Process Modeling and Dynamic Simulation for EAST Helium Refrigerator

In this paper,the process modeling and dynamic simulation for the EAST helium refrigerator has been completed.The cryogenic process model is described and the main components are customized in detail.The process model is controlled by the PLC simulator,and the realtime communication between the process model and the controllers is achieved by a customized interface.Validation of the process model has been confirmed based on EAST experimental data during the cool down process of 300-80 K.Simulation results indicate that this process simulator is able to reproduce dynamic behaviors of the EAST helium refrigerator very well for the operation of long pulsed plasma discharge.The cryogenic process simulator based on control architecture is available for operation optimization and control design of EAST cryogenic systems to cope with the long pulsed heat loads in the future.

Dynamic Modeling and Simulation of a Commercial Naphtha Catalytic Reforming Process

A first principles-based dynamic model for a continuous catalyst regeneration (CCR) platforming process, the UOP commercial naphtha catalytic reforming process, is developed in this paper. The lumping details of the naphtha feed and reaction scheme of the reaction model are given. The process model is composed of the reforming reaction model with catalyst deactivation, the furnace model and the separator model, which is capable of capturing the major dynamics that occurs in this process system. Dynamic simulations are performed based on Gear numerical algorithm and method of lines (MOL), a numerical technique dealing with partial differential equations (PDEs). The results of simulation are also presented. Dynamic responses caused by disturbances in the process system can be correctly predicted through simulations.

Interrelations Between Socio-economic Development and Environmental Quality:a Simulation Integrating System Dynamics Models with GIS

System dynamics (SD) theory has long been deployed in modeling complex non-linear interrelationships but, so far it has not been common to do the kind of modeling in support of bringing environmental sustainability policies to practice. This is largely because the challenge of including spatial data has not yet been well met. Potential for adoption of SD and GIS methods in combination is exemplified with the results of a decision-support exercise designed for simulation and prediction of the dynamic inter-relationships between socio-economic development and environmental quality for the "Wen, Pi, Du" county in Sichuan province, southwestern China.

START-UP AND DYNAMIC PROCESSES SIMULATION OF A DISTILLATION COLUMN

A new dynamic non-equilibrium mixing-pool model for simulating start-up and dynamic re-sponse of a distillation column is reported.The proposed model is established on the basis ofconsidering the two dimensional flow/mixing behavior of actual trays in a distillation column.Com-parison is made among the computed results of the start-up time and the dynamic response time bythe proposed and five other typical models.It is found that the computed time for both dynamicprocesses is longer by the model which considers any flow/mixing pattern than by the model withoutsuch concern.The inertia effect of flow/mixing seems to be important and can not be ignored inmodeling the transient process of distillation.The proposed model,which is believed to be suitableto large column,seems somewhat useful in predicting industrial distillation dynamics.

Stochastic dynamic simulation of railway vehicles collision using data-driven modelling approach

Using stochastic dynamic simulation for railway vehicle collision still faces many challenges,such as high modelling complexity and time-consuming.To address the challenges,we introduce a novel data-driven stochastic process modelling(DSPM)approach into dynamic simulation of the railway vehicle collision.This DSPM approach consists of two steps:(i)process description,four kinds of kernels are used to describe the uncertainty inherent in collision processes;(ii)solving,stochastic variational inferences and mini-batch algorithms can then be used to accelerate computations of stochastic processes.By applying DSPM,Gaussian process regression(GPR)and finite element(FE)methods to two collision scenarios(i.e.lead car colliding with a rigid wall,and the lead car colliding with another lead car),we are able to achieve a comprehensive analysis.The comparison between the DSPM approach and the FE method revealed that the DSPM approach is capable of calculating the corresponding confidence interval,simultaneously improving the overall computational efficiency.Comparing the DSPM approach with the GPR method indicates that the DSPM approach has the ability to accurately describe the dynamic response under unknown conditions.Overall,this research demonstrates the feasibility and usability of the proposed DSPM approach for stochastic dynamics simulation of the railway vehicle collision.

