Flow simulation in Electro-Static-Precipitator (ESP) ducts with turning vanes

Flow simulation in inlet ducts along with several turning vanes used in electrostatic precipitator (ESP) are analysed to understand the flow pattern at its exit locations. The geometry of inlet duct has been extracted from the Plant Design Manufacturing System (PDMS) and refined with turning vanes placed at several locations. The domain of duct geometry around turning vanes are decomposed with several volumes and filled with hexahedral elements with the help of stat-of-art mesh generator - Hypermesh. The resulting computational grid has been used in TASCflow solver to predict its flow pattern in the duct. Simulation for the specified conditions predicts uneven flow distribution in the ESP inlet duct. Due to large flow recirculation and turbulent losses in the duct, non-uniform averaged mass flow rates are noticed at duct exit locations. Simulation results suggest that the improvement of flow distribution in the duct through optimization can be tried by placing more turning/splitter vanes in the inlet duct. In order to ensure that the results obtained from TASCflow are meaningful and in right direction, in the absence of measurement data, simulation was benchmarked with other industry standard commercial flow solvers. The observations made from these popular solvers confirm the findings obtained using the TASCflow solver. The analysis with multiple solvers indicates that Fluent provides quick results, while better visualization can be made using CFX solver. The Star-CD solver, which captures the turbulent losses accurately takes more time for convergence provides alternatives.     

双螺杆挤出机流场数值模拟中流道进出口边界条件的探讨

在对双螺杆挤出机流场的数值模拟中,流道进出口边界条件的设置一直是一个颇具争议的问题。由于事先无法获得计算域进出口平面上的真实边界条件,研究人员在进行双螺杆挤出机的流场分析时,大都采用放松边界条件。为了考察放松边界条件对双螺杆挤出机流场数值模拟结果的影响,本文采用聚合物流动分析软件POLYFLOW,在流量恒定的前提下对双螺杆挤出机流道进出口给定三种不同分布形式的速度边界条件,对其流场进行了数值模拟。数值计算结果表明,在体积流量恒定的条件下,流道进出口不同分布形式的速度边界条件对流场的影响主要集中在进出口附近区域,但对离进出口边界较远的流场影响很小。一般而言,当计算域所对应的螺杆较长时,可以忽略流道进出口的放松边界条件所引起的误差;当计算域较短时,不宜直接采用放松边界条件,而应根据螺杆的实际构型．在计算域的进出口增加适当长度的发展段。     

二元超声速进气道数值仿真建模过程自动化

研究高速巡航导弹动力装置优化问题,针对进气道结构严重影响速度的提高,为减少人工建模的工作量,以提高数值仿真分析工作效率和满足二元超声速进气道设计方案的快速评比和选型的需要,提出建立流场计算域通用的结构化分区几何模型,统一基于所构造的基准进气道模型,一次性人工划分进气道结构化计算网格,根据边界几何控制,运用网格映射和比例变换方法,编程自动化实现由基准进气道计算网格映射生成实际结构不同的系列化二元进气道计算网格。用建立的模型进行仿真。结果证明,减少了建模工作量和提高了工作效率。     

Advanced control of a reverse osmosis desalination unit

An experimental investigation of constrained model predictive control (CMPC) for a reverse osmosis (RO) desalination unit has been conducted. For comparison purposes, results with traditional PID-type control have also been obtained. The experimental unit consists of a series of four cellulose acetate membranes. A 486-PC is used as the data acquisition and control computer. It is interfaced to the experimental unit via analogue-to-digital and digital-to-analogue converter boards. The models required for CMPC and PID-type controls are obtained by step testing. The RO system has four outputs and two inputs. The outputs are (1) permeate flow rate, (2) permeate conductivity, indicative of the salt content in the product, (3) trans-membrane pressure, and (4) inlet pH. The inputs are (1) flow rate of reject water and (2) inlet acid flow rate. The production objectives are to produce the specified flow rate of permeate, having the desired salt content, subject to the constraints that the inlet pH and the trans-membrane pressure are within specified bounds. It is shown that CMPC can achieve these goals. It is also demonstrated that CMPC can maximize the throughput subject to the constraints on the other three outputs. A comparison of the results with CMPC and PI control reveals the excellent capability of CMPC for RO desalination plant operations.     

