颗粒团影响循环流化床内气固流场的PIV测试

利用自行构建的可用于循环流化床内流动特性测试的PIV系统对一台高4m截面200mm×200mm的冷态循环流化床进行了PIV测试研究。采用适合于较高粒子浓度的互相关处理MQD方法来处理PIV图像,获得了循环流化床内颗粒团运动对流场内颗粒速度的动态影响。结果表明:(1)颗粒团可能出现在流场截面内的各个位置,形状和速度都随时间的变化而变化;(2)颗粒团对床内的气固流动行为有较大的影响。只要有颗粒团出现,无论它的流动方向与主流颗粒的流动方向异同,气流和分散固粒都受到它的驱动向不同方向运动;(3)在颗粒团增长过程中,随着时间的增加,流场截面内颗粒平均速度虽然有波动,但总的变化趋势是增加的。     

Velocity measurement in solid–liquid flows using an impact probe

The use of a modified impact type of probe for velocity field measurement in the flow of multi-sized (d₅₀=71 μm) particulate slurries is described. The impact probe has a sensor similar to a two hole offset probe but has a modified pressure sensing system which prevents blockage of the probe by the solid particles. The probe system has been successfully used in slurry flows over a wide range of solid concentrations (0–40% by weight) and flow velocities (1.67–2.95 m/s). The data presented in this paper have revealed some special features of velocity distribution in the flow of multi-sized particulate suspensions.     

基于虚拟仪器的多相流量计量系统

介绍了以虚拟仪器技术为基础的应用双能γ射线衰减和互相关流速测量技术的多相流量测量系统。提出了系统的硬件组成，根据多相测量的原理，描述了用图形语言LabVIEW编程的算法。     

Studying local liquid velocity in liquid–solid packed bed using the newly developed X-ray DIR technique

Combination of X-ray Digital Industrial Radiography (DIR) and Particle Tracking Velocimetry (PTV) techniques for local liquid velocity measurement (V_LL) has been newly developed and successfully applied for trickle bed reactor (TBR). The technique was validated against newly developed fiber optical probe technique. This work attempts to highlight the applicability of this newly developed technique on a liquid–solid packed bed reactor. In this work, liquid was represented by water and solids were represented by EPS beads. The EPS beads were chosen because of its low density property. Three superficial liquid velocities (V_SL) were applied to the system. The experiment was replicated four times. The digital industrial radiography (DIR) consists of a complementary metal oxide semiconductor (CMOS) digital detector and X-ray source. Results of this work suggest that the technique has been successfully applied and comparable with previous work that has been done in the literature. It also suggests that there will be a maximum measurable interstitial liquid velocity when it travel inside the packed bed. The measured V_LL can have a maximum range that is between 4 and 4.7 times that of its V_SL. For V_SL=0.42±±2%, the V_LL-Max is in between 1.7 cm/s and 1.9 cm/s, V_SL=0.84±±2%, the V_LL-Max is in between 3.6 cm/s and 4.0 cm/s, and for V_SL=1.11±±2%, the V_LL-Max is in between 4.3 cm/s and 4.8 cm/s.     

提高FDM模型表面质量的方法

通过阐述熔融材料堆积成形(FDM)技术的工作原理,从成形方式和成形过程等方面分析造成模型表面质量不高的原因,提出通过在CAD数字模型设计阶段对其进行前期处理从而提高模型表面质量的简单方法,经过多次试验获得良好的效果。     

A study on the slip velocity on a pair of asymmetric electrodes for AC-electroosmosis in a microchannel

In numerical studies on microscale electroosmotic flows, the electric double layer (EDL) effect is usually predicted by solving the traditional Navier-Stokes equation subjected to the slip velocity induced by the electric-charged wall as a boundary condition. Recently, Suh and Kang (Physical Review E 77, 2008) presented the asymptotic solutions of the ion transport equations near a polarized electrode under the action of an AC field, and then proposed a new theoretical model of the slip velocity on the electrode considering the ion adsorption effect. In the present paper, we apply the model to a two-dimensional AC-electroosmotic flow in a microchannel to calculate the slip velocity on a pair of coplanar asymmetric electrodes embedded on the bottom wall, and then experimentally measure the slip velocity using the micro-PIV technique to validate the theoretical model. Comparison shows an excellent overall match between the theoretical and experimental results, except for on the narrow electrode at low frequencies. Next, we numerically perform parametric studies regarding the AC frequency, effective Stern-layer thickness and ion adsorption effect to further understand the characteristics of the AC electroosmotic flow. Results show that, as the frequency increases, the slip velocity also increases. In addition, the velocity decreases with increasing either Stern-layer thickness or ion adsorption effect. This paper was recommended for publication in revised form by Associate Editor Dongshin Shin Sangmo Kang received a B.S. and M.S. degrees from Seoul National University in 1985 and 1987, respectively, and then had worked for five years in Daewoo Heavy Industries as a field engineer. He also achieved a Ph.D. degree in the field of Mechanical Engineering from the University of Michigan in 1996. Dr. Kang is currently a Professor at the Division of Mechanical Engineering at Dong-A University in Busan, Korea. Dr. Kang’s research interests are in the area of micro- and nanofluidics and turbulent flow combined with the computational fluid dynamics.     

