旋风分离器减阻杆减阻的数值研究

文中首次利用数值方法对旋风分离器进行了减阻杆减阻的研究。应用CFD计算流体力学软件FLUENT,对某种型号的Stairmand高效型旋风分离器的三维有旋流场速度和压力进行了数值模拟,计算了减阻杆的减阻效率。流场和减阻效率的数值结果与实验数据吻合较好,证明对旋风分离器减阻杆减阻研究时所采用的网格划分方法、RSM湍流模型和边界条件是可靠的,为数字设计高效率的减阻杆提供了简便可靠的办法。     

进气型式对并联旋风分离器流场的影响

采用FLUENT软件模拟催化裂化三旋中并联旋风分离器进气型式的不同对内部流场的影响,主要对比了不同进气型式下入口处的流场分布、分离空间内的切向速度与压降的差异。研究结果表明,采用U型进气型式,分离器压降与速度略大,且比较容易引起环形空间内不利于分离器的二次流动;采用D型进气型式,分离器芯管下口处向内的径向速度较大,容易形成“短路流”。2种进气型式均会造成入口处的涡流,在气固分离过程导致颗粒的沉积以及管道的磨损,其对分离效率的影响有待试验进一步测量。     

基于分离器工作参数优化及性能分析

旋风分离器基于离心力将固体颗粒或液滴从气流中分离,结构简单且分离效率高,具有很高的实用价值。本文利用SolidWorks软件进行三维建模,利用Flow Simulation功能进行有限元分析,根据腔内流场、压力云图和粒子轨迹研究进行性能参数优化,最终得出旋风分离器在出口流速为2m3/s时分离性能最优。     

基于LabVIEW系统进行旋风分离器内筒减阻装置的试验研究

对LabVIEW软件的特点、功能作了阐述,介绍了其在旋风分离器内筒减阻装置试验研究中的具体应用。实践证明:采用LabVIEW数据采集分析系统,对试验及研发工作起到较大促进作用。开发设计了一种针对旋风分离器的内筒高效减阻装置,并对安装内筒减阻罩的旋风分离器的阻力损失和分离效率进行了试验研究,探讨了不同入口风速、不同固气比条件对旋风分离器的性能影响。对结果进行了理论分析,结果表明:对于相同规格的旋风分离器,内筒减阻罩能起到优化旋风分离器阻降且把分离效率控制在合理数值范围内的作用,不同风速,不同固气比条件下,内筒减阻罩的最大减阻幅度为43.36%,而分离效率最大降幅只有8.78%。     

聚碳酸酯液液分离器进料构件的流体力学模拟

测定了聚碳酸酯(PC)物料电导率随水油相体积比的变化,确定生产中物料为水包油型乳液,即分散相为PC胶液,连续相为水。采用F1uent商用软件对液液分离器内部流场进行了数值模拟,通过得到的分离器内部流线分布和轴向速度标准偏差分布,考察了不同进料口位置、挡板位置以及不同整流构件尺寸对液液分离器内部流场的影响。研究发现,进料口位置为中部,挡板位置距离进料口为50mm,整流构件开孔率为40%,长度为150mm时,分离器内的流场质量最佳,为液液分离器进料构件的进一步优化研究提供了参考。     

汽水分离器的动态数学模型和仿真研究

对汽水分离器的基本结构和原理进行分析,建立了热力系统的动态数学模型。并进行了仿真研究。与实验数据比较本模型具有一定的精度。并在软件的实现上具有一定的创新性。在模块化建模和状态空间在热力系统的仿真上具有一定的通用性价值。     

基于fluent的旋流器分级控制系统设计

目前,应用重介旋流器分选过程智能控制策略、极群组破碎分离水力旋流器参数化方法局限于单参数优化,难以控制微小尺寸变形,基于该问题,设计了基于fluent的旋流器分级控制系统。使用开关型交流稳压电源,为系统提供可靠电能。利用Q941F电动调节球阀,执行对应区间动作。使用BST6800系列压力变送器,实现底流流量控制。采用上装式气动阀门开关结构,增强阀门可靠性。通过人机交互模块,显示执行任务。根据基于fluent的数值模拟原理,计算进入旋流器的颗粒直径。结合Gambit模型和网格划分方法,仿真模拟分析切向速度、横向速度和径向速度三个方向分量分布情况。使用两套控制输出量调节旋流器进料速度,获取最佳分级尺寸,保证旋流器分级过程的稳定性。由实验结果可知,该系统最高分级效率为98%,最低为90%,具有高效分级效果。     

环流式旋风除尘器设计软件的开发

对于旋风除尘器的设计主要依靠手工计算进行,其过程繁琐且难以保证其准确性。针对旋风除尘器设计的特点,利用Visual Basic 6．0及AutoCAD工具开发了一个环流式旋风除尘器设计软件CycloneDraw。通过该软件用户只需输入操作条件,即可得到旋风除尘器的结构简图。该软件具有设计计算、数据库查询、生成设备图等功能。用户界面友好、操作方便、运行可靠稳定。     

旋风除尘器流场仿真分析

为分析旋风除尘器的速度场和分离效率,通过计算流体力学(Computational Fluid Dynamics,CFD)方法研究典型的旋风除尘器的强旋流场.用ANSYS Workbench提供的Geometry和Mesh软件进行三维几何建模和非结构网格划分,以高炉煤气的除尘为例进行流场仿真.湍流模拟采用雷诺应力模型,分离效率预测采用基于拉格朗日方法的离散相模型(Discrete Phase Model,DPM).通过分析压力场和速度场的分布,得到旋风除尘器中的内、外旋流结构;该结构并非完全稳定,涡轴存在一定的摆动.仿真结果表明选用的旋风除尘器模型对高炉煤气有良好的除尘效率.     

