富氧底吹熔炼炉内气液两相流动的数值模拟

以某公司的富氧底吹熔池熔炼炉为原型,运用数值模拟的方法对炉内氧气铜锍两相流动进行三维瞬态模拟,研究炉内气泡主要参数、气含率分布规律、氧枪出口附近压力变化以及液面波动情况。并借助于高速摄像仪设备,对水模型实验中气泡形成、合并、变形及破碎过程进行研究,所得结果与模拟结果进行比较。结果表明:所建立的数学模型是合理的。氧气铜锍两相流动模拟结果表明,炉内气泡形成时间为0.12~0.25 s,生成频率为4~5 Hz,其短轴大小集中在3.5d~6.5d(d为氧枪直径尺寸);气泡停留时间为0.2~0.4 s,其在熔池内的平均上浮速度约为4 m/s;7°和22°氧枪出口气泡后座现象出现的平均频率分别为5 Hz和7 Hz,作用时间为0.06 s;高效反应区存在于熔池上部区域;气相搅动液相所形成的表面重力波在沉淀区传播的过程中,波幅衰减很快,当波传播到出渣口附近时,液面趋于静止。     

Cold model on bubble growth and detachment in bottom blowing process

The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography and digital image processing. For these configurations, the experiments reveal that the bubble growth consists of a petal-like stage, an expansion stage and a detachment stage. The petal-like shape is qualitatively described through the captured images, while the non-spherical bubbles are analyzed by the aspect ratio. The bubble size at the detachment is quantified by the maximum caliper distance and the bubble equivalent diameter. Considering the dependence on the opening ratio, different prediction models for the ratio of maximum caliper distance to hydraulic diameter of the nozzle outlet and the dimensionless bubble diameter are established. The comparative analysis results show that the proposed prediction model can accurately predict the bubble detachment size under the condition of multi-hole nozzles.     

结晶器吹氩过程离散相运动行为模拟

本文通过建立欧拉-拉格朗日模型模拟钢液-氩气-夹杂物体系,研究气泡间的聚合、夹杂物之间的聚合、气泡对夹杂物的粘附机制。得到结晶器内流场、离散相（氩气泡、夹杂物）的大小、运动速度等信息。通过对大量离散粒子信息的统计得出气泡对去除夹杂物的影响。     

空泡应用于管道内粒子移除的研究

研究了刚性管道中粒子在振动空泡的作用下移除的过程,振动空泡由一个55 V的低压电路产生。高速相机记录了空泡作用下粒子的动力学行为及空泡的形状变化过程,高速相机的帧率设为15000 f／s。结果表明：粒子的移除速度受空泡产生的初始位置和空泡在管道中的轴向长度的影响。     

透气砖底吹净化铝熔体的除气效率分析

在线测量了透气砖底吹净化装置的除气效果,从除气动力学方程出发建立了除气效率的计算模型,计算了气泡尺寸,并考虑气体受热膨胀和合泡的影响对其进行了修正.试验结果表明,除气效率随N2流量的增加而增大,当采用N2作为净化气体时,除气效率在40%以内,而采用N2-Cl2混合气体时,除气效率提高约10%.修正后计算得出通过透气砖吹入铝液中的气泡尺寸约为4 mm,除气效率计算值与试验结果较吻合.除气过程中气泡利用效率为50%～70%.从动力学角度分析得出了提高除气效率的主要途径.     

Numerical modeling of effect of slot on bubble motion in aluminum electrolytic process

A transient three-dimensional (3D) model was established to understand the bubble motion in an industrial electrolytic process. An anode with a new design was tested. It incorporates two slots that allow an efficient removal of gas bubbles. The electromagnetic fields were described by solving Maxwell's equations. The bubble movement was studied with two-way coupling Euler–Lagrange approach. The interplay of current density and bubble nucleation rate was included. The collision and coalescence of bubbles were considered. Random walk module was invoked for involving the chaotic effect of the turbulence. The numerical results were validated by experimental measurements. The results indicate that the current distribution and the bubble nucleation periodically change. Due to the slot, the bubble elimination heavily increases. The contribution of the slot to the bubble removal exceeds 50% in the case of three currents, and the promotion of the slot decays with increasing the current.     

锡石颗粒与氢气泡间的碰撞粘附行为(英文)

运用回收率和细粒锡石-气泡间的碰撞机制研究颗粒-气泡间的相互作用。用单泡浮选管进行浮选实验,考查不同条件下细粒锡石的浮选行为。结果表明,浮选回收率受颗粒和气泡尺寸的影响很大,在浮选回收率最高时,颗粒和气泡间存在一个最佳的匹配范围。运用高速摄影仪观察并捕捉颗粒-气泡间的碰撞、粘附、脱附过程,在已有理论的基础上,分析颗粒-气泡间的碰撞-粘附现象并解释浮选实验结果,通过捕捉图片证明颗粒-气泡间的粘附模型,发现颗粒-气泡间的桥连作用。锡石、气泡尺寸的大小影响锡石-气泡间的相互作用,这不仅影响锡石-气泡间的碰撞粘附行为,并最终影响细粒锡石的浮选回收率。     

