Behavior of a Single Bubble in Quiescent and Flowing Liquid inside a Cylindrical Tube

The velocity of a single bubble in quiescent and flowing liquid was studied to gain information on the structure of bubble- and slug-flows of gas-liquid two-phase flow.

In the experiments, tap water was used at room temperature and the bubbles were generated by injecting air with a syringe. The bubble velocities were evaluated from photographs taken by multiflash exposure. The tube diameters adopted were 5, 1 and 0.5 cm for the flowing liquid experiments and 1, 0.5 and 0.2 cm for the quiescent liquid experiments. The average liquid velocities varied from about 0 to 2 m/sec.

The results indicated that the velocity of a single bubble in flowing liquid was the sum of the local liquid velocity in the vicinity of the bubble and of the velocity of rise of bubble in quiescent liquid. For Taylor bubbles, the local liquid velocity is given by the maximum liquid velocity near the center of the channel.

The velocities of spherical and ellipsoidal bubbles are determined by the balance of forces acting on them, but that of the Taylor bubble appears to be determined by a different mechanism. A good explanation of such a mechanism is Taylor instability at the gas-liquid interface well removed from the channel wall.     

Zero-Dimensional Analysis of Burn Control with Compression-Decompression

A simple but realistic method of active feedback control of a self-ignited tokamak reactor by major radius compression-decompression is presented, in which the thermal fusion output power and the ion temperature are envisaged as the variables that could be adopted as object of control. Error inherent in the measuring system for the controlled variable is taken into account in the analysis. Numerical calculations based on a point reactor model are performed, which indicate that the proposed method of control is capable of completely suppressing thermal runaway without involving any significant change in the major radius or in the fusion output power. Matching the reactor output to changes in load is shown also to be possible from a numerical example. The thermal stability of an igniting plasma governed by this feedback control is analyzed without prescribing any particular transport scaling. It is revealed that the control is achievable for a suitably chosen gain even with a response time lag longer than the thermal runaway time. Strong dependence of the stability on the scaling law is indicated.     

Effect of Particle Recycling on Burn Control by Compression-Decompression

As a part of the development of a subcriticality monitoring system, a system which has a time series data acquisition function for detector signals and a real time evaluation function of the α value with the Feynman-α method was established, with which the kinetic parameter (α value) was measured at the STACY heterogeneous core. Hashimoto's difference filter was implemented in the system, enabling the measurement in a critical condition. The measurement result of the new system agreed with the pulsed neutron method. The α value was also evaluated by the newly developed algorithm of α-mode calculations for the Monte Carlo method, which was compared with the experimental value. Those computational and experimental α values show agreement within their uncertainties.     

聚苯乙烯/Al双介质调制靶的研制

介绍了用于流体力学不稳定性实验的聚苯乙烯（CH）/Al双介质调制靶的制备方法。采用激光微加工工艺在50 μm厚Al箔表面制备了调制周期为55 μm、峰谷差为4.7 μm的调制图形;采用旋涂工艺在Al箔表面制备了20 μm厚CH薄膜,经过后期的微切割、微装配工艺,得到了宽度为200 μm、总厚度为70 μm的CH/Al双介质调制靶。该靶型于2010年在“神光-Ⅱ”激光装置中进行了流体力学不稳定性实验。     

冷轧钢卷“心型卷”缺陷的预报及防治技术开发

针对冷轧钢卷卸卷及冷却过程中的"心型卷"缺陷问题,结合冷轧薄带卷取过程中钢卷配置内套筒的设备及相关工艺特点,详细分析了"心型卷"缺陷产生的原因,首次引入了表征"心型卷"发生概率的钢卷失稳因子新概念,从统计学角度给出了"心型卷"缺陷的判断条件,并在此基础上,提出了"心型卷"预报技术,开发出了基于设备参数优化选择的经济实用型"心型卷"治理技术,编制了冷轧钢卷‘心型卷’缺陷预报及套筒选择软件,降低了冷轧钢卷卸卷及冷却过程中"心型卷"缺陷发生率。     

Prediction model for steel/slag interfacial instability in continuous casting process

In a continuous casting process, mould powder is typically adopted to cover molten steel, which prevents liquid steel from oxidation by air, preserves heat for the top layer of liquid steel, lubricates the initial shell and so on. However, mould powder may deteriorate the quality of the final product if the entrapment of mould powder forms, which is usually caused by the instability of the steel/slag interface. In the current work, a model to predict the critical point of interfacial instability for liquid–liquid stratified flow was developed based on the Kelvin–Helmholtz instability. To prove the validity of the prediction model, a water model experiment was carried out in a rectangular container. In this experiment, oil and water were used to simulate slag and molten steel respectively. The results of the water model prove that the prediction model is correct. Applying the prediction model to a steel–slag system, the critical velocity of molten steel for mould powder entrapment is 0.463–0.541?m?s^??1. When considering the most severe chemical reaction, the critical velocity decreases to 0.29?m?s^??1. The lowest critical velocity of molten steel is 0.264?m?s^??1 when the viscosity of the slag and steel/slag interfacial tension is extremely low.     

并网型风力发电系统电压稳定研究现状

风力发电作为目前应用最广泛的新能源,其接入电力系统后对电网电压稳定的影响得到了人们的广泛研究。由于风力发电不同于常规能源发电,所以影响并网型风力发电系统电压稳定的因素也和常规电力系统范畴内影响电压稳定的因素有所不同。分析研究并网型风力发电系统运行特性,了解其电压失稳机理,进一步为保证系统电压稳定以避免发生电压崩溃提出相应的控制策略,是当今学术界的一个重要研究方向。文中对上述问题的相关研究成果进行了综述,并做了相应总结。     

聚合物膜上的微尺度金属导线在力电耦合作用下的屈曲行为(英文)

研究一种典型的微尺度康铜线/聚合物膜结构在力电耦合作用下的屈曲行为。根据卸载后康铜线从聚合物基底上屈曲的现象,评估康铜线与聚合物基底间的界面韧性。此外,力电耦合作用还会诱发新的失稳模态。在电载荷和拉伸载荷作用下,康铜线易在屈曲时发生断裂。在电载荷和压缩载荷作用下,康铜线易在屈曲区域的顶部发生折叠,偶尔还会向聚合物基底内部方向发生屈曲。分析了这些失稳模态的产生机理。     

焦页非常规页岩气井优快钻井技术

重庆涪陵焦石坝地区上部地层岩性致密、研磨性强、可钻性差,长兴组浅层气活跃且含硫,三开水平段长、摩阻大、泥质页岩层易垮塌。钻井面临的突出问题是机械钻速低、井控难度大、钻井周期长。针对上述气藏钻井难点,重点从钻井工艺、维持井壁稳定以及钻井液方面进行分析,优化钻具结构、优选钻头选型、抑制井壁失稳以加快焦石坝区块钻井速度。"油基螺杆+高效PDC钻头"配合优质钻井液,经过焦页12平台4口井的实践应用,大大缩短了钻井周期,焦页12-4HF井创下了中石化集团公司非常规页岩气水平井最长水平段记录,提速效果显著。