Three-dimensional transient numerical simulation for gas exchange process in a four-stroke motorcycle engine

Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing method and the snapper technique made the valves move smoothly. The flow structure and pattern in a complete engine cycle were described in detail. Tumble ratios around the x-axis and y-axis were analyzed. Comparison of computed pressure with experimental pressure under motored condition revealed that the simulation had high calculation precision; CFD simulation can be regarded as an im-portant tool for resolving the complex aerodynamic behavior in motorcycle engines.

基于Plant Simulation的航空发动机维修生产线工序优化

针对航空发动机维修生产线生产效率较低的问题,考虑航空发动机大修工序间关系复杂度高、动态性及工时不确定等特点,采用Plant Simulation生产系统仿真软件对大修生产线建立仿真模型。在对工序流程、维修区域和工时等分析的基础上,通过仿真模型对26个维修工序工位从堵塞时间、工作时间和等待时间3个方面进行分析,识别得出叶轮性能恢复、涡轮转子性能恢复和试车3个瓶颈工序。对不同影响因素开展仿真优化与敏感性分析,得出瓶颈工序的优化措施及效果评价。

Numerical simulation of tritium behavior under a postulated accident condition for CFETR TEP system

China Fusion Engineering Test Reactor(CFETR)is China's self-designed and ongoing next-generation fusion reactor project.Tritium confinement systems in CFETR guarantee that the radiation level remains below the safety limit during tritium handling and operation in the fuel cycle system.Our tritium technology team is responsible for studying tritium transport behavior in the CFETR tritium safety confinement systems of the National Key R&D Program of China launched in 2017,and we are conducting CFETR tritium plant safety analysis by using CFD software.In this paper,the tritium migration and removal behavior were studied under a postulated accident condition for the Tokamak Exhaust Processing system of CFETR.The quantitative results of the transport behavior of tritium in the process room and glove box during the whole accident sequence(e.g.,tritium release,alarm,isolation,and tritium removal)have been presented.The results support the detailed design and engineering demonstration-related research of CFETR tritium plant.

Mathematical modeling and analysis of thermodynamic processes in a twin-rotor piston engine

In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characteristics of the working processes in the TRPE, corresponding differential equations were established and then simplified by period features of the TRPE. Finally, the major boundary conditions were figured out. The changing trends of mass, pressure and temperature of working fuel in the working chamber during a complete engine cycle were presented. The simulation results are consistent with the trends of an actual working cycle in the TRPE, which indicates that the method of simulation is feasible. As the pressure in the working chamber is calculated, all the performance parameters of the TRPE can be obtained. The major performance indicators, such as the indicated mean effective pressure, power to weight ratio and the volume power, are also acquired. Compared with three different types of conventional engines, the TRPE has a bigger utilization ratio of cylinder volume, a higher power to weight ratio and a more compact structure. This indicates that TRPE is superior to conventional engines.

基于Pro/Engineer的装配过程动态仿真与干涉检验

分析了装配仿真的关键技术 ,利用 4x4矩阵和矩阵变换描述装配元件的位姿和运动 ,阐述了将定位操作向装配运动映射的原理。介绍了利用Pro/Engineer中的结构图Skeleton模块和Programming模块实现装配过程动态仿真和干涉检验。

