管内气液螺旋环状流动可以通过设置固定叶片的旋流器形成,旋流器的结构极大地影响了形成的螺旋环状流动的稳定性。对此,选取了四种典型旋流器结构开展三个典型来流工况下螺旋环状流形成的实验研究。通过图像处理结合概率密度函数(probab...管内气液螺旋环状流动可以通过设置固定叶片的旋流器形成,旋流器的结构极大地影响了形成的螺旋环状流动的稳定性。对此,选取了四种典型旋流器结构开展三个典型来流工况下螺旋环状流形成的实验研究。通过图像处理结合概率密度函数(probability density function,PDF)拟合的方法分析了形成螺旋环状流的稳定性,同时结合液膜波动特性与旋流器内部作用过程分析发现:平板式及平板有中心柱式旋流器在不同来流工况下产生的液膜相较于螺旋叶片式A/B旋流器都更加稳定,相同工况下的失稳距离也更长,而螺旋叶片式A/B旋流器产生的螺旋环状流的稳定性较差,在更短的距离内即发生了螺旋环状流失稳现象;不同工况下液相折算速度的上升有助于提高液膜稳定性与螺旋环状流失稳距离,从而形成更稳定的螺旋环状流;叶片作用下流体内部压力梯度和气液相分布规律高度相关,压力梯度和周向速度是形成螺旋环状流动的主要因素,并且压力梯度和周向速度的大小一定程度决定了螺旋环状流动气液交界面的稳定性。展开更多
On account of limited knowledge of the breakup of power law liquid film, the process of its disintegration and atomization was studied by using a planar liquid film. A linear stability analysis was adopted to predict ...On account of limited knowledge of the breakup of power law liquid film, the process of its disintegration and atomization was studied by using a planar liquid film. A linear stability analysis was adopted to predict the breakup characteristics of the power law film. The predicting formulas of stripping breakup length and diameter of ligament were put forward presently. Through high-speed photography and laser light sheet illumination,different breakup characteristics of flat power law film under different conditions were derived. The characteristic dimension of breakup regimes were defined and extracted. The effects of several parameters(injection pressure,ambient pressure, nozzle structure and fluid property) on the stripping breakup length and spray angle were investigated. The results revealed that increasing both the velocity of liquid film and the ambient pressure facilitated the breakup of film, reduced the stripping breakup length and enlarged the spray angle in different extents. The comparison between theoretical and experimental results was conducted to validate the feasibility of the linear stability theory.展开更多
We report the epitaxial growth of YBCO （YBa2Cu3O7） films on YSZ （Yttria-stabilized Zirconia） （100） substrates by chemical solution deposition. The precursor solution was prepared by dissolving stoichiometric amo...We report the epitaxial growth of YBCO （YBa2Cu3O7） films on YSZ （Yttria-stabilized Zirconia） （100） substrates by chemical solution deposition. The precursor solution was prepared by dissolving stoichiometric amounts of acetates of Y（OOCCH3）3·4H2O, Ba（OOCCH3）2 and Cu（OOCCH3）·2H2O in an aqueous solution of oxalic acid （H2C2O4） and following the sol-gel route. This solution was directly dripped onto YSZ （100） substrates with the help of a Fisher pipette. To form the YBCO film, the sample was crystallized by annealing at 860 ℃ for 12 h in an oxidizing atmosphere. The characterization was performed by XRD （X-ray diffraction） analysis which revealed high intensity （001） reflections and denoted that most of the grains were c-axis oriented. Randomly oriented grains and other phases such as Y2BaCuO5 and CuO were also detected. The superconducting YBCO phase is demonstrated from the susceptibility versus temperature measurements which indicate a superconducting critical temperature ≈ 90 K. In addition, a surface morphology analysis was performed by optical microscopy and atomic force microscopy which revealed an average roughness of 0.2197 μm.展开更多
A heat and mass transfer model was proposed for the thin liquid film on the hot solid surface cooled by the impinging small droplets, with consideration of the effect of the droplet impact, surface tension, thermocapi...A heat and mass transfer model was proposed for the thin liquid film on the hot solid surface cooled by the impinging small droplets, with consideration of the effect of the droplet impact, surface tension, thermocapillary, evaporation/condensation, and van der Waals attraction. The nondimensional equation for predicting the evolution of the interface of the thin liquid film was derived in the presented model with the relevant boundary conditions. The stability of the thin liquid film impacted by cool small droplets is discussed.展开更多