Inlet conditions for large eddy simulation: A review

The treatment of inlet conditions for LES is a complex problem, but of extreme importance as, in many cases, the fluid behaviour within the domain is determined in large part by the inlet behaviour. The reason why it is so difficult to formulate inlet conditions is because the inlet flow must include a stochastically-varying component: ideally this component should ‘look’ like turbulence whilst at the same time be as simple as possible to implement and modify. We review methods for accomplishing this reported in the literature, these being ‘precursor simulation’ methods and ‘synthesis’ methods, and implement our own novel versions of these using the code OpenFOAM. Conclusions have been drawn about the relative merits of the different approaches, based on the physical realism of the results and the ease of construction and use.     

集中供热系统中防止“窃热”行为的动态监控网络

建立了一套新的热量表动态监控网络,通过该网络可以防止“窃热”现象。国内的大多数热量表都没有联网,少数联网的热量表也仅是为了远程抄表收费方便的目的,在该抄表网络上没有动态、实时地传输各个热量表的热水流量、进出口温度等数值。建立的热量表动态监控网络对该抄表网络进行了很大改进,在该抄表网络上可以动态、实时地传输各个热量表的热水流量、进出口温度等数值,并通过对这些数据进行分析,可以有效防止“窃热”现象的发生。     

LNG船液货装卸系统仿真计算与实现

液化天然气(LNG)船液货装卸过程中,需严格控制装卸时间,但由于装卸系统的复杂性,设计装卸系统时很难准确得到LNG在管路中的流动状态平衡控制。针对上述问题,提出了一种面向LNG船液货装卸系统结构的计算方法,根据图论和有限元软件构建装卸系统拓扑模型,形成双层反馈控制结构,建立仿真装卸模型,计算任意时间点的管网节点压头和管路流量情况。采用Visual C++编制了图形化界面的仿真计算软件进行仿真。仿真结果与实际情况基本符合,表明装卸方法具有实用性,能对LNG船液货装卸系统的设计起借鉴作用。     

小型无人直升机纵横角动态耦合辨识建模

针对小型无人直升机耦合建模问题提出了一种频域解耦辨识建模方法,该方法通过处理针对耦合辨识的实验数据得到指定频域范围内被辨识耦合的频域特性,对频域特性进行拟合从而获得耦合模型.提出了适用于多输入输出(MIMO)系统的频域特性计算方法,定义了一种复合相干函数并证明其能够用于表达在耦合通道辨识中输入输出的相关性.基于该方法,对一种小型无人直升机在悬停状态的纵横角动态耦合模型进行了辨识,并将耦合模型加入到直升机仿真模型中考察其对模型预测精度的影响.模型预测输出与实际输出的比较表明,相较于普通模型,考虑了耦合动态的仿真模型能够更为精确地预测实际输出.     

Application of the two-step Lax and Wendroff FCT and the CE-SE method to flow transport in wall-flow monoliths

Gas dynamic codes are computational tools applied to the analysis of air management in internal combustion engines. The governing equations in one-dimensional elements are approached assuming compressible unsteady non-homentropic flow and are commonly solved applying finite difference numerical methods. These techniques can also be applied to the calculation of flow transport in complex systems such as wall-flow monoliths. These elements are characterized by alternatively plugged channels with porous walls. It filters the particulates when the flow goes through the wall from the inlet to the outlet channels. Therefore, this process couples the solution of every pair of inlet and outlet channels. In this study, the adaptation of the two-step Lax and Wendroff method and the space-time Conservation Element and Solution Element method is performed to be applied in the solution of flow transport in wall-flow monolith channels. The influence on the prediction ability is analysed by a shock-tube test and experimental data obtained under impulsive flow conditions.     

