Droplet Image Feedback Control System in Evaporation Experiment

In order to realize the steady-state droplet evaporation, image feedback control system is designed based on DSP. The system has three main functions: to capture and store droplet images during the experiment; to calculate droplet geometrical and physical parameters such as volume, surface area, surface tension and evaporation velocity at a high-precision level; to keep the droplet volume constant. The DSP can drive an injection controller with the PID control to inject liquid so as to keep the droplet volume constant. The evaporation velocity of droplet can be calculated by measuring the injected volume during the evaporation. The structure of hardware and software of the control system, key processing methods such as contour fitting and experimental results are described.     

The Image Processing of Droplet for Evaporation Experiment in SJ-10

We have completed an experiment for droplet evaporation processing using Young-Laplace fitting, exponent fitting, polynomial fitting and ellipse fitting, which could be used for multiple shapes of droplets. The droplet evaporation experiment test was an important science experiment in SJ-10. In order to get the change process of the physical parameter, such as the touching edges and the droplet evaporation rate, we had gained the contour edge image of the droplet and used mathematic method to do the fitting analysis. The accuracy of the physical parameter was depended on the accuracy of the mathematic fitting. Using the original Young-Laplace fitting method could not process all the images of evaporation and liquid interface from the space experiment facility of SJ-10, especially the smaller droplet images. We could get more accurate contour fitting and result using the new method described in this article. This article proposes a complete solution, including edge detecting and contour fitting. In edge detecting, Canny detector was applied to extract droplet edge. In contour fitting, Young-Laplace fitting, exponent fitting, polynomial fitting and ellipse fitting are designed to fit the contour of droplets, which make the solution apply to all of droplets in SJ-10.     

Measurement of the Diffusion Coefficient of Miscible Fluids Using Both Interferometry and Wiener's Method

Measurements of the diffusion coefficient of two miscible liquids are reported. The liquids are various combinations of pure silicone oils and those to which small amounts of solvents are added to control the difference in density between the fluids. The liquids were placed in a quartz cell such that the interface is initially horizontal. As the fluids diffuse, the profile of the index of refraction near the interface is time dependent and is related to the local concentration of the diffusing fluids. The concentration gradient profile was measured by a shearing interferometer incorporating a Wollaston prism, as well as Wiener's method. In the latter technique, a 45° light sheet was passed through the test cell, and the local deflection of the light beam was measured. The average diffusion coefficient was obtained by analysis of the measured concentration gradient profile, assuming that the diffusion process is one-dimensional and is characterized by a constant value of the diffusion coefficient.     

A New Method of Processing Mach–Zehnder Interference Fringe Data in Determination of Diffusion Coefficient

Laser holographic interferometry is the newest method to measure the mass diffusion coefficient and has been widely used in recent years. The processing of interference fringe images is a critical step of getting the final precise experimental results. On the basis of Fourier transformation and phase measurements, a new method of processing Mach–Zehnder interference fringes is introduced in this article. By experimental verification and uncertainty analysis, the accuracy of this method is validated. Mass diffusion coefficients of ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, two new fuel additives in air were measured with the method introduced in this study.     

用于各向异性扩散滤波的热传导系数构造方法

针对传统各向异性扩散滤波算法难以在噪声环境下有效估计边界像素,本文提出了一种热传导系数构造方法.该方法结合了各向异性扩散和各向同性扩散的优点,将每次迭代运算分解为两步:第一步采用各向同性扩散降低图像噪声,并完成热传导系数的计算;第二步运用各向异性扩散,实现真正的图像滤波.试验证明该方法能够在大尺度加性和乘性混合噪声环境...     