The stability of the thin liquid film in a capillary is important to the phase-change heat transfer process in miniature or micro structures. From the basic equations for motion and heat transfer at the interface of t...The stability of the thin liquid film in a capillary is important to the phase-change heat transfer process in miniature or micro structures. From the basic equations for motion and heat transfer at the interface of the film, its stability is theoretically studied. With evaluation of the effects and relative magnitudes of various driving forces and with the use of long-wave theory in addition to linear stability analysis, the controlling equations are simplified and an evolution equation for the film’s thickness is obtained. Detailed analysis on the evolution equation shows that instability occurs first in the meniscus region and the instability condition varies with boundary conditions, geometrical scales and thermal properties. The numerical results ape well with earlier ones with some favorable extensions and improvements.展开更多
We demonstrated a method to fabricate functional hybrid film patches that were used to form Pickering emulsions （PEs）. The hybrid patches were made of carbon nanotubes, Fe3O4 nanoparticles, octadecyltrimethoxysilane...We demonstrated a method to fabricate functional hybrid film patches that were used to form Pickering emulsions （PEs）. The hybrid patches were made of carbon nanotubes, Fe3O4 nanoparticles, octadecyltrimethoxysilane, and poly（diallyldimethylammonium chloride）. The aqueous phase of the hybridpatch stabilized PEs can be easily separated by applying a magnetic field. The hybrid-film-patch stabilized PEs are extremely stable and lasted for eight months at room temperature. Furthermore, they are easily ruptured by adding ethanol, and regenerated by vortexing the patches in aqueous/oil mixtures, enabling the inner hydrophilic side of the patches to be easily modified with metal nanoparticles. As an example, palladium nanoparticles were embedded into the surface of the hybrid patches using an in situ reduction method. The Pd functionalized patch formed PEs showed an excellent catalytic performance for the hydrogenation of acetone with a yield of 99.5%. The same batch of Pd functionalized patches was recycled 13 times without loss of the catalytic activity. The hybrid-patch formed PEs have a great potential in the catalytic field.展开更多
文摘管内气液螺旋环状流动可以通过设置固定叶片的旋流器形成,旋流器的结构极大地影响了形成的螺旋环状流动的稳定性。对此,选取了四种典型旋流器结构开展三个典型来流工况下螺旋环状流形成的实验研究。通过图像处理结合概率密度函数(probability density function,PDF)拟合的方法分析了形成螺旋环状流的稳定性,同时结合液膜波动特性与旋流器内部作用过程分析发现:平板式及平板有中心柱式旋流器在不同来流工况下产生的液膜相较于螺旋叶片式A/B旋流器都更加稳定,相同工况下的失稳距离也更长,而螺旋叶片式A/B旋流器产生的螺旋环状流的稳定性较差,在更短的距离内即发生了螺旋环状流失稳现象;不同工况下液相折算速度的上升有助于提高液膜稳定性与螺旋环状流失稳距离,从而形成更稳定的螺旋环状流;叶片作用下流体内部压力梯度和气液相分布规律高度相关,压力梯度和周向速度是形成螺旋环状流动的主要因素,并且压力梯度和周向速度的大小一定程度决定了螺旋环状流动气液交界面的稳定性。
基金Supported by the National Natural Science Foundation of China(11172205,11372219,51176137)
文摘On account of limited knowledge of the breakup of power law liquid film, the process of its disintegration and atomization was studied by using a planar liquid film. A linear stability analysis was adopted to predict the breakup characteristics of the power law film. The predicting formulas of stripping breakup length and diameter of ligament were put forward presently. Through high-speed photography and laser light sheet illumination,different breakup characteristics of flat power law film under different conditions were derived. The characteristic dimension of breakup regimes were defined and extracted. The effects of several parameters(injection pressure,ambient pressure, nozzle structure and fluid property) on the stripping breakup length and spray angle were investigated. The results revealed that increasing both the velocity of liquid film and the ambient pressure facilitated the breakup of film, reduced the stripping breakup length and enlarged the spray angle in different extents. The comparison between theoretical and experimental results was conducted to validate the feasibility of the linear stability theory.