Modeling of microstructure evolution of AZ80 magnesium alloy during hot working process using a unified internal state variable method

In this paper, a unified internal state variable(ISV) model for predicting microstructure evolution during hot working process of AZ80 magnesium alloy was developed. A novel aspect of the proposed model is that the interactive effects of material hardening, recovery and dynamic recrystallization(DRX) on the characteristic deformation behavior were considered by incorporating the evolution laws of viscoplastic flow, dislocation activities, DRX nucleation and boundary migration in a coupled manner. The model parameters were calibrated based on the experimental data analysis and genetic algorithm(GA) based objective optimization. The predicted flow stress, DRX fraction and average grain size match well with experimental results. The proposed model was embedded in the finite element(FE) software DEFORM-3 D via user defined subroutine to simulate the hot compression and equal channel angular extrusion(ECAE) processes. The heterogeneous microstructure distributions at different deformation zones and the dislocation density evolution with competitive deformation mechanisms were captured.This study can provide a theoretical solution for the hot working problems of magnesium alloy.

Process Modeling of Ferrofluids Flow for Magnetic Targeting Drug Delivery

Among the proposed techniques for delivering drugs to specific sites within the human body, magnetic targeting drug delivery surpasses due to its non-invasive character and its high targeting efficiency. Although there have been some analyses theoretically for magnetic drug targeting, very few researchers have addressed the hydrodynamic models of magnetic fluids in the blood vessel of human body. This paper presents a mathematical model to describe the hydrodynamics of ferrofluids as drug carriers flowing in a blood vessel under the applied magnetic field. A 3D flow field of magnetic particles in a blood vessel model is numerically simulated in order to further understand clinical application of magnetic targeting drug delivery. Simulation results show that magnetic nanoparticles can be enriched in a target region depending on the applied magnetic field intensity. Magnetic resonance imaging confirms the enrichment of ferrofluids in a desired body tissue of Sprague-Dawley rats. The simulation results coincide with those animal experiments. Results of the analysis provide the important information and can suggest strategies for improving delivery in favor of the clinical application.

大电流真空电弧开断过程瞬态特性仿真分析

针对开断过程中传统稳态模型无法表征真空电弧动态特性问题,以工频电流下开断峰值为10 kA大电流真空电弧为研究对象,搭建等离子体弧柱区二维物理模型,在已有双温磁流体动力学稳态模型中引入密度、温度、压力及速度等流场参数时变项,同时利用动网格技术控制弧柱区变化速率,模拟触头分闸过程,综合考虑电流及开距变化情况下等离子体各物理场参数变化,以获取开断时电弧微观流场瞬态特性,探究开断过程中电弧形态及能量变化。分析结果可知:离子压力、温度、电子温度和阳极表面能流密度均随动、静触头分离而减小;离子速度无明显变化;等离子体不断向外扩散,由于电流减小,金属蒸汽源也逐渐减少,极间等离子体密度降低,阳极尚未达到活跃程度,最终电弧熄灭。

基于机理与数据混合驱动的湿法磷酸生产过程代理建模与优化

基于Aspen Plus平台,结合Fortran编制的磷矿酸解反应和结晶动力学模型子程序完成了整个半水-二水湿法磷酸工艺流程的严格机理建模,并用工业数据进行了模型的校正;然后采用拟Monte Carlo随机模拟产生高质量样本数据集,并用机器学习算法建立了磷酸生产过程代理模型。结果表明,通过本方法获得的代理模型可实现磷酸生产过程关键参数的准确预测,如案例中随机森林代理模型的预测性能最好,大部分误差控制在2.5%以内,最大不超过10%。基于此代理模型,对生产过程的操作参数进行了优化计算,结果表明在成品磷酸P_(2)O_(5)浓度下限为37%,SO_(4)^(2-)浓度上限为5%的约束条件下,可获得最大磷收率98%,优化效果明显,且满足技术生产指标,可为生产的实时优化操作与设计改造提供方案和数据支持。

鄱阳湖水利枢纽对江湖洪期水动力过程的影响

鄱阳湖作为通江湖泊,其洪水大小由多因素共同决定,湖区洪灾频繁。鄱阳湖水利枢纽工程建设后将对洪期复杂水动力过程造成影响。为评估其影响,建立了包括鄱阳湖湖区和尾闾以及长江九江到八里江段在内的平面二维水动力模型,对1954年大洪水和1991年倒灌2种灾害型洪期过程进行情景模拟,分析了枢纽对长江和湖区可能造成的影响。结果表明:枢纽工程使湖口出流过程更加平缓,具有一定的削峰作用,对长江洪水位基本无影响;1954年大洪水过程,枢纽使湖区水位升高,代表水文站水位壅高最大值为0.021 m;1991年倒灌过程,枢纽使湖区水位降低,湖区水位变化的趋势与湖口流量变化趋势一致,相位稍滞后于流量过程。研究成果可为江湖水安全管理提供技术支撑。