采用响应面法的复合板结构噪声优化设计

针对复合材料层合板结构出现的噪声问题,将响应面法RSM(Response Surface Method)与遗传优化算法相结合,提出一种降低复合材料层合板声压级的优化方法。该方法基于四边形复合材料层合板结构建立有限元分析模型,通过三因子试验设计点设计试验计划表,结合最小二乘法构建复合材料层合板声压级的2阶响应面近似模型。以影响层合板噪声的显著因子为设计变量,层合板的声压级为设计目标,采用遗传算法对响应面近似模型进行优化,结果表明,使用该方法对复合材料层合板的噪声特性进行分析,可明显提高优化效率并为工程实际提供参考。     

多孔介质质扩散系数的参数估计方法及测定方法

提出一种在第三类边界条件下,通过使数值计算的湿分蒸发与规律实测值之间的最佳逼近,以瞬态确定计算多孔介质质扩散系数的参数估计方法。设计并制造了对流蒸发实验装置。在假设质扩散系数为含湿量线性函数的情况下,对石膏板和水泥板的质扩散系数进行了测量和计算。测试及计算方法简单可行,测定时间较稳态方法大大缩短,因此比较实用。     

Peculiarities of Droplet Evaporation under Radiative and Convective Heating

Technical Physics Letters - We propose a new method for determining the rate of evaporation of a lone levitating droplet under the action of radiative heat flux. Results of experimental...     

二次序列响应面法分析重力坝的动力可靠度

提出了用二次序列响应面法分析重力坝可靠度的方法。该方法用界面元法对重力坝进行确定性计算,在适当的区间内用统计的方法确定各变量的样本点,经过若干次重复计算,由界面元法的计算结果可以得到该结构的响应面函数,然后由这一函数算出重力坝可靠度的近似值。用同样方法可得第二、第三个响应面函数,并使可靠度计算结果逐渐达到良好的精度要求。这一方法与统计可靠度分析方法相比可以减少大量的计算工作量。对于包含混凝土特性和坝上游水位等随机变量的重力坝,本文用上述方法计算了一些关键时刻重力坝抗裂的动力可靠度,并据此分析了在整个地震过程中该坝抗裂可靠指标β（t）随时间t的变化规律。     

Response Surface Designed Experiment for Door Closing Effort

This study employed a Draper-Lin small-composite response surface design to determine the optimal dimensional-factor levels to minimize the door-closing effort for a new automobile project. It was found that the factor levels that minimize the closing effort did not lead to robust manufacturing conditions. Likewise, the factor levels needed to produce a robust process did not lead to a sufficiently low closing effort. Various compromises were considered; namely, the minimum closing effort obtainable subject to selected semirobust conditions. The net result was that it was not possible to obtain sufficiently robust factor conditions, while achieving a suitably low value for closing effort.     

盐水溶液液滴真空闪蒸特性实验研究

针对盐水 (Na Cl) 溶液液滴真空环境下的闪蒸过程进行实验研究, 获得了不同浓度下盐水液滴的形态及温度变化特征。结果表明:由于盐水液滴浓度和真空压力的影响, 其真空闪蒸过程较纯水液滴更为复杂;盐水液滴在真空环境中会经历五种典型形态:稳态蒸发, 气泡生长-蒸发, 稳态蒸发-凝固, 气泡生长-凝固, 析盐。当盐水浓度达到共晶浓度22.4%时, 会发生析盐现象;盐水浓度较低 (<5%) 时, 会发生凝固现象。盐水液滴析盐过程较凝固过程持续时间长, 且会持续放出热量, 将液滴加热至较高温度。多次实验对比发现, 最终环境压力较低 (p_a<1000 Pa) 且液滴初始温度较高时, 析盐过程明显且迅速。     

响应曲面法研究碳钢在模拟烟气冷凝液中的腐蚀行为

电厂烟气冷凝液有较强腐蚀性,引起腐蚀的因素较多。采用响应曲面法研究了模拟烟气冷凝液中影响腐蚀的主要因素pH值、Cl-浓度与温度对碳钢腐蚀速率的影响,通过单因素极化曲线测定了碳钢的腐蚀电流密度。结果表明:随着溶液pH值的降低、Cl-浓度的增大和溶液温度的升高,腐蚀电流密度增大。在此基础上,运用响应曲面法中的BBD模型设计试验条件,测试并分析了碳钢在不同条件下的腐蚀速率,发现对碳钢腐蚀速率的影响程度从大到小依次为pH值﹥温度﹥Cl-浓度。     