Migrating a Desktop Simulator of a Chemical Process to the Cloud

This paper shows how a desktop simulation can be migrated into its cloud equivalence using Windows Azure. It is undeniable that simulators are expensive and cost-intensive regarding maintenance and upgrading, and thus, it is not always feasible to buy such a simulator. Therefore, it will be of great significance if we have an approach, which provides simulators with services through the Internet with the aim of making them accessible from anywhere and at any time. That is, researchers and developers can focus on their actual researches and experiments and the intended output results. The cloud simulation infrastructure of this contribution is capable of hosting different simulations with the ability to be cloned as cloud services. The simulator example used here mimics the process of a distillation column to be seen as a widely used plant in several industrial applications. The cloud simulation core embedded in the cloud environment is fully independent from the developed user-interface of the simulator meaning that the cloud simulator can be connected to any user-interface. This allows simulation users such as process control and alarm management designers to connect to the cloud simulator in order to design, develop and experiment their systems on a “pay-as-you-go” basis as it is the case of most cloud computing services, aimed at providing computing services as utilities like water and electricity. For coding convenience, Windows Azure was selected for both developing the cloud simulation and hosting it in the cloud because of the fact that the source code of the desktop simulator is already available in C# based on dot Net technology. From a software technical point of view, UML graphical notations were applied in order to express the software requirement specifications of the distributed cloud simulation, representing a widespread technology in the object-oriented design and analysis.

Software Architecture for Modeling and Simulation of Underwater Acoustic Information Systems

The simulation of underwater acoustic information flow is an important way to research sonar performance and its engagement effectiveness in the ocean environment.This paper analyzes the significance of modeling an open and sophisticated simulation software architecture by object-oriented method,and introduces the modeling processes and expression method of simulation architecture.According to the requirements of simulation system and the underwater acoustic information flow,the logical architecture of simulation software system is modeled by the object-oriented method.A use-case view captured the system requirements.The logical view shows the logical architecture of software system.The simulation software is decomposed into the loose coupling constituent parts by layering and partitioning the packages for maintainability.The design patterns enabled the simulation software to have good expansibility and reusability.The simulation system involving multi-targets and multi-sonar is developed based on the architecture model.Practices show that the model meets the needs for simulating an open and sophisticated system.

点火位置对X型转子发动机燃烧过程的影响

为探究X型转子发动机独特燃烧室内复杂湍流场与点火位置的耦合作用对混合气燃烧过程的影响,建立了X型转子发动机的三维计算流体动力学模型,并与试验结果进行对比验证,数值研究了不同点火位置下X型转子发动机缸内燃烧过程,揭示了点火位置对火焰传播、燃烧特性及污染物形成的影响规律。结果表明,在压缩末期,X型转子发动机燃烧室内形成了包括涡流和单向流的复杂湍流场,这与点火位置的耦合作用显著影响火焰传播过程。为了获得较高火焰传播速度,点火位置不宜布置在漩涡区处。点火位置位于凹坑中部时,可以充分利用四周空间和涡团与单向流场过渡处形成的较高速度场加速火焰传播,从而提前燃烧重心,增加放热速率,而且峰值压力提高了25%,指示热效率超过30%;同时其也具有较低的HC和CO排放量;但是由于其缸内峰值温度较大,导致NO排放量增加。

数字图像处理及应用虚拟仿真实验平台设计

针对数字图像处理及应用实验教学的需要,结合当下图像处理技术的热点应用,利用虚拟仿真技术、交互操作等信息化手段进行实验教学,设计并开发了数字图像处理及应用虚拟仿真实验教学平台。实验教学平台包含交通标志数字图像处理、图像分类、图像识别、视频处理、自动驾驶应用等5个虚拟仿真实验教学资源,共13个交互实验步骤。该平台特色显著、虚实结合,达到了良好的教学效果,为“新工科”背景下的虚拟仿真实验教学提供有益的参考。

矿物加工虚拟仿真实验教学建设及实践——以中南大学矿业学科为例

针对新时代矿业行业对专业人才的要求,以培养学生全周期工程思维和提高其工程胜任力为目标,采用虚拟仿真的教学手段,突破矿产资源加工过程中高温、高危、高成本等限制,解决传统教学无法开展全流程实验及生产极端工况操作等难题,将科研成果融入实验教学,有机融合数据库技术、虚拟仿真、专家系统、智能算法,让学生通过自主选题、自主探究学习、自主流程设计、自主设备搭建、自主调试运行,设计与资源特性相适应的工艺流程、生产设备及操作参数,实景体验工业生产过程异常工况,使其成为具有实干担当、开拓创新、国际视野和竞争力的矿业卓越人才。