区间过程激励下刚柔耦合系统动态不确定性分析的序列模拟方法

针对动态不确定性激励作用下的刚柔耦合系统动力学问题,提出了一种基于区间过程模型的动力学不确定性序列模拟方法,旨在通过区间过程序列抽样及刚柔耦合动力学序列模拟计算结构振动与机构运动等系统动态响应的上下边界。介绍了中心刚体柔性梁刚柔耦合系统动力学方程的构建与数值求解方法。针对动态不确定性激励作用下的刚柔耦合系统动力学分析,引入区间过程模型及其区间K-L展开对动态不确定性进行了度量和高效表征,提出了一种求解系统机构运动与结构振动等动力学响应上下边界的序列模拟方法。该方法利用序列模拟策略识别当前模拟序列中对动态响应上边界或下边界具有贡献的区间过程参数样本集,作为下一模拟序列中的局部加密抽样中心,可有效避免直接蒙特卡罗模拟在计算动力学响应上下边界时因过多无效抽样模拟而导致的低效收敛问题。最后,通过三个算例对所提方法的有效性进行了验证。研究结果表明,对于刚柔耦合系统大范围运动及振动响应上下边界的求解,序列模拟方法相比于直接蒙特卡罗模拟方法具有更好的计算效率和计算精度。

焦炭塔建模与数值计算的研究进展

综述焦炭塔的生焦模型、焦炭塔的模拟方法(包括计算流体力学、有限元分析、流程模拟)以及石油焦化过程的反应动力学研究进展,指出验证反应动力学模型的普适性,发展动态混合模拟方法,开发石油焦化工艺模型是焦炭塔建模与数值计算的发展方向。

基于MATLAB/Simulink动力换档变速箱换挡过程仿真研究

文章重点对动力换挡行星变速箱换挡过程的建模和仿真进行了研究,讨论了换档离合器通用数学模型的建立方法,分析了建模过程所涉及的摩擦力矩,最后通过用MATLAB/Simulink对国产ZL-50轮式装载机行星变速箱换挡过程进行仿真模拟。经仿真得出主、被动摩擦盘接合时转速变化规律,经给定不同的油压时间和油压上升规律找出满足车辆换挡平顺性、换挡接合时间在允许范围内的较佳的油压变化规律和摩擦力矩。用所得到值能满足主被动盘的接合速度在10r/s左右,接合时间在2.4s之内,被动盘的角加速度在2.5倍的重力加速度6m/s^(2)范围内。

基于Simul8的半导体生产线建模关键技术研究

在对半导体硅片制造生产线进行建模和仿真的过程中,提出了非动态加工区和动态加工区的分类思想,给出了各自基于Simul8的实现方法。对于高度复杂的动态加工区,给出了3种解决方法,从仿真速度上比较其优劣。仿真应用表明,提出的半导体生产线分类方法有效改进了仿真的性能,使仿真指导生产具有可行性。

不同损伤模型下超高性能混凝土SHPB试验数值模拟对比

目的探讨不同损伤模型下超高性能混凝土SHPB试验数值模拟效果的差异性。方法应用大型有限元程序LS-DYNA,结合UHPC材料特性,明确了KCC、HJC和CSC模型中关键参数的取值,建立了超高性能混凝土SHPB试验数值仿真模型。在此基础上,开展不同损伤模型下UHPC试件波形、动态应力-应变曲线、弹性模量和动力增大系数(DIF)值模拟结果与实测结果的对比,探讨不同损伤模型下超高性能混凝土SHPB试验动态破坏进程。结果CSC模型在低速冲击下能更好地模拟UHPC材料的实测波形和动态应力-应变曲线,而在中高应变率下KCC模型和HJC模型得到的计算波形以及动态应力-应变曲线与实测值吻合度更好;低应变率下三种损伤模型得到的DIF值相差不大,但随着应变率提高,CSC模型在一定程度上将低估UHPC材料的动力特性;UHPC试件破碎程度随应变率的增加而增大,相对于CSC模型在冲击破坏时表现出的核心存留现象,KCC模型和HJC模型分别表现出明显的整体塌陷和边缘塌陷现象。结论对于UHPC材料,CSC模型适用于低速冲击下SHPC试验数值模拟,而KCC模型和HJC模型适用于中高应变率下数值模拟。