文摘We report the epitaxial growth of YBCO （YBa2Cu3O7） films on YSZ （Yttria-stabilized Zirconia） （100） substrates by chemical solution deposition. The precursor solution was prepared by dissolving stoichiometric amounts of acetates of Y（OOCCH3）3·4H2O, Ba（OOCCH3）2 and Cu（OOCCH3）·2H2O in an aqueous solution of oxalic acid （H2C2O4） and following the sol-gel route. This solution was directly dripped onto YSZ （100） substrates with the help of a Fisher pipette. To form the YBCO film, the sample was crystallized by annealing at 860 ℃ for 12 h in an oxidizing atmosphere. The characterization was performed by XRD （X-ray diffraction） analysis which revealed high intensity （001） reflections and denoted that most of the grains were c-axis oriented. Randomly oriented grains and other phases such as Y2BaCuO5 and CuO were also detected. The superconducting YBCO phase is demonstrated from the susceptibility versus temperature measurements which indicate a superconducting critical temperature ≈ 90 K. In addition, a surface morphology analysis was performed by optical microscopy and atomic force microscopy which revealed an average roughness of 0.2197 μm.
基金Project supported by the Shanghai Leading Academic Discipline Project (Grant No.Y0103).
文摘A heat and mass transfer model was proposed for the thin liquid film on the hot solid surface cooled by the impinging small droplets, with consideration of the effect of the droplet impact, surface tension, thermocapillary, evaporation/condensation, and van der Waals attraction. The nondimensional equation for predicting the evolution of the interface of the thin liquid film was derived in the presented model with the relevant boundary conditions. The stability of the thin liquid film impacted by cool small droplets is discussed.
文摘The stability of the thin liquid film in a capillary is important to the phase-change heat transfer process in miniature or micro structures. From the basic equations for motion and heat transfer at the interface of the film, its stability is theoretically studied. With evaluation of the effects and relative magnitudes of various driving forces and with the use of long-wave theory in addition to linear stability analysis, the controlling equations are simplified and an evolution equation for the film’s thickness is obtained. Detailed analysis on the evolution equation shows that instability occurs first in the meniscus region and the instability condition varies with boundary conditions, geometrical scales and thermal properties. The numerical results ape well with earlier ones with some favorable extensions and improvements.
基金This work was supported by the National Natural Science Foundation of China （Nos. 21273059 and 21003032）, State Key Laboratory of Urban Water Resource and Environment （Harbin Institute of Technology） （No. 2014DX09）, the Fundamental Research Funds for the Central Universities （No. HIT. KISTP. 201407）, and Harbin Science and Technology Research Council （No. 2014RFXXJ063）.
文摘We demonstrated a method to fabricate functional hybrid film patches that were used to form Pickering emulsions （PEs）. The hybrid patches were made of carbon nanotubes, Fe3O4 nanoparticles, octadecyltrimethoxysilane, and poly（diallyldimethylammonium chloride）. The aqueous phase of the hybridpatch stabilized PEs can be easily separated by applying a magnetic field. The hybrid-film-patch stabilized PEs are extremely stable and lasted for eight months at room temperature. Furthermore, they are easily ruptured by adding ethanol, and regenerated by vortexing the patches in aqueous/oil mixtures, enabling the inner hydrophilic side of the patches to be easily modified with metal nanoparticles. As an example, palladium nanoparticles were embedded into the surface of the hybrid patches using an in situ reduction method. The Pd functionalized patch formed PEs showed an excellent catalytic performance for the hydrogenation of acetone with a yield of 99.5%. The same batch of Pd functionalized patches was recycled 13 times without loss of the catalytic activity. The hybrid-patch formed PEs have a great potential in the catalytic field.
