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Miroslav Jicha – 1st expert on this subject based on the ideXlab platform

  • twin fluid atomization of viscous liquids the effect of Atomizer construction on breakup process spray stability and droplet size
    International Journal of Multiphase Flow, 2015
    Co-Authors: Marek Mlkvik, Philipp Stahle, Heike P Schuchmann, Volker Gaukel, Jan Jedelsky, Miroslav Jicha

    Abstract:

    Abstract This study focuses on the low-pressure spraying of viscous liquids ( μ
     = 60, 147 and 308 mPa s) using four types of internal-mixing twin-fluid Atomizers. We compare two well-known designs, namely the Y-jet and “outside in gas” (OIG) effervescent Atomizers, with our new design (CFT) and an “outside in liquid” (OIL) configuration for the effervescent Atomizer. The Atomizers were operated by two gas inlet pressures (0.14 and 0.28 MPa) and various gas-to-liquid ratios (GLR = 2.5%, 5%, 10% and 20%). The comparison focused on internal liquid–gas flow, spray stability, primary breakup, and droplet size. The primary breakup was investigated using a high-speed camera. A near-nozzle spray pattern was related to the ratio of forces, which affects liquid deformation, by dimensionless numbers. The breakup was driven mainly by air resistance in the OIG, OIL, and CFT Atomizers and by surface tension in the Y-jet Atomizer. The OIL and Y-jet Atomizers provided the most stable spray, regardless of the working regime or atomized liquid. The OIL Atomizer produced the smallest droplets at low GLRs, while the droplet sizes for the Y-jet Atomizer increased significantly at low GLRs. For the OIG Atomizer, spray stability was influenced by the GLR, with the best stability being achieved at a GLR of 10% and 20%. The presence of large droplets at a low GLR caused an increase in droplet size. Switching the inlet ports of the effervescent Atomizer (OIG–OIL) affected the internal flow, which differed under the same working regimes for these two configurations. The internal flow pattern of the OIL Atomizer was estimated to be annular for all regimes, while for the OIG Atomizer, it changed from a plug to slug flow with an increase in the GLR.

  • Performance of Twin-Fluid Atomizers for Atomization of Viscous Solutions
    EPJ Web of Conferences, 2015
    Co-Authors: Marek Mlkvik, Philipp Stahle, Volker Gaukel, Jan Jedelsky, Matouš Zaremba, Miroslav Jicha

    Abstract:

    Presented paper deals with a comparison of two internally mixing twin fluid Atomizers. The well – known Y- jet Atomizer and so called outside-in-liquid effervescent Atomizer (OUIL) were investigated. The working regimes were defined by the pressure drop (Dp) and the gas to the liquid ratio (GLR). The internal and the external two-phase flows of both Atomizers were studied. The influence of the mixing mechanism on the internal flow was evaluated by the gas to the liquid momentum ratio (F). In advance, the stability of the separated flow (liquid film) was examined in term of the critical wavelength of the surface disturbances (lc). The external flow was observed by the high – speed camera. The influence of the basic forces on the deformation of the liquid was determined by a dimensionless criterion w·m / s. The values of F 3, where the liquid momentum overcomes the gas momentum. The values of w·m / s > 20 for both Atomizers indicates the dominant influence of the viscosity and the drag force on the breakup process.

  • investigation and comparison of spray characteristics of pressure swirl Atomizers for a small sized aircraft turbine engine
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Lukas Durdina, Jan Jedelsky, Miroslav Jicha

    Abstract:

    Abstract The quality of liquid fuel atomization highly affects the formation of gaseous pollutants and particulate matter emissions from combustion processes. Spray characteristics of two geometrically different pressure-swirl Atomizers for a turbojet engine in light aircraft were measured on a cold test bench. A spill-return Atomizer and its intended replacement simplex Atomizer were investigated using Particle Image Velocimetry (PIV) and Phase-Doppler Anemometry (PDA). Single-camera and stereoscopic PIV measurements yielded velocity distributions in the axial cross-section of the spray cone. PDA measurements provided drop-size distribution and axial velocity data. Acquired results reveal significant differences in spray characteristics of the nozzles investigated at the same fuel injection pressures. The simplex nozzle produced spray with Sauter mean diameters lower by 5–20 μm depending on the regime, its spray was more stable but its shape greatly varied with fuel injection pressure. These differences are discussed in detail, their analysis indicate a potential for spray improvement provided by the novel Atomizer design and elucidates the possible impact of the nozzle replacement on the combustion process.