<Emphasis Type="Italic">In-situ</Emphasis> X-ray fluoroscopic observation for motion of bubbles in liquid iron for correction of drag coefficient used in numerical simulation

Rising of Ar bubble in C-saturated liquid iron was investigated in-situ by employing a high power X-Ray fluoroscope (maximum power of 450 kV and 4.5 mA) coupled with a high speed camera. This analysis enabled to track the actual motion of rising bubble in the liquid iron. After post-processing of X-Ray images, size, shape, velocity, and trajectory of the bubble were obtained. The bubbles were found to be not spherical, but ellipsoidal. Their average size could be estimated about 1.1×10^-2 m. The bubbles wobbled during rising and arrived at their terminal velocities within 0.1 sec. The obtained terminal velocities revealed that the governing forces acting on the motion of ellipsoidal bubble were inertia and surface force. This was quite different from that of spherical bubble which was widely used in the assumption for the numerical analysis. As a result, widely applied equation for the drag coefficient (C_D = 24 (1 + 0.15Re^0.687) / Re) is seen to be applicable only for low Re regime, and this was also confirmed by the drag coefficient derived from the present experimental observation. Therefore, it is suggested to use the following equation for the drag coefficient C_D = max [24 (1 + 0.15Re^0.687) / Re, 8Eo / 3(Eo + 4)]. Numerical simulation for the Ar bubble behavior in the three dimensional (3D) continuous casting mold was conducted in order to evaluate the effect of the drag coefficient for the behavior of spherical and ellipsoidal bubbles. The numerical results showed that the increased CD based on ellipsoidal regime affected the entire fluid in the mold.     

使用半工业化机械浮选机评估矿浆黏度变化对浮选气泡大小的影响

浮选过程中矿浆的黏稠度是由矿浆温度、矿粒浓度、矿粒细度等决定,它对浮选效率的影响一直受到工业界的极大重视。在实际生产中,一些自然因素和操作参数的变化,如季节性温度的浮动,矿石硬度、矿石性质的变化等产生的矿浆黏稠度的浮动,导致气泡尺寸和分布规律产生浮动,进而使选矿回收率等经济指标下滑。即便如此,在科研中矿浆黏稠度的相关研究并未受到重视。本研究的重点是黏稠度和气泡尺寸在浮选过程中的关系。试验采用半工业化美卓700 L机械浮选机和McGill大学独有的气泡观测仓,通过调整液体温度来改变黏稠度,在充分屏蔽其他浮选操作条件的情况下形成了气泡-黏稠度的关系图。结果显示了气泡尺寸D32和黏稠度（μ/μ20）之间呈现0.776的指数关系,有较强的关联性。本研究结果对实际生产中通过控制黏稠度来优化气泡尺寸,乃至浮选经济指标具有借鉴意义。     

基于提升小波变换的镁熔液弱目标检测方法

镁熔液表面第一气泡的识别是镁熔液含氢量快速现场检测的关键技术。由于温度和振动的影响使镁熔液图像的信噪比和对比度都较低,而且气泡目标像素少。先利用9/7提升小波进行变换,提取高频部分;再利用高频部分进行重构;然后对重构后的图像进行帧差法相减,最后进行自适应阀值处理,检测出弱目标。实验结果表明该算法能够有效地检测出复杂背景下的第一气泡。     

COMPARISON BETWEEN THEORETICAL FORMULA AND EXPERIMENTAL RESULTS ON BUBBLE ELECTROPHORESIS

ＣＯＭＰＡＲＩＳＯＮＢＥＴＷＥＥＮＴＨＥＯＲＥＴＩＣＡＬＦＯＲＭＵＬＡＡＮＤＥＸＰＥＲＩＭＥＮＴＡＬＲＥＳＵＬＴＳＯＮＢＵＢＢＬＥＥＬＥＣＴＲＯＰＨＯＲＥＳＩＳ￥ＸｕＪｉｒｕｎ；ＫｅｌｓａｌｌＧＨ（Ｐ．Ｏ．Ｂｏｘ１３９，ＮｏｒｔｈｅａｓｔｅｒｎＵｎｉ...     

铝液微气泡精炼的模拟试验研究

利用气泡计测量的方法研究了熔池内气泡数量、大小和分布及其影响因素，对气液两相区宏观和微观结构进行了研究。测定了在不同喷枪转速和供气量条件下的气泡直径和气体容量。结果表明，气泡频率和含气率在喷头附近分布很高，在其它部位分布是均匀的。在一定供气量条件下，气泡直径随喷枪转速增加而减小。     

泡沫铝气泡长大动力学

利用海岛模型导出金属流体中气泡长大的连续性方程、运动方程和扩散质量守恒方程,与气泡表面的质量守恒、西华特定律和理想气体状态方程构成气泡长大动力学方程组,在确定粘度、扩散系数和表面张力以及忽略部分惯性力的基础上,对动力学方程组进行了求解,得到金属流体中气泡长大动力学方程,可用于描述泡沫铝气泡长大过程中时间、温度、第二相质量分数及压强各参数对气泡半径变化的影响,是金属流体中气泡演变过程动力学的首次理论描述。     

