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Jérôme Bellettre - One of the best experts on this subject based on the ideXlab platform.
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Energy analysis of secondary droplet Atomization schemes
International Communications in Heat and Mass Transfer, 2020Co-Authors: D. Antonov, N Schlegel, P.a. Strizhak, Dominique Tarlet, Jérôme BellettreAbstract:This paper presents the energy analysis of the secondary Atomization of droplets with various componentcompositions. We use the following four schemes together or separately: initial droplets colliding with eachother, interaction with a solid wall, droplet transformation due to the oncoming air flow, and micro-explosivebreakup of a droplet being heated. We consider the kinetic energies of primary (pre-Atomization) and secondary(post-Atomization) droplets and determine the heat spent on Atomization. To show the need to atomize secondarydroplets, we establish the differences between the heat released per unit time during the combustion ofprimary and secondary droplets. We also show that the least energy-consuming scheme is the one involvingdroplets colliding with each other and the most effective one in terms of fine aerosol production is the schemewith the micro-explosive droplet breakup. The latter may increase the liquid surface area more than tenfold. Theresearch findings show that the energy spent on the Atomization of fuel droplets is less than 1% of the energyreleased from their combustion. A combination of several Atomization schemes becomes more effective withlarger initial liquid droplets and their complex component composition.
Zhicun Xue - One of the best experts on this subject based on the ideXlab platform.
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Experimental study on the Atomization and particle evolution characteristics in an impinging entrained-flow gasifier
Chemical Engineering Science, 2019Co-Authors: Gong Yan, Qinghua Guo, Zhicun XueAbstract:Abstract Based on the bench-scale opposed multi-burner (OMB) impinging entrained-flow gasifier and advanced visualization apparatus, studies on the coal water slurry (CWS) Atomization process in gasifier were carried out. Morphological classification of the CWS Atomization was discussed in detail. The particle size distribution of CWS after Atomization was obtained by image processing algorithm and statistical method. The primary Atomization modes in gasifier can be divided into: Rayleigh-type breakup and superpulsating breakup. Besides, the spray angle and breakup length are negatively correlated with the oxygen-CWS relative velocity. The secondary Atomization modes can be divided into: no breakup, tensile breakup, shear breakup and synergistic breakup. The statistical analysis shows that the particle size of the CWS after Atomization show a negative correlation with the oxygen-CWS relative velocity. The greater the difference in relative velocity between oxygen and CWS, the better the Atomization effect, but excessive oxygen velocity results in reduced gasification efficiency.
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in situ Atomization and flame characteristics of coal water slurry in an impinging entrained flow gasifier
Chemical Engineering Science, 2018Co-Authors: Zhicun Xue, Qinghua Guo, Yan Gong, Yifei WangAbstract:Abstract Based on the bench-scale impinging entrained-flow gasifier with coal water slurry (CWS) as the feedstock and the development of advanced visualization techniques, the in-situ Atomization and flame characteristics of CWS were investigated. A new imaging system was applied to capture the images around the burners in the operating condition. After image post-processing, the instantaneous flame, time-averaged flame and oscillation of the flame were discussed. With the statistical method, the droplet size distribution, oscillation of the droplet concentration and time-dependent droplet size were obtained to analyze the efficiency and stability of the Atomization process. The instantaneous flame shows that the Atomization and gasification process is turbulent. The time-average CWS flame shows that the Atomization angle decreases with an increase in the ratio of elemental oxygen to elemental carbon (O/C ratio). The oscillation of the flame and the Atomization process demonstrate that in-situ Atomization is closely related to the CWS flame. The diameter and number of droplets after primary Atomization decrease with the increase of the O/C ratio. The decreases in median diameter and unconsumed CWS rate demonstrate that the increase in O/C ratio improves the efficiency of the Atomization process. The reduction in oscillation scopes of the droplet concentration and size demonstrates that the increase in O/C ratio improves the stability of the Atomization process. In addition, the droplet concentration c in three different O/C conditions is 17.8 kg·m−3, 5.9 kg·m−3 and 1.6 kg·m−3 which demonstrates that the CWS is the dilute phase in the OMB gasifier.
Jianhui Zhang - One of the best experts on this subject based on the ideXlab platform.
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Study on the Influencing Factors of the Atomization Rate in a Piezoceramic Vibrating Mesh Atomizer
Applied Sciences, 2020Co-Authors: Qiufeng Yan, Wanting Sun, Jianhui ZhangAbstract:On the basis of previous study in our research group, the phenomenon of the dynamic tapered angle was founded, the occurrence of Atomization is regarded to derive from the combined effects of the dynamic variation of the micro-tapered aperture, and the difference between forward and reverse flow resistance has been explained by both theories and experiments. It has been revealed that the main influencing factors of the Atomization rate are driving voltage, driving frequency, and so on, while the root causes of the various Atomization rates still need to be further clarified. In this paper, a micro-tapered aperture worked as a micron-sized tapered flow tube valveless piezoelectric pump in periodic variation. The working principle of such a micro-tapered aperture atomizer was analyzed in detail, and the corresponding formula of the Atomization rate was also established. Through measuring the Atomization rates at different working frequencies (f), it was established that when the f was set as 122 kHz, the Atomization rate reached a maximum value. By building the relationship between the Atomization rate and voltage at a fixed resonance frequency, it can be seen that the Atomization rate increased with the increase of driving voltage. Subsequently, in order to measure their Atomization rates, the micro-tapered apertures of three different outlet diameters were applied, so that the Atomization rate was enhanced with the increase of the micro-tapered aperture diameter. Moreover, through examining the Atomization rates at different temperatures, it was observed that the Atomization rate rose with increasing temperature; while changing the liquid concentration, the Atomization rate was also enhanced by the increase in its concentration. Apparently, the impact factors including working frequency, driving voltage, outlet diameter, temperature, and liquid concentration all exert some effects on the Atomization rate. It is worth noting that at the first stage, these influence factors indirectly work on the micro-tapered aperture structure or flow state, followed by further effects on the flow resistance. As above-mentioned, in this work, we considered that the root cause influencing the Atomization rate in a piezoceramic vibrating mesh atomizer can be attributed to the flow resistance.
