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Analysis of hot leg natural circulation under station blackout severe accident

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Nuclear Science and Techniques 2007年第2期18卷 123-128页

作者： deng jian CAO Xuewu School of Nuclear Science and Engineering Shanghai Jiaotong University Shanghai 200240 China

Under severe accidents, natural circulation flows are important to influence the accident progression and result in a pressurized water reactor (PWR). In a station blackout accident with no recovery of steam generator (SG) auxiliary feedwater (TMLB' severe accident scenario), the hot leg countercurrent natural circulation flow is analyzed by using a severe-accident code, to better understand its potential impacts on the creep-rupture timing among the surge line, the hot leg, and SG tubes. The results show that the natural circulation may delay the failure time of the hot leg. The recirculation ratio and the hot mixing factor are also calculated and discussed.

关键词：压水堆全场断电严重事故热管段自然循环

THREE-DIMENSIONAL FLOW AROUND TWO TANDEM CIRCULAR CYLINDERS WITH VARIOUS SPACING AT Re=220

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Journal of Hydrodynamics 2006年第1期18卷 48-54页

作者： deng jian REN An-lu ZOU jian-feng Department of Mechanics Zhejiang University Hangzhou 310027 China

The flow around two tandem circular cylinders was studied by a three-dimensional numerical simulation of the Navier-Stokes equations at Re=220 . The improved virtual boundary method was applied to model the no-slip boundary condition of the cylinders. The results show that as the spac ing ratio L/D≥4 , the three dimensionality occurs in the wake. When L/D≤3.5 the wake keeps a two-dimensional state at the Reynolds number Re=220 . The critical spacing for the appearance of three-dimensional instability obtained is at the range 3.5〈 L/D 〈 4, similar to the critical spacing found in two-dimensional case. Two sources of instability from upstream and downstream cylinder generate a complicat ed vortex structures in the wake, investigated by streamlines topology analysis in the streamwise plane. Many other interesting problems were also addressed in this paper.

关键词： three-dimensional Navier-Stokes equations,virtual boundary method flow around two tandem circular cylinders three-dimensional vortex structure

Hydrogen and steam distribution following a small-break LOCA in large dry containment

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Nuclear Science and Techniques 2007年第3期18卷 181-185页

作者： deng jian CAO Xuewu School of Nuclear Science and Engineering Shanghai Jiaotong University Shanghai 200240 China

The hydrogen deflagration is one of the major risk contributors to threaten the integrity of the containment in a nuclear power plant, and hydrogen control in the case of severe accidents is required by nuclear regulations. Based on the large dry containment model developed with the integral severe-accident analysis tool, a small-break loss-of-coolant-accident (LOCA) without HPI, LPI, AFW and containment sprays, leading to the core degradation and large hydrogen generation, is calculated. Hydrogen and steam distribution in containment compartments is investi- gated. The analysis results show that significant hydrogen deflagration risk exits in the reactor coolant pump (RCP) compartment and the cavity during the early period, if no actions are taken to mitigate the effects of hydrogen accu- mulation.

关键词：氢蒸发严重事故氢分布小破口事故

NUMERICAL SIMULATION OF FLOW-INDUCED VIBRATION ON TWO CIRCULAR CYLINDERS IN TANDEM ARRANGEMENT

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Journal of Hydrodynamics 2005年第6期17卷 660-666页

作者： deng jian REN An-lu CHEN Wen-qu Department of Mechanics Zhejiang University Hangzhou 310027 China

Flow-induced vibration of two circular cylinders in tandem arrangement elastically mounted with a massspring-damping system was studied by solving the primitive variable Navier Stokes equations incorporating the Arbitrary Lagrangian-Eulerian （ALE） method. The convection term and dissipation term were discretized using the third-order upwind compact scheme and the fourth-order central compact scheme, respectively. The typical spacing between the cylinders is 4 diameters, which is close to the critical value. The dynamic response of the vibrations on two cylinders with two-degreeof-freedom motion is different from that of an isolated cylin der, and also different from that of a cylinder vibrating in the wake of a fixed upstream one. Different flow patterns were found in the wake, and proved to be relevant to the discontinuities observed in the response of the oscillatory cylinders.

关键词： flow by two cylinders flow-induced vibration high-order compact scheme dynamic response

Ideality analysis and general laws of bubble swarm microflow for large-scale gas-liquid microreaction processes

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Chinese Journal of Chemical Engineering 2022年第10期50卷 56-65页

作者： Lin Sheng Yuchao Chen jian deng Guangsheng Luo The State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China

The flow ideality of bubbly microflow remains unclear even though it is vital for the design of microreactors,especially the ideality of bubble swarm microflow for large-scale gas-liquid microreaction *** work is the first time to report the ideality analysis of the microbubble swarm in a relatively large *** bubble swarm microflow has undergone two conditions:quasihomogeneous plug flow and liquid phase/gas-liquid qua si-homogeneous phase two-phase laminar *** the deviations of void fraction and bubble velocity from the ideal plug flow can divide into two parts,and the two transition points simultaneously happen at the velocity ratio of *** exists a critical capillary number to maintain the quasi-homogeneous plug flow,which could be regarded as the general laws for the design of gas-liquid ***,a novel model is developed to predict the bubble *** work could be very helpful for the large-scale gas-liquid microreactors design.

