流体驱动旋转装备应用与数值模拟方法研究进展

流体驱动旋转装备在能量转换及能量回收等过程中应用广泛。近年来,流体驱动旋转装备新结构不断涌现,其应用也得到了拓展,逐步与海水淡化、制冷、混合、测速等过程结合。在此发展过程中,计算流体力学为流体驱动旋转装备的设计优化提供了新途径。本文综述了流体驱动旋转装备在能源工程、化学工程等领域的应用,总结了流体驱动旋转装备数值模拟方法研究进展,对比了主动旋转及被动旋转两种模拟方法,指出被动旋转模拟在流体驱动旋转装备研究中的意义,展望了流体驱动旋转技术在超重力装备中的应用前景。     

絮凝反应池中流体的CFD模拟及应用性能

絮凝反应是原水预处理工艺(混合-反应-沉淀)的重要环节,对整个工艺过程的水处理效果影响极大。本文针对絮凝反应过程中絮体颗粒生长所需的水力学条件,采用计算流体力学(CFD)软件分析了所设计搅拌絮凝反应池运行的可行性,通过控制絮体颗粒生长的流场,使絮体在其中可以生长至合适的尺度。研究结果表明,采用优化之后的反应设备,可以节约絮凝剂用量约20%,降低了生产费用,避免过量絮凝剂对水体造成的二次污染,并且提高了出水效果。     

微絮凝强化过滤工艺的应用研究及问题分析

北方的冬季受污染水体温度较低,传统的净水工艺在处理低温低浊度水时,加大药剂投加量也难以发挥理想的效果,使得出水浊度较高,达不到相应的出水水质要求。论述了微絮凝强化过滤工艺的原理、特点和适用条件,并对工艺应用过程中的主要参数进行了优化分析。希望微絮凝强化过滤工艺能够得到进一步的应用和发展。     

旋转填料床气相流场数值模拟

为解决旋转填料床内部流场较为复杂,实验流体力学基础理论研究缺乏的问题,通过计算流体力学软件FLUENT,采用正交试验法研究了填料转速、气体进口速度和填料的孔隙率对于气体流场径向速度不均匀系数的影响情况。结果表明,当填料转速1 000 r/min、气流速度2 m/s、填料孔隙率0.5时,能使径向速度保持最好的均匀性分布,同时影响RPB截面径向气流速度均匀性按显著程度依次为填料孔隙率〉气体进口速度〉填料转速。     

基于分形学的絮凝理论研究进展

絮凝过程中形成的絮体具有自相似性和标度不变性等特点,是一个典型的分形体。但传统的絮凝理论并未考虑絮体的分形结构,因而存在一定的缺陷。本文主要介绍了引入分形理论后,絮凝形态学和絮凝动力学的发展状况,重点阐述了絮体分形结构与其粒径、强度、密度、沉降速度等之间的关系,以及分形理论对Smoluchowski方程、传统絮体生长模式理论的改进。此外,本文同时指出分形学与絮凝理论的结合在很多方面尚未总结出系统的普适规律,尤其是非线性絮凝动力学仍需进一步完善。     

CFD数值模拟在微涡絮凝中的应用

传统的絮凝理论是基于层流的条件得到的结果,而实际絮凝反应中,流体的流态是以湍流占优势的,不存在整体和恒定不变的速度梯度,因此微涡絮凝较传统絮凝更为复杂,其内部流态分布对絮体的形成具有重要作用,但目前试验无法获取其流态分布。随着计算机硬件的更新,计算能力不断提高,许多学者开始使用CFD数值模拟对种种复杂的实际问题进行计算模拟,以湍动能k、湍动能耗散率ε、涡旋速度梯度、涡旋尺寸作为评价指标,对微涡絮凝进行研究。     

多通道流动电泳的计算流体力学模拟与实验研究(Ⅱ)流场模拟与设备放大研究

采用计算流体力学方法对多通道流动电泳中的流场分布进行了模拟,显示出焦耳热引起的自然对流导致腔室中出现沿电场方向上的溶液主体流动,由此影响到蛋白质的宏观迁移速率,这与实验现象是一致的.系统地考察了电泳分离过程中的自然对流作用及其影响因素,提出以蛋白质分离率作为参数来表征自然对流对电泳分离的影响.通过计算模拟了设备构型及缓冲溶液特性对分离度的影响.以此为基础确定了沿分离腔室长度进行设备放大的方案并进行了实验验证,理论预期与实验结果一致.     