一种新颖的闭环频域辨识方法及其在大滞后系统Smith预估控制中的应用

提出了一种大滞后系统的频域辨识方法并将其用于 Smith预估控制 .这种辨识方法不需要困难的信号设计和单独的信号发生设备 ,能够以闭环的方式测试系统指定相位处的频率特性并最终得到系统的传递函数模型 .由于所提出的辨识方法的特点 ,它非常适用于 Smith预估控制方案 ,实现对工业过程中大滞后系统的有效控制 .对一个高阶大滞后过程的仿真取得了非常好的效果 ,表明了所提出方法的有效性     

Gas flow meter for application in medical equipment for respiratory control: study of the housing

The study of the housing of a gas flow meter for use in medical equipment for respiratory control will be presented in this paper. The sensor is of the thermal type with dimensions 1.4 mm×0.9 mm. The housing is developed so as to assure conditions of laminar flow in a flow range from −200 to +200 standard liters per minute (SLPM). An analytical approach is first used to determine the main housing configuration. The type and the position of a bypass tube, which is fixed to the main flow tube, are studied in detail. Extensive simulations of the flow in different housing configurations and different conditions at the inlet and outlet of the housing were performed, using the finite element analysis (FEA) software package ANSYS. The optimum housing was finally fabricated and evaluated in oxygen flow. Excellent agreement of experimental results with simulation was obtained.     

融合异构特征的子空间迁移学习算法

特征迁移重在领域共有特征间学习,然而其忽略领域特有特征的判别信息,使算法的适应性受到一定的局限. 针对此问题,提出了一种融合异构特征的子空间迁移学习（The subspace transfer learning algorithm integrating with heterogeneous features,STL-IHF）算法.该算法将数据的特征空间看成共享和特有两个特征子空间的组合,同时基于经验风险最 小框架将共享特征和特有特征共同嵌入到支持向量机（Support vector machine,SVM）的训练过程中.其在共享特征子空间上实现知识迁移的 同时兼顾了领域特有的异构信息,增强了算法的适应性.模拟和真实数据集上的实验结果表明了所提方法的有效性.     

一种分布式环境下基于角色的访问控制模型

针对访问控制模型在分布式系统下的局限性,提出一种分布式系统下的基于角色的访问控制模型。该模型以传统RBAC为基础,对其进行了扩展,一方面通过将角色扩展为职能角色和任务角色,另一方面为任务角色增加一个属性,用以标识该角色所赋予的主体属于本域还是外域,避免了采用对等角色直接进行角色分配的简单化处理。从而一方面有利于最小权限的实现,另一方面实现了对本域和外域的主体访问请求采用不同的策略,使基于角色的控制应用范围从集中式的控制领域扩展到分布式的控制领域,以适应不断发展的分布式环境系统的需求。     

基于遗传算法的高空台进排气控制仿真研究

高空模拟试验台进/排气系统是实现地面模拟发动机空中飞行高度、速度条件的核心试验设备,其控制效果的优劣直接影响着高空模拟试验的精度。而控制参数的选择是决定一个控制系统动态特性的关键要素,通过对遗传算法的研究,将该算法应用到进/排气系统进气压力自动控制系统中,对自动控制系统的PID控制参数进行优化,仿真结果表明,遗传算法以其优秀的全局寻优能力,能够对进/排气系统发动机进气压力自动控制系统PID控制参数进行较好地优化,使得控制系统获得良好的控制效果。     

前输出轴涡轴发动机高空台进气装置设计及验证

对某前输出轴涡轴发动机高空模拟试验进气装置进行了设计,通过三维数值仿真的方法对比分析了典型工况进气涡壳内有无整流装置情况下发动机进口的流场品质,确定在增加整流装置的情况下,发动机进口压力不均匀度小于1%,温度不均匀度小于1%。为降低进气装置压力损失,对进气装置进行了优化设计,仿真结果表明,在最大流量下,压损降低了30%。最后通过吹风试验验证了流场品质满足设计要求,解决了涡壳进气方式产生的流场畸变问题。同时将导管流量数据与导流盆流量数据进行对比,证明了导流盆测流量方案的合理性。该设计可在此类涡轴发动机高空模拟试验中推广运用。     

