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Effect of internal bubbly flow on pipe vibrations

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Science china(Technological sciences) 2010年第2期53卷 423-428页

作者： ZHANG MingMing & XU JianZhong Institute of engineering thermophysics, chinese academy of sciences, {3., china 1. Institute of engineering thermophysics Chinese Academy of Sciences Beijing 100190 China

This paper presents an experimental investigation on wall vibrations of a pipe due to injection of a uniform bubble cloud into the pipe flow. For different bubble void fractions and averaged bubble sizes, the vibrations were measured using accelerometers. To understand the underlying physics, the evolution of the vibration spectra along the streamwise direction was examined. Results showed that wall vibrations were greatly enhanced up to 25 dB, compared with no bubble case. The characteristics of the vibration were mainly dependent on void fraction. These vibrations were believed to be caused by two mechanisms: acoustic resonance and normal modes of the bubble cloud. The former, originating from the interaction between the first mode of the bubble cloud and the first acoustic mode of the pipe, persisted along the entire pipe to enhance the vibration over a broad band frequency range, while the later, due to the process of bubble formation, successively decayed in the streamwise direction.

关键词： pipe vibration bubbly flow acoustic resonance normal mode decay rate

Flow Instability and Its Control in Compression Systems

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Journal of Thermal Science 2003年第1期12卷 1-9页

作者： Jingyi ChenInstitute of engineering thermophysics, chinese academy of sciences, {3. 100080, china Institute of engineering thermophysics Chinese Academy of Sciences Beijing China

This paper reviews the development in the research of flow instability and its control over the recent ten or more years. This development was largely stimulated by the novel idea of active control of the aerodynamic instability in compressors. Three topics are covered in the paper, which appeared as the major themes towards the goal of stability enhancement. The first topic is the pre-stall behavior of rotating stall, which plays a vital role in designing the control scheme and discovering the convenient route to find the causal factors of flow disturbances potentially leading to stall. The second topic is the mechanism of blade passage flow during stall and its inception, which is the basic knowledge needed to manipulate the blade design for the stability improvement and eventually to predict the unsteady performance of the compressor system. The third topic is the recent trend of the control strategy based on the learning of active vs. passive methods. To introduce to the discussion of these topics, a brief description of the history of the recent development is given at the beginning of the paper. In discussing each topic, future works are also highlighted to enhance the further development of this long-standing problem in turbomachinery research and application.

关键词： compressors rotating stall pre-stall active/passive control wavelet.

chinese Guidelines for the Diagnosis and Management of Atrial Fibrillation

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Journal of Geriatric Cardiology 2024年第3期21卷 251-314页

作者： Chang-Sheng MA Shu-Lin WU Shao-Wen LIU Ya-Ling HAN chinese Society of Cardiology chinese Medical Association Heart Rhythm Committee of chinese Society of Biomedical {3. beijing Anzhen Hospital Capital Medical University Guandong Provincial People’s Hospital Shanghai First People’s Hospital General Hospital of Northern Theater Command 不详

Atrial fibrillation(AF)is the most common sustained cardiac arrhythmia,significantly impacting patients’quality of life and increasing the risk of death,stroke,heart failure,and *** the past two decades,there have been significant breakthroughs in AF risk prediction and screening,stroke prevention,rhythm control,catheter ablation,and integrated *** this period,the scale,quality,and experience of AF management in china have greatly improved,providing a solid foundation for the development of guidelines for the diagnosis and management of *** further promote standardized AF management,and apply new technologies and concepts to clinical practice in a timely and comprehensive manner,the chinese Society of Cardiology of the chinese Medical Association and the Heart Rhythm Committee of the chinese Society of Biomedical engineering have jointly developed the chinese Guidelines for the Diagnosis and Management of Atrial *** guidelines have comprehensively elaborated on various aspects of AF management and proposed the CHA2DS2-VASc-60 stroke risk score based on the characteristics of AF in the Asian *** guidelines have also reevaluated the clinical application of AF screening,emphasized the significance of early rhythm control,and highlighted the central role of catheter ablation in rhythm control.

