Laser diagnostics of combustion-generated nanoparticles

Combustion-generated fine particulate matter (such as soot) is an important source of environmental and health concerns, and can impact the performance of combustion equipment. Molecular precursors of particles will condense into small clusters, which will in turn collide and merge with other molecules and clusters. In latter stages, small spherical clusters, commonly referred to as primary particles or monomers, form the basis of what are known as fractal aggregates: dendrite-like structures with a high surface to volume ratio, often characterized by their monomer radius, a, mass-averaged root-mean-square radius (a.k.a. radius of gyration, Rg), and fractal dimension, Df. The size and structure of the solid structures are major determinants for their impact.

This thesis focuses on the laser-based study of combustion-generated nanoparticle growth in premixed flames, in particular of soot and silica. The latter is considered as a product of the siloxanes that may be found in trace amounts in biogas, while soot is formed during the incomplete combustion of hydrocarbons. Although extensive research with a focus on aggregate particle growth has been done before, additional experimental work is required to add to our understanding of the processes involved and the influence of parameters like temperature, particle volume fraction and fuel/air ratio. An additional interest is that in the effect of hydrogen addition to the fuel. Hydrogen can not only serve to improve the unfavorable combustion characteristics of biogas, but since it does not produce soot and carbon dioxide may also be used to reduce pollutant emission.

Dissertation: http://hdl.handle.net/11370/36b5a86f-54a3-4425-a7b7-8931de779090