Based on the linear instability analysis, the study on the relationship between breakup modes and gas-liquid interfaces of a viscous annular liquid jet moving in two swirling gas streams has been car- ried out. From t...Based on the linear instability analysis, the study on the relationship between breakup modes and gas-liquid interfaces of a viscous annular liquid jet moving in two swirling gas streams has been car- ried out. From the numerical results of the dispersion equation, the relevancy of the breakup mode between an annular liquid jet and two liquid jets of limiting cases, namely the cylindrical liquid jet and hollow gas jet, as well as the effects of injecting factors on the instability of an annular liquid jet, is studied in detail. Considering the effects of inner and outer interface radii on the instability of the jet, it is proved that the para-sinuous mode mainly relates to the inner interface, whereas the para-varicose mode mainly relates to the outer interface. The results also indicate that all the forces produced by liquid jet have similar impacts on either the instability of para-sinuous mode or para-varicose mode due to the fact that they can affect both inner and outer gas-liquid interfaces. On the other hand, all the forces exerting only on the inner interface have more powerful effects on the instability of para-sinuous mode, and all the forces exerting only on the outer interface have more powerful effects on the insta- bility of para-varicose mode. That is to say, the effects of forces are weakened greatly when penetrating the liquid jet.展开更多
The experimental investigation on a liquid-liquid spray process by dispersing water in corn oil was conducted.The drop formation in the spraying process was observed through analyzing photographs from camera.The obser...The experimental investigation on a liquid-liquid spray process by dispersing water in corn oil was conducted.The drop formation in the spraying process was observed through analyzing photographs from camera.The observation showed that with increase of electrostatic voltage,the drop formation presented a dripping mode as well as cloudy spraying mode in turn and the drops displayed different characteristics in pattern and movement under two kinds of modes.The existing condition and the characteristics of two modes were presented.The quantitative analysis of spraying droplet diameter distributions was performed at different voltages by means of particle image analyzer and the theory of spraying droplet distribution.The result showed that for liquid-liquid electrostatic spray,the droplet size distribution could be mathematically described by Rosin-Rammler distribution.With increase of voltage,the droplet became fine in size and uniform in size distribution.Comparing with water-in-gas spray,the probability density function curve for droplet size distribution was not symmetrical with respect to its peak value,viz,the diameter distribution for the relatively smaller droplets was narrower than that for other larger droplets.With increase of voltage,the distribution for larger droplets became narrow and the curve shape of probability density function became nearly symmetric.展开更多
In order to reduce or avoid the fluctuations from interface breakup, a meandering microchannel with curved multi-bends(44 turns) is fabricated, and investigations of scaling bubble/slug length in Taylor flow in a rect...In order to reduce or avoid the fluctuations from interface breakup, a meandering microchannel with curved multi-bends(44 turns) is fabricated, and investigations of scaling bubble/slug length in Taylor flow in a rectangular meandering microchannel are systematically conducted. Based on considerable experimental data,quantitative analyses for the influences of two important characteristic times, liquid phase physical properties and aspect ratio are made on the prediction criteria for the bubble/slug length of Taylor flow in a meandering microchannel. A simple principle is suggested to predict the bubble formation period by using the information of Rayleigh time and capillary time for six gas–liquid systems with average deviation of 10.96%. Considering physical properties of the liquid phase and cross-section configuration of the rectangular mcirochannel,revised scaling laws for bubble length are established by introducing Ca, We, Re and W/h whether for the squeezing-driven or shearing-driven of bubble break. In addition, a simple principle in terms of Garstecki-type model and bubble formation period is set-up to predict slug lengths. A total of 107 sets of experimental data are correlated with the meandering microchannel and operating range: 0.001 b CaTPb 0.05, 0.06 b WeTPb 9.0,18 b ReTPb 460 using the bubble/slug length prediction equation from current work. The average deviation between the correlated data and the experimental data for bubble length and slug length is about 9.42% and9.95%, respectively.展开更多
基金the Natural Science Foundation of Tianjin (Grant Nos. 05YFJMJC11100 and 07JCYBJC03900)
文摘Based on the linear instability analysis, the study on the relationship between breakup modes and gas-liquid interfaces of a viscous annular liquid jet moving in two swirling gas streams has been car- ried out. From the numerical results of the dispersion equation, the relevancy of the breakup mode between an annular liquid jet and two liquid jets of limiting cases, namely the cylindrical liquid jet and hollow gas jet, as well as the effects of injecting factors on the instability of an annular liquid jet, is studied in detail. Considering the effects of inner and outer interface radii on the instability of the jet, it is proved that the para-sinuous mode mainly relates to the inner interface, whereas the para-varicose mode mainly relates to the outer interface. The results also indicate that all the forces produced by liquid jet have similar impacts on either the instability of para-sinuous mode or para-varicose mode due to the fact that they can affect both inner and outer gas-liquid interfaces. On the other hand, all the forces exerting only on the inner interface have more powerful effects on the instability of para-sinuous mode, and all the forces exerting only on the outer interface have more powerful effects on the insta- bility of para-varicose mode. That is to say, the effects of forces are weakened greatly when penetrating the liquid jet.
