Soot nanoparticle sizing in counterflow flames using in-situ particle sampling and differential mobility analysis verified with two-colour time-resolved laser-induced incandescence
Fabian P. Hagen, Petros Vlavakis, Malte Seitz, Thomas Klövekorn, H. Bockhorn, Rainer Suntz, Dimosthenis Trimis
Abstract
The emphasis of this work is on the development of an intrusive particle sampling system to track the evolution of soot nanoparticles in ethylene counterflow diffusion flames. The overarching objective is to determine the mobility size distributions in a spatially resolved manner using the developed probe system coupled with differential mobility analysis, i.e., a scanning mobility particle sizer (SMPS). The probe system involves a tailor-made quartz probe, gas supply, pressure control periphery, and a traverse system enabling a precise positioning along the flame axis. In preliminary experiments, the dilution ratio of the quartz probe as function of boundary conditions as well as particle losses during intrusive particle sampling are studied. To demonstrate the capability of the developed particle sampling system, results from ethylene counterflow diffusion flames with different fuel mass fractions and strain rates are presented and compared with results derived by non-intrusive laser-based diagnostics, i.e., two-colour time-resolved laser induced incandescence (2C-TiRe-LII). Results of these experiments indicate that the particle sampling system is capable of tracking the development of particle size distributions – independent of the distribution function, i.e., mono-, bi- or multimodal shape – in counterflow flames. Likewise, the agreement between soot volume fractions and particle size distributions measured via intrusive particle sampling coupled with differential mobility analysis and non-intrusive laser-based 2C-TiRe-LII is excellent at varying the fuel mass fractions and strain rates of the ethylene counterflow flames.