that fuel species most strongly affected the particle inception process, as opposed to the surface growth process, and support an interpretation that inception controls the maximum amount of soot formed. Studies of concentration and temperature variations indicated that temperature effects dominate. The analysis yielded an apparent activation energy of 94.5 kcalmole for the temperature dependence, while the fuel concentration dependence, represented as X0n, was given by n 0. 3. Studies of soot aggregates found in these flames yielded higher values of volume-mean diameter, a larger surface area per unit volume, and lower values of the aggregate number concentration as compared to spherical particle assumptions. Operating pressure studies indicated that a power law representation of the form Pn, represented soot volume fraction dependence on the pressure, P, and confirmed the strong sensitivity of soot formation to pressure. Finally, high pressure diffusion flame studies revealed the onset of buoyant instabilities induced by changes in the pressure. A joint series of experiments and computations provided strong evidence to support that these studies isolate Richardson number as the only variable parameter. Soot Formation, Soot Particles, Diffusion Flames.