用Sanchez-Lacombe状态方程改进高分子-溶剂体系扩散系数模型

将Sanchez-Lacombe状态方程与Vrentas-Duda模型相结合,提出改进的高分子-溶剂体系扩散系数模型。改进的模型利用高分子结构单元的范德华体积导出高分子自由体积分数表达式,仅利用状态方程的特征参数和高分子的玻璃化温度确定用于扩散过程的有效自由体积。与Vrentas-Duda模型相比,改进的模型避免进行高分子的粘弹性实验回归自由体积参数;与前期研究相比,计算过程避免查阅数据手册获得高分子热膨胀系数,因此模型的预测性增强。对4种溶剂在3种高分子中自扩散系数和互扩散系数的计算结果表明,改进的模型具有较好的预测精度。     

遗传算法在响应曲面拟合中的应用

响应曲面方法（RSM）是一种重要的实验设计优化方法,但是当影响因素和响应输出之间的关系异常复杂时,RSM难以拟合影响因素和响应输出之间的响应曲面.遗传算法（GAs）是一种借鉴生物界自然选择和进化发展起来的高度并行、随机、自适应搜索算法,具有强大的搜索能力.本文将遗传算法引入RSM,通过对遗传算法各参数的设计和改进,克服了传统遗传算法易局部收敛的问题.     

一种测定液体表面张力系数的新方法

针对现有的测定液体表面张力系数的方法存在设备昂贵、测定结果容易受各种因素干扰而测试精度不足等问题,提出了一种使用不等内径U型管,采用局部力平衡方法结合拉普拉斯方程,以及MATLAB图像处理和LabVIEW虚拟仪器系统,测定液体表面张力系数的方法。与现有的测定液体表面张力系数的拉脱法相比,该方法具有测试精度高、样品需要量少、测试成本低等特点。     

测量液体表面张力系数的新方法

介绍了一种利用梅特勒-托利多AB265-S分析天平测量液体表面张力系数的新方法。由实验可以知道，对同一液体，其表面张力系数随着温度的升高而减少，在液体中加入某些活性物质会显著改变液体表面张力，而且随着浓度的增加，表面张力系数减小。     

压力系数分析法的低噪声鼻锥设计

在航空声学风洞内进行气流内的噪声测量时,需要在传声器前端安装鼻锥,以降低流场波动对传声器振膜的干扰噪声。目前使用的鼻锥,当流速超过40 m/s时,自噪声大幅度提高,因而无法用于更高速度的流场测试。利用一种鼻锥低噪声设计的分析方法,分析鼻锥表面的压力系数分布规律,并提出一种降低鼻锥自噪声的改进形式,降低不稳定的静态压力的干扰。将鼻锥的透声孔设置在压力稳定区域,可减少流场内不稳定压力波动对被测声波信号的干扰,提高测试结果的准确性,满足更高速度的流场测试需求。     

铜纳米液滴蒸发过程的分子动力学模拟

本文利用Material Studio软件成功地模拟了铜纳米液滴在真空条件下(10Pa),温度为1573~2073K的变化情况。通过研究铜液滴在蒸发过程中的均方位移(MSD),径向分布函数(RDF)及液滴直径大小的变化得出如下结论:随着模拟温度的升高,进入气相的铜原子越来越多,由于流体的各向同性,使液滴最终接近球形。当温度从1773K升温至1873K后,液滴的直径明显变小,这是因为在此温度区间体系从液相转变为气相,此时会有大量铜原子从液滴溢出进入气相,从而导致液滴变小。     

Theoretical Investigation on Rapid Evaporation of a Saline Droplet During Depressurization

This paper reports a theoretical investigation on rapid evaporation of a saline droplet during depressurization. A mathematical model was developed to simulate the droplet temperature variation by considering the ambient pressure change, the heat transfers due to evaporation and convection at the droplet surface, accompanying the heat and mass transfer inside the droplet. The component diffusion and the temperature gradient inside the droplet were mainly discussed by comparing the numerical droplet temperature with the experimental data. The result shows that, the variation of internal concentration is small, while the temperature gradient within the droplet is significant during the evaporation process. In addition, the influencing factors of the droplet temperature variation were analyzed, such as: the final ambient pressure, theinitial salt concentration and the initial droplet temperature. The present model calculations help to understand the thermodynamic process of rapid evaporation of a saline droplet during depressurization.