建设项目全过程工程咨询价值增值机理仿真研究

研究全过程工程咨询价值增值机理,以促进全过程工程咨询的推广。从建设项目全生命周期出发,对全过程工程咨询项目价值增值的原理和影响因素进行识别和分析,运用系统动力学(SystemDynamics,SD)的方法,构建了全过程工程咨询服务模式价值增值系统模型,通过仿真分析揭示了全过程工程咨询服务模式的价值增值机理。结果显示:建设单位采用全过程工程咨询模式时,建设单位效益、咨询服务方效益及社会效益都会在项目建设全过程得到不同程度的提高。验证了项目决策、建设、运维之间的深度融合与项目建设阶段中设计与施工之间信息的流通,提升了项目规避风险的能力,拓宽了项目目标达成的途径。

Numerical Simulation System for Casting Process in Concurrent Engineering

According to the implementing principle and application background of the Concurrent Engineering (CE) project, studies on the integration of numerical simulation system for casting process with CE, simulation of turbulent phenomena in filling process of casting by Algebraic Stress Model (ASM), computation efficiency of filling process and quantitative prediction of shrinkage cavity and porosity under feeding condition of several risers are discussed. After the simulation of casting process of typical magnesium based alloy casting with complicated structure, remarkable success in assuring the quality is also presented.

“过程全面精准”考核在化工原理实验课程中改革与探索

针对化工原理实验教学考核方式单一和学生学习兴趣低等难题,在教学中引入虚拟仿真和“互联网+”技术,构建全新“线上线下混合式”教学模式,实行闯关式学习方式,将教学大纲考核点细化,分步骤给分,部分实验实行分类教学,根据权重赋分,形成全面考核体系。线下实验实行线上控制给分,实验过程中学生可以随时查看成绩,调整学习状态。建立网络机器人答疑平台,在线答疑,真正实现全过程教学,提高化工原理实验教学质量,助力于中国高等教育的创新改革。

基于变体马尔可夫博弈的自动引导车任务协同处理

为了提高转运仓库的转运效率,提出了一种基于变体马尔可夫博弈的自动引导车任务协同处理(VMG-AGV任务协同处理)方法。在利用FlexSim构建转运仓库模型的基础上对ProcessFlow、全局表、任务分配器、AGV等组件或实体进行参数、脚本设计,将VMG-AGV任务协同处理方法与传统的“一车带一物”拣选方法进行对比实验。仿真结果表明:新方法与传统方法相比,4辆AGV的平均利用率提高了11%,在制品平均运输量提高了40%,4台出库合成器平均每小时增加出库4.5单。

基于随机骨料的混凝土边界效应影响研究

为了研究混凝土构件内的骨料边界效应,分别采用图像识别技术和随机骨料建模技术分析了真实的骨料分布、形状、长径比、粒径及表面棱角数量等因素对骨料密度分布曲线及边界效应的影响规律。研究结果表明:骨料密度分布曲线呈现先上升、随后下降、最终趋于稳定或略有震荡的规律,且不受骨料几何形态影响,稳定时对应的密度分数略高于平均骨料密度分数;骨料密度曲线峰值厚度约为骨料最小粒径,边界效应层厚度约为骨料平均粒径,且这二者均随着骨料粒径及长径比的增加逐渐增大;在骨料的几何形态特征因素中,骨料粒径对密度分布曲线、峰值厚度及效应层厚度影响较为显著,影响程度强于其他的几何形态特征。