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Effect of the Dynamic Cone Angle on the Atomization Performance of a Piezoceramic Vibrating Mesh Atomizer
Applied Sciences, 2019Co-Authors: Chuanyu Wu, Jianhui ZhangAbstract:In this paper, we find that the dynamic cone angle of a piezoceramic atomizer is linked to periodic changes in the volume of the micro-cone hole of the atomizer, and such changes affect Atomization performance. Firstly, we explained the theory of the dynamic cone angle inside the vibrating mesh atomizer. Then, we analyzed the flow status of liquid in the micro-cone hole, and the one-way flow Rof the liquid is caused by the difference of diffuser and nozzle flow resistance. The volume change of the micro-cone hole and the liquid chamber can produce Atomization. Furthermore, we developed the experiment to measure the Atomization rate, Atomization height, and the diameter of the atomized particles. The experiments reveal that the Atomization rate and height are much larger when the vibrating mesh atomizer is working in the forward path than in the reverse one. The Atomization rate and Atomization height increase as the working voltage increases. Meanwhile, with increasing driving voltage to the piezoceramic actuator, the Atomization particle size decrease and the atomized particle size distribution is more concentrated. Finally, the size of the micro-cone hole was measured using a microscope with different direct current (DC) voltages, further demonstrating the existence of the dynamic cone angle.
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The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer.
Sensors, 2018Co-Authors: Jianhui Zhang, Jun Huang, Ying WangAbstract:Because little is known about the Atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The Atomization mechanism of a micro-tapered aperture atomizer was described, and the Atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse Atomization rates were measured at various voltages, and the influence of the micro-tapered aperture and its variation on the Atomization rate was characterized. The resonance frequency of the piezoelectric vibrator was obtained using a laser vibrometer, and the Atomization rates were measured at each resonance frequency. From experiments, we found that the Atomization rates at the first five resonance frequencies increased as the working frequency increased. At the fifth resonance frequency (121.1 kHz), the Atomization rate was maximized (0.561 mL/min), and at the sixth resonance frequency (148.3 kHz), the Atomization rate decreased significantly (0.198 mL/min). The experimental results show that the vibration characteristics of the piezoelectric vibrator have a relatively strong impact on the Atomization rate. This research is expected to contribute to the manufacture of micro-tapered aperture atomizers.
D. Antonov - One of the best experts on this subject based on the ideXlab platform.
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Energy analysis of secondary droplet Atomization schemes
International Communications in Heat and Mass Transfer, 2020Co-Authors: D. Antonov, N Schlegel, P.a. Strizhak, Dominique Tarlet, Jérôme BellettreAbstract:This paper presents the energy analysis of the secondary Atomization of droplets with various componentcompositions. We use the following four schemes together or separately: initial droplets colliding with eachother, interaction with a solid wall, droplet transformation due to the oncoming air flow, and micro-explosivebreakup of a droplet being heated. We consider the kinetic energies of primary (pre-Atomization) and secondary(post-Atomization) droplets and determine the heat spent on Atomization. To show the need to atomize secondarydroplets, we establish the differences between the heat released per unit time during the combustion ofprimary and secondary droplets. We also show that the least energy-consuming scheme is the one involvingdroplets colliding with each other and the most effective one in terms of fine aerosol production is the schemewith the micro-explosive droplet breakup. The latter may increase the liquid surface area more than tenfold. Theresearch findings show that the energy spent on the Atomization of fuel droplets is less than 1% of the energyreleased from their combustion. A combination of several Atomization schemes becomes more effective withlarger initial liquid droplets and their complex component composition.
Yifei Wang - One of the best experts on this subject based on the ideXlab platform.
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in situ Atomization and flame characteristics of coal water slurry in an impinging entrained flow gasifier
Chemical Engineering Science, 2018Co-Authors: Zhicun Xue, Qinghua Guo, Yan Gong, Yifei WangAbstract:Abstract Based on the bench-scale impinging entrained-flow gasifier with coal water slurry (CWS) as the feedstock and the development of advanced visualization techniques, the in-situ Atomization and flame characteristics of CWS were investigated. A new imaging system was applied to capture the images around the burners in the operating condition. After image post-processing, the instantaneous flame, time-averaged flame and oscillation of the flame were discussed. With the statistical method, the droplet size distribution, oscillation of the droplet concentration and time-dependent droplet size were obtained to analyze the efficiency and stability of the Atomization process. The instantaneous flame shows that the Atomization and gasification process is turbulent. The time-average CWS flame shows that the Atomization angle decreases with an increase in the ratio of elemental oxygen to elemental carbon (O/C ratio). The oscillation of the flame and the Atomization process demonstrate that in-situ Atomization is closely related to the CWS flame. The diameter and number of droplets after primary Atomization decrease with the increase of the O/C ratio. The decreases in median diameter and unconsumed CWS rate demonstrate that the increase in O/C ratio improves the efficiency of the Atomization process. The reduction in oscillation scopes of the droplet concentration and size demonstrates that the increase in O/C ratio improves the stability of the Atomization process. In addition, the droplet concentration c in three different O/C conditions is 17.8 kg·m−3, 5.9 kg·m−3 and 1.6 kg·m−3 which demonstrates that the CWS is the dilute phase in the OMB gasifier.