10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Thermophoretic Collection of Soot Samples Taken from within a Co-Flow Diffusion Flame
JOCHEN A.H. DREYER, Maurin Salamanca, Jethro Akroyd, Sebastian Mosbach, Markus Kraft, University of Cambridge
Abstract Number: 740 Working Group: Combustion
Abstract Soot is the second biggest contributor to climate change after CO2 and has adverse effects on human health, making its mitigation a major field of academic and industrial research. Deepening our understanding of soot formation requires detailed information regarding the soot composition, size, and morphology as a function of fuel structure and combustion conditions. Some powerful and frequently used tools for soot characterisation are electron microscopy, Fourier-transform infrared spectroscopy (FTIR), or Raman spectroscopy. All of these techniques require soot collection under well-defined conditions to assure that the collected sample is representative of the soot in the combustion system.
Laminar flames are commonly used to study soot formation in a simplified version of real combustion systems. Soot aerosol samples from within the flame can be taken by drawing a small amount of aerosol through an orifice and immediately diluting it with an inert gas to quench chemical reactions and prevent further particle growth. Some reported methods to collect soot samples from such aerosols are filtration or micro-orifice uniform deposition impactors (MOUDI).
The aim of this work is the development of a thermophoretic nanoparticle collector that facilitates soot collection from an aerosol stream taken from within the flame. The advantage is that existing equipment for taking and diluting the sample can be used and that such a device could be used in conjunction with other devices such as a SMPS or DMS. As opposed to filtration with additional pressure drops in the sampling lines, which further increase with collection time, the thermophoretic collection does not require adjustment of the sample dilution devices. The challenge is the relatively high flow rates frequently encountered when flame samples are quenched and diluted.
Different parameters for the thermophoretic collection were explored, namely the gap separating the hot and cold plate, their temperature difference, and the sample collection time. We demonstrate how a DMS500 can be used to take samples from within a flame to measure the soot particle size distribution while a fraction of the soot is simultaneously deposited on a substrate. This approach facilitates the direct correlation between the location in the flame where the sample was taken, the measured particle size distribution, and the results obtained from characterising the collected soot layer. Such information provides valuable insight into soot composition and formation during hydrocarbon combustion.