Laminar separation bubbles: Dynamics and control

This work is an experimental investigation of the dynamics and control of the laminar separation bubbles which are typically present on the suction surface of an aerofoil at a large angle of attack. A separation bubble is produced on the upper surface of a flat plate by appropriately contouring the top wall of the wind tunnel. First, a basic (unforced) separation bubble is obtained to set a benchmark for further experiments. Parametric study is done where the reference velocity is decreased to quantify its effect on the aspect ratio of the bubble. It is found that with decrease in Reynolds number, the height of the bubble increases at a greater rate than the length. This feature could be useful in characterising separation bubbles especially from the point of view of low Reynolds number aerofoil design. Artificial disturbance is introduced at two different initial amplitudes (infinitesimal and finite) upstream of separation location and hotwire anemometry is used to trace the wave packet as it is advected downstream. The evolution of wave packets is seen to take place in two distinct stages. Finite amplitude forcing causes periodic quenching of the bubble. Interestingly, even an infinitesimally small forcing is seen to modify and thereby control the separation bubble.     

集散控制系统故障导致空分设备停车分析

介绍了因集散控制系统故障导致空分设备停车的经过及原因,并提出了解决的方法及今后运行中需注意的问题。     

空分设备自动变负荷先进控制技术

以南钢20000m3/h空分设备为例,介绍国产大型空分设备自动变负荷控制系统的设计思路、优化控制及方案、技术特点、控制目标和控制策略等。阐述空分设备自动变负荷技术实现国产化的意义。     

先进控制技术在国产大型空分设备中的应用

根据邯钢2套35000 m3/h空分设备运行特点,结合自动变负荷技术,设计并应用了以多变量模型预测控制为主的先进控制技术,实现了空分设备稳定、高效运行。详细介绍先进控制系统的控制器方案设计、中间点建立和安全切换程序、操作界面以及自动变负荷与先进控制技术结合运行操作。     

空分设备自动控制技术的发展现状与展望

介绍目前空分设备的控制系统状态及控制技术水平,分析空分用户的用氧特点,阐述空分设备自动控制技术的发展趋势,提出随动变负荷概念在DCS系统内的实现展望,并且明确了空分设备对寻优控制技术的需求。     

大型空分设备空压机控制系统的设计和研究

针对大型空分设备对离心空压机的要求,以及为实现空压机安全、高效运行的目标,对空压机的控制系统进行设计、研究,提出了控制系统具体的测控内容和目标,对不同的控制内容进行了理论设计,开发了适合空压机DCS控制系统的监测、控制软件。     

大型空分装置的空气透平压缩机自动控制

简述了大型空分装置空气透平压缩机自动控制的原则、实施方法 ,详细介绍了基本控制、防喘振保护控制等大型透平压缩机主要控制的内容     

一种具有双控制比例因子的最优间隔超球分类器

针对支持向量描述只考虑目标类训练样本,结合支持向量机最优分类超平面和支持向量描述的思想,引入了异常样本信息的监督机制,建立了最优间隔超球分类器模型,以一个最小的超球包含目标类训练样本和一个尽可能大的超球体将非目标样本隔离在超球体外,使决策超球面与该两个超球面以最大间隔分离,保证了描述精度和泛化性能,同时,为更好地排除对两类样本数据分布中野点的干扰,提出了一种双控制比例因子的控制方法,更加灵活地实现软间隔分类,仿真实例验证了该分类器具有比SVDD更好的分类性能     

空分设备自动变负荷控制技术综述

综述国内外大型空分设备的自动变负荷控制技术的发展状况,分析自动变负荷控制技术的难点,着重对空分设备先进控制系统结构和操作流程、模型预测控制基本原理及其在空分领域的研究成果等进行了较全面的阐述,最后对空分设备自动变负荷技术的发展进行了展望。     

空分设备误停车综合治理的探讨

在空分设备运行过程中,往往会因为仪控误联锁、误操作和电网电压波动等因素导致空分设备非计划停车,造成较大的经济损失。介绍了空分设备常见非计划性误停车的类型,从工艺管理和技术防范两方面入手进行原因分析,并提出防范措施,为降低空分设备运营成本提供参考。     

Flow separation control in open-channel bends

The investigation of fluid flow in sharp open-channel bends is key to controlling undesired sedimentation in natural river reaches. The difficulties are associated with controlling the flow separation in meanderings. Flow separation decreases the width of the flow, and consequently, the conveyance capacity while increasing erosion and mixing. This study proposes a novel approach to reduce the flow separation at the inner banks of sharp open-channel bends. Three-dimensional numerical experiments were conducted. To find the most reliable procedure, five turbulence models were examined. The employed numerical approach is formulated within the framework of the finite volume method and the volume of fluid (VOF) technique to solve the Navier–Stokes equations. Water levels and velocity profiles are obtained in different sections of the channel and are compared to experimental studies of a 90° sharp open-channel bend. A close agreement is observed using the RSM (Reynolds stress model) turbulence model. Moreover, the evaluation of acquired velocity profiles demonstrates that in a regular bend, the lowest velocity occurs near the inner bank, where it has a flow separation tendency. The same numerical procedure is employed to simulate water flow through a sharp converging open-channel bend. The measurements of velocity profiles and velocity vectors in the curved sections support the idea that decreasing the channel width considerably reduces the overall velocity variations in cross-sectional areas of the test case and is effective to control flow separation.     

