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Modeling droplet vaporization and combustion with the volume of fluid method at a small Reynolds number

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第5期13卷 361-374页

作者： xiao-bin ZHANG Wei ZHANG xue-jun ZHANG Institute of Refrigeration and Cryogenics Zhejiang University Hangzhou 310027 China

The volume of fluid(VOF) formulation is applied to model the combustion process of a single droplet in a hightemperature convective air free stream *** calculations solve the flow field for both phases,and consider the droplet deformation based on an axisymmetrical *** chemical reaction is modeled with one-step finite-rate mechanism and the thermo-physical properties for the gas mixture are species and temperature dependence.A mass transfer model applicable to the VOF calculations due to vaporization of the liquid phases is developed in consideration with the fluctuation of the liquid *** model is validated by examining the burning rate constants at different convective air temperatures,which accord well with experimental data of previous *** phenomena from the simulations,such as the transient history of droplet deformation and flame structure,are also qualitatively accordant with the descriptions of other numerical ***,a different droplet deformation mechanism for the low Reynolds number is explained compared with that for the high Reynolds *** calculations verified the feasibility of the VOF computational fluid dynamics(CFD) formulation as well as the mass transfer model due to vaporization.

关键词： Droplet Vaporization Combustion process Volume of fluid(VOF) Numerical simulation

Interaction of subway LIM vehicle with ballasted track in polygonal wheel wear development

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Acta Mechanica Sinica 2011年第2期27卷 297-307页

作者： Ling Li Xin-Biao xiao xue-Song Jin State Key Laboratory of Traction Power Southwest Jiaotong University 610031 Chengdu China

This paper develops a coupled dynamics model for a linear induction motor （LIM） vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen– Hedrick–Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system （LMS）, Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.

关键词： Linear induction motor Uneven wear Wheel out of roundness Vehicle-track coupling dynamics

Roles of membrane and organic fouling layers on the removal of endocrine disrupting chemicals in microfiltration

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Journal of Environmental Sciences 2018年第10期30卷 176-184页

作者： Wenchao xue Kang xiao Peng Liang Xia Huang State Key Joint Laboratory of Environmental Simulation and Pollution Control School of Environment Tsinghua University Department of Environmental Engineering Faculty of Engineering Chulalongkorn University College of Resources and Environment University of Chinese Academy of Sciences

To understand the adsorption behavior of endocrine disrupting chemicals（EDCs） is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfiltration system. The dynamic adsorption of four representative EDCs, namely estriol（E3）, 17β-estradiol（E2）, 17α-ethynylestradiol（EE2）, and 4-nonylphenol（4-NP） in a microfiltration system was investigated using the Thomas＇ *** product of the equilibrium constant and the total adsorption capacity of the membrane,Ka, for E3, E2, EE2, and 4-NP were 4.91, 9.78, 15.6, and 826, respectively, strongly correlating with the compound octanol–water partition coefficient（KOW）. Adsorption appeared to be enhanced when organic fouling formed on the surface of membrane, indicating the role of an additional adsorption column for EDCs acted by a fouling layer in microfiltration. Results of a comparison between the Ka values for clean membrane and fouled membrane illustrated that the significant contribution made by fouling layers may be attributed to the foulant layer＇s hydrophobicity（in the case of calcium humate layer） and thickness（in the case of calcium alginate layer）. This study provided a novel perspective to quantitatively analyze the dynamic adsorption behavior of trace pollutants in membrane process.

关键词： Endocrine disrupting chemicals Microfiltration membrane Dynamic adsorption Thomas' model Organic membrane fouling

Advances in the design and development of SARS-CoV-2 vaccines

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Military Medical Research 2022年第4期9卷 484-513页

作者： xue-Liang Peng Ji-Si-Yu Cheng Hai-Lun Gong Meng-di Yuan xiao-Hong Zhao Zibiao Li Dai-Xu Wei Key Laboratory of Resource Biology and Biotechnology in Western China Ministry of EducationSchool of MedicineDepartment of Life Sciences and MedicineNorthwest UniversityXi'an 710069China Institute of Materials Research and Engineering A*STAR(Agency for ScienceTechnology and Research)2 Fusionopolis WayInnovis#08-03Singapore 138634Singapore.

