电路原理及实验考试改革的一次实践--将单相交流电转变为三相交流电的研究

介绍了笔者在浙江大学“电路原理及实验”考试改革中所做的研究课题——“将单相交流电转变为三相交流电的研究”。该项研究提出了两种简单有效的变换方法，并设法将其运用到实际带载情况，去驱动三相电动机；通过理论分析、机辅仿真和实验验证，结果表明该方法在特定输出功率情况下是可行的。最后笔者阐述了考试改革的亲身体验，真切地感受到知识、能力、素质的培养在考试改革中得到了充分体现。     

基于不平衡损耗非线性光纤环镜的双波长功率均衡实验研究

在波分复用（WDM）光纤网络中，存在很多因素会造成信道间的功率差异。针对波分复用光网络中功率均衡的需求，提出了利用带有不平衡放置的损耗结构的非线性光纤环镜（NOLM）来实现多信道功率均衡的技术方案。理论上分析了该方案利用自相位调制（SPM）效应产生均衡作用的基本原理，指出了该方案所能达到的最佳均衡指标。通过两波长10Gb／s幅度调制信道的实验，观察了不平衡损耗结构非线性光纤环镜（L-NOLM）的输出功率的变化过程，验证了它的均衡效果，当输入信道功率差异为7dB时，输出信道功率最大差异不超过2dB。该方案结构简单，无需解复用、复用，响应速度快，具有自适应均衡的特点。     

照明光瞳非对称性对光刻成像质量的影响

研究了照明光瞳非对称性对光刻成像质量的影响。通过PROLITH软件计算了环形与四极照明条件下,光瞳非对称性对图形位置偏移量、曝光图形内水平线条与垂直线条的宽度差、曝光图形上密集线条与孤立线条之间线宽偏差的影响。研究结果表明,光瞳非对称性主要影响曝光图形的位置偏移量,光瞳非对称性引起的图形位置偏移量与光瞳非对称性的大小成线性关系。根据套刻精度的误差分配原则,计算得到光瞳非对称性的容限为5%。     

涂布流动和涂布材料的流变性能

本文列举涂布工艺的实例,给出基本流动方程。叙述了涂布材料流变性质的某些例子。评述了:①棱形条纹;②斜面流动的稳定性;③“桔皮”现象;④在表面张力作用下薄膜表面变平的过程;⑤三相线的奇异性。最后,为了很好地理解涂布现象,考虑了旋转甩涂过程。      

气液固三相反应过程固体溶解增强因子

基于双膜理论,考虑了气液液膜内、固液液膜内传质过程,推导出一个较确切的描述液固相界面随反应进行发生变化时伴有气体吸收与固体溶解并在液膜内发生瞬间反应的模型,给出一个描述三相反应过程的固体溶解增强因子的表达式。用本模型计算的固体溶解增强因子能很好地描述实验数据。     

油气水三相流中的复杂相态及压力降研究

将水平管划分为三个测量段,以空气、水和高粘度油体为工质,研究了油气水三相流中由流动引起的液－液复杂相态及其所对应的三相流压力降。试验研究发现,油气水三相流在三个测量段中可由流动引起不同的液－液相态,致使对应于相同的油、气、水三相体积通量,三相流阻力损失存在多值性。对不同的液－液相态建立了与之适应的阻力损失计算模型,模型预测结果与试验结果吻合     

三相交流电参数综合监测仪的设计

本文介绍了一种具有完整交流参数的三相监控器的设计,并讨论了系统的硬件组成,各功能部分的电路设计和系统的软件设计,给出了单片机的数据采集和分析处理方法等。     

Micromodel Observation of the Role of Oil Layers in Three-Phase Flow

We have studied the flow of a non-aqueous phase liquid (NAPL, or oil), water and air at the pore scale using a micromodel. The pore space pattern from a photomicrograph of a two-dimensional section through a Berea sandstone was etched onto a silicon wafer. The sizes of the pores in the micromodel are in the range 3–30,m and are the same as observed in the rock from which the image was taken. We conducted three-phase displacement experiments at low capillary numbers (in the order of 10^-7) to observe the presence of predicted displacement mechanisms at the pore scale. We observed stable oil layers between the wetting phase (water) and the non-wetting phase (gas) for the water–decane–air system, which has a negative equilibrium spreading coefficient, as well as four different types of double displacements where one fluid displaces another that displaces a third. Double imbibition and double drainage are readily observed, but the existence of an oil layer surrounding the gas phase makes the other double displacement combinations very unlikely.     

On the movement of an LNAPL lens on the water table

The penetration of light nonaqueous phase liquids (LNAPLs) in quantities that lead to an accumulation in the form of a lens above the water table is considered. First, the three-phase vertical gravity-capillary equilibrium of water, NAPL, and air above the water table is specified. The hypothesis of ‘vertical equilibrium phase distribution’ is used to derive averaged asymptotic equations describing NAPL flow as a thin lens floating above the water table. Some problems of unsteady NAPL lens movement and the development of a NAPL mound, spreading along an inclined or horizontal phreatic surface are discussed and the analytical solutions are obtained.     

Thermal and hydraulic performance of a three-phase fluidized bed cooling tower

An experimental study was made of the thermal and hydraulic characteristics of a three-phase fluidized bed cooling tower. The experiments were carried out in a packed tower of 200 mm diameter and 2.5 m height. The packing used was spongy rubber balls 12.7 mm in diameter and with a density of 375 kg/m³. The tower characteristic was evaluated. The air-side pressure drop and the minimum fluidization velocity were measured as a function of water/air mass flux ratio (0.4–2), static bed height (300–500 mm), and hot water inlet temperature (301–334 K).

The experimental results indicate that the tower characteristics KaV/L increases with increases in the bed static height and hot water inlet temperature and with decreases in the water/air mass flux ratio. It is also shown that the air-side pressure drop increases very slowly with increases in air velocity. The minimum, fluidization velocity was found to be independent of the static bed height.

The data obtained were used to develop a correlation between the tower characteristics, hot water inlet temperature, static bed height, and the water/air mass flux ratio. The mass transfer coefficient of the three-phase fluidized bed cooling tower is much higher than that of packed-bed cooling towers with higher packing height.