弃渣扰动对藏东山地草甸坡面产流产沙的影响

[目的]明晰铁路修建中弃渣工程扰动引起的水土流失响应,揭示弃渣堆积前后及其植被恢复对藏东生态脆弱的山地草甸区坡面尺度水土流失的影响。[方法]选取未扰动、轻度扰动、重度扰动、覆土恢复4个类型的坡面,建立原位径流小区,通过人工模拟降雨试验,开展了坡面产流产沙过程的研究。[结果](1)坡面的溅蚀量随扰动强度的增大而增加,下坡向的溅蚀量为上坡溅蚀量的1.14~2.67倍。(2)轻度扰动坡面、重度扰动坡面和覆土恢复坡面的初始产流时间分别缩短为未扰动坡面的53.8%~66.7%,34.6%~46.7%,86.7%~92.9%。(3)未扰动坡面、轻度扰动坡面、重度扰动坡面和覆土恢复坡面的产流速率分别为44~86,104~147,200~373,46~95 ml/(min·m^(2)),产沙速率分别为0.026~0.055,0.05~0.098,1.034~2.189,0.047~0.077 g/(min·m^(2))。[结论]覆土恢复坡面的水土保持能力较轻度扰动和重度扰动坡面有显著提高,但距未扰动坡面仍有差距,需采取其他植被或工程措施对工程扰动坡面加以恢复。

基于产教深度融合的化工过程模拟教学模式

以化工过程模拟课程教学案例改革为例,通过案例教学法、团结互助法、课堂延伸法、实训仿真法,推行“产学合作协同育人”机制。教师与企业工程师共同调整和完善专业培养目标,培养研究生实践能力及创新能力。通过“校企合作,深度优化”、“虚实结合,共建共享”、“双线混融,知行合一”的方式构建“学创一体”的化工过程模拟教学模式,形成独具特色的一体化、多层次、模块化、重开放的虚拟仿真实验教学新模式,基于实际案例分析将化工过程模拟课程建设成精品资源共享课和精品视频公开课。

《材料成形过程数值模拟》课程的案例型教学实践与持续改进

结合工程教育专业认证的持续改进要求,针对《材料成形过程数值模拟》课程理论性强、内容范围广、实践操作要求高的特点,推行案例型教学改革,通过导入企业工程案例、学校科研项目不断优化教学内容,通过引入企业工程师参与课程评价、反馈,不断完善评价方法。同时,与企业联合推进校企协同育人,将螺钉紧固件的热镦、热处理工艺等工程实际需求融入课程建设,促使教学内容更贴近材料成形“高精尖”制造业发展前沿,提高了工科专业仿真类课程培养学生解决复杂工程问题的能力。

压燃式甲醇发动机缸内燃烧过程仿真

以某四缸压燃发动机为研究对象,建立内燃机的缸内燃烧模型并通过实验值对模型进行标定和验证;分别改变内燃机进气温度、喷油时刻等工况参数,研究甲醇缸内燃烧情况。计算分析结果表明:进气温度增加,着火提前,燃烧滞燃期缩短,燃烧区域和高温区域面积增大,混合气在压缩上止点时刻的温度升高,缸内最高压力值减小,焰前基元反应速度升高;喷油时刻提前,燃烧提前,缸内最高压力、缸内温度峰值升高。仿真计算结果为压燃式甲醇发动机的燃油系统设计和燃烧控制提供了依据。

Machining Process Simulator for Concurrent Engineering

Integration is a key component of CIMS and concurrent engineering is an important step in realizing CIMSprocess integration. Concurrent engineering is itself dependent on an effective machining process simulator that verifies the machining process. A machining process simulator for concurrent engineering CMPS was developed at CIMSERC to meet the need for an effective simulator. This paper introduces the CMPS structure. key techniques. including geometry model construction and kinematics. NC code translation. collision and interference checks, material removal simulation. machining animation. etc. The model uses the solid Ray-representation method and the Voxelsplus B-representation algorithm. The Ray-representation method simplifies the Boolean operation process and improves the material removal simulation speed. The Voxels plus B-representation algorithm quickly detects collisionand interference problems. Finally. CMPS is applied to an actual NC milling process as an example.