PAM-絮体强化低浊细泥悬浮液絮凝试验研究

针对难沉降低浊细泥悬浮液,采用有机药剂PAM,以出水浊度和絮体平均沉降速度为评价指标,对投加PAM-絮体强化PAM处理低浊细泥悬浮液的絮凝效果进行了试验研究。对比了单独投加PAC和PAM的处理效果,同时还研究了絮凝剂用量、PAM-絮体投加量、水力条件、药剂投加顺序以及水样浊度等因素对处理效果的影响。研究结果表明:向悬浮液中投加一定数量、适当大小的PAM-絮体,不仅能充分发挥PAM絮凝沉降时间短的优势,同时可显著降低出水浊度,减少药剂用量,降低成本,具有强化絮凝的效果。     

苯乙烯热聚合搅拌反应器的数值模拟

为了解聚合反应过程的传热规律和反应现象,以苯乙烯热聚合搅拌反应器为研究对象,通过计算流体力学(CFD)方法对苯乙烯热聚合反应的动力学模型进行耦合,建立该反应器的三维非稳态模型。通过UDF添加组分输运方程源项和能量方程源项,研究强放热反应体系热点分布及发展历程。重点考察物料黏度、搅拌速度对聚合反应器内速度场和温度场分布的影响。结果表明:物料黏度的增加,阻碍了远离搅拌桨区域内物料的对流传热,易在反应器顶部形成局部高温;提高搅拌速度可以使反应器内温度分布更加均匀,但会加剧聚合反应,造成反应器内平均温度升高。研究结果为揭示典型化工过程系统热失控的演化机理,预防热失控反应的发生提供了理论依据。     

气浮接触区气泡聚并行为的数值模拟

在气浮接触区内,聚并会导致气泡直径增大,对分离效果产生影响。采用相群平衡模型对接触区气泡聚并行为进行数值模拟,研究了气泡聚并发生的原因及来液流量、回流流量对气泡聚并的影响。首先分别应用Schiller-Naumann、Grace和Tomiyama3种曳力系数模型进行模拟,所得气泡直径均与实验值吻合,无明显差异,选定Schiller-Naumann曳力系数模型对气浮中两相流动进行模拟。通过对模拟结果进行分析,表明回流入口周围上下行流过渡区域存在较大速度梯度,是导致气泡聚并的关键因素。最后研究了来液流量和回流流量对接触区气泡尺寸的影响,接触区上部气泡直径随回流流量增大而明显增大,原因在于增大回流流量使得过渡区域速度梯度升高,气泡聚并频率提高;而来液流量对气泡尺寸基本无影响。     

气体辅助注射充填流动模拟研究概述

论述了气辅流动模拟需解决的主要问题, 例如气辅模拟中不同参数对成型的影响、预测缺陷、指导工艺及模具设计等.讨论了流动模拟中压力场、温度场、自由移动边界的几种数值实现方法以及厚度比、时间增量的确定.     

Models for the Numerical Simulation of Bubble Columns: A Review

This work reviews the state‐of‐the‐art models for the simulation of bubble columns and focuses on methods coupled with computational fluid dynamics (CFD) where the potential and deficits of the models are evaluated. Particular attention is paid to different approaches in multiphase fluid dynamics including the population balance to determine bubble size distributions and the modeling of turbulence where the authors refer to numerous published examples. Additional models for reactive systems are presented as well as a special chapter regarding the extension of the models for the simulation of bubble columns with a present solid particle phase, i.e., slurry bubble columns.     