关键词： prevention sustained diagnosis

Experimental Research on Antiscale and Scale Removal by Ultrasonic Cavitation

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Journal of Thermal Science 2009年第1期18卷 65-73页

作者： LI Hong-xia,HUAI Xiu-lan,CAI Jun and LIANG Shi-qiangInstitute of engineering thermophysics,chinese academy of sciences,{3.,100190,china Professor Institute of engineering thermophysics Chinese Academy of Sciences Beijing China

Aiming at the scale problem in heat-transfer equipments, experimental investigation on antiscale and scale removalby ultrasonic cavitation is performed. By means of microscopic magnifying photography system, thesedimentary phenomenon can be observed. The experimental research reveals the influencing rule of acoustic intensity,cavitational distance, liquid temperature and solution concentration. The experimental results indicate thatliquid temperature has different effects on antiscale and scale removal. Different experimental liquids are used forantiscale and scale removal experiments. The results show that every liquid has a respective Cavitational activetemperature. When ultrasonic is used for antiscale, the smaller acoustic intensity is, the better effect is. But, whenultrasonic is used for scale removal, acoustic intensity has a reverse influence. In addition, biggish solution concentrationis propitious to antiscale for long-time running. Distance of test sample to ultrasonic transducer alsohas certain influence on antiscale and scale removal. The smaller the distance to ultrasonic transducer is, the bettereffects antiscale and scale removal have.

关键词： ultrasonic cavitation acoustic cavitation antiscale scale removal acoustic intensity

Dynamic behaviors of cavitation bubble for the steady cavitating flow

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Journal of Thermal Science 2009年第4期18卷 338-344页

作者： Jun CAI,Xiulan HUAI and Xunfeng LIInstitute of engineering thermophysics,chinese academy of sciences,P.O.Box 2706,{3.,china Professor Institute of engineering thermophysics Chinese Academy of Sciences P.O.Box 2706 Beijing 100190 China

In this paper, by introducing the flow velocity item into the classical Rayleigh-Plesset dynamic equation, a newequation, which does not involve the time term and can describe the motion of cavitation bubble in the steadycavitating flow, has been obtained. By solving the new motion equation using Runge-Kutta fourth order methodwith adaptive step size control, the dynamic behaviors of cavitation bubble driven by the varying pressure fielddownstream of a venturi cavitation reactor are numerically simulated. The effects of liquid temperature (correspondingto the saturated vapor pressure of liquid), cavitation number and inlet pressure of venturi on radial motionof bubble and pressure pulse due to the radial motion are analyzed and discussed in detail. Some dynamicbehaviors of bubble different from those in previous papers are displayed. In addition, the internal relationshipbetween bubble dynamics and process intensification is also discussed. The simulation results reported in thiswork reveal the variation laws of cavitation intensity with the flow conditions of liquid, and will lay a foundationfor the practical application of hydrodynamic cavitation technology.

关键词： cavitation bubble bubble dynamics hydrodynamic cavitation cavitating flow process intensification

Research of the Gas-solid Flow Character Based on the DEM Method

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Journal of Thermal Science 2011年第6期20卷 521-526页

作者： Xueyao Wang and Yunhan Xiao Research Center for Clean Energy and Power,chinese academy of sciences Key Laboratory of Advanced Energy and Power,chinese academy of sciences (Institute of engineering {3.),beijing,100190,china Research Center for Clean Energy and Power Chinese Academy of Sciences Beijing China Key Laboratory of Advanced Energy and Power Chinese Academy of Sciences (Institute of Engineering Thermophysics) Beijing China

Numerical simulation of gas-solid flow behaviors in a rectangular fluidized bed is carried out three dimensionally by the discrete element method (DEM).Euler method and Lagrange method are employed to deal with the gas phase and solid phase *** collided force among particles,striking force between particle and wall,drag force,gravity,Magnus lift force and Saffman lift force are considered when establishing the mathematic ***-sphere model is used to describe the collision of *** addition,the Euler method is also used for modeling the solid phase to compare with the results of *** flow patterns,particle mean velocities,particles' diffusion and pressure drop of the bed under typical operating conditions are *** results show that the DEM method can describe the detailed information among particles,while the Euler-Euler method cannot capture the micro-scale *** matter which method is used,the diffusion of particles increases with the increase of gas *** the gathering and crushing of particles cannot be simulated,so the energy loss of particles' collision cannot be calculated and the diffusion by using the Euler-Euler method is *** addition,it is shown by DEM method,with strengthening of the carrying capacity,more and more particles can be schlepped upward and the dense suspension upflow pattern can be ***,the results given by the Euler-Euler method are not consistent with the real situation.

