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Miroslav Jicha - One of the best experts on this subject based on the ideXlab platform.
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twin fluid atomization of viscous liquids the effect of Atomizer construction on breakup process spray stability and droplet size
International Journal of Multiphase Flow, 2015Co-Authors: Marek Mlkvik, Philipp Stahle, Heike P Schuchmann, Volker Gaukel, Jan Jedelsky, Miroslav JichaAbstract: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.
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Performance of Twin-Fluid Atomizers for Atomization of Viscous Solutions
EPJ Web of Conferences, 2015Co-Authors: Marek Mlkvik, Philipp Stahle, Volker Gaukel, Jan Jedelsky, Matouš Zaremba, Miroslav JichaAbstract: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.
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investigation and comparison of spray characteristics of pressure swirl Atomizers for a small sized aircraft turbine engine
International Journal of Heat and Mass Transfer, 2014Co-Authors: Lukas Durdina, Jan Jedelsky, Miroslav JichaAbstract: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.
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development of an effervescent Atomizer for industrial burners
Energy & Fuels, 2009Co-Authors: Jan Jedelsky, Miroslav Jicha, Jaroslav Slama, Jan OtahalAbstract:The present work is conducted with the purpose of developing an effervescent Atomizer for industrial burners that will generate a fine and steady spray in large turn-down ratio. The Atomizer is fed with light heating oil (LHO) and uses air as an atomizing medium. First, a basic classification is made of the published design concepts of effervescent Atomizers investigated by different researchers. Three distinct types of such Atomizers are recognized. A single-hole, plain-orifice Atomizer with an “outside-in” gas injection configuration was chosen for this study. The basic geometric parameters that may significantly influence Atomizer performance are described. An experimental study of the effervescent Atomizer was conducted to evaluate the influence of operational conditions and that of several geometric parameters on the drop size in the spray. The Sauter mean diameter of drops was measured using a phase/Doppler particle analyzer. The study covers the size and number of aerator holes, their location, and...
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Effervescent Atomizer: influence of the internal ge ometry on atomization performance
2007Co-Authors: Jan Jedelsky, Jan Otahal, Miroslav JichaAbstract:Our work is being conducted with the aim to develop an effervescent Atomizer for industrial burners th at will generate a fine and stable spray in large turn-down ratio. The single-hole, plain orifice Atomizer is powered with light heating oil and uses air as an atomizing medi um in the "outside-in" gas injection configuration. Published design concepts of the effervescent Atomizer are de scribed. Based on the published results several des ign parameters are modified: size and number of aerator holes, the ir location and diameter of the mixing chamber. Inf luence of these parameters on spray performance is studied at atomizing pressures 0.1, 0.3 and 0.5 MPa and gas-t o-liquid-ratio (GLR) of 2, 5 and 10%. mixing system on performance of effervescent Atomizers. It is shown that optimization of the ato mizer design can improve the spray characteristics. Surpr ising diversity of design modifications can be seen in different papers. However it is not fully possible to generalize these results made for different efferve scent Atomizer concepts and for liquids of different phys ical properties (typically water). Moreover currently on ly SMD is often evaluated and other important spray parameters (spray cone angle, velocity profiles, entrainment number and mass flux) are neglected. The SMD varies with spray position and this feature is often neglected. In this study we bring an overview of de sign concepts investigated by different researchers toge ther with specification and description of important geometric parameters. Our work is being conducted with the aim to develop an effervescent Atomizer fo r industrial burners that will generate fine and stab le spray in large turn-down ratio. The single-hole, pl ain orifice Atomizer is powered with light heating oil and uses air as an atomizing medium in the "outside-in" gas injection configuration. Several design parameters are modified: size and number of aerator holes, their location and diameter of the mixing chamber. Influe nce of these parameters on the spray performance is stu died at atomizing pressures 0.1, 0.3 and 0.5 MPa and GLR of 2, 5 and 10%. A near nozzle spray visualization by digital camera illustrates the atomization process at different operation modes.
Jan Kratzer - One of the best experts on this subject based on the ideXlab platform.