文摘在实验的基础上,基于RNG k-ε模型对常压下气体中心式同轴离心(gas-centered swirl coaxial,GCSC)喷嘴喷雾形态和破碎模式进行了三维仿真研究。采用网格自适应加密(adaptive mesh refinement,AMR)技术、耦合水平集和流体体积(coupled level-set and volume of fluid,CLSVOF)方法对气液界面进行捕捉。结果表明,液体质量流率(m_(l))不变,随着气体质量流率(m_(g))的增加,中心气流的引射作用增强,液膜内外压差增大,雾化锥角减小,并对其流动特性进行了分析;而m_(g)不变时,液膜在喷嘴出口的径向速度与切向速度随m_(l)的增大而增大,导致雾化锥角增大。同时根据气液质量流率比(gas-liquid mass flow rate,GLR),将喷雾的破碎模式分为穿孔破碎、气泡破碎和气动破碎。
文摘The experimental investigation on a liquid-liquid spray process by dispersing water in corn oil was conducted.The drop formation in the spraying process was observed through analyzing photographs from camera.The observation showed that with increase of electrostatic voltage,the drop formation presented a dripping mode as well as cloudy spraying mode in turn and the drops displayed different characteristics in pattern and movement under two kinds of modes.The existing condition and the characteristics of two modes were presented.The quantitative analysis of spraying droplet diameter distributions was performed at different voltages by means of particle image analyzer and the theory of spraying droplet distribution.The result showed that for liquid-liquid electrostatic spray,the droplet size distribution could be mathematically described by Rosin-Rammler distribution.With increase of voltage,the droplet became fine in size and uniform in size distribution.Comparing with water-in-gas spray,the probability density function curve for droplet size distribution was not symmetrical with respect to its peak value,viz,the diameter distribution for the relatively smaller droplets was narrower than that for other larger droplets.With increase of voltage,the distribution for larger droplets became narrow and the curve shape of probability density function became nearly symmetric.
基金Supported by the National Natural Science Foundation of China(21476037,21606034).
文摘In order to reduce or avoid the fluctuations from interface breakup, a meandering microchannel with curved multi-bends(44 turns) is fabricated, and investigations of scaling bubble/slug length in Taylor flow in a rectangular meandering microchannel are systematically conducted. Based on considerable experimental data,quantitative analyses for the influences of two important characteristic times, liquid phase physical properties and aspect ratio are made on the prediction criteria for the bubble/slug length of Taylor flow in a meandering microchannel. A simple principle is suggested to predict the bubble formation period by using the information of Rayleigh time and capillary time for six gas–liquid systems with average deviation of 10.96%. Considering physical properties of the liquid phase and cross-section configuration of the rectangular mcirochannel,revised scaling laws for bubble length are established by introducing Ca, We, Re and W/h whether for the squeezing-driven or shearing-driven of bubble break. In addition, a simple principle in terms of Garstecki-type model and bubble formation period is set-up to predict slug lengths. A total of 107 sets of experimental data are correlated with the meandering microchannel and operating range: 0.001 b CaTPb 0.05, 0.06 b WeTPb 9.0,18 b ReTPb 460 using the bubble/slug length prediction equation from current work. The average deviation between the correlated data and the experimental data for bubble length and slug length is about 9.42% and9.95%, respectively.
