基于能量平衡原理的锅炉再热汽温反向建模

一个好的汽温模型对机组再热汽温的调节有着重要意义.再热汽温反映了再热器出口蒸汽能量的变化,由能量平衡原理所决定,采用偏最小二乘反向建模的方法对再热蒸汽吸热量进行建模,并结合入口蒸汽能量便可得到再热汽温变化的模型.与传统的直接对汽温建模方法相比,该方法避免了对再热汽温的直接非线性黑箱建模,使模型具有清晰的结构,并提出了具有明确物理意义的单位流量蒸汽吸热能力的概念,便于运行人员掌握和分析汽温变化的本质.结合机组实际运行数据建模,结果表明:非线性偏最小二乘回归的方法能够克服热力系统变量间的多重相关性,所建立的模型具有较高的精度,能够根据模型分析再热汽温异常的原因,量化已有的运行经验,使运行人员快速掌握系统特性,同时也为先进控制策略的应用提供了数据基础.     

粉末薄层选区激光烧结温度场数值模拟与实验研究

单层粉末的激光烧结温度场对三维结构熔结成型有着直接影响。通过对工程塑料粉末选区激光烧结过程能量作用形式的分析,构建了粉体与金属基板界面接触热阻的导热模型和扫描烧结的移动热源模型;利用有限元法对功率为10～25W,光斑直径为0.24mm的激光逐行扫描烧结过程的温度场进行了数值模拟;通过温度场分布模拟和激光烧结实验得到了单层厚度为0.5mm的PA6粉末行扫描间距的优化区间为0.3～0.4mm,获得了熔结质量较好、厚度均匀的平板形烧结物,为进一步优化工艺参数提供了基础。     

模糊内模控制在再热汽温中的应用研究

对基于燃烧器摆角的锅炉再热汽温被控对象进行调节量扰动试验,针对该被控对象具有大惯性、大滞后、参数时变等特性,提出一种模糊内模控制方案,仿真研究结果表明该控制方案具有良好的控制品质、抗干扰能力和鲁棒性。     

P460NL1钢焊接热影响区再热脆化的研究

通过模拟焊接热影响区粗晶区组织,对模拟后的试样进行不同温度下的消除应力退火处理,测得其相应的冲击韧性,确定了P460NL1钢的再热脆化的温度区间,并通过对断口的分析,找出了产生再热脆化的原因,从而确定了最佳的消除应力退火温度。     

铸坯表面温度场测量仪的研究

基于面阵CCD(charge coupled device)的测温系统可以有效克服氧化皮对铸坯表面温度测量的干扰,近年来成为高温测量领域研究的热点。但CCD的非线性关系导致动态测温范围窄、低温段测量精度低。基于窄带带通滤光片建立了单光谱辐射CCD测温模型,据此研制了由滤光片、CCD、CCD信号处理器及DSP构成的铸坯表面温度场测量仪。通过一点标定和自适应调整光积分时间,扩展了CCD测温范围,同时改善了低温段的测量精度,使各温度段测量结果趋于等精度分布;采用4级流水线机制及DSP、工控机(industrial personal computer,IPC)2级数据处理结构,提高了系统的实时性;该仪器还具有暗电流补偿和以太网传输功能。通过黑体炉标定和现场测量,结果表明研制的测温仪满足铸坯表面温度场测量要求。     

Experimental investigation of the temperature fade in the cavitation zone of full journal bearings

This paper describes an experimental investigation with a rig for measuring the surface temperatures and pressures in single bore journal bearings. The test bearing was equipped with small bores, where the pressure was altered by means of a vacuum pump. The whole bearing arrangement can also be operated at different ambient pressures ranging from atmospheric down to −0.06 MPa. Oil temperatures at inlet and outlet are also measured. Experiments show a considerable drop in the temperature of oil undergoing a drop in pressure. The overall temperature level of the bearing system did not seem to affect the magnitude of the temperature drop. Experiments where the bearing system was operated at sub-ambient pressures revealed an increased temperature drop in the cavitation zone. Pressures higher than ambient were measured within the cavitation zone while the bearing was operated at sub-atmospheric pressure. The higher pressures are believed to be caused by evaporation of oil. It is therefore proposed that the temperature drop observed in the cavitation zone of journal bearings is primarily caused by evaporation of oil. However, isentropic decompression of the gases in the oil is also believed to play a role.     