Jan Kratzer – 2nd expert on this subject based on the ideXlab platform

  • atomization of lead hydride in a dielectric barrier discharge Atomizer optimized for atomic absorption spectrometry and studied by laser induced fluorescence
    Spectrochimica Acta Part B: Atomic Spectroscopy, 2020
    Co-Authors: Michal Albrecht, Jiří Dědina, Martina Mrkvickova, Milan Svoboda, Jakub Hranicek, Jan Vorac, Pavel Dvořak, Jan Kratzer

    Abstract:

    Abstract Atomization of lead hydride in a plane-parallel volume dielectric barrier discharge (DBD) Atomizer coupled to a high voltage power supply source with sinusoidal waveform (28.5 kHz) was optimized with detection by atomic absorption spectrometry. Argon was found as the best discharge gas under a flow rate of 175 mL min−1 while the DBD optimum peak-to-peak high voltage was 25 kV. The performance of the novel DBD Atomizer was compared to that of a conventional externally heated quartz tube Atomizer (QTA) operating at 900 °C and 100 mL min−1 Ar carrier gas flow rate. Sensitivity and limit of detection (LOD) in QTA reached 0.21 s ng−1 Pb and 0.6 ng mL−1 Pb, respectively, while they reached 0.04 s ng−1 Pb and 2.3 ng mL−1 Pb in DBD. Laser-induced fluorescence (LIF) was employed to investigate the spatial distribution of free Pb atoms as well as to quantify lead hydride atomization efficiency in both Atomizers. Free Pb atoms were present only in a central region of DBD Atomizer. Atomization efficiency of lead hydride was quantified by LIF to be 23 ± 7%. On the contrary, free Pb atoms were distributed homogeneously along the whole optical arm in the QTA with atomization efficiency reaching 88 ± 18%.

  • preconcentration and atomization of arsane in a dielectric barrier discharge with detection by atomic absorption spectrometry
    Analytical Chemistry, 2016
    Co-Authors: Petr Novak, Jiří Dědina, Jan Kratzer

    Abstract:

    Atomization of arsane in a 17 W planar quartz dielectric barrier discharge (DBD) Atomizer was optimized, and its performance was compared to that of a multiple microflame quartz tube Atomizer (MMQTA) for atomic absorption spectrometry (AAS). Argon, at a flow rate of 60 mL min–1, was the best DBD discharge gas. Free As atoms were also observed in the DBD with nitrogen, hydrogen, and helium discharge gases but not in air. A dryer tube filled with NaOH beads placed downstream from the gas–liquid separator to prevent residual aerosol and moisture transport to the Atomizer was found to improve the response by 25%. Analytical figures of merit were comparable, reaching an identical sensitivity of 0.48 s ng –1 As in both Atomizers and limits of detection (LOD) of 0.15 ng mL–1 As in MMQTA and 0.16 ng mL–1 As in DBD, respectively. Compared to MMQTA, DBD provided 1 order of magnitude better resistance to interference from other hydride-forming elements (Sb, Se, and Bi). Atomization efficiency in DBD was estimated to…

Jiří Dědina – 3rd expert on this subject based on the ideXlab platform

  • atomization of lead hydride in a dielectric barrier discharge Atomizer optimized for atomic absorption spectrometry and studied by laser induced fluorescence
    Spectrochimica Acta Part B: Atomic Spectroscopy, 2020
    Co-Authors: Michal Albrecht, Jiří Dědina, Martina Mrkvickova, Milan Svoboda, Jakub Hranicek, Jan Vorac, Pavel Dvořak, Jan Kratzer

