AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Measuring Nanometric Carbonaceous Materials from a Sooting Ethylene Premixed Flame with the Particle Size Magnifier
FRANCESCO CARBONE, Kevin Gleason, Juha Kangasluoma, Michel Attoui, Joonas Vanhanen, Alessandro Gomez, Yale University
Abstract Number: 98 Working Group: Combustion
Abstract The use of the Particle Size Magnifier (PSM, Airmodus Oy.) system based on diethylene glycol (DEG) condensation growth, paved the way to the measurement of neutral and charged particles and molecular clusters in the sub 3 nm dimensional range with optical counters. The preliminary application of PSM measurements to investigate nanoparticle synthesis in metal doped flames indicated that a very high fraction of sub 3nm molecular clusters are electrically charged. Confirming such a finding in a variety of conditions would assess the role of electrostatic interactions for the nucleation of particles in flames. In this study on soot inception, the PSM system is used in an extensively studied ethylene/air premixed flame. Samples were extracted at several Heights Above the Burner (HABs) via a rapid dilution and charge conditioning system developed at Yale and were classified in terms of electrical mobility using a Half-Mini Differential Mobility Analyzer. The charge-conditioned, mono-mobile samples were treated in the PSM at different levels of DEG supersaturation, to calibrate the detection efficiency of the system for flame generated carbonaceous materials of several sizes, charge state and hydrogen content. Regardless of dilution level, results at low HABs, where soot precursor molecular clusters are small and have significant hydrogen content, demonstrate that the PSM system can detect carbonaceous materials carrying a positive (negative) charge as small than 1.2nm (1.4nm) but the detection efficiency is polarity- and composition- dependent. The detection efficiency values and its polarity dependence are both reduced at larger HABs, where the flame products lost some hydrogen. The polarity dependence of the efficiency may be related to different chemical composition of materials carrying charges of opposite polarity. This type of measurements, with a systematic assessment of PSM system efficiency to detect electrically neutral materials, will allow an accurate determination of the fraction of materials being electrically charged in flames.