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Sensitivity Analysis of air gap Motion with Respect to Wind Load and Mooring System for Semi-Submersible Platform Design

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China Ocean Engineering 2016年第4期30卷 535-548页

作者：霍发力聂焱杨德庆董刚崔锦 Jiangsu University of Science and Technology Zhenjiang 212003China School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China Grenland Group(China)Ltd. Shanghai 201206China

A design of semi-submersible platform is mainly based on the extreme response analysis due to the forces experienced by the components during lifetime. The external loads can induce the extreme air gap response and potential deck impact to the semi-submersible platform. It is important to predict air gap response of platforms accurately in order to check the strength of local structures which withstand the wave slamming due to negative air gap. The wind load cannot be simulated easily by model test in towing tank whereas it can be simulated accurately in wind tunnel test. Furthermore, full scale simulation of the mooring system in model test is still a tuffwork especially the stiffness of the mooring system. Owing to the above mentioned problem, the model test results are not accurate enough for air gap evaluation. The aim of this paper is to present sensitivity analysis results of air gap motion with respect to the mooring system and wind load for the design of semi-submersible platform. Though the model test results are not suitable for the direct evaluation of air gap, they can be used as a good basis for tuning the radiation damping and viscous drag in numerical simulation. In the presented design example, a numerical model is tuned and validated by ANSYS AQWA based on the model test results with a simple 4 line symmetrical horizontal soft mooring system. According to the tuned numerical model, sensitivity analysis studies of air gap motion with respect to the mooring system and wind load are performed in time domain. Three mooring systems and five simulation cases about the presented platform are simulated based on the results of wind tunnel tests and sea-keeping tests. The sensitivity analysis results are valuable for the floating platform design.

关键词： mooring system air gap semi-submersible platform radiation damping viscous drag

EXPERIMENTAL INVESTIGATION ON WAVE RUN-UP CHARACTERISTICS ALONG COLUMNS AND air gap RESPONSE OF SEMI-SUBMERSIBLE PLATFORM

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Journal of Hydrodynamics 2011年第5期23卷 625-636页

作者： SHAN Tie-bing YANG Jian-min LI Xin XIAO Long-fei State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai 200240 China

This article mainly concentrates on a large-volume drilling semi-submersible platform, aiming to reveal wave run-up characteristics along square columns and give the relationship between air gap distributions and wave parameters. The tests with fixed model were conducted firstly on its encountering a series of monochromatic waves. A wide range of wave slope （H/L ） were selected to investigate the air gap response in detail. As can be seen, larger wave steepness will generally cause smaller air gap in the same wave period, which indicates nonlinear effects of incoming wave can amplify wave elevation. Model tests with mooring condition were also conducted in the same wave conditions. As was expected, the maximum relative wave elevation reduces obviously compared with the fixed one. However, wave shape close to columns show higher harmonic characteristics due to interaction between waves and the columns of semi-submersible platform. Meaningful conclusions from the model tests are drawn in this article, which is helpful in air gap design of floating offshore platform to a certain extent. In addition, the experimental results will provide an important reference for further research on validation and update of theoretical models of air gap.

关键词： wave run-up air gap diffraction-radiation effects wave steepness

Analytical Analysis and Performance Characterization of Brushless Doubly Fed Induction Machines Based on General air-gap Field Modulation Theory

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Chinese Journal of Electrical Engineering 2021年第3期7卷 4-19页

作者： Peng Han Ming Cheng Xinkai Zhu Zhe Chen Ansys Inc.San JoseCA 95134USA School of Electrical Engineering Southeast UniversityNanjing 210096China Department of Electrical Engineering North China Electric Power UniversityBaoding 071003China Department of Energy Technology Aalborg UniversityAalborg 9220Denmark

air-gap magnetic field modulation has been widely observed in electric machines.In this study,we present an analytical analysis and performance characterization of brushless doubly fed induction machines(BDFIMs)fed by two independent converters from the perspective of air-gap field modulation.The spiral-loop winding is studied in detail as an example to show the generalized workflow that can also be used to analyze other short-circuited rotor winding types,such as nested-loop and multiphase double-layer windings.Magnetic field conversion factors are introduced to characterize the modulation behavior of special rotor windings and facilitate their comparison in terms of cross-coupling capability,average torque,and harmonic content of the air-gap flux density waveforms.The stator magnetomotive force(MMF),rotor MMF,and resultant air-gap MMF are considered,based on which the closed-form inductance formulas are derived,and the torque equation is obtained along with the optimal current angle for maximum torque operation by using the virtual work principle.The design equations are then developed for the initial sizing and geometry scaling of the BDFIMs.Transient finite element analysis and experimental measurements are performed to validate the analysis.

关键词： AC machines air gap magnetic field spatial harmonic frequency domain modulation rotor windings

Effect of air gap under Fabric on Thermal Protective Performance Using an Improved Apparatus

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Journal of Donghua University(English Edition) 2011年第6期28卷 595-598页

作者：李小辉卢业虎周亮李俊王云仪 Protective Clothing Research Center Fashion InstituteDonghua University Key Laboratory of Clothing Design and Technology Ministry of EducationDonghua University

The bench top test is one of the most important and effective methods to evaluate the total thermal protective performance(TPP) of firefighters' protective clothing,which is greatly influenced by the air gaps entrapped.In this paper,to investigate the effect of air gap width on TPP,a new improved apparatus with two height changeable buttons to hold the thermal sensor was developed to get a series of air gap sizes from 0 mm to 40 mm.The TPP of two types of flame-resistant outer fabrics was measured with TPP test apparatus respectively.Analysis of temperature rise with each air gap width was made to determine the effects of different air gaps on protective performance.It was indicated that air gap size had great effect on TPP of fabrics in the bench top test.An air gap width above 8 mm was suggested for the thermal protective clothing design.

