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Effects of Atmospheric Pressure on Developmental Characteristics and the Stability of Air Entraining Agent for Concrete

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Journal of Wuhan University of Technology(Materials Science) 2024年第4期39卷 979-989页

作者：李立辉牛开民 TIAN Bo CHEN Xin FU Ziqian ZHU Xuwei School of Civil Engineering Chongqing Jiaotong UniversityChongqing 400074China Transportation Science and Engineering Harbin Institute of TechnologyHarbin 150090China Research Institute of Highway Ministry of TransportBeijing 100088China

In order to ascertain the effects of atmospheric pressure on developmental characteristics and the stability of AEA(air-entraining agent)solution bubbles,AEA solution experiments and AEA solution bubble experiments were,respectively,conducted in Peking(50 m,101.2 kPa)and Lhasa(3,650 m,63.1 kPa).Surface tensions and inflection-point concentrations were tested based on AEA solutions,whilst developmental characteristics,thicknesses and elastic coefficients of liquid films were tested based on air bubbles of AEA *** study involved three types of AEAs,which were TM-O,226A,and *** experimental results show that initial sizes of TM-O,226A,and 226S are,respectively,increased by 43.5%,17.5%,and 3.8%.With the decrease of ambient pressure,the drainage rate and the drainage index of AEA solution bubbles *** experiments show that the liquid film thicknesses of all tested AEA solution bubbles are in micron *** the atmospheric pressure decreases from 101.2 to 63.1 kPa,the liquid film thicknesses of three types of AEA solutions decrease in various degrees;and film elasticities at critical thicknesses *** film of 226S solution bubbles is the most stable,presenting as a minimum thickness *** should be noted that elastic coefficient of liquid film only represents the level at critical thickness,thus it can not be applied as the only evaluating indicator of bubble *** a type of AEA,factors affecting the stability of its bubbles under low atmospheric pressure include initial bubbles size,liquid film thickness,liquid film elasticity,ambient temperature,etc.

关键词： air-entraining agent surface tension bubble size liquid film thickness liquid film elasticity atmospheric pressure

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Effect of bubble morphology and behavior on power consumption in non-Newtonian fluids’aeration process

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Chinese Journal of Chemical Engineering 2024年第1期65卷 243-254页

作者： Xiemin Liu Jing Wan Jinnan Sun Lin Zhang Feng Zhang Zhibing Zhang Xinyao Li Zheng Zhou Key Laboratory of Mesoscopic Chemistry of Ministry of Education(MOE) School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China Dalian Research Institute of Petroleum and Petrochemicals SINOPECDalian 116045China

Due to a prolonged operation time and low mass transfer efficiency, the primary challenge in the aeration process of non-Newtonian fluids is the high energy consumption, which is closely related to the form and rate of impeller, ventilation, rheological properties and bubble morphology in the reactor. In this perspective, through optimal computational fluid dynamics models and experiments, the relationship between power consumption, volumetric mass transfer rate(kLa) and initial bubble size(d0) was constructed to establish an efficient operation mode for the aeration process of non-Newtonian fluids. It was found that reducing the d0could significantly increase the oxygen mass transfer rate, resulting in an obvious decrease in the ventilation volume and impeller speed. When d0was regulated within 2-5 mm,an optimal kLa could be achieved, and 21% of power consumption could be saved, compared to the case of bubbles with a diameter of 10 mm.

关键词： Non-Newtonian fluids aeration process Power consumption Volumetric mass transfer rate bubble size

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CFD-PBM simulation of bubble coalescence and breakup in top blown-rotary agitated reactor

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Journal of Iron and Steel Research(International) 2022年第2期29卷 223-236页

作者： Pin Shao Shi-xu Liu Xin-cheng Miao School of Materials and Metallurgy University of Science and Technology LiaoningAnshan114051LiaoningChina

Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for *** important models of bubble coalescence and breakup mechanisms were considered and compared,and water model experiment was carried out to verify and optimize the mathematical *** influence of different operating parameters including paddle arrangement,stirring speed and top blowing flow rate on the bubble size and distribution was *** results show that the predicted bubble size and distribution present a good agreement with the experimental results using the improved Luo–Laakkonen combination *** the position of the stirring paddle moves from the center to the side wall,the bubble distribution in the reactor becomes more uniform,and the bubble size gradually *** the increase in the paddle rotation speed,the bubble size ***,this effect begins to weaken when the paddle rotation speed exceeds 150 r/*** the top blowing flow rate will increase the bubble size in the reactor,but it has a weak effect on bubble *** the top blowing rate exceeds 2.0 m^(3)/h,the bubble size in the bath is basically not less than 5 mm.

关键词： Top blown-rotary agitated reactor bubble coalescence bubble breakup bubble size CFD-PBM Numerical simulation

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Experimental study of non-uniform bubbles in a plume

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Journal of Hydrodynamics 2022年第1期34卷 116-124页

作者： Xin-wei Ye Hao-jie Zhou Dong-dong Shao Xiao-jing Niu State Key Laboratory of Hydroscience and Engineering Department of Hydraulic EngineeringTsinghua UniversityBeijing100084China State Key Laboratory of Water Environment Simulation School of EnvironmentBeijing Normal UniversityBeijing100875China

The bubble plume is an important flow phenomenon, ubiquitous in many fields. The non-uniform bubbles in a plume are often simply considered as uniform and moving with a same slip velocity in an integral model. This study aims to have a better understanding of the behavior of the non-uniform bubbles in a plume. A set of experiments are conducted in a transparent water tank, in which the air plumes are generated through different injectors to vary the spectrum of the bubble size. The shadow images of the bubbles are simultaneously recorded with the illumination of a plane backlight. The algorithm used in the image analysis for tracing the bubbles is a newly developed multi-frame method based on the predictor-corrector method, with a good accuracy in estimating the size and the velocity of the overlapped bubbles based on the bubble shadow images. The bubbles are divided into several groups by their equivalent diameters with an interval of 0.5 mm. The spectrums of the bubble size and the void fraction are measured. It is found that the bubbles of different sizes show different dynamics features, resulting in a difference in the radial distribution. It is shown that the large bubbles gather in the center of the plume, while the medium bubbles spread the widest and even wider than the small bubbles. The difference can be explained by the effects of the transverse lift force and the amplitude of the bubble oscillation.

关键词： bubble plume experiment image analysis bubble size transverse lift force

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bubble CHARACTERISTICS IN A TWO-DIMENSIONAL VERTICALLY VIBRO-FLUIDIZED BED

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China Particuology 2005年第4期3卷 224-228页

作者： Tao Zhou Hiroyuki Kage Hongzhong Li College of Chemistry & Chemical Engineering Central South UniversityChangsha 410083 P. R. China Department of Applied Chemistry Kyushu Institute of Technology Kitakyushu 804-8550 Japan Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 P R. China

Measurement of bubble size and local average bubble rise velocity was carried out in a vertically sinusoidal vibre-fluidized bed. Glass beads of Geldart group B particles were fluidized at different gas velocities, while the bed was vibrated at different frequencies and amplitudes to study their effects on the bubble behavior. This is compared with the case of no vibration in a two-dimensional bed and it is concluded that with vibration the local average bubble size dbav, decreases significantly, especially at minimum bubbling velocity. The average bubble size increases slightly with increasing vibration frequency and amplitude. The local average bubble rise velocity is higher than that with no vibration, though with increasing vibration frequency and amplitude, it does not change significantly.

关键词： bubble size vibro-fluidized bed bubble size distribution measurement of bubble

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