一种钢坯标识设备主箱体机构优化与仿真

为了能够区别钢厂生产出来的钢的型号,课题组设计出了一款能在钢坯表面喷字的钢坯标识设备。在对钢坯标识设备进行冷调试喷字的过程中出现了主箱体振动的状况,影响写字效果。通过对现有的钢坯标识设备进行结构优化,对优化后的方案进行三维UG建模,同时进行ABAQUS静力学分析和有限元动力学模态分析。通过研究结果表明优化后的主箱体在工作时的振动得到了明显的改善,喷字效果得到明显的提高。     

630MW超临界机组再热汽温控制策略研究与应用

本文针对华能太仓电厂二台630MW超临界机组再热汽温的大滞后及时变性的特点,在获得其被控过程动态数学模型的基础上,采用先进的预测控制和智能前馈技术,提出了新型的再热汽温控制系统,实现了以调节再热烟气挡板为主、喷水调节为辅的再热汽温控制。实际应用表明,新型的再热汽温控制系统不仅有效减小了再热汽温的动态偏差,提高了再热汽温的平均温度,而且有效减少了再热喷水量,明显提高了再热汽温的控制品质和运行经济性。     

The fabrication and preservation of nanostructures on silicon wafers with a native oxide layer

This study used nano‐oxidation lithography to create oxidized circular nanostructures on a silicon wafer with a native oxide layer (NOL). We also investigated the impact of wet etching on the size of circular oxidized nanostructures and examined how the method and duration of preservation affect them. Experimental results show that the height and width of oxidized circular nanostructures increase proportionally with applied voltage. After wet etching, an increase in applied voltage resulted in a marked increase in the width of the circular nanostructures, a decrease in the inner diameter, and little variation in height. We further demonstrated that in a moist environment, the oxidation process continues, resulting in a further increase in height and width. During the initial stages of preservation, these changes occurred rapidly; however, the increase was negligible after 30 days. We propose the concept of reaction area (RA) ratio to explain the above phenomenon and provide evidence to support these claims. Our results led us to a simple and yet effective method of preserving oxidized circular nanostructures, called the electrostatic patch preservation (EPP) method, to overcome problems associated with changes in size occurring during the preservation of silicon nanostructure molds. SCANNING 34: 347–356, 2012. © 2012 Wiley Periodicals, Inc.     

钢坯修磨机台车张力控制系统的仿真研究

建立了钢坯修磨机钢丝绳张力控制系统,并且对阀控张紧液压缸伺服系统的所有液压元件和修磨机柔性负载系统进行了建模,通过MATLAB/SIMULINK仿真软件,主要分析了预紧力对钢丝绳受力的影响,并且对开环无反馈、力环反馈,以及位移反馈控制系统的仿真结果进行了比较,得出了可靠的结论。     

在锌纳米晶镀层上热氧化时氧化锌纳米针的形成与生长机制

Senuconductor ZnO has been widely studied as a short-wave-length light-emitting,transparent conducting and piezoelectric materials due to its wide bandgap(3.37 eV)with large exciting binding energy(60 meV)[1].There are many synthesis methods used for growing ZnO nanostructurc according to a so-called vaporliquid-solid(VLS)or vapor-solid(VS)mechanisms[2-3].     

