Development and application of thermal mathematical model of iron ore pellet bed in grate

Based on the analysis of heat transfer mechanics, physical and chemical change of pellet drying and preheating process in grate, the mathematical model is established and solved by three-diagonal matrix algorithm. With Visual Basic 6.0 a simulation software is developed. The model is verified by measurements at a domestic pellet plant, and the temperature distribution of pellet bed is gained. Meanwhile, the influence of different operation parameters on the pellet thermal process is studied. The results can be taken as a basis of practical production control and the grate optimizing design.     

Numerical simulation on temperature and stress fields in beryllium during cutting process

The temperature and stress fields in beryllium during high speed cutting process were studied by employing a thermo-mechanically coupled finite element method (FEM). The results show that the temperatures in beryllium increase only a little during the cutting process. Both of the residual stresses for along and normal to the cutting direction are tensile stresses in the surface of beryllium after cutting. The cutting force and thrust force are about 280 and −250 kN/m at the steady stage, respectively. The main effects of coolant on the cutting process are to decrease the friction coefficient and heat between the tool and the workpiece, so to reduce the temperature, but almost no effects are made for stress. This study is helpful to enhance the understanding for stress formation and optimize the process parameters of beryllium.     

Research on temperature field and thermal stress of liquefied natural gas carrier with incomplete insulation

The insulation of membrane type liquefied natural gas (LNG) carrier is composed of plywood boxes filled with perlite. Within the service period, considering of the effects of load conditions, such as sloshing, wave load, it is possible to have some damage of the plywood box, leakage of perlite, and failure of the insulation box. LNG carrier without whole protection of effective insulation is dangerous. Hull structure is extremely fragile when exposed to ultra-low temperature. In order to solve these problems, firstly a study on insulation boxes’ character and work condition is carried out and some presuppositions of partial disabled insulation are put forward. Secondly the thermal system of LNG carrier is analyzed to find out an effective way to simulate the thermal action of close air between outer and inner hull. Then a calculation about temperature field and thermal stress is done by MSC/PATRAN&NASTRAN. At the end it is concluded that LNG carrier with incomplete insulation is dangerous and needs to be avoided.     

承台大体积混凝土里表温差梯度与温差应力有限元模拟

针对大体积混凝土因水化热引起的早期开裂问题, 以内蒙古老山沟公路大桥承台为依托, 建立了大体积混凝土三维有限元模型, 分析了粉煤灰掺量、浇筑温度、环境温度与养护措施对承台中心温度、里表温差与表面拉应力的影响。模拟结果表明: 混凝土表面拉应力随粉煤灰掺量增大而减小, 当掺量超过30%时, 降幅增大, 中心温度、里表温差和表面拉应力均随其掺量增大而减小, 可见掺加粉煤灰可有效降低混凝土水化热, 防止表面温差裂缝的产生; 当浇筑温度从5℃到30℃变化时, 中心最高温度从40.3℃升至58.1℃, 里表最大温差从8.6℃升至19.0℃, 表面最大拉应力从0.93 MPa升至1.66 MPa, 且随浇筑温度的增大, 中心最高温度和里表最大温差产生的时间有所提前, 表面拉应力呈线性增大趋势; 里表温差和表面拉应力都随环境温度增大而减小, 且表面拉应力与环境温度基本呈线性关系; 养护条件越好, 里表温差越小, 表面拉应力明显降低, 且前期表面拉应力增速减慢, 峰值出现时间推迟, 有利于裂缝控制。     

颗粒材料双轴试验离散元数值模拟(英文)

为了得到颗粒材料的力学参数与试验条件之间的关系, 选取5组粒径范围的颗粒材料, 利用离散元方法生成初始试件, 并数值模拟了其双轴试验, 分析了不同围压对材料弹性模量和强度的影响, 以及不同加载速率下材料的弹性模量、泊松比和强度的变化规律。提取了围压为10MPa与加载速率为0.03m.s-1时5组试件的应力-应变曲线, 从微观角度给出了荷载作用后试件中的裂缝分布。模拟结果表明: 随着围压的增大, 5组试件的弹性模量和强度增大, 增长趋势相对平缓, 但粒径为9.50~13.20mm的试件出现较大波动; 加载速率与弹性模量、泊松比、强度和裂缝初始应力基本呈二次多项式关系, 最小判定系数为0.9009, 最大为0.9959;在5组试件中, 随着粒径的增大, 由应力-应变曲线得到的应力峰值减小。     