注射成型过程数值模拟的辩证认识

注射成型模拟软件的发展十分迅速,本文从基础层面讨论数值软件的根本问题     

注拉吹成型工艺的计算机模拟

为了研究注拉吹工艺参数对制品性能的影响，利用POLYFLOW软件模拟分析了塑料瓶的拉伸-吹塑过程，预测了成型瓶子的厚度分布，并与实测值进行对比。结果表明：改变拉伸速率，对瓶坯的厚度分布有很大的影响，速率过大或者过小都会产生不利的影响；模拟计算对于成型瓶子最终的厚度分布有较好的预测能力。     

Numerical Process and Plant Simulation Methods

This paper represents an attempt to explicitly map the conceptual activities which constitute a process design task into a series of well-posed, complete and general numerical procedures. In spite of the fact that there is substantial number of design manuals and design procedures which process engineers can consult to choose the most proper approach to a particular problem, there is a remarkable lack of generality on the one side (procedures which apply to the design of a wastewater treatment process cannot be used even in principle to design a fluidized bed system), and an obvious receptivity on the other side (all procedures involve mass and energy balances at some point). With the advance of numerical techniques, virtually every procedure has been computerized, so that engineers can avail themselves of a multitude of computer tools in the majority of their process design activities: as a result of the lack of coordination among different producers though, the situation for what codes are concerned is very confusing: there are many codes which perform nominally the same task, giving (sometimes substantially!) different results when applied to the very same problem; each code sue its won set of property tables, its own I/O format, etc. Finally, with very few exceptions, these codes are not mutually compatible, i.e. the output from any of them cannot be used as the input to any of the other, not only because of the respective formats, but rather because the quantities taken to represent a certain physical process are not the same in different codes. This is a very unsatisfactory state of affairs, both for the final user and for the software producer. Unfortunately, this seems to be a problem for which commercial, technical and historical reasons make it very difficult to find a solution in the short term. The author is convinced that an early exposure to this problem and to a new approach to its solution can only benefit our engineering students, and has therefore endeavored, together with his coworkers, to devise a “modular approach” to the solution of process simulation problems. The material presented here has been originated by a series of lectures and seminars developed in the last three years for master and doctoral level students in Mechanical Engineering. The result of this “distillation” process maybe yet unripe, as they are definitely not complete: but the implications, also in terms of practical application, are very promising, and the approach deserves more attention in the future. The order of presentation of the material is historical/logical: it beings with the old fashioned slide-rule calculations and proceeds towards the most recent developments of AI base methods. The path is made clear from the very beginning: we are trying to extract from the various engineering activities all the essential knowledge which pertains to the engineer himself, with the final goal of transferring this body of knowledge - in some form suitable to machine communication - to a “universal-process simulator”, which can then be applied with a high degree of confidence to variety of particular process simulations.     

BMC固化过程的数值模拟

通过数值模拟,预测ＢＭＣ在固化过程不同时刻的温度分布和固化度分布,为实际生产中的模具温度和固化时间提供了理论依据。     

气辅注射充模流动压力及速度场数值模拟

本文以矩形平板为例,在等温条件下对气辅注塑成型过程中充填区域内熔体流动的速度场和压力场进行了数值模拟,给出了不同时刻熔体内的等压力线和流线图。本文的目的是为了揭示气辅注塑成型过程中熔体的流动过程,以便指导生产     

分解槽搅拌过程数值模拟研究

建立了一个工业分解槽的计算流体力学CFD模型,采用稳态多重参考系法以及欧拉一欧拉多相流模型对槽内固液两相搅拌过程进行数值模拟计算。分析了流体速度分布、颗粒相分布以及搅拌功率变化过程。     

低NOx型分解炉内部过程的数值模拟研究

本文在实践和计算流体动力学的基础上，针对NC型低NOx分解炉内部过程进行了数值分析和研究，结果表明：分解炉内各物理量场均具有均匀分布的特征，能够避免因不均匀造成分解炉运行的局部失效问题；采用炉底部增加还原气氛燃烧区段和均匀分料的控制方法，可以有效地脱除或控制NOx过量排放，达到控制的目的。