火电厂再热汽温的SMITH预估控制算法应用研究

针对火电厂再热汽温控制系统的大惯性、大迟延和时变性,采用传统的PID调节规律难以取得较满意的调节效果。ABB Bailey公司的SMITH预估控制算法不仅具有传统SMITH预估控制器克服大滞后、大惯性的特性,把此算法运用到再热汽温控制系统中,还具有较强的抗内外干扰和对象变化适应的能力。仿真结果验证了其有效性。     

An investigation of the tribological interaction between die damage and billet deformation during MMC extrusion

This study deals with material flow behaviour during the extrusion process of a metal-matrix composite (MMC), and the effects of this behaviour on the damage to die flat surfaces. AA 6063 aluminium matrix composite billets reinforced with SiC particles (167 μm) were prepared using the stir-casting method for extrusion. Extrusion of the MMC billets were conducted at 500 °C with a ram speed of 2 mm s⁻¹ and an extrusion ratio of 25:1 under laboratory conditions. The extrusion die with two different channel profiles was manufactured from AISI H13 steel that was hardened, tempered and grounded. The flow patterns of the deformed billet during the MMC extrusion determine the positions of the SiC particles in the deformation zone. While some of the SiC particles flow within the deformed material, some flow at the deformed billet surface; these SiC particles play the most important role in the damage mechanism of the die-bearing surface and the geometry of the dead metal zone (DMZ). The possible damage to the die-bearing surfaces is severe at the entrance of the die bearing. On the other hand, some SiC particles are broken in this zone due to the severe deformation stress of the MMC billet.     

传感器灵敏度温度的补偿及调整

本文介绍了传感器灵敏度温度的影响因素,灵敏度温度的补偿方法及调整方法,可以提高灵敏度温度补偿的精度和效率。     

Experimental investigation and 3D finite element prediction of the white layer thickness, heat affected zone, and surface roughness in EDM process

An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand, an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.     

Numerical simulation investigation on centrifugal compressor performance of turbocharger

In this paper, the mathematical model of the flow filed in centrifugal compressor of turbocharger was studied. Based on the theory of computational fluid dynamics (CFD), performance curves and parameter distributions of the compressor were obtained from the 3-D numerical simulation by using CFX. Meanwhile, the influences of grid number and distribution on compressor performance were investigated, and numerical calculation method was analyzed and validated, through combining with test data. The results obtained show the increase of the grid number has little influence on compressor performance while the grid number of single-passage is above 300,000. The results also show that the numerical calculation mass flow rate of compressor choke situation has a good consistent with test results, and the maximum difference of the diffuser exit pressure between simulation and experiment decrease to 3.5% with the assumption of 6 kPa additional total pressure loss at compressor inlet. The numerical simulation method in this paper can be used to predict compressor performance, and the difference of total pressure ratio between calculation and test is less than 7%, and the total-to-total efficiency also have a good consistent with test.     

Effects of temperature and grain size on phase-field-crystal deformation simulation

We performed deformation simulations of nanocrystalline structures under different temperature and grain-size conditions using the phase-field-crystal (PFC) method with an isovolumetric numerical scheme proposed by Hirouchi et al. [Development of numerical scheme for phase field crystal deformation simulation. Comput Mater Sci 2009;44:1192-7.], and we discussed the deformation behavior of bicrystalline and polycrystalline metallic materials during plastic deformation in detail. As a result, we were able to observe typical plastic deformation behavior such as the generation, annihilation and movement of dislocations as well as grain rotation and grain boundary (GB) migration depending on the grain size and temperature. It was concluded that the PFC method with the isovolumetric deformation scheme is a powerful tool for simulating polycrystalline metals, because the obtained behaviors were in qualitative agreement with the results obtained by molecular dynamics (MD) simulations and experiments.     

叶梁热压面温度均匀性分析及仿真模拟

利用有限元软件ANSYS模拟仿真叶梁热压成型过程中热压面温度变化,分析热压面温度不均匀的原因.通过实验得到的预测性数据,为叶梁热压设备加热机构的分布改进提供了一些必要的参考数据和设计依据.实验得到的叶梁成型温度圴匀一致,总体误差在±0.5℃,最高温度和最低温度之差小于0.2%.