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Novel flow behaviors induced by a solid particle in nanochannels: Poiseuille and Couette

Chinese Science Bulletin 2014年第20期59卷 2478-2485页

作者： Cheng-Zhen Sun Wen-Qiang Lu Bo-Feng Bai Jie Liu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University College of Physical Sciences University of Chinese Academy of Sciences

We conducted a molecular dynamics(MD)simulation to address the novel flow behaviors induced by a solid particle in *** basic flows,i.e.,Poiseuille and Couette,are involved in this *** Poiseuille flow,the distribution of number density exhibits fluctuations in the center of channel and near the walls,which are caused by the strong interactions from the atoms of particle and *** stronger external driving forces,the fluid atoms move toward the center of channel and some cavities appear in the fluidic *** external driving forces and bigger particles make the fluid moving quickly in *** Couette flow,the particle rotates under the velocity difference among particle atoms in the shear *** fluid atoms near the walls become infrequent and move to the center of *** velocities of the centrally-located fluid atoms decrease owing to the particle,resulting in an untypical non-linear Couette *** summary,the solid particle brings new fluid–solid interface and interactions,which induce several novel behaviors in nanochannel flows.

关键词：流动行为纳米通道固体粒子 Poiseuille流诱发 Couette流强相互作用固体颗粒

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Hydrogen production by catalytic gasification of cellulose in supercritical water

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Frontiers of Chemical Science and engineering 2008年第2期2卷 176-180页

作者： Yu GUAN Aixia PEI Liejin GUO State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Cellulose,one of the important components of biomass,was gasified in supercritical water to produce hydrogen-rich gas in an autoclave which was operated batch-wise under high-pressure.K_(2)CO_(3) and Ca(OH)2 were selected as the catalysts(or promoters).The temperature was kept between 450uC and 500uC while pressure was maintained at 24–26 *** reaction time was 20 *** results showed that the two catalysts had good catalytic effect and optimum amounts were observed for each *** 0.2 g K_(2)CO_(3) was added,the hydrogen yield could reach 9.456 mol?kg21 which was two times of the H2 amount produced without *** 1.6 g Ca(OH)2 was added,the H2 yield was 8.265 mol?kg21 which is lower than that obtained using K_(2)CO_(3) as catalyst but is still 1.7 times that achieved without *** with the results obtained using K_(2)CO_(3) or Ca(OH)2 alone,the use of a combination of K_(2)CO_(3) and Ca(OH)2 could increase the H2 yield by up to 2.5 times that without catalyst and 25%and 45%more than that obtained using K_(2)CO_(3) and Ca(OH)2 alone,*** was found that methane was the dominant product at relatively low *** the temperature was increased,the methane reacts with water and is converted to hydrogen and carbon dioxide.

关键词： biomass hydrogen production supercritical water gasification hydrogen

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Performance of vertical axis water turbine with eye-shaped baffle for pico hydropower

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Frontiers in Energy 2022年第4期16卷 683-696页

作者： Zhuohuan HU Dongcheng WANG Wei LU Jian CHEN Yuwen ZHANG Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai 20093China Department of Mechanical and Aerospace Engineering University of MissouriColumbiaMO 65211USA

t A series of inline pico hydropower systems,which could be used in confined space,especially for water distribution networks(WDNs),was designed and *** turbine with an eye-shaped vertical water baffle was developed to evaluate the hydraulic performance.A three-dimensional dynamic mesh was employed and the inlet velocity was considered as the inlet boundary condition,whereas the outlet boundary was set as the ***,numerical simulations were conducted and the standard k-εturbulence model was found to be the best capable of predicting flow features through the comparison with the experimental *** effects of the opening diameter of the water baffle and installation angle of the rotor on the flow field in the turbine were *** results suggested that the water baffle opening at d=30 mm and the rotor at a 52°angle could achieve the highest efficiency of 5.93%.The proper eye-shaped baffle not only accelerates the fluid flow and generates positive hydrodynamic torque,but also eliminates the flow *** scheme proposed in this paper can be exploited for practical applications in the water pipelines at various conditions and power requirements.

