First observations on break-up of particle agglomerates in shock waves

Brandt, O.; Rajathurai, A.M.; Roth, P.

doi:10.1007/bf00776178

Cited by 26 publications

(13 citation statements)

References 2 publications

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“…Note that, as pressure gradient and Re D follow a linear relationship, the figure also illustrates a correlation between fragmentation and particle kinetic energy. These observations are consistent with those made by Brandt et al (1987) and by Froeschke et al (2003). Fragmentation was not observed for SiO 2 particles.…”

Section: Phenomena Involvedsupporting

confidence: 82%

Aerosol Retention in the Vicinity of a Breach in a Tube Bundle: An Experimental Investigation

Sánchez-Velasco

Prá

Herranz

2010

Aerosol Science and Technology

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This article summarizes the main results of a bench-scale program focused on experimentally assessing the aerosol retention near the tube breach in a tube bundle. The major variables investigated were particle nature (polydispersed TiO 2 agglomerates vs. solid, monodisperse SiO 2 spheres) and Re D (0.8−2.7·10 5 ). In addition, comparisons to other data sets provided insights into the particle aerodynamic size effect on retention efficiency. Results showed that particle nature substantially affects aerosol retention in the tube bundle: mass retention efficiency was low for TiO 2 agglomerates (less than 30%) whereas it was much higher for SiO 2 particles (around 85%). Retention efficiency is also affected by Re D : its sensitivity was found to follow a log-normal behavior with a maximum retention attained at Re D near 1·105 . This evolution with Re D was similar for both types of compounds. Particle size also influences retention efficiency: the bigger the TiO 2 agglomerates the lower retention efficiency (no data were available for SiO 2 ). Among all these variables, particle nature was noted to have a prime importance for in-bundle retention, whereas Re D and particle aerodynamic size, although also affect retention efficiency, did not play such a key role. In light of the results, the presence of retention-inhibiting mechanisms such as fragmentation, resuspension or bouncing has been discussed. The data recorded will enhance the overall understanding of the governing mechanisms involved and will serve as a database against which compare model predictions. Nevertheless, further experimental data would be desirable to set up a sound database.

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Section: Phenomena Involvedsupporting

confidence: 82%

Aerosol Retention in the Vicinity of a Breach in a Tube Bundle: An Experimental Investigation

Sánchez-Velasco

Prá

Herranz

2010

Aerosol Science and Technology

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“…As an agglomerate of nanoparticles passes through the Mach disc, the rapid changes in pressure, density, and velocity across the Mach disc produce an impulse that may shatter the agglomerate into many smaller pieces. The experimental studies by Brandt et al 34 and by Strecker and Roth 60 showed that normal shock waves were very effective in reducing the average agglomerate size in a shock tube. In Brandt et al, 34 the reduction in agglomerate size was correlated to the pressure drop across the normal shock, and agglomerates consisting of 40 nm SiO 2 primary particles were fragmented to an average size of 400-500 nm when the pressure drop across the normal shock was about 0.1 MPa.…”

Section: à19mentioning

confidence: 98%

“…The experimental studies by Brandt et al 34 and by Strecker and Roth 60 showed that normal shock waves were very effective in reducing the average agglomerate size in a shock tube. In Brandt et al, 34 the reduction in agglomerate size was correlated to the pressure drop across the normal shock, and agglomerates consisting of 40 nm SiO 2 primary particles were fragmented to an average size of 400-500 nm when the pressure drop across the normal shock was about 0.1 MPa. In Strecker and Roth, 60 as the primary particles were of a larger size (325 nm), the agglomerates were primarily in the form of dimers and trimers.…”

Section: à19mentioning

confidence: 98%

“…Brandt et al 34 investigated the effect of shock waves on deagglomeration of nanopowder agglomerates in a shock-tube filled with argon. Two types of nanopowders, Degussa Aerosil OX50 and Aerosil TT600 (both silica powders, d p ¼ 40 nm, but with different bonding surface energy levels), were studied and the agglomerate sizes were measured by in situ laser scattering.…”

Section: Introductionmentioning

confidence: 99%

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Deagglomeration of nanoparticle aggregates via rapid expansion of supercritical or high‐pressure suspensions

To¹,

Davé²,

Yin³

et al. 2009

AIChE Journal

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Deagglomeration of suspensions of alumina and titania nanopowders (i.e., nanoparticle aggregates) via rapid expansion of supercritical suspensions (RESS) or high-pressure suspensions (REHPS) was studied. The size distribution of fragmented nanopowders was characterized by online Scanning Mobility Particle Spectrometer (SMPS) and Aerodynamic Particle Sizer (APS), and by offline Scanning Electron Microscopy (SEM). SMPS and SEM measurements indicate that the average agglomerate sizes were well below 1 lm, consistent with the length scales observed in our complementary RESS/REHPS mixing experiments using alumina and silica nanopowders. The APS measurements, on the other hand, were affected by reagglomeration during sampling and yielded an agglomerate size range of 1 to 3 lm. Analysis of the RESS/ REHPS process through compressible flow models revealed that both the shear stress in the nozzle and the subsequent impact of the agglomerates with the Mach disc in the free expansion region can lead to micron or sub-micron level deagglomeration. V

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“…Strongly sintered aggregates require substantial energy for segmentation, however, the severity of the reflected shock could in fact break-up large agglomerates or weakly formed aggregates [20]. This holds for all powder grades, but based on the TEM derived PSDs, such effects would statistically be more important for Fe85, yielding an APPS at the start of combustion of notably less than 85 nm and consequently even larger average surface area (and reactivity) for Fe85 c.f.…”

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confidence: 99%

Study of Oxidation and Combustion Characteristics of Iron Nanoparticles under Idealized and Enginelike Conditions

et al. 2016

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The present work includes findings from in-principle feasibility studies on iron nanopowder combustion under idealized, engine-like and real engine conditions. The study was conducted under the scope of recent interest of metallic nanoparticles as alternative fuels for Internal Combustion Engines (ICE). More specifically, Fe nanoparticles of different morphology and size were studied with respect to their oxidation characteristics via Thermo-Gravimetric Analysis (TGA), as well as in customized shock-tube, constant volume vessel and CI engine configurations.Combusted powder samples were, in all cases, examined via in-situ and ex-situ techniques for the identification of combustion products and their morphologies.Findings facilitated determination of the main phenomena involved during oxidation.The results verified that combustion of Fe nanoparticles in an engine environment is feasible. Notable differences in the morphological structure of the products formed were identified among the various oxidation/combustion techniques employed.

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First observations on break-up of particle agglomerates in shock waves

Cited by 26 publications

References 2 publications

Aerosol Retention in the Vicinity of a Breach in a Tube Bundle: An Experimental Investigation

Aerosol Retention in the Vicinity of a Breach in a Tube Bundle: An Experimental Investigation

Deagglomeration of nanoparticle aggregates via rapid expansion of supercritical or high‐pressure suspensions

Study of Oxidation and Combustion Characteristics of Iron Nanoparticles under Idealized and Enginelike Conditions

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