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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, 2020Co-Authors: Michal Albrecht, Jiří Dědina, Martina Mrkvickova, Milan Svoboda, Jakub Hranicek, Jan Vorac, Pavel Dvořak, Jan KratzerAbstract: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%.
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preconcentration and atomization of arsane in a dielectric barrier discharge with detection by atomic absorption spectrometry
Analytical Chemistry, 2016Co-Authors: Petr Novak, Jiří Dědina, Jan KratzerAbstract: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 - One of the best experts on this subject based on the ideXlab platform.
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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, 2020Co-Authors: Michal Albrecht, Jiří Dědina, Martina Mrkvickova, Milan Svoboda, Jakub Hranicek, Jan Vorac, Pavel Dvořak, Jan KratzerAbstract: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%.
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preconcentration and atomization of arsane in a dielectric barrier discharge with detection by atomic absorption spectrometry
Analytical Chemistry, 2016Co-Authors: Petr Novak, Jiří Dědina, Jan KratzerAbstract: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...
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A sapphire tube Atomizer for on-line atomization and in situ collection of bismuthine for atomic absorption spectrometry
Journal of Analytical Atomic Spectrometry, 2013Co-Authors: Stanislav Musil, Jiří DědinaAbstract: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.
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Quartz tube Atomizers for hydride generation atomic absorption spectrometry: mechanism for atomization of arsine. Invited lecture
Journal of Analytical Atomic Spectrometry, 1992Co-Authors: Jiří Dědina, Bernhard WelzAbstract:The mechanism for the atomization of arsine was studied in externally heated quartz tube Atomizers of various designs. A continuous flow of arsine was generated either by reaction with sodium tetrahydroborate or by direct arsine sampling from a cylinder. The latter, together with precautions taken to ensure that inadvertent addition of oxygen to the system was minimized, made possible full control of the composition of the atmosphere in the Atomizer. The effect of Atomizer design, purge gas type, purge gas flow rate and Atomizer temperature on the oxygen supply required for optimum sensitivity and on the curvature of the calibration graph was investigated. An extremely low supply of oxygen is required for efficient atomization of arsine in heated Atomizers with narrow inlet arms. At sub-optimum oxygen supply flow rates, calibration graphs are curved significantly, and gradually approach a limiting absorbance, which depends on the flow rate of the oxygen if hydrogen is the main component in the purge gas. If there is an excess of argon over hydrogen in the purge gas, the calibration exhibits a roll-over. At least a slight stoichiometric excess of hydrogen over oxygen is essential for the atomization. The results of the experiments gave a deeper insight into the mechanism of radical formation involved in atomization of the hydride in quartz tube Atomizers. The influence of various experimental parameters on the cross-sectional density of hydrogen radicals in a radical cloud, which controls atomization efficiency, was established. Possibilities for improvement of analytical performance, as a consequence of the results, are discussed.
Jan Jedelsky - One of the best experts on this subject based on the ideXlab platform.
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twin fluid atomization of viscous liquids the effect of Atomizer construction on breakup process spray stability and droplet size
International Journal of Multiphase Flow, 2015Co-Authors: Marek Mlkvik, Philipp Stahle, Heike P Schuchmann, Volker Gaukel, Jan Jedelsky, Miroslav JichaAbstract: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.
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Performance of Twin-Fluid Atomizers for Atomization of Viscous Solutions
EPJ Web of Conferences, 2015Co-Authors: Marek Mlkvik, Philipp Stahle, Volker Gaukel, Jan Jedelsky, Matouš Zaremba, Miroslav JichaAbstract: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.
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investigation and comparison of spray characteristics of pressure swirl Atomizers for a small sized aircraft turbine engine
International Journal of Heat and Mass Transfer, 2014Co-Authors: Lukas Durdina, Jan Jedelsky, Miroslav JichaAbstract: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.
