Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

Wißdorf, Walter; Müller, David; Brachthäuser, Yessica; Langner, Markus; Derpmann, Valerie; Klopotowski, Sebastian; Polaczek, Christine; Kersten, Hendrik; Brockmann, Klaus J.; Benter, Thorsten

doi:10.1007/s13361-016-1415-z

Cited by 24 publications

(35 citation statements)

References 31 publications

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“…A proposed empirical correlation from [Sandia, 2009] underestimates the flow rate by a factor of 5. However, an empirical correlation found in [Wißdorf 2016] appears to be in good agreement with measurements.…”

Section: Progress Report On Model Development For the Transport Of Aerosol Through Microchannelssupporting

confidence: 68%

Progress Report on Model Development for the Transport of Aerosol Through Microchannels

Chatzidakis¹

2020

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Accuracy of consequence assessments could be improved by accounting for the leak path deposition of aerosol in the source term. Recent experimental measurements from Sandia (2018) provided evidence of partial microchannel plugging due to particulate deposition. This filtration effect is relevant to the source term assessments and it is not unreasonable to anticipate that aerosol deposition in more realistic geometries could even lead to complete plugging of the leak path. This report summarizes current progress (as of end of Q3 FY 2020) on the development of a phenomenological model of aerosol transport, deposition, and plugging through microchannels. The purpose is to introduce a generic, reliable numerical model for the prediction of aerosol transport, deposition, and plugging in leak paths while accounting for potential plugging formation. This report includes (1) an overview of recent additions and improvements on the recently developed numerical model to analyze the various deposition processes in leak paths, to provide quantitative estimates of penetration factors, and to gain an understanding of the variables that affect them and (2) a summary of recent benchmarking results of the model's validity with recent experimental measurements from Sandia.It is found that aerosol deposition on canister walls would occur from a cloud with homogeneous distribution due to thermal flow convection and is only possible when the particles penetrate into the stagnant boundary layer in contact with the walls. Typically, larger particles (>1 μm) are removed by gravitation deposition whereas smaller particles (<0.1 μm) deposit due to diffusive deposition. A temperature difference of 0.01 o C in a canister with an effective wall length of four meters is capable of keeping an aerosol cloud consisting of particles smaller than 20 μm homogenously distributed inside the canister. This is a direct consequence of the large difference between convective flow velocity, in the order of 10-20 cm/s or higher, and particle's settling velocity which is several orders of magnitude lower (~10 -3 cm/s).Further, it is shown that within enclosure volumes within range of typical canisters, a homogeneously distributed monodisperse aerosol will decay exponentially due to gravitational settling with a decay constant for particles of 1 μm aerodynamic diameter is 0.02 hr -1 and a half-life of 34.6 hrs. For 0.1 μm aerodynamic diameter the decay constant is 0.002 hr -1 with a half-life of 346 hrs. Similarly, for 10 μm aerodynamic diameter, the decay constant is 0.2 hr -1 with a half-life of 3.46 hrs. Coagulation and diffusive deposition are expected to decrease these times even further.

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Section: Progress Report On Model Development For the Transport Of Aerosol Through Microchannelssupporting

confidence: 68%

Progress Report on Model Development for the Transport of Aerosol Through Microchannels

Chatzidakis¹

2020

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“…For selected heights above the burner, the capillary was modeled as a plug-flow reactor (PFR) with an imposed temperature profile corresponding to the radial distribution of temperature inferred from the bidimensional temperature map, and inlet conditions corresponding to those calculated using the impinging jet approach described above. The flow rate inside the PFR was calculated at each height above the burner using the correlation given for a turbulent flow inside the capillary given in Wißdorf et al 49 .…”

Section: Methodsmentioning

confidence: 99%

Insight into the Ozone-Assisted Low-Temperature Combustion of Dimethyl Ether by Means of Stabilized Cool Flames

et al. 2021

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The low-temperature combustion kinetics of dimethyl ether (DME) were studied by means of stabilized cool flames in a heated stagnation plate burner configuration, using ozone-seeded premixed flows of DME/O 2 . Direct imaging of CH 2 O* chemiluminescence and Laser Induced Fluorescence of CH 2 O were used to determine flame front positions in a wide range of lean and ultra-lean equivalence ratios and ozone concentrations, for two strain rates. Temperature and species mole fraction profiles along the flame were measured coupling thermocouples, gas chromatography, micro-chromatography and quadrupole mass spectrometry analysis. A new kinetic model was built on the basis of the Aramco 1.3 model, coupled with a validated submechanism of O 3 chemistry, and was updated to improve the agreement with the obtained experimental results and experimental data available in the literature. Main results show the efficiency of the tested model to predict the flame front position and temperature in every tested condition, as well as the importance of reactions typical of atmospheric chemistry in the prediction of cool flame occurrence. The agreement on the fuel and major products is overall good, except for methanol, highlighting some missing kinetic pathways for the DME/O 2 /O 3 system, possibly linked to the direct addition of atomic oxygen on the fuel radical, modifying the products distribution after the cool flame.

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“…To model the gas flow through the PCF we assume a turbulent, isothermal gas flow through the core that resembles the flow of a compressible gas through a cylindrical pipe with diameter d and length L [27]. In this regime the different gas pressures at the entrance and exit of the NC-PCF, P 0 and P L , lead to a longitudinal pressure profile along the spatial coordinate z, which can be approximated as Pz ≈ P 0 z∕LP 2 L − P 2 0 1∕2 .…”

Section: A Methodsmentioning

confidence: 99%

Quasi-phase-matched high-harmonic generation in gas-filled hollow-core photonic crystal fiber

Wiegandt

Anderson

et al. 2019

Optica

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High-order harmonic generation (HHG) provides a promising tabletop source of coherent short wavelength radiation. However, the low generation efficiency limits the mean photon flux of HHG sources when driven with low average power, kHz repetition rate lasers. The HHG flux could be increased by employing MHz repetition rate driving lasers. However, the low pulse energy necessitates tight focusing, which limits the effective interaction volume. Generating harmonics in a gas-filled photonic crystal fiber (PCF) mitigates this problem, but for both free focus and PCF targets, the HHG conversion efficiency is optimized at technologically challenging multibar gas pressures. Here, we perform HHG with μJ-level driving pulses in a hollow-core PCF. We observe dramatic 60-fold enhancement of the HHG flux through a time-multiplexed multimodal quasi-phase-matching technique at low gas pressures. We also observe high harmonic photon energies up to 61.6 eV with continuous spectral tunability made possible by controlled ionization-induced blue shifting of the driving laser. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

Cited by 24 publications

References 31 publications

Progress Report on Model Development for the Transport of Aerosol Through Microchannels

Progress Report on Model Development for the Transport of Aerosol Through Microchannels

Insight into the Ozone-Assisted Low-Temperature Combustion of Dimethyl Ether by Means of Stabilized Cool Flames

Quasi-phase-matched high-harmonic generation in gas-filled hollow-core photonic crystal fiber

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