气固下行流化床反应器Ⅱ气固两相的流动规律

气固下行流化床反应器气固两相流动过程是比较复杂的，沿轴向气固两相运动可分为第一加速、第二加速和恒速３个运动段，沿径向局部气体速度、颗粒速度和颗粒浓度都具有不同程度的不均匀性。而这种不均匀性是由气固两相顺重力场湍动运动所决定的。和循环床提升管相比，下行管反应器气固两相沿径向分布的不均匀性得到有效地改善，气固可以实现超短接触操作，因而是一种新型高效气固超短接触反应器     

Near Wall Studies of Pulp Suspension Flow Using LDA

A detailed study of the flow behaviour in the near wall region of pulp suspensions up to 4.7% have been performed using Laser Doppler Anemometry (LDA) in pipe flow. Axial mean velocity profiles show a distinct plug flow and an increase of the plug region as the flow rate decreases and fibre concentration increases. An attempt is made to relate the LDA data‐rate to fibre concentration, which indicates a dilution region at 1‐2 mm from the wall that is larger than the annulus region. The dilution region increases with increasing flow rate, decreasing concentration and when using longer pulp fibres.     

陀螺稳定装置载体角振动仿真模型构建方法

建立了坦克装甲车辆行驶角振动和陀螺稳定装置载体角振动关系的数学模型,实现了在坦克装甲车辆行驶振动条件下火炮稳定性能的计算机仿真测试,为评价火炮控制系统的设计提供了一种依据。     

<Emphasis Type="Italic">In situ</Emphasis> monitoring of solid fat content by means of pulsed nuclear magnetic resonance spectrometry and ultrasonics

An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC. TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r ²>0.9) in a linear fashion (v=2.601 SFC+1433.0).     

高强混凝土受火后力学性能变化规律的研究

对受火后的混凝土试件进行了抗压强度、抗折强度和劈裂抗拉强度试验,讨论了温度、强度等级、试件尺寸、含水量对其高温后力学性能的影响。研究表明,受火后,抗折强度较抗压强度下降更快;高强度的混凝土在600℃前抗压强度下降不多;大尺寸混凝土试件较小尺寸混凝土试件的残余抗压强度下降慢;混凝土试件的含水率越高,相对残余抗压强度越低。采用超声波速度法和质量损失法对火灾高温后混凝土内部结构的变化进行了探讨。     

Prediction of minimum velocity and minimum bed pressure drop for gas-solid fluidization in conical conduits

Experimental investigations have been carried out for spherical and non-spherical particles using beds comprised of single-sized particles and mixtures in the size and particle density ranges of 439 to 1524 μm and 1303 to 4948 kg/m³, respectively. Five conical fluidizers with varying apex angles of 8.86, 14.77, 19.60, 32.0 and 43.2 degrees were used. Experimental values of minimum velocity and bed pressure drop with air as the fluidizing medium have been compared with their respective values obtained from different models available in the literature. Deviations for each chosen model have been presented.     

Settling velocities of particles in bubbly gas-liquid mixtures

The axial dispersion-sedimentation model is commonly used to describe the axial concentrations of solids in three phase bubble columns at low liquid velocities. When the two parameters of this model, the particle settling velocity and the solids axial dispersion coefficient, are uncoupled by the use of various assumptions, physically unrealistic values of these parameters often result. Direct experimental measurements of solids settling rates in bubbly gas-liquid mixtures were carried out. The measured mean settling velocities decreased slightly with gas flow rate and were equal to or slightly less than the single particle free settling velocity in the liquid alone. Solids axial dispersion coefficients were also obtained from the solids settling rate distribution data, and gave values considerably less than the experimental liquid axial dispersion coefficient.     

Flow characteristics of hyperboloid stirrers

The flows in a fully-baffled vessel with a diameter T = 144 mm driven by hyperboloid stirrers of diameters D = 773 and 27/3 have been visualised and characterised by local measurements of velocity and turbulence and by power number. The results were obtained for a range of rotational speeds from 6 to 40 rev/s. The visualisation showed that the larger stirrer gave rise to a radial jet and that the smaller stirrer formed a jet inclined towards the base of the vessel so that there was a tendency for the system of two vortices, one above and one below the jet, to give way to a single vortex as the clearance between the stirrer and the base of the vessel was reduced. The velocity measurements revealed bulk-flow values an order of magnitude less than that of the maximum radial velocity in the jet, that the maximum radial velocity was 24% of the circumferential velocity of the tip of the stirrer, and that the radial velocities were proportional to the rotational speed. The flows generated by the hyperboloid stirrer were less vigorous than those of Rushton impellers of similar radius and were associated with power numbers 28 times less. The power number did not vary with rotational speed or with clearance within the measured range. The contrast with propeller and disc stirrers is less pronounced, but the hyperbolic profile is likely to find application and the present results provide a basis for choice.     

Theoretical Model for Calculating Electric-Power Curves Depicting Accelerated Flyer by Exploding Foil

A theoretical model for calculating electric-power curves of small-size foil during its electrical explosion is given.This technique is based on temperature dependence of foil conductivity.After taking into account the energy conversion of the foil explosion,the power-time curve is applied to the hydrodynamic code.One-dimensional numerical simulations of electric-explosion driving flyers are performed using this code.Calculated flyer velocities lie within ±8% of experimental data from Lawrence Livermore Nat...     

中国南方岩溶区岩溶地下河系统复杂水流运动特征

岩溶地下河系统水流运动多受控于岩溶多重介质环境,其主干空间展布、水体贮存、水流运动、水循环等规律的变化具多因多果性。在中国南方岩溶区岩溶地下河系统物质和能量转换的基础上,分析了其形成和演化等相关条件,研究和总结了其水流运动方向的多重性、速度的多变性、地表地下方式的转化性、时空配置的多样性及水流运动演变规律;根据维数、压力、流态等不同原则,将中国南方岩溶地下河系统水流运动方式进行分类。结合中国南方岩溶地下河系统研究现状,提出今后需加强与实践的重点。