吸附压缩CO_(2)储能系统动态特性研究

吸附压缩二氧化碳储能系统(Adsorption Compressed Carbon Dioxide Energy Storage System, ACCES)可克服CO_(2)高密度存储、充放及系统高效运行等技术难题,市场前景广阔,但对其动态特性缺乏深入认识,阻碍了系统设计与安全调控运行技术的发展。本文基于模块化建模思想建立了2 MW ACCES的动态仿真模型,用于模拟系统启动过程中各设备运行参数的变化规律。结果表明:储能阶段压缩机启动后轴功率迅速上升,并在120 s后稳定,且压缩机级数越高,所需稳定时间越长;释能阶段膨胀机轴功率从峰值下降,在500 s时稳定在915.6 kW、811.2 kW和601.8 kW;设定释能过程质量流量波动±1%,膨胀机输出轴功率波动范围接近±1%,需防范可能引起的电网冲击等问题。所建模型及研究结果为深入认识系统动态特性、系统设计和安全调控运行提供了有效的分析工具和数据参考,对推进ACCES的应用具有实际意义。

乏燃料连续溶解过程的动态仿真模型研究

本文通过分析乏燃料芯块与硝酸之间溶解反应的质量传递过程,以及溶解液中溶质的质量传递过程,基于质量衡算得到了乏燃料芯块溶解过程的动态溶解模型,并利用Comsol和Matlab软件建立了求解溶解模型的仿真程序。仿真结果表明,在温度90℃、硝酸进料浓度6 mol/L、进料流率11 L/min、回流量35 L/min的工艺条件下,溶解液需要270 min达到出料要求,而达到平衡所需时间为2000 min。达到平衡后的溶解液出料中,铀浓度为253.23 g/L、硝酸浓度为2.78 mol/L,能满足出料要求。模拟结果的全过程质量平衡计算表明,模拟结果与理论计算值的相对误差为2.57%。模拟结果中溶质浓度变化趋势与实际过程基本一致,溶解器内铀浓度总体上呈先迅速升高、后较快减小、最后又缓慢减小,而硝酸浓度总体变化趋势则与铀浓度的变化趋势相反。以上结果表明,本研究所建立的回转式连续溶解器动态溶解仿真模型能较好地描述该溶解器中乏燃料的实际溶解行为,能为实际生产过程中乏燃料溶解工艺段提供仿真数据支撑。

基于系统动力学模型的江西省水资源承载力评价

为研究江西省水资源承载力现状,缓解江西省用水压力,结合江西省水资源特点构建水资源承载力评价指标体系,以历史数据为支撑,构建水资源承载力系统动力学模型,并设计4种发展情境,通过模型仿真得到不同情境下的各指标参数变化,基于层次分析法确定指标权重,计算不同情境下的水资源承载力变化。结果表明:①在现状发展情境下,江西省的水资源承载力处于轻微超载状态;②高速发展情境下,江西省水资源承载力超载情况愈加严重;③在节水治污和综合发展情境下,水资源承载力均得到改善,后者的改善程度更高。综合发展情境是符合江西省可持续发展的最优发展情境。该研究可为江西省水资源管理规划提供参考与依据。

混流式水轮机启动状态下转轮与尾水管压力场特征分析

为了研究混流式水轮机在启动过程中产生的水力激振,通过数值模拟方法,研究了非定常流场中转轮与尾水管压力场变化特征,揭示了混流式水轮机在启动过程中压力场幅值和频率的变化与涡绳的发展过程之间的内在关系。结果表明:在启动过程中,转轮内同一个叶片的同一个表面不同位置的点受到的压力变化趋势并不相同,甚至存在相反的情况;叶片表面压力最大压力值出现在靠近叶尖位置,其压力约为平稳运行时的110.9%;最小压力值出现在叶根处,其压力约为平稳运行时的95.8%;且无论混流式水轮机在启动状态下还是最佳效率点,叶片压力面均存在低周的压力脉动;转轮经历静止到最佳效率点的压力波动幅度大约为稳定运行时的一半,而尾水管在启动状态下压力波动幅度与稳定运行时的压力波动基本相当。

数控卧式内腔加工专机动力学建模及仿真分析

针对数控卧式内腔加工专机的动力学特性,基于子结构法进行了机械系统动力学建模,通过有限元仿真验证所建立模型的正确性。通过拉格朗日方程建立整机动力学方程,采用吉村允孝法求出专机各子结构间的结合面动力学参数,应用有限元软件对机床三维CAD模型进行模态分析,将获得的结果与解析法求解结果进行对比,两者的最大相对误差为7.42%。结果表明:所建立的动力学模型可以有效模拟内腔加工专机的动力学特性,为之后进行专机的数字孪生研究奠定基础。