离心式杂质泵内颗粒分布规律的研究

利用Fluent软件对离心式杂质泵内部流场进行数值计算,将其内部流动可视化,分别计算了不同颗粒直径和泵进口固相浓度多个工况下泵内的两相流流场,得到了叶轮和蜗壳内的固相浓度分布。分析了不同进口固相浓度以及不同颗粒直径条件下,颗粒在叶轮和蜗壳内的分布规律。     

Application of in-line ultrasound Doppler-based UVP–PD rheometry method to concentrated model and industrial suspensions

The in-line ultrasound Doppler-based UVP–PD rheometry method was evaluated for non-invasive, real-time rheological characterization of complex model- and industrial suspensions. The method is based on the combination of ultrasound velocity profile (UVP) and pressure drop (PD) measurements. Experiments were carried out in pressure driven, steady shear flow at different volumetric flow rates in a flow loop, designed to mimic industrial conditions. Results showed that instantaneous velocity profiles and rheological properties could be monitored in real-time, in-line. A much wider range of model and industrial suspensions was covered compared to what has so far been reported in literature. Investigated suspensions differed in particle sizes, distributions, shapes and suspension characteristics. The agreement was good between shear viscosities measured in-line and off-line using conventional rheometers for particles smaller than the shear gap in the concentric cylinders. The UVP–PD method is applicable to suspensions for which conventional, off-line rheometers fail due to shear gap size restrictions. The UVP–PD method can be a valuable tool for process monitoring since rapid changes in rheology during processing can be monitored in real-time, in-line.     

STUDY ON THE LUBRICATION FACTOR OF INVOLUTE SPUR GEARS

Based on a lot of numerical solutions to the problems of the thermal non-Newtonian elasto-hydrodynamic lubrication and some fatigue tests with rollers the lubrication factor of involute spur gears (called gear for short) is investigated. The results suggest that gear lubrication effects bear close relations to a dimensionless parameter D which is synthetically determined by gearing rotational speed,load,material,dimension and lubricant viscosity.When D<8,the gear fatigue life increases as the lubricant viscosity is increased;When D>8,however,the life decreases with the viscosity addition,which is in marked contrast to the lubrication factor Z recommended by the International Standard for Computing Cylindrical Gear Strength.At the end,a set of formulae for calculating gear lubrication factors suitable for different working conditions are advanced.     

Thermophoretic transport and deposition of particles in vertical tube flow with variable wall temperature and thermal radiation

A particulate two phase flow with variable wall temperature has been studied for examining the deposition of particles in the thermal radiation and mixed convection flow associated with the manufacture of optical fiber preforms. The two-dimensional governing equations of continuity, momentum and energy have been solved numerically including the effects of thermal radiation and buoyancy (upward or downward flow) in the vertical tube flow. A particle trajectory model has been adopted to predict the particle transport, and P-1 approximation has been used to evaluate the radiation heat transfer. In the upward flow case, a high deposition efficiency is obtained and the deposition zone of the downward flow is broader than that of the upward flow. Thermal radiation makes the deposition zone broader and the deposition efficiency smaller.     

TWO-DIMENSIONAL PARTICLE IMAGE VELOCIMETRY（PIV） MEASUREMENTS IN A TRANSPARENT CENTRIFUGAL PUMP

A special transparent centrifugal pump is designed. Detailed optical measurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pump impeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow is surveyed at three load conditions qV/Vd = 0.4, qV/qVd = 1.0, qVlqVd = 1.5, respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub and shroud of the impeller are presented. At design load, the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow without separation. The distributions of the relative velocity on different plane along the pump shaft are very different and there is always a low velocity zone near the pressure-side of the blade at both low and design flow rate, but the low-velocity-zone at the low flow rate is much larger than that at the design one. The study demonstrates that the PIV technique is efficient in providing reliable and detailed velocity data o     

Dual colorimetric and fluorescent determination of iron (III) using a novel squaraine dye

A novel squaraine dye, 6-carboxy-2-[[3-[1,3-dihydro-3,3-dimethy-1-ethyl-2H-indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-3,3-trimethy-3H-indolium, has been synthesized. The squaraine dye was found to be a dual colorimetric and fluorescent probe for the determination of iron (III) in CH₃CH₂OH/H₂O (4:1, v/v) exhibiting high selectivity and sensitivity. The binding of squaraine dye +Fe³⁺ was studied by a Job’s plot and Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopies. The result indicates that the squaraine dye may be utilized as a naked-eye and real-time probe for the efficient determination of Fe^3+.     

High-accuracy ultrasonic temperature measurement based on MLS-modulated continuous wave

Ultrasonic temperature measurement has the potential to improve measurement accuracy by increasing the length of a received signal due to its excellent performance with noise resistance. However, when the distance between the transmitter and receiver is limited, the received signal can be polluted by strong multiple echoes, which can significantly degrade temperature accuracy. This paper proposes a method for high-resolution ultrasonic temperature measurement. With the use of a maximum length sequence (MLS)-modulated continuous wave, the obstructive effect of echoes is effectively suppressed. A hybrid method is employed for accurate time-of-flight (TOF) estimation by incorporating both cross-correlation and phase shift (PS), which is the basis of highly accurate temperature measurement. The experimental results in distilled water show that the proposed method estimates TOF with a standard deviation of less than 0.3 ns, and temperature errors consistently remain within ±0.04 °C.     

EXPERIMENTAL RESEARCH OF NANO-CUTTING BY USING SCANNIN G PROBE MICROCOPE

0 INTRODUCTIONNanotechnolOgy becomes particularly interestingnowadays, because the increasing needs of itsapplications are demanded with the development ofhish technology, not only in scientific but also inengineering field, esPecialy in electronic and opticalindustries. As long as nanotechnology is mentioned, itwill be concerned that machining at nanometer scale,which is sometimes called nanomachining. Thereare two similar ultra-precision machining inconventional method, i. e. ultrapre…