关键词： vertical axis water turbine eye-shaped vertical water baffle pico hydropower

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Evaluation of frictional pressure drop correlations for air-water and air-oil two-phase flow in pipeline-riser system

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Petroleum Science 2024年第2期21卷 1305-1319页

作者： Nai-Liang Li Bin Chen School of Low-carbon Energy and Power Engineering China University of Mining and TechnologyXuzhou221116JiangsuChina State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049ShaanxiChina

Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.

关键词： Frictional pressure drop Pipeline-riser Gas-liquid two-phase flow Severe slugging Correlation

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High tension cyclic hydrocarbons synthesized from biomass-derived platform molecules for aviation fuels in two steps

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Green Energy & Environment 2023年第1期8卷 331-337页

作者： Zhanchao Li Yizhuo Wang Qing Li Liqing Xu Hong Wang Frontier Institute of Science and Technology Xi'an Jiaotong UniversityXi'an710054China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an710054China

Synthesizing ring structure aviation fuels from biomass-derived platform molecules is challenging,especially for bridged ring structure aviation fuels which are typically achieved from fossil-derived ***,we report the synthesis of a series of ring structure biofuels in two steps by a combination of a solvent-free Michael-cyclization reaction and a hydrodeoxygenation(HDO)reaction from lignocellulosederived 5,5-dimethyl-1,*** biofuels are obtained with high overall yields up to 90%,which exhibit high densities of 0.81 g cm^(-3)-0.88 g cm^(-3)and high volumetric neat heat of combustion(VNHOC)values of 36.0 MJ L^(-1)-38.6 MJ L^(-1).More importantly,bridged-ring structure hydrocarbons can also be achieved in two steps by a combination of a Robinson annulation reaction and an HDO reaction to afford the final products at high overall yields up to 90%.The bridged-ring structure products have comparable high densities and high VNHOC values to the best artificial fuel JP-10(0.94 g cm^(-3)and 39.6 MJ L^(-1)).The results demonstrate a promising way for the synthesis of high-density aviation fuels with different fuel properties at high yields.

关键词： Biofuels 5,5-Dimethyl-1,3-cyclohexanedione Solvent-free Michael-cyclization Robinson annulation Green reaction

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Flame mode transitions in outer recirculation zone of lean premixed prevaporized n-decane/air swirling flames

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Experimental Thermal and Fluid Science 2025年 168卷

作者： Wenjun Lin Weijie Zhang Hongfang Liu Zhihao Gao Xiao Cai Jinhua Wang Zuohua Huang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center Mianyang 621000 China

The outer recirculation zone (ORZ) flame modes and their transition were experimentally investigated in lean premixed prevaporized n-decane/air swirling flames. The flame structure and flow field were measured employing simultaneous CH 2 O/OH-PLIF and OH-PLIF/PIV laser diagnostics. The ORZ temperature was estimated with thermocouples. Three ORZ flame modes were identified: (1) mode II, characterized by extensive CH 2 O but nearly absent OH in the ORZ; (2) mode III, with flickering CH 2 O and OH in the ORZ; (3) mode IV, with flickering OH in the ORZ but nearly without CH 2 O. Besides, the mode I is defined as the inner shear layer (ISL) flame and mode V is the ISL/outer shear layer (OSL) flame. A theoretical diagram from mode I to V is achieved describing transition from the ISL to ISL/OSL flames. It is confirmed that the presence of CH 2 O in the ORZ results from the first-stage low-temperature autoignition, which is validated to be predictable with the ignition Damköhler number ( D a i g ) after examining the fluid residence time and ignition delay time. It is found that the high-temperature ORZ flame indicated by the flickering OH radicals cannot be predicted merely using D a i g . Instead, the increased flame speed and intensified ISL flame propagation into the ORZ due to the elevated equivalence ratio influence a lot, which can also be promoted by the shear layer vortices. These processes are expected to motivate the entrainment of hot burnt gas into the ORZ thus to form the high-temperature ORZ flame. The flickering ORZ flame is undesirable due to the potentially induced combustion instabilities, and this work can broaden its understanding and provide insights for its suppression.

