AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Effect of Fuel Composition on Monomer Size in an Inverted Hydrocarbon Flame
JUSTIN DAVIS, Yifei Guan, Igor Novosselov, University of Washington
Abstract Number: 701 Working Group: Nanoparticles and Materials Synthesis
Abstract The effect of hydrocarbon fuel composition on soot monomer size is investigated. Though the size of ultrafine particulate matter from combustion is known to vary, the effect fuel composition has on the carbon monometer size has not been reported. The knowledge of monomer size is an important parameter for aerosol agglomeration studies, health exposure studies, material synthesis, and other applications. An inverted flame reactor (IFR) is used for the experimental study on monomer size dependence of fuel composition. The diffusion flame in the IFR provides unique conditions to study soot growth, including the laminar nature of the flame and a long residence time to promote the formation of carbon soot particles. Four gaseous fuel are used: methane, propane, ethylene and acetylene. Volumetric flow rates of the fuel and air are varied to achieve similar flow patterns, with long residence times enabling soot formation for all four fuels. The soot formed in the experiments is measured using an SEM and ImageJ software. The results show monomer diameters ranging from 20nm to 80 nm: with methane producing the smallest monomer size, followed by propane, ethylene, and acetylene. A chemical reaction network (CRN), consisting of a hydrocarbon pyrolysis (fuel rich) region, followed by a diffusion flame front (stoichiometric) region, and a recirculation pathway, was constructed based on CFD simulations. The CRN is used to gain insight into the formation mechanism of carbon soot monomers using a hydrogen abstraction C$_(2)H$_(2) addition (HACA) mechanism. Monomer volume was found to be proportional to C$_(2)H$_(2) mole fraction inside the hydrocarbon pyrolysis region for the fuels tested.