基于树形结构的ARINC429解码库设计方法研究

在进行总线测试时,工程人员需要查询接口控制文件,并将接收到的二进制数转换为十进制,导致故障定位时间较长。针对该问题,提出了一种基于树形结构文件格式的ARINC429总线数据描述方法,并利用此描述方法基于XML建立了接口控制文件解码库。该解码库包含ARINC429数据字的传输速度、参数名称和参数单位等各种信息,能够实现ARINC429规范中BNR、BCD和DIS的解码。将该解码库应用于某型国产飞机航电系统通信导航半实物仿真平台进行验证,结果表明,仿真平台能够识别采集板卡接收到的数据并进行解码,能够做到仿真测试软件与编码库的分离,提高了可维护性,降低了仿真测试软件中解码代码的总量,且具有高度可移植性。     

基于虚拟化技术的卫星控制系统软件构件库运行监控与可信验证技术

动态系统建模工具可以按照设定的仿真步长对控制器的行为动态模拟,也可以在仿真环境下模拟控制器所在的系统架构和动态数据交互,因此传统的卫星控制系统方案设计时一般采用在同一模型建模体系进行,并进行相应的控制算法设计。但是由于动态系统建模工具其自身的时钟步长和数据流处理逻辑,不能完全模拟目标机的内部ALU逻辑和真实外围设备工作行为,可能与真实物理环境要求的系统有一定的出入,造成对承载卫星控制器功能的目标机CPU处理系统存在一定程度的失真,影响仿真效果。提出了一种基于虚拟化技术的卫星控制系统软件构件库可信验证技术,使用虚拟化技术实现对真实物理目标机功能的完全模拟,运用软件非干涉运行监控技术,获取可信的开发证据和应用证据,利用协同仿真组件和卫星控制系统方案设计的控制算法模型对各个软件构件进行动态同步仿真验证。     

进气道流量调节阀控制装置设计

由于飞机发动机进气道试验中空气流量需精确控制,需要采用一种响应迅速,且较为容易实现计算机精确控制的机械电子系统。该气道流量调节控制装置采用C8051F021单片机与易于单片机控制的步进电机来实现系统控制功能,用5×4的键盘作为输人来对电机的状态进行控制,键盘输入的数据送至单片机,并用数码管显示输入的行程和整个系统的运行工况与位移传感器的测量值,单片机输出信号控制步进电机的运行;系统设置了串口通信,通过MAX232接口电路实现控制系统与上位机的数据通信,通过上位机实现对进气道流量的控制。     

Reduced order modeling of a two-dimensional flow with moving shocks

The objective of this paper is to demonstrate the ability of proper orthogonal decomposition, in combination with domain decomposition, to produce accurate reduced order models (ROMs) for two-dimensional high-speed flows with moving shock waves. To demonstrate this ability, a blunt body flow with quasi-steady shock motion is considered. The blunt body flow contains a strong bow shock that is moved via a change in inlet Mach number and angle of attack. Accuracy is quantified by comparing surface pressures obtained from the ROMs with those from the full order simulation under the same free stream conditions. The order reduction, and computational performance of the ROM is also quantified relative to the full order simulation. The robustness of the ROM to varying flow parameters is explored. A non-Galerkin quasi-implicit steady state implementation is considered.     

化工过程模拟类库的设计标准计与方法

将面向对象思想应用于化工过程模拟领域,提出了为重用而系统地建立了化工过程模拟类库的思想。文中给出了化工过程模拟类库应具有的基本特征（设计标准）,即正确性、一致性、扩展性和重用性。结合过程模拟的概念的应用,介绍了类库开发中采用的具体类、抽象类和层次类等典型类结构。另外,对类库设计中进行的域分析和类抽象作了详细说明。类抽象是类库重用的保证,域分析是类抽象的基础。