关键词： Thermocouples

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Gas flow in a Stratified Porous Medium with Crossflow

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Journal of Thermal Science 2002年第1期11卷 35-40页

作者： Sun Hedong Gao Chengtai Qian Huanqun Zhou Fangde State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049China Department of Petroleum Engineering Xi’an Petroleum InstituteXi’an 710065China

A new model called semi-permeable wall model is presented for multilayer gas reservoir. The model is used to study the influence of crossflow on pressure transient well tests and other single-phase flow problems. It is suggested here to use this model to approximate the actual multilayer gas reservoir, so that the problem is greatly simplified mathematically. Its differential equation is established here for multilayer gas reservoirs, and is linearized by normalized pseudo pressure and pseudo time. Simulation program is developed by finite-difference method when all layers are perforated. The feature of wellbore pressure and rate is clarified by analyzing the results of numerical simulation.

关键词： multi-layer gas reservoir semi-permeable wall model numerical simulation transient well-test wellbore storage skin factor.

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Coupling Effect of Heat Transfer and flow Resistance in the Rifled Tube Water Wall of a Ultra-Supercritical CFB Boiler

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Journal of Thermal Science 2019年第5期28卷 1078-1088页

作者： LI Yaode YANG Dong OUYANG Shijie LIU Dan WANG Wenyu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China North China Electric Power Test and Research Institute Co. Ltd Tianjing 300000 China

The coupling factor is used in this study to characterise the combined effect of the heat transfer and resistance characteristics of a rifled tube. Boundary layer theory is utilised to investigate the relationship between the comprehensive coefficient and Reynolds number in two regions, namely, higher and lower than pseudo-critical enthalpy. Results indicate that mass flux exerts a decisive negative influence on the coupling effect, and the impacts of pressure and heat flux are weak. The overall effect decreases rapidly as the mass flux increases, but it increases in the area behind the quasi-critical enthalpy. The coupling effect is also affected by specific heat ratio, thermal acceleration and buoyancy. The correlations of heat transfer and friction resistance are deduced with high precision according to experimental data.

关键词： supercritical pressure heat transfer frictional resistance coupling effect

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Enhanced efficiency in Concentrated Parabolic Solar Collector(CPSC) with a porous absorber tube filled with metal nanoparticle suspension

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Green Energy & Environment 2018年第2期3卷 129-137页

作者： Mohammad Hatami Jiafeng Geng Dengwei Jing Mechanical Engineering Department Esfarayen University of Technology (EUT) International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector(CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction(φ), Darcy number(Da) and Rayleigh number(Ra), on the Nusselt number(Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe_3O_4, Al_2O_3, TiO_*** the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector.

关键词： Concentrating parabolic solar collector Porous absorber tube Nanofluid Nusselt number Finite Element Method

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Experimental Study of Drop Deformation and Breakup in Simple Shear flows

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Chinese Journal of Chemical engineering 2007年第1期15卷 1-5页

作者：林长志郭烈锦 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

The experimental results of the deformation and breakup of a single drop immersed in a Newtonian liq-uid and subjected to a constant shear rate which generated by counter rotating Couette apparatus were presented in this paper. From experimental observations, the breakup occurred by three mechanisms, namely, necking, end pinching, and capillary instability. Quantitative results for the deformation and breakup of drop are presented. The maximum diameter and Sauter mean diameter of daughter drops and capillary thread radius are linearly related to the inverse shear rate and independent of the initial drop size, the dimensionless wavelength which is the wave-length divided by the thread width at breakup is independent of the shear rate and initial drop size, and the deforma-tion of threads follows a pseudo-affine deformation for Cai/Cac larger than 2.

关键词： drop deformation breakup Couette shear flow

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