Numerical simulation of multi-pass rolling force and temperature field of plate steel during hot rolling

Rolling force and temperature field are important parameters in the hot rolling process of plate steel. Most researchers use ANSYS/LS-DYNA and MSC.Marc to simulate the hot rolling process, however, software DEFORM-3D is not used widely in this field. Therefore, in this study, the commercially available finite element analysis software DEFORM-3D is used to simulate the distribution of rolling force, stress-effective, strain-effective and temperature field during the hot rolling process of plate steel with the size of 0.220m×2.070m×1.904m. Both the simulated rolling force and temperature of the multi-pass are compared with the measured results. It is shown that the simulated values by the finite element method are approximate to the measured values in the hot rolling of plate steel. So the simulation can provide an important reference and optimization to make rolling process and parameters in steel factory.     

工业窑炉燃气污染控制的相关问题讨论

控制大气污染的重要手段之一是对燃烧过程加以优化控制.文中,.在分析产生污染原因的基础上,指出恰当的空气燃气比是保证充分燃烧的关键,并以轧钢加热炉燃烧过程控制为例,简要讨论了复杂燃烧过程的对象特性、可供选择的控制策略和优化的控制算法.成功的工程实践表明,只要对燃烧过程进行优化控制,废气污染是可以控制的.     

基于FLAC3D的寒区正融土坡稳定性数值模拟分析

为研究季节冰冻区土质边坡在春融期常发生的浅层滑坡,基于连续介质显式拉格朗日有限差分法,耦合温度、土体自重以及渗流力的共同作用,建立季冻区正融土坡实体模型。当外界温度由-5℃升高至10℃时,模拟得出土体边坡内部的塑性区分布特征和剪应变增量的发展趋势,给出季冻区正融边坡的最不利受力位置并分析破坏形式,分析结果可为季节冰冻区土质边坡的稳定性分析提供借鉴。     

Rigid sensor allocation and placement technique for reducing the number of sensors in thermal monitoring

Using embedded thermal sensors, dynamic thermal management (DTM) techniques measure runtime thermal behavior of high-performance microprocessors so as to prevent thermal runaway situations. The number of placed sensors should be minimized, while guaranteeing accurate tracking of hot spots and full thermal characterization. In this paper, we propose a rigid sensor allocation and placement technique for determining the minimal number of thermal sensors and the optimal locations while satisfying an expected accuracy of hot spot temperature error based on dual clustering. We analyze the false alarm rates of hot spots using the proposed methods in noise-free, with noise and sensor calibration scenarios, respectively. Experimental results confirm that our proposed methods are capable of accurately characterizing the temperatures of microprocessors.     

阳宗隧道试验段动态开挖过程的数值模拟研究

根据昆明—石林高速公路阳宗隧道S5型支护衬砌设计优化调整方案和XK38+926断面现场监控量测数据,进行位移反分析,得到计算所需的围岩弹性模量E和侧压力系数K_0;然后运用有限元方法,对其试验洞段上下台阶开挖动态施工过程进行仿真数值模拟研究,从而反馈调整和指导施工。     

ETFE气枕共同作用模型的数值模拟与试验验证

基于气枕系统的共同作用理论,提出一种新的气枕数值建模方法,按照该方法建立了ETFE气枕共同作用有限元模型,并设计制作了一个正六边形ETFE气枕足尺模型,对其进行了形状测试和加载测试.研究结果表明：ETFE气枕形态分析与荷载分析的数值结果与试验结果吻合良好,共同作用有限元模型能够准确、有效地完成ETFE气枕静力分析.     

Three-dimensional geoscience modeling and simulation of gas explosion in coal mine

Gas explosion is one of the most serious events in coal mine. In consideration of the limitation of past research method about gas explosion, three-dimensional (3D) modeling and simulation are suggested. This paper analyzes the research achievements on 3D modeling, and studies the modeling method of strata and laneway based on geoscience modeling. After the 3D modeling of strata and laneways, the simulation of gas explosion (such as gas exploding, color, burning, virtual wandering and rock caving) is performed. The research method is meaningful for safety analysis and safety survey.     