涟钢30000m~3/h空分设备仪控系统调试改进

简介涟钢30000 m3/h空分设备所用现场仪表及DCS控制系统,详细叙述了调试过程中发现的空分设备仪控系统存在的不足,分析原因并采取改进措施后,很好地实现了仪控系统的各项功能。     

Exposure to lateral collision in signalized intersections with protected left turn under different traffic control strategies

This paper proposes an original definition of the exposure to lateral collision in signalized intersections and discusses the results of a real world experiment. This exposure is defined as the duration of situations where the stream that is given the right-of-way goes through the conflict zone while road users are waiting in the cross-traffic approach. This measure, obtained from video sensors, makes it possible to compare different operating conditions such as different traffic signal strategies. The data from a real world experiment is used, where the adaptive real-time strategy CRONOS (ContRol Of Networks by Optimization of Switchovers) and a time-plan strategy with vehicle-actuated ranges alternately controlled an isolated intersection near Paris. Hourly samples with similar traffic volumes are compared and the exposure to lateral collision is different in various areas of the intersection and various traffic conditions for the two strategies. The total exposure under peak hour traffic conditions drops by roughly 5 min/h with the CRONOS strategy compared to the time-plan strategy, which occurs mostly on entry streams. The results are analyzed through the decomposition of cycles in phase sequences and recommendations are made for traffic control strategies.     

EDPF-NT分散控制系统在空分装置上的应用

阐述了EDPF NT分散控制系统的组成和主要技术性能 ,其特点是具有高可靠性、高通讯速率、高精度 ,良好的可维护性、适应性、可扩展性。介绍了在 5 40 0m3 /h空分装置上的应用及为稳定空分工况在控制方式上进行的几点卓有成效的改进。     

空气低温分离技术的某些进展

本文结合大型制氧机流程的发展 ,以全低压外压缩流程、内压缩流程及一种在空分上塔和下塔间设置闪蒸分离器 /塔的新流程为例 ,简要介绍了空气低温分离技术的发展。     

A framework to engineer production control strategies and its application in electronics manufacturing

One of the most challenging tasks of companies with complex and discrete production systems is to determine an appropriate production control strategy (PCS). The PCS is crucial, as it influences inventory, costs, and service. We propose a framework to address the most important questions of PCS engineering: limiting work in process, positioning the order penetration point (OPP), and coping with demand uncertainty upstream the OPP. Thereby, uncertain advance demand information in the form of forecasts is considered and desirable characteristics of push and pull strategies are combined. A serial manufacturing system with multiple products, variable processing times, and uncertain advance demand information is examined. The model is formulated as a queuing network model and solved numerically by discrete-event simulation. The framework and a resulting hybrid control strategy are applied to a case study from electronics manufacturing, where a significant improvement potential is identified.     

进口ITCC控制系统结合国产DCS控制系统在特大型空分设备中的应用

介绍进口ITCC控制系统TS3000结合国产DCS控制系统ECS100在灵谷化工KDON-50000/72600型空分设备中的应用,叙述了空压机防喘振控制的工作原理和具体控制过程;分析了液氧泵的自动切换控制。     

DCS控制系统无显示数据时空分设备的操作

介绍了当DCS控制系统无显示数据时,为避免空分设备停车而造成生产损失,采取通过监测仪表变送器来掌控各工艺指标的操作方法。具体叙述了根据各主要工艺指标现场仪表变送器的显示变化而采取的操作措施。     

5000m~3/h空分设备液氮气液分离器运行控制分析

简介仪征化纤5000 m3/h空分设备中液氮气液分离器的工作原理和作用,分析气液分离器的工作状态及其对空分设备主塔运行工况的影响,论述用压力控制气液分离器工作状态的可行性,阐述其工作状态控制方法的改造建议。     

谈空分设备自动变负荷控制技术

为了实现空分设备变负荷技术 ,要进行项目准备、系统仿真和动态测试。强调了变负荷操作的关键是保持精馏工况的稳定 ,以及保持工况稳定须注意的问题