关键词： Bubble swarm Flow ideality Viscous fluids Gas-liquid microreactor

Continuous, homogeneous and rapid synthesis of 4-bromo-3-methylanisole in a modular microreaction system

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Chinese Journal of Chemical Engineering 2020年第8期28卷 2092-2098页

作者： Pei Xie Kai Wang jian deng Guangsheng Luo The State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China

4-Bromo-3-methylanisole is mainly used to synthesize black fluorane dye(2-anilino-3-methyl-6-dibutylaminofluorane, ODB-2), which is one of the most important heat and pressure-sensitive dyes in the manufacture of thermal papers. Compared to the industrial heterogeneous batch process, a continuous homogeneous bromination technology in a modular microreaction system has been developed, and 4-bromo-3-methylanisole has been successfully prepared through high-selective mono-bromination of 3-methylanisole with Br2 solution in CHCl3. In optimal conditions, the content of bis-brominated byproducts can be controlled less than 0.5%,which is superior to the industrial standard with 99.5% 3-methylanisole conversion at very short residence time and mild reaction temperature.

关键词： 4-bromo-3-methylanisole bromination continuous synthesis modular microreaction system mixing enhancement

Experimental investigation on pressure-buildup characteristics of a water lump immerged in a molten lead pool

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Nuclear Science and Techniques 2023年第3期34卷 25-39页

作者： Zi-jian deng Song-Bai Cheng Hui Cheng Sino-French Institute of Nuclear Engineering and Technology Sun Yat-Sen UniversityZhuhai 519082China

Motivated to understand the pressure-buildup characteristics in a circumstance of a water droplet immerged inside a heavy liquid metal pool,which is a key phenomenon during a Steam Generator Tube Rupture accident of Lead-cooled Fast Reactor,many experiments have been conducted by injecting water lumps into a molten lead pool at Sun Yat-sen *** order to deepen the understanding of the influence of melt material,this lead experiment was compared with a Lead-Bismuth-Eutectic(LBE)experiment in the *** both experiments,a steam explosion occurred in a small part of the experi-mental runs,which generally leads to strengthened pressure *** the non-explosion experimental cases,the impact of all parameters employed in lead experiments(i.e.,water lump volume,water lump shape,molten pool depth,and temperature of water and melt)on the pressure buildup is non-negligible and similar to that in our previous experiments using ***,limited pressure buildup with an increase in water lump volume was also observed.A slightly more violent pressure buildup tends to appear in the lead experiments than in the LBE experiments under the same experimental conditions,which may be due to the higher thermal conductivity of lead than of *** a few experimental runs with a relatively low melt temperature close to the melting point of lead,local solidification of liquid lead was observed,restricting pressure *** the lead and LBE experiments,the calculated melt kinetic energy conversion efficiencyηhas a relatively small value(not exceeding 1.6%),and theηvalues have an overall positive correlation with the impulse on the molten pool.

关键词： Lead-cooled fast reactor Steam generator tube rupture accident Pressure-buildup characteristics Experimental study Melt material

Parameter effects on high-speed UAV ground directional stability using bifurcation analysis

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Chinese Journal of Aeronautics 2021年第11期34卷 1-14页

作者： Qiaozhi YIN Xiaohui WEI Hong NIE jian deng State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing 210016China MIIT Key Laboratory of Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle(UAV)to veer off the *** order to investigate the combined effects of the key structural and operational parameters on the UAV ground directional stability from a global perspective,a fully parameterized mathematical high-speed UAV ground nonlinear dynamic model is developed considering several nonlinear *** bifurcation analysis procedure of a UAV ground steering system is introduced,following which the simulation efficiency is greatly improved comparing with the time-domain simulation *** the numerical continuation method is employed to investigate the influence of the nose wheel steering angle and the global stability region is *** bifurcation parameter plane is divided into several parts with different stability properties by the saddle nodes and the Hopf bifurcation *** find that the UAV motion states will never cross the bifurcation curve in the nonlinear ***,the dual-parameter bifurcation analyses are presented to give a complete description of the possible steering *** is also found that BT bifurcation appears when the UAV initial rectilinear velocity and the tire frictional coefficient *** addition,results indicate that the influence of tire frictional coefficient has an opposite trend to the influence of initial rectilinear ***,using bifurcation analysis method to identify the parameter regions of a UAV nonlinear ground dynamic system helps to improve the development efficiency and quality during UAV designing phase.

关键词： Bifurcation analysis Ground directional stability High-speed UAV Nonlinear system Numerical continuation

Study on modal characteristics and vibration reduction of an aircraft rotor–stator brake-induced squeal system

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Acta Mechanica Sinica 2020年第6期36卷 1350-1359,I0004页

作者： Qiaozhi Yin Xiaohui Wei Hong Nie jian deng State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing210016China Nanjing Center for Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China

Based on the modal coupling theory,the rotor and stator contact stiffness and axial relative velocity are considered to build an electric aircraft brake dynamic system model in this *** the complex modal analysis and transient dynamic analysis methods are used to study the aircraft brake squeal performance and vibratory *** unstable vibration modes indicate that the out-of-plane vibration plays an important role and the feed-in energy is larger than the output energy in the brake rotor–stator module so that brake squeal takes *** the influences of the contact stiffness,friction damping and frictional coefficient on the brake squeal system are carried out,laying the foundation for the three proposed vibration suppression *** show that the coefficient negative-slope condition will intensify the ***,a linear relationship between the squeal factor and the frictional coefficient is obtained to provide a guidance to predict squeal stability under more *** reduction design shows that adding a damping layer to the brake mechanism and chamfering the edge of braking stators both can reduce brake squeal effectively,while slotting braking stators is invalid in aircraft braking system.

关键词： Aircraft rotor-stator bake-induced vibration Brake squeal-Vibration stability Modal coupling Vibration suppression