双机RTWT模式的视觉机器人实时仿真系统设计

在全面讨论了以Matlab为软件平台实时仿真方法的基础上,提出了双机RTwT（Real—TimeWindowsTarget）模式的实时仿真系统构架,设计了双目视觉两轮机器人实时目标跟踪系统．相比于传统RTwT模式,该构架大幅度地提高了实时仿真系统的数据处理能力,拓宽了硬件的适用范围．在实时系统测试前,对所使用的位置角度同步、异步控制器及同步补偿算法对目标捕捉性能的影响进行了全仿真研究,仿真结果表明：采用同步控制策略捕捉时间较短,而采用异步控制策略运行轨迹较短,两者各具优势;当扰动不是很大时,同步补偿算法对同步控制的影响较大,能有效缩短捕捉时间和运行轨迹,而对异步控制的影响较小．     

Numerical simulation of drawdown and land deformation in pumping-recovery tests performed on a circular excavation

A mathematical model, which not only fully couples fluid flow and solid skeleton deformation in unsaturated porous elastic media but also considers deformable diaphragm walls, is formulated in axially symmetric cylindrical coordinates for drawdown and land deformation. Based on this model, pumping-recovery tests in various conditions are numerically simulated to reveal the effects of elastic modulus of soil E and initial saturated hydraulic conductivity K_(sat0) on hydraulic head and land deformation. The heterogeneity with respect to E and K_(sat0) is separately taken into account. Large elastic modulus of soil contributes to both dewatering process and deformation control. Either large or small initial saturated hydraulic conductivity may cause relatively high groundwater table, while the larger one leads to smaller displacements.     

基于负弛度法的接触网建模与仿真

基于整体求解的思想, 通过接触网在张力和自重作用下的垂向位移, 对接触网模型进行重构, 并给接触线预留一定的负弛度, 以保证经过几次负弛度计算后, 接触线到达初始平衡位置时保持水平, 由此得到满足初始平衡条件的吊弦长度, 确定了接触网在初始平衡位置的几何参数和应力分布, 同时将负弛度法和传统方法进行对比研究。对比结果表明: 用负弛度法得到的吊弦长度比传统方法略长, 吊弦长度最大相对偏差为0.75%;用负弛度法计算的接触网单元应力随单元几何位置的不同而变化, 而传统方法得到的单元应力是恒定的, 单元应力最大相对偏差为0.55%。可见, 两种方法得到的吊弦长度和应力分布有很好的一致性, 负弛度法更有利于后续的弓网系统动力学计算, 而且对于多跨的复杂接触网模型, 负弛度法也同样有效。     

燃料电池船舶舱内氢气泄漏扩散的数值模拟

利用FLUENT软件研究了不同条件下氢气在燃料电池船舶舱内的泄漏扩散规律和分布情况; 基于瞬态气体泄漏扩散模型,运用数值模拟方法,建立了船舶舱内氢气泄漏扩散的数值模型,结合影响氢气泄漏扩散的不同因素,对比分析了泄漏位置、泄漏孔径和通风条件等因素对船舶舱内氢气泄漏扩散的影响,得到了不同条件下氢气在船舶舱内的扩散规律和分布情况。分析结果表明：船舶舱内氢气泄漏扩散过程包括初始喷射、浮力上升和湍流扩散; 燃料电池舱的顶部角落和每排燃料电池发电系统之间的上部是氢气探测报警器的最佳安装位置,不同泄漏条件下氢气均在舱室顶部出现较多积聚; 不同位置和不同孔径泄漏孔的危险性在泄漏初期存在差异,但随着泄漏的持续进行,风险演变规律相近,约60 s后泄漏点附近氢气浓度均接近100%;在燃料电池舱设置防爆型排风机,采用强制抽风措施加快氢气的外排,可以显著减少氢气向其他舱室的扩散,当抽风速度为1 m·s^-1时,氢气从燃料电池舱室排放到船舶舷外区域,没有氢气进入控制舱和乘客舱,可有效保障控制舱和乘客舱的安全; 强制送风会加速氢气向船艉舱、控制舱和乘客舱的扩散,增大氢气的扩散范围,加剧了氢气泄漏的危险性。     

A new method based on the non-isothermal kinetic equation to estimate the critical temperature of thermal explosion for energetic materials using non-isothermal DSC

A method for estimating the critical temperature of thermal explosion for energetic materials using differential scanning calorimetry (DSC) measurement is derived from the Semenov’s thermal explosion theory and the non-isothermal kinetic equation based on Harcourt-Esson’s kinetic equation. The result obtained from this method coincides completely with that of the Hu-Yang-Liang-Wu method.