    Abstract:

    Abstract Atomization of lead hydride in a plane-parallel volume dielectric barrier discharge (DBD) Atomizer coupled to a high voltage power supply source with sinusoidal waveform (28.5 kHz) was optimized with detection by atomic absorption spectrometry. Argon was found as the best discharge gas under a flow rate of 175 mL min−1 while the DBD optimum peak-to-peak high voltage was 25 kV. The performance of the novel DBD Atomizer was compared to that of a conventional externally heated quartz tube Atomizer (QTA) operating at 900 °C and 100 mL min−1 Ar carrier gas flow rate. Sensitivity and limit of detection (LOD) in QTA reached 0.21 s ng−1 Pb and 0.6 ng mL−1 Pb, respectively, while they reached 0.04 s ng−1 Pb and 2.3 ng mL−1 Pb in DBD. Laser-induced fluorescence (LIF) was employed to investigate the spatial distribution of free Pb atoms as well as to quantify lead hydride atomization efficiency in both Atomizers. Free Pb atoms were present only in a central region of DBD Atomizer. Atomization efficiency of lead hydride was quantified by LIF to be 23 ± 7%. On the contrary, free Pb atoms were distributed homogeneously along the whole optical arm in the QTA with atomization efficiency reaching 88 ± 18%.

  • preconcentration and atomization of arsane in a dielectric barrier discharge with detection by atomic absorption spectrometry
    Analytical Chemistry, 2016
    Co-Authors: Petr Novak, Jiří Dědina, Jan Kratzer

    Abstract:

    Atomization of arsane in a 17 W planar quartz dielectric barrier discharge (DBD) Atomizer was optimized, and its performance was compared to that of a multiple microflame quartz tube Atomizer (MMQTA) for atomic absorption spectrometry (AAS). Argon, at a flow rate of 60 mL min–1, was the best DBD discharge gas. Free As atoms were also observed in the DBD with nitrogen, hydrogen, and helium discharge gases but not in air. A dryer tube filled with NaOH beads placed downstream from the gas–liquid separator to prevent residual aerosol and moisture transport to the Atomizer was found to improve the response by 25%. Analytical figures of merit were comparable, reaching an identical sensitivity of 0.48 s ng –1 As in both Atomizers and limits of detection (LOD) of 0.15 ng mL–1 As in MMQTA and 0.16 ng mL–1 As in DBD, respectively. Compared to MMQTA, DBD provided 1 order of magnitude better resistance to interference from other hydride-forming elements (Sb, Se, and Bi). Atomization efficiency in DBD was estimated to…

  • A sapphire tube Atomizer for on-line atomization and in situ collection of bismuthine for atomic absorption spectrometry
    Journal of Analytical Atomic Spectrometry, 2013
    Co-Authors: Stanislav Musil, Jiří Dědina

    Abstract:

    Sapphire was tested as a new material for volatile species Atomizers. Bismuthine was chosen as a convenient model for volatile species. The fundamental approach adopted was to compare the performance of a sapphire-based Atomizer with a quartz Atomizer in both modes of operation (on-line atomization versus in situ collection) under equal experimental conditions including design and size of both Atomizers. Only the temperature range compatible with the quartz Atomizers (up to 1000 °C) was investigated. The employment of the modular Atomizer design made it possible to comply with the principal requirement of the same design and size of both Atomizers: both the Atomizers differed only in the material of the exchangeable optical tube (a plain tube with a central orifice). No significant difference between quartz and sapphire regarding atomization as well as in situ collection was found and virtually the same analytical characteristics were achieved. Excess of O2 over H2 was employed for efficient trapping and efficient and very fast volatilization was achieved by means of auxiliary H2. Under optimized conditions the collection efficiencies of 97 ± 3% and 94 ± 4% were achieved for the sapphire and quartz tube, respectively, and the limits of detection of around 30 pg ml−1 were achieved for 1 ml sample volume. The advantages and future prospects of the use of the sapphire tube are highlighted and discussed.