Sizing and grading methods with consideration of footwear styles

Sizing and grading are very important in footwear production, directly influencing the fit and comfort of footwear. Currently, the footwear industry relies on traditional sizing and grading systems, which vary around the world. Modern measuring technologies, such as 3D scanning and modeling, are starting to be used in footwear mass production. Sizing and grading of footwear is closely related to the sizing and grading of foot. This study investigates the application of principal component analysis (PCA) in sizing and grading methods and the influence of footwear styles based on 3D foot shapes. Three sizing and grading methods were simulated and evaluated. Results show that, compared to the traditional method, the sizing and grading using PCA method provides less modeling error, hence will result in better fit. Furthermore, the prediction error for various footwear styles are significantly different and the footwear fit near the sole could be achieved easier than instep and ankle region. This indicates that various sizing and grading rules can be applied focusing on different footwear styles in order to develop optimal sizes.Relevance to industryThe proposed new sizing and grading method could benefit the footwear industry since it provides a better fit comparing to the traditional method. The influence of footwear styles on prediction error gives more detailed insights for manufacturers to further understand the fitting result when applying the different sizing and grading methods.     

Assessing creative problem-solving with automated text grading

The work aims to improve the assessment of creative problem-solving in science education by employing language technologies and computational–statistical machine learning methods to grade students’ natural language responses automatically. To evaluate constructs like creative problem-solving with validity, open-ended questions that elicit students’ constructed responses are beneficial. But the high cost required in manually grading constructed responses could become an obstacle in applying open-ended questions. In this study, automated grading schemes have been developed and evaluated in the context of secondary Earth science education. Empirical evaluations revealed that the automated grading schemes may reliably identify domain concepts embedded in students’ natural language responses with satisfactory inter-coder agreement against human coding in two sub-tasks of the test (Cohen’s Kappa = .65–.72). And when a single holistic score was computed for each student, machine-generated scores achieved high inter-rater reliability against human grading (Pearson’s r = .92). The reliable performance in automatic concept identification and numeric grading demonstrates the potential of using automated grading to support the use of open-ended questions in science assessments and enable new technologies for science learning.     

Phase equilibrium calculation of multi-component gas separation of supersonic separator

A mathematical model for phase equilibrium prediction of multi-component gas separation process inside a supersonic separator is established and an efficient numerical solution method is designed. The model and the numerical method are then used to predict the phase equilibrium characteristics and the separation performance of a field test natural gas supersonic purification separator. The predicted results are generally in good agreement with the field test measurements, which proves that the phase equilib...     

分阶段二次变异的多目标混沌差分进化算法

提出一种结合分阶段二次变异和混沌理论的改进差分进化(DE)算法,以解决多目标约束优化问题.其核心思想是,在DE进化前期采用基于非支配解的随机二次变异来提高算法的全局寻优能力,进化后期采用基于非支配解的混沌二次变异来提高DE的局部寻优能力.通过对典型测试问题的仿真实验验证了所提出的算法能在全局搜索性能与局部搜索性能之间维持较好平衡,而且保持了DE算法的简洁性能,其收敛性、分布度和均衡性均优于标准DE.     

基于计算机视觉的烟叶自动分级系统硬件设计

介绍了一种基于计算机视觉烟叶自动分级系统的硬件组成,该系统由输送装置、称重系统、视觉系统、均匀照明室4部分组成。输送装置可将烟叶打散摊平,使烟叶保持一定的厚度呈现给CCD摄像头;称重系统采用电子皮带秤完成烟叶的在线实时称重,并将数据发送至计算机内存;视觉系统同时监视、采集烟叶图像信息送至计算机内存进行处理;照明系统为CCD摄像头均匀、恒定的光源,保证图像的清晰。实验证明了系统的可行性,其辅助机构与烟叶实时分级决策算法尚待进一步的研究。     

Improving essay peer grading accuracy in massive open online courses using personalized weights from student's engagement and performance

Most massive open online courses (MOOC) use simple schemes for aggregating peer grades, taking the mean or the median, or compute weights from information other than the instructor's opinion about the students' knowledge. To reduce the difference between the instructor and students' aggregated scores, some proposals compute specific weights to aggregate the peer grades. In this work, we analyse the use of students' engagement and performance measures to compute personalized weights and study the validity of the aggregated scores produced by these common functions, mean, and median, together with two others from the information retrieval field, the geometric and harmonic means. To test this procedure, we have analysed data from a MOOC about Philosophy. The course had 1,059 students registered, and 91 participated in a peer review process that consisted in writing an essay and rating three of their peers using a rubric. We compared the aggregation scores obtained using weighted and nonweighted versions of the functions. Our results show that the correlation between the aggregated scores and the instructor's grades can be improved in relation to peer grading, when using the median and weights are computed according to students' performance in chapter tests.     

基于改进窄带水平集的三维肝脏肿瘤分割

三维肝脏肿瘤识别是当前研究的热点问题,如何准确快速地从腹部CT序列中分割出肝脏肿瘤是肝部病变诊断的基础。针对水平集方法在进行分割时收敛速度较慢,设置窄带宽度固定不灵活的缺点,先利用分水岭算法,对肝脏图像进行“过分割”,搜索初始轮廓所在的分水岭块作为窄带区域进行标记,在窄带区域内用水平集算法使初始轮廓线收敛至准确轮廓。再以其边缘作为相邻CT序列的肿瘤初始轮廓,找出初始轮廓线所在的分水岭块,构成新的窄带,用水平集算法对轮廓线进行迭代分割出肿瘤。重复该过程,直至完成整个肝脏序列图像的肿瘤图像分割,进行三维重建。