Since the end of 2019,coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has spread *** RNA genome of SARS-CoV-2,which is highly infectious and prone to rapid mutation,encodes both structural and non-structural *** is currently the only effective method to prevent COVID-19,and structural proteins are critical targets for vaccine ***,many vaccines are in clinical trials or are already on the *** review highlights ongoing advances in the design of prophylactic or therapeutic vaccines against COVID-19,including viral vector vaccines,DNA vaccines,RNA vaccines,live-attenuated vaccines,inactivated virus vaccines,recombinant protein vaccines and bionic nanoparticle *** addition to traditional inactivated virus vaccines,some novel vaccines based on viral vectors,nanoscience and synthetic biology also play important roles in combating ***,many challenges persist in ongoing clinical trials.

关键词： Severe acute respiratory syndrome coronavirus 2 Coronavirus disease 2019 Vaccine Synthetic biology Nanoscience

Buckling of a stiff thin film on a compliant substrate under anisotropic biaxial prestrain

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Science China(Physics,Mechanics & Astronomy) 2016年第2期59卷 57-66页

作者： Zhi Cheng Ou xiao Hu Yao xiao Qing Zhang xue Jun Fan School of Civil Engineering and Transportation South China University of TechnologyGuangzhou 51064China Department of Mechanical Engineering Lamar UniversityBeaumont 77710USA

The structure of stretchable electronics is based on the buckling of a thin film on a compliant substrate. Under anisotropic biaxial prestrains, this structure may buckle into several patterns, including cylindrical, checkerboard, and undulating patterns. The displacement and energy of each pattern are deduced analytically. By comparing their minimum potential energies, the critical buckling condition of each pattern is determined. After secondary bifurcation, the checkerboard pattern occurs just above the critical prestrains, but the undulating pattern dominates other regions. The buckling amplitude and wavenumber of the undulating pattern are shown under biaxial prestrains. Even if the structure is under equi-biaxial prestrains, it may buckle into an asymmetric undulating pattern.

关键词： film substrate buckling biaxial anisotropic undulating

Forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy

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Rare Metals 2018年第5期37卷 399-406页

作者： xiao-Dai Yue Jia-Rong Li xiao-Guang Wang Zhen-xue Shi Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

The forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy were investigated. The microstructures were observed with optical microscope （OM） and field emission microscope （FEM） after homogenization-solution heat treated at 1328℃ and 1350 ℃ for 2 h, 6 h and 9 h. Results indicate that when heat treated at 1328 ℃, pores appear at the interface of eutectic and matrix at first and then leave in the matrix with the shrink of eutectic. When heat treated at 1350 ℃, incipient melting happens at first, and some of them have a pore in the center. After that, with the homogenization-solution process, incipient melting microstructure fades away gradually. By analyzing the results with thermodynamics and kinetics methods, it is concluded that some pores nucleate during directional solidification and then become larger and visible during homogenization-solution heat treatments; some pores are generated by incipient melting, yet such pores are difficult to be distinguished from other pores; imbalanced elements cross-diffusion induces to the forming and growing of pores too, and such imbalanced diffusion also plays an important part on the growth of all preexisting pores.

关键词： Single crystal superalloy Pore Homogenization Solution Heat treatment Incipient melting

The 2022 record-breaking high temperature in China:Sub-seasonal stepwise enhanced characteristics,possible causes and its predictability

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Advances in Climate Change Research 2023年第5期14卷 651-659页

作者： Yuan-Yuan MA Yi-Ting CHEN xiao-xue HU Qian-Rong MA Tai-Chen FENG Guo-Ling FENG di MA Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of Physical Science and Technology Yangzhou UniversityYangzhou 225127China College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000China School of Atmospheric Sciences Key Laboratory of Tropical Atmosphere-Ocean SystemMinistry of EducationSun Yat-sen UniversityZhuhai 519082China Southern Marine Science and Engineering Guangdong Laboratory Zhuhai 519082China