关键词： air gap thermal protective performance(TPP) bench top test firefig hter’s protective clothing

Numerical Estimation of the Thermal Response of Thermal Protective Clothing-air gap-Human Skin Micro-system

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Journal of Donghua University(English Edition) 2016年第4期33卷 569-573页

作者：田明伟王祯刘康炜胡馨之朱士凤曲丽君陈韶娟周泉 College of Textiles and Clothing Qingdao University Qingdao 266071 China Laboratory of New Fiber Materials and Modern Textile The Growing Base for State Key Laboratory Qingdao UniversityQingdao 266071 China Collaborative Innovation Center for Marine Biomass Fibers Materials and Textiles of Shandong Province Qingdao UniversityQingdao 266071 China SINOPEC Safety Engineering Institute Qingdao 266071 China Central Laboratory The Affiliated Hospital of Qingdao University Qingdao 266071 China

Thermal protective clothing has been recognized as the primary shielding against emergency fire hazard and inflammable gas leakage. Therefore,the thermal response of human covered with thermal protective clothing under high temperature is the key work to investigate the thermal insulation of thermal protective clothing. A coupling model composed of thermal protective clothing,air gap and human skin is established and the temperature of the micro-system is numerically solved via the finite element method( FEM).Especially,the heat transfer of air gap located between clothing and human skin considering conduction and radiation is established while the human skin layers involve the effect of blood perfusion. Then the effect of thermophysical properties( thermal conductivity and volumetric capacity) of fabric and thickness of fabric and air on the thermal response of the micro-system is elucidated and compared.The results indicate that the volumetric heat capacity of fabric is the key parameter to affect the thermal shielding performance of thermal protective clothing,and the thicker fabric thickness and air gap thickness can improve the thermal protective properties of the micro-system.

关键词： thermal protective clothing air gap human skin thermal response finite element method(FEM)

Transmission properties of frequency selective structures with air gaps

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Chinese Physics B 2010年第12期19卷 460-465页

作者：蒙志君王立峰吕明云武哲 School of Aeronautic Science & Engineering Beihang University

The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

关键词： air gap frequency selective structure periodic array radome

Cooling phenomena in blast furnace hearth

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Journal of Iron and Steel Research(International) 2018年第10期25卷 1010-1016页

作者： Ke-xin Jiao Jian-liang Zhang Zheng-jian Liu Yong Deng Chun-lin Chen School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China CSIRO Mineral Resources Clayton South VIC 3169 Australia State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing Beijing 100083 China

Cooling water provides the best protection for refractory in the blast furnace hearth. Stable and suitable water quality and abundant cooling water are the basis for long service life of the hearth. Some phenomena about cooling system in the commercial blast furnaces were described, and reasonable explanations of these phenomena were analyzed. The results show that increasing the amount of cooling water and reducing the inlet temperature of cooling water can increase the cooling effect significantly in the case of water scaling. Heat flux in the blast furnace hearth is the average heat flux of cooling stave, and the erosion of carbon brick is uneven. There is no direct connection between the actual erosion condition and the heat flux in the hearth. The change trend of thermocouple temperature and heat flux in the hearth can reflect whether the gaps exist among the bricks or not, providing an effective guidance for industrial production and the evaluation of safety state in the hearth. And, the film boiling will not occur in the normal cooling system in the blast furnace hearth.

关键词： Blast furnace hearth Cooling system Heat flux - Film boiling - Scale deposit air gap

Heat Transfer and Deformation Behavior of Shell Solidification in Wide and Thick Slab Continuous Casting Mold

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Journal of Iron and Steel Research(International) 2014年第S1期21卷 1-9页

作者： Jing-xin SONG Zhao-zhen CAI Feng-yun PIAO Miao-yong ZHU School of Materials and Metallurgy Northeastern University

With the considerations of the behaviors of shell deformation, mold flux film and air gap dynamic distribution in shell/mold gap, a two dimensional slice-travel transient thermo-mechanical coupled model of simulation shell solidification in wide and thick slab continuous casting mold was developed by using the commercial program ANSYS. The evolutions of strand-mold system thermal behaviors, including the air gap formation and the mold flux film dynamical distribution in shell/mold gap and shell temperature field, and the evolutions of shell deformation and stress distribution of peritectic steel solidified in a 2120 mm wide and 266 mm thick slab continuous casting mold were analyzed. The results show that the air gap formation and the thick mold flux film distribution mainly concentrate in the regions 0–21 mm and 0–7 mm, 0–120 mm and 0–100 mm off the shell wide and narrow faces corners, and thus the hot spots are given rise to form in the regions 15–55 mm and 15–50 mm off the shell wide and narrow face corners. The shell server deformation occurs in the off-corners in the middle and lower parts of the mold. The stress evolution in shell surface is tensile stress, while that in shell solidification front is compressive stress.

关键词： continuous casting mold heat transfer shell deformation air gap numerical simulation

A MATHEMATICAL HEAT TRANSFER MODEL INSTATIC AND CONTINUOUS CASTING

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Acta Metallurgica Sinica(English Letters) 2004年第6期17卷 776-784页

作者： R. Ghasemzadeh Metallurgy Department Iran University of Science and Technology Narmak Tehran 16844 Iran

The application of a heat flow model to describe the thermal characteristics of freezing alloys with narrow mushy zones from a refrigerated mould wall was outlined. The extension of the model was to treat the continuous casting of metals with low thermal conductivity, such as steels, which will be outlined. The model was based on the mathematical expedient for replacing thermal resistance of the metal/mould interface by virtual adjuncts of metal/mould material. It provided a good description of the pool profile and the technique exhibits advantages in terms of both computation and versatility of application.

关键词： air gap pool profile mushy zone directional solidification