关键词： DEM gas-solid flow numerical simulation

Study on Dynamical Behavior of Turbulent Premixed V-flames

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Journal of Thermal Science 2003年第4期12卷 381-384页

作者： Baorui Wang Kun Yuan Xiaoqian ZhangInstitute of engineering thermophysics, chinese academy of sciences, {3. 100080, china Institute of engineering thermophysics Chinese Academy of Sciences Beijing China

Differential interference contrast method was applied to investigate the flickering characteristics of V-flame in terms of both temporal and spatial scales. The flow characteristics of incident premixed combustibles were measured by means of laser Doppler anemometry (LDA). The characteristics of wake flow behind the stabilizing rod were obtained with numerical simulation. While the integral temporal scale of incident turbulence is about 1ms, the integral spatial scale about 2 mm, the characteristic flickering time scale is about 83.ms and spatial scale about 10 mm. The flame flickering frequency is more than 12 Hz, does not comply with the wake vortex shedding frequency, which is about 110 Hz. It is well-known that the flickering of V-flame is affected by both the incident turbulence and the wake flow after the stabilizing rod, but the result of the paper shows that the relationship between flickering characteristics and flow characteristics is much more complicated by the chemical reaction.

关键词： premixed flame turbulence numerical simulation.

The Simulation of Influence of Different Coals on the Circulating Fluidized Bed Boiler's Combustion Performance

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Journal of Thermal Science 2003年第2期12卷 185-187,184页

作者： Yumei Yong Qinggang LuInstitute of engineering thermophysics, chinese academy of sciences, 100080 {3., china Institute of engineering thermophysics Chinese Academy of Sciences Beijing China

The combustion performance of the boiler largely depends on the coal type. Lots of experimental research shows that different fuels have different combustion characteristics. It is obvious that fuel will change the whole operating performance of Circulating Fluidized Bed Combustion (CFBC). We know even in a pilot-scale running boiler, the measurement of some parameters is difficult and costly. Therefore, we developed the way of simulation to evaluate the combustion performance of chinese coals in CFB. The simulation results show that, different coals will result in different coal particle diameter and comminution depending on their mineral component and the change will affect the distribution of ash in CFBC system. In a word, the computational results are in accordance with experimental results qualitatively but there are some differences quantitatively.

关键词： coal circulating fluidized bed combustion simulation.

Unsteady Numerical Simulation of Hot Streak/Blades Interaction and Film Cooling

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Journal of Thermal Science 2010年第5期19卷 402-409页

作者： Weilin Yi,Lucheng Ji and Yunhan Xiao Research Center for Energy and Power,chinese academy of sciences,beijing,china Key Laboratory of Advanced Energy and Power,chinese academy of sciences,(Institute of engineering thermophysics),beijing,china P.O.Box 2706,beijing 100190,china Research Center for Energy and Power Chinese Academy of Sciences Beijing China Key Laboratory of Advanced Energy and Power Chinese Academy of Sciences (Institute of Engineering Thermophysics) Beijing China beijing China

Deeply research on management and application of hot streak is an important way to breakthrough technique obstacle of aero engine hot *** method is a useful instrument to investigate the correlative *** the paper developed independently three dimensional unsteady parallel computational code-MpiTurbo based on Fortran 90 and MPI at Linux operating *** unsteady numerical simulation was carried out to investigate impacts of the factors,which included circumferential locations of hot streak and clocking positions of blade rows,on the thermal environment of a 1+1 counter-rotating *** results clearly indicated that clocking positions of hot streak/blade row and blade row/blade row had great influence on the time-averaged temperature distribution of the third blade ***,it can be effective for improving thermal environment of turbine to optimize blade parameters and clocking *** film cooling layout was designed by the repetitious steady simulation based on source term *** the flow structure detail was given by the unsteady simulation.

关键词： hot streak turbine parallel computation film cooling