In the summer of 2022,an unprecedented and long-lasting high temperature swept central-eastern China,causing significant societal ***,the sub-seasonal characteristics,causes and predictability of this extreme high temperature event are not well *** on the locations,intensities and causes of the high temperature,we divided it into three stages:early(13 June-3 July),sustained(4-28 July),and enhancement(29 July-30 August)*** high temperature during the early stage mainly occurred in north-central China with an anomaly of 2.5℃compared with climatology(1981-2010),while the last two stages occurred in the middle and lower Yangtze River Basin with anomalies of 2.8 and 3.8℃*** high temperature during the three stages were all regulated by the strengthening and westward extension of the western Pacific subtropical high(WPSH)but involved different physical *** the early stage,it was mainly caused by the anticyclones over the Mongolia and Northwest Pacific and enhanced by the minor impact of *** the sustained stage it was influenced by relatively more stronger WPSH and South Asia high(SAH)and the relatively minor impact of the anticyclone over the north-western South *** the enhancement stage,the high temperature was mainly caused by a combination of the record-breaking WPSH and SAH and the strong European blocking ***,the exceptionally powerful WPSH was well correlated with the sea surface temperature gradient induced by the developing La Niñ*** ECMWF and NCEP models reasonably predicted the location and intensity of the high temperature in the early stage,but poorly predicted that in the sustained and enhancement stages partly because of the failure prediction of the WPSH's enhancement and westward *** ECMWF model's more accurate prediction of the WPSH may contribute to its better forecasting of the heatwaves.

关键词： High temperature Sub-seasonal characteristics Western Pacific subtropical high La Niña development phase Predictability

Online Power System Voltage Stability Index for LCC HVDC Using Local Measurements

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CSEE Journal of Power and Energy Systems 2023年第1期9卷 100-110页

作者： David Li Conghuan Yang Ying xue xiao-Ping Zhang Department of Electronic Electrical and Systems EngineeringSchool of EngineeringUniversity of BirminghamBirmingham B152TTUK Guangzhou Maritime University GuangzhouChina School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

This paper proposes an online power system voltage stability index(PVSI Online)that quantifies power system voltage stability in real time between an AC network and LCC HVDC using only local *** methods relied on using telecommunications to inform a change in a predetermined AC network *** proposed method uses local measurements of voltage and current from the HVDC using a newly developed,numerically robust technique called Moving Window Covariance to detect a change in the AC network in real *** network parameters are fed to a newly devised index that accurately models and captures the dynamics of the interaction between an LCC HVDC and AC *** index is used to quantify stability,but also to advise network *** an onset of instability due to network degradation,the proposed index can provide a power order value for the HVDC to restore *** as a self-contained module that can be implemented within a HVDC scheme.

关键词： LCC HVDC local measurements Moving Window Covariance numerical drift online PVSI PVSI Online real time SCR SCL self-contained

Effects of Mg/PTFE pyrotechnic compositions on reignition characteristics of base bleed propellants and heating mechanism

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Defence Technology（防务技术） 2022年第1期18卷 94-108页

作者： xiao-chun xue Long-ze Ma Yong-gang Yu Schooi of Enerey and Power Engineering Nanjing Universiry of Science and Techmology Narine lianesu 210094 China BYD Compary Liruied ShenzheL Guanedong 518118 Chna

The effects of magnesium/polytetrafluoroethylene(Mg/PTFE)pyrotechnic compositions on the coupled flow field and reignition mechanism are important aspects governing the perfommance and range of base bleed projectiles(BBPs).Owing to a decrease in pressure and temperature when the BBP leaves the muzzle,rapid depressurization occurs,which extinguishes the base bleed *** Mg/PTFE py-rotechnic composition pressed in the igniter of the base bleed unit(BBU)provides additional energy to the BBU via a chemical ***,the extinguished base bleed propellant is reignited under the effect of high-temperature combustion gas jets from the *** this study,a numerical analysis is conducted to evaluate the effects of PTFE and Mg granularity as well as Mg/PTFE pyrotechnic *** to the rapid depressurization,the temperature and pressure was found to decrease fordifferent Mg/PIFE pyrotechnic ***,the depressurization time increased as the PTFE granularity increased,the Mg granularity decreased,and the Mg content *** the pressure in the combustion chamber of the BBU decreased to the atmospheric pressure,the combustion gas jets from the igniter expand upstream(rather than downstream).However,these combustion gas jets exhibit different axial and radial expansion characteristics depending on the pyrotechnic compositions used,The results show that the reignition delay time,ta,of the base bleed propellant was 377.608,94.27,387.243,523.966,and 221.094 ms for cases A-E,***,it was concluded that the Mg/PTFE pyrotechnic composition of case B was the most beneficial for the reignition of the base bleed propellant,with the earliest addition of energy and mass to the BBP.

关键词： Thermal effect High-temperature combustion gas Mg/PTFE pyrotechnic Compositions Reignition