相界面逸出惰性气泡时相间传质

本文针对液-液两相接触时的传质过程,以流体动力学理论及相间传质的渗透理论为基础,根据界面上惰性气泡逸出界面时流体流动及传质过程的特征,导出了气泡促进的相间传质系数的数学关系式。该关系式表明,流体中传质速率不仅与逸出气泡的体积速度的平方根成正比,同时与气泡大小、界面上气泡分布密度等参数有关。该关系式能较好地描述文献中的实验数据。     

Modeling the effect of cavity shape on cavitation behavior during hot working

The effect of cavity shape on cavitation behavior was established using a mesoscale-modeling approach for the two limiting cases of (i) the growth and coalescence of an initial cavity array with no nucleation of new cavities and (ii) the growth and coalescence of cavities including continuous nucleation. The simulations conducted dealt with two-dimensional situations. It was also assumed that the cavity aspect ratio remained constant throughout the deformation-and-cavitation process. Simulation predictions revealed that the average cavity size, as a function of strain, is essentially independent of whether the cavities were spherical or elliptical.     

电解气泡析出时电位波动的频谱分析

结合恒电流阶跃和信号处理技术，用统计直方图和快速傅里叶变换(FFT)对电解槽中电解气泡产生时电极电位的波动信号进行了统计和频谱分析。采用MatLab语言及其提供的信号处理工具箱构造算法，获得电位波动在频域上的波形信号，通过计算功率谱密度PSD随频率的变化，分析了电解气泡行为特性，获得平均气泡脱离速率、气泡脱离的平均直径以及平均气泡体积等特性参数。研究结果表明：用电位波动的直方图和FFT频谱分析可以获得有关电极表面气泡释放行为的信息，如气泡脱离时电位波动的平均幅值、平均气泡脱离速率、气泡脱离的平均直径以及电解气泡平均体积等特性参数，以用于分析研究电解过程电极界面的气泡行为。     

THERMAL NUCLEATION AND GROWTH OF He BUBBLES IN He IMPLANTED STAINLESS STEELS

Nucleation and growth of He bubbles at different annealing temperatures T≤1023 K in stain-less steels HR-2 and SS321,implanted with He~+(40-70 keV.1×10~(16)-6×10~(17) He~+/cm~2),were ohserved under TEM.T=0.45T_m seems to be a transitiontemperature.The He bubbles continue mainly their nucleation at 0.3T_m< T<0.45T_m,andgrow predominantly at T≥0.45T_m,due probably to migration and coalescence by surfacediffusion of metal atoms around the bubbles.The apparent activation energies for the growthare found to he 0.41 and 0.31 eV for HR-2 and SS321 respectively.The bubble density inHR-2 is greater than that in SS321 within whole measuring temperature range,and the onsettemperature of rapid swelling is also higher.It is believed that the resistance of HR-2 to He issuperior to that fo SS321.     

镁合金ZK60-RE半固态坯的微观组织演变

采用常规铸造法和等径道角挤压分别制备了镁合金ZK60-RE半固态坯;用金相显微镜研究了2种半固态坯料在等温热处理过程中的微观组织演变。结果表明：与传统铸造方法制备的半固态坯相比,采用等径道角挤压制备的半固态坯的晶粒细小、圆整,适合于半固态成形。在等温热处理过程中,2种坯料晶粒粗化的机制是合并长大和Ostwald长大。铸态坯料晶粒液相来源于非平衡凝固时在晶内产生的共晶组织,以及在随后的合并长大过程中晶粒所包裹的液相。随着保温时间的延长,铸态坯料的晶粒尺寸变化情况是：增大、减小然后又增大;而挤压态坯料的晶粒尺寸呈单一增大趋势。     

Synthesis of TiC<Subscript>x</Subscript> Powder via the Underwater Explosion of an Explosive

In this study, a novel approach to the explosive synthesis of titanium carbide (TiC) is discussed. Nonstoichiometric TiC_x powder was produced via the underwater explosion of a Ti powder encapsulated within a spherical explosive charge. The explosion process, bubble formation, and synthesis process were visualized using high-speed camera imaging. It was concluded that synthesis occurred within the detonation gas during the first expansion/contraction cycle of the bubble, which was accompanied by a strong emission of light. The recovered powders were studied using scanning electron microscopy and X-ray diffraction. Submicron particles were generated during the explosion. An increase in the carbon content of the starting powder resulted in an increase in the carbon content of the final product. No oxide byproducts were observed within the recovered powders.     

Bubble size estimation using interfacial morphological information for mineral flotation process monitoring

To relate froth structural information with mineral flotation performance, segmentation analysis was performed on froth images characterized by fully occupied convex bubbles with white spots effect. An improved valley edge detection method was proposed to extract structural features and overcome fake white spot edges seriously affecting the segmentation performance. After preprocessing, detection template was designed based on the local minimal intensity, and a binary image containing segmented boundaries was obtained by applying logical rules, thinning and filtering. Statistical features such as bubble size were estimated for control purpose. Experimental results demonstrate that the proposed method avoids over-segmentation or ill-segmentation caused by uneven illumination, and the industrial application reveals the reliability of bubble size estimation.