Impacts of hydrogen addition on micro and nanostructure of soot particles formed in C2H4/air counter diffusion flames

Abstract

In the present study, the impacts of hydrogen addition on micro and nanostructures of soot particles were evaluated in an ethylene-air counter diffusion flame configuration. To quantitatively interpret the impacts of hydrogen addition to the counter diffusion flame, the hydrogen was added in the fuel stream and its content (in volume %) was gradually increased up to 25%. Soot particles formed within hydrogen added flames were then sampled and imaged using a high resolution transmission electron microscopy (HRTEM) to visualize their micro and nanostructures. In addition, a series of numerical investigations were also performed to build a bridge between molecular gas phase species and the soot micro and nanostructures. Adding the hydrogen to the fuel stream was found to decrease the size of soot microstructures and enhance the formation of fullerenic nanostructures defined as highly curved carbon lamella. The abundance of hydrogen in the flames deactivated the surface site of soot particles, leading to reductions in the size of soot microstructures. Also the hydrogen addition was found to be related to the increased formation of PAHs containing 5-membered rings that helps to develop the curvatures in the carbon lamella.