SEPARATOR FOR LIQUID-LIQUID DISPERSIONS

An apparatus for separation of fine liquid dispersions is described and its performance characteristics are studied. It provides high separational efficiency at high flowrates and small pressure drop. The emulsion enters axially in a cylindrical cartridge, then flows radially through a multi-layer packing where phase separation takes place. The coalesced phase forms a film, which is continuously lead to the interface. The main features of the unit are outlined and a comparison with other similar units is made.     

a~4的本征态的相位和粒子数起伏

详细地计算了a~4的四个正交归一本征态的相位起伏、粒子数起伏与粒子数—相位不确定关系。讨论了相位起伏、粒子数起伏的特性和产生粒子数—相位最小不确定关系的条件,并与压缩真空态进行了比较。     

EVALUATION OF MINIMUM FLUIDIZING VELOCITY IN GAS FLUIDIZED BED FROM PRESSURE FLUCTUATIONS*

A new experimental method for the evaluation of minimum fluidizing velocity in gas fluidized beds is proposed based on the pressure fluctuations measurements. The minimum fluidizing velocity is determined solely from the measurements in the fluidized bed regime, unlike the traditional method, where experiments in the fixed bed regime are also necessary. Using the proposed method the on-line evaluation and prediction of the minimum fluidizing velocity is possible which is important for the control of industrial fluidized bed reactors.     

Experimental investigation of bubble behavior in gas-solid fluidized bed

In this work, to investigate the source of pressure fluctuations, behavior of a single bubble in a two-dimensional gas–solid fluidized bed was studied. Pressure sensors located at different heights of the bed measured presure fluctuations, and simultaneously a high speed camera was used to pursue all steps from formation to eruption of bubbles. Two types of particles were applied with different sizes and densities. Experiments showed that the maximum amplitude of formation was independent of the bubble diameter. But, it depended on density of particles, velocity of injection and the distance from bed surface. When injection stopped, there was a minimum in pressure profile related to the higher dense phase voidage for a higher superficial gas velocity after injection. Also, the maximum pressure fluctuation of bubble eruptions was related to the bubble diameter, density and size of particles. It was concluded that pressure fluctuations of formation, passing and eruption of bubbles in fluidized beds are originated due to changes in dense phase voidage, bed voidage and movement of particles during bubble eruption.     

一种突发直扩信号盲检测算法

针对突发直扩信号的盲检测问题,提出一种基于波动相关和滑动-延迟-相关相结合的盲检测算法.算法重点研究了突发直扩信号的存在性检测和信号起止点的捕获问题.首先利用波动相关法解决了信号的存在性检测问题,并精确估计出直扩信号的扩频周期,然后通过滑动-延迟-相关的方法准确捕获信号的起止点位置,最终实现信号的盲检测.仿真结果表明,该算法判决精度高,且抗频偏,在信噪比为-7dB时其检测概率可达90％以上.     

SHIP‐LOCK–INDUCED SURGES IN AN IMPOUNDED RIVER AND THEIR IMPACT ON SUBDAILY FLOW VELOCITY VARIATION

The majority of large rivers are fragmented by dams, and navigation is often supported by the installation of ship locks. Despite their ubiquitous existence, the effect of ship locks on river basin hydrodynamics is rarely considered in an environmental context. Ship‐lock operation induces single‐wave crests or troughs called surges, which propagate along the basin and are subject to reflection at the up‐ and downstream impoundments. We used pressure sensors and acoustic Doppler current profiler measurements to investigate the effects of up‐ and downstream ship locking on the water level and the current velocity dynamics in a 12.9‐km‐long basin of the impounded river Saar (Germany). Ship lifting at the lower dam and the associated water export from the basin results in a negative surge propagating upstream, whereas a descending ship‐lock operation at the upper dam of the basin creates a positive surge propagating downstream. Both types of waves are subject to positive reflection at the opposing dams. Frequent lock operations lead to a complex pattern of multiple superimposing surges. The resulting water level fluctuations are comparable in magnitude with those associated with discharge variations due to hydropower peaking but occur at much shorter timescales. Associated with the water surface displacement during wave passage is a corresponding increase or decrease of the longitudinal current velocity. The magnitude of wave‐induced velocity fluctuations can exceed mean flow velocities by a factor of three and, depending on wave type and direction, can result in a reversal of the main flow direction of the river. Because of their longevity of several hours and superposition effects, ship‐lock–induced surges govern 66.3% and 45.4% of the subdaily variations in flow velocity and water level, respectively. This article concludes with a discussion of the potential effects of lock‐induced flow dynamics in impoundments on oxygen dynamics and methane ebullition. Copyright © 2013 John Wiley & Sons, Ltd.     

DIRECT NUMERICAL SIMULATIONS OF TURBULENT CHANNEL FLOWS WITH CONSIDERATION OF THE BUOYANCY EFFECT OF THE BUBBLE PHASE

Turbulent channel flows with consideration of the buoyancy effect of the bubble phase is investigated by means of the Direct Numerical Simulation(DNS).This two-phase system is solved by a two-way coupling Lagrangian-Eulerian approach.The Reynolds number based on the friction velocity and the half-width of the channel is 194,and the gravitational acceleration varies from-0.5 to 0.5,ranging from the upflow to the downflow cases.This study aims to reveal the influence of buoyancy on the turbulence behavior and the bubble motion.Some typical statistical quantities,including the averaged velocities and velocity fluctuations for the fluid and bubble phases,as well as the flow structures of the turbulence fluctuations,are analyzed.     

STOCHASTIC BEHAVIOR OF FLUIDIZED PARTICLES IN A LIQUID-SOLID FLUIDIZED BED

In a liquid-solid fluidized bed, the apparently irregular or stochastic behavior of particles gives rise to various flow regimes depending on parameters such as the particle size, liquid flow rate, static bed height and axial position in the bed. It is highly plausible that this irregular behavior manifests itself as pressure fluctuations; thus, the effects of these parameters on the particle behavior or the particle flow regime were investigated through measurement and spectral analysis of the pressure fluctuations. The results indicate that the amplitude of pressure fluctuations exhibits a maximum and that the decay constant in the autocorrelation function attains its minimum at the intermediate liquid flow rate where the particle flow regime undergoes transition from the cluster circulation to the individual quasi random motion. The model composed of the periodic and stochastic components of pressure fluctuations, is in good accord with the experimental results in terms of both the autocorrelation and power spectral density functions.     

Electrochemical noise analysis of cathodically polarised AISI 4140 steel. II. Identification of potential fluctuation sources for unstressed electrodes

In this second part of the study of electrochemical noise (EN) generated by hydrogen evolution on a vertical cylindrical AISI 4140 steel electrode under galvanostatic control in 0.5 M sulphuric acid, the potential fluctuations induced by the growth and detachment of hydrogen bubbles at the electrode surface were analysed. They could be related to fluctuations of various quantities: electrode active surface due to bubble screening effects, concentration of dissolved hydrogen in the electrolyte close to the electrode surface, and metal-hydrogen interactions (MHI) on or beneath the electrode surface. The existence of MHI and their influence on faradaic potential fluctuations could be revealed by comparing the noise features on steel and platinum. The influence on EN of the charging cathodic current density, the presence of dissolved oxygen in the solution, and the electrode rotation speed was investigated in the absence of stress applied to the electrode. In the third paper of this series, the effect of hydrogen embrittlement on potential fluctuations of stressed electrodes will be examined.