Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements

R. Tischendorf, M. Bieber, R. Kneer, H.-J. Schmid, in: PARTEC 2019 International Congress on Particle Technology, 2019.

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Abstract
Nanoparticle synthesis based on flame spray pyrolysis represents a high potential method for designed nanoparticles with unique properties. For this process, it is not yet sufficiently understood whether and to what extent the atomization of the precursor mixture influences the local reaction conditions within the flame – and subsequent particle formation. Within the research program SPP1980, the influence of atomization on particle formation in spray flames is investigated by the cooperation of three research groups from different disciplines. The numerical and experimental investigation of jet disintegration and droplet formation is part of the WSA and the ITV from University Aachen - thus, the local temperature, concentration and velocity fields within the spray flame are determined, which form the groundwork for the particle formation. Based on this, our chair from University Paderborn investigates the fundamental correlations of particle formation within the spray flame. Therefore, the spatial change in particle properties such as size distributions or particles fractal dimensions within the flame is both numerically calculated and experimentally determined. Our numerical investigations of particle formation must include kinetics for the simultaneously appearing phenomena of nucleation, aggregation, sintering, and growth along the flame. Therefore, Lagrange approaches, population balances, and Monte Carlo simulations are used to calculate particle size distributions and particle structures. It is expected, that our numerical calculation will represent a realistic predictive model for particle formation in turbulent spray flames. To proof our investigations, a flame spray system was set up which is able to experimentally determine the particle properties along the flame. Thereby a special challenge is to take representative samples from the flame, tailored for the respective measurement method. In a first approach, SMPS measurements are used to investigate the evolution of the particle size distributions as well as HR-TEM measurements for particle structure analysis. Since the high temperatures and particle number concentrations, the extraction of a representative SMPS sample is challenging. Due to agglomeration and reaction, the particle properties along the measuring section can change abruptly within a few milliseconds. For the detection of particle size distributions, both a hole in a tube system and a straight tube system were used and compared allowing a high and fast sample dilution. For HR-TEM measurement, there are two major challenges in the extraction of thermophoresis samples. First, the sample should be taken at a defined location. For this requirement, the sampling grid should be protected along the way to the sample position by a shuttering technique. Thus, both a mechanical and an electronic shuttering system were build up and compared. Second, an adequate exposure time must be adhered in order to enable correct image evaluation. By setting the parameters of our shutter systems, a simple manipulation of the sampling time is possible. In order to determine the flame disturbance from SMPS and HR-TEM sampling, the combustion chamber is equipped with six optical ports allowing an in-situ examination of the flame structure by shadowgraphy and schlieren technique. In our presentation, first experimental and numerical results describing particle formation in spray flames are compared. Doing this, the particle size distributions and fractal structures are shown at various positions within the flame. By comparing different sampling methods, the experimental results are critically examined. It is expected, to have first investigations showing a correlation between jet disintegration, local flame reaction conditions and particle properties.
Publishing Year
Conference
PARTEC 2019 International Congress on Particle Technology
Conference Location
Nürnberg
Conference Date
2019-09-04 – 2019-04-11
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Tischendorf R, Bieber M, Kneer R, Schmid H-J. Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements. In: PARTEC 2019 International Congress on Particle Technology; 2019.
Tischendorf, R., Bieber, M., Kneer, R., & Schmid, H.-J. (2019). Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements. PARTEC 2019 International Congress on Particle Technology, Nürnberg.
@inproceedings{Tischendorf_Bieber_Kneer_Schmid_2019, title={Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements}, publisher={PARTEC 2019 International Congress on Particle Technology}, author={Tischendorf, Ricardo and Bieber, M. and Kneer, R. and Schmid, H.-J.}, year={2019} }
Tischendorf, Ricardo, M. Bieber, R. Kneer, and H.-J. Schmid. “Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements.” PARTEC 2019 International Congress on Particle Technology, 2019.
R. Tischendorf, M. Bieber, R. Kneer, and H.-J. Schmid, “Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements,” presented at the PARTEC 2019 International Congress on Particle Technology, Nürnberg, 2019.
Tischendorf, Ricardo, et al. Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements. PARTEC 2019 International Congress on Particle Technology, 2019.
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