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development of an effervescent Atomizer for industrial burners
Energy & Fuels, 2009Co-Authors: Jan Jedelsky, Miroslav Jicha, Jaroslav Slama, Jan OtahalAbstract:The present work is conducted with the purpose of developing an effervescent Atomizer for industrial burners that will generate a fine and steady spray in large turn-down ratio. The Atomizer is fed with light heating oil (LHO) and uses air as an atomizing medium. First, a basic classification is made of the published design concepts of effervescent Atomizers investigated by different researchers. Three distinct types of such Atomizers are recognized. A single-hole, plain-orifice Atomizer with an “outside-in” gas injection configuration was chosen for this study. The basic geometric parameters that may significantly influence Atomizer performance are described. An experimental study of the effervescent Atomizer was conducted to evaluate the influence of operational conditions and that of several geometric parameters on the drop size in the spray. The Sauter mean diameter of drops was measured using a phase/Doppler particle analyzer. The study covers the size and number of aerator holes, their location, and...
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Effervescent Atomizer: influence of the internal ge ometry on atomization performance
2007Co-Authors: Jan Jedelsky, Jan Otahal, Miroslav JichaAbstract:Our work is being conducted with the aim to develop an effervescent Atomizer for industrial burners th at will generate a fine and stable spray in large turn-down ratio. The single-hole, plain orifice Atomizer is powered with light heating oil and uses air as an atomizing medi um in the "outside-in" gas injection configuration. Published design concepts of the effervescent Atomizer are de scribed. Based on the published results several des ign parameters are modified: size and number of aerator holes, the ir location and diameter of the mixing chamber. Inf luence of these parameters on spray performance is studied at atomizing pressures 0.1, 0.3 and 0.5 MPa and gas-t o-liquid-ratio (GLR) of 2, 5 and 10%. mixing system on performance of effervescent Atomizers. It is shown that optimization of the ato mizer design can improve the spray characteristics. Surpr ising diversity of design modifications can be seen in different papers. However it is not fully possible to generalize these results made for different efferve scent Atomizer concepts and for liquids of different phys ical properties (typically water). Moreover currently on ly SMD is often evaluated and other important spray parameters (spray cone angle, velocity profiles, entrainment number and mass flux) are neglected. The SMD varies with spray position and this feature is often neglected. In this study we bring an overview of de sign concepts investigated by different researchers toge ther with specification and description of important geometric parameters. Our work is being conducted with the aim to develop an effervescent Atomizer fo r industrial burners that will generate fine and stab le spray in large turn-down ratio. The single-hole, pl ain orifice Atomizer is powered with light heating oil and uses air as an atomizing medium in the "outside-in" gas injection configuration. Several design parameters are modified: size and number of aerator holes, their location and diameter of the mixing chamber. Influe nce of these parameters on the spray performance is stu died at atomizing pressures 0.1, 0.3 and 0.5 MPa and GLR of 2, 5 and 10%. A near nozzle spray visualization by digital camera illustrates the atomization process at different operation modes.
Xinrong Zhang - One of the best experts on this subject based on the ideXlab platform.
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application of atmospheric pressure dielectric barrier discharge plasma for the determination of se sb and sn with atomic absorption spectrometry
Spectrochimica Acta Part B: Atomic Spectroscopy, 2006Co-Authors: Sichun Zhang, Xinrong ZhangAbstract:Abstract The atomization of hydride-forming elements, Se, Sb and Sn, has been studied with an atmospheric pressure dielectric barrier discharge Atomizer. The elements were first converted to hydride through the reaction with NaBH4. Then the hydride were atomized in the Atomizer and detected by atomic absorption spectrometry. The effects of operational parameters such as power, gas flow rate and concentrations of HCl and NaBH4 were investigated. Compared with other hydride atomization methods, the proposed Atomizer shows the following features: (1) small size, which is preferable for the miniaturization of the total analytical system; (2) low temperature, which would be helpful for further improvement in the compactness of the total analytical system; (3) low power consumption, which is also necessary for the development of analytical instrumentation for in situ detection of environmentally important elements. The analytical performance of the Atomizer has also been investigated. The detection limits of Sb, Se and Sn obtained with the present method were 13.0, 0.6 and 10.6 μg l− 1. This detector is a very promising technique for hydride detection.
