Comparison of gas particle flow prediction from large eddy simulation and Reynolds-averaging Navier-Stokes modeling

In order to account for the effect of particle existence on gas-particle turbulence flow in large-eddy simulation (LES), a new gas-particle turbulent kinetic energy subgrid-scale (SGS) turbulence model is established, and the effect of particle wake is also considered in gas turbulent kinetic energy SGS turbulence model. Simulation of gas-particle turbulence flow in backward-facing step is carried out by LES using present model and by unified second-order moment (USM) model. The prediction statistical results including mean velocity and fluctuation velocity by LES using present model are in reasonable agreement with the experimental results. It is shown that present model is with higher calculating accuracy than USM model, which indicates that the turbulent kinetic energy SGS turbulence model is suitable.     

高填方块碎石夯实地基变形三维数值模型

根据场区的工程地质条件和高填方资料建立地质模型, 运用现场试验所获得的参数和3DFLAC程序对高填方块碎石夯实地基的变形进行数值模拟, 分析地基沉降和侧向变形及可能发生剪切破坏的位置, 模拟和分析结果与实际基本一致。     

Three-dimensional numerical simulation of splat formation on substrates in plasma spraying

Plasma sprayed coatings are built up by the accumulation of splats formed by the impacting, spreading and solidifying of molten droplets on the substrate. A three-dimensional computational model including heat transfer and solidification is established to simulate the formation process of a single splat using the computational fluid dynamics (CFD) software, FLUENT. The fluid flow and energy equations are discretized and solved according to typical finite volume method on an unstructured grid. A volume of fluid (VOF) tracking algorithm is used to track the droplet flow with free surface. In order to understand the splat formation mechanism, the process of splat formation caused by impacting and spreading of a molten nickel droplet on a polished mild steel surface is simulated. On this basis, the simulations of impact of a molten droplet on substrate with different conditions including the surface morphology, thermal conductivity, initial temperature of the substrate and the thermal contact resistance are presented. The results clearly show the effect of those parameters on the shape of the final splat and splash behaviors.     

三大件转向架货车动力学建模与仿真

介绍了ADAMS及ADAMS／Rail动力学仿真软件的模块组成及功能，建立了三大件转向架货车的非线性数学模型，其中转向架中央悬挂装置中斜楔摩擦块的建模直接采用更接近实际的接触模型。应用ADAMS／Rail软件对货车系统的运动稳定性、曲线通过性及运行平稳性等动力学性能进行了分析，发现通过一定的技术改造，三大件转向架货车具有良好的动力学性能。结果表明该软件能够建立较复杂的车辆系统仿真模型，分析结果较合理。     

Study on simulation modeling and evaluation of equipment maintenance

Aiming at the actual demand for the maintenance support of new general equipments, this paper analyzes the structure and circulation of maintenance support system, builds the simulation model of running process by entity flow chart method, and constructs the basic frame of the simulation model. The generating method of random variables and the advancing process of the simulation clock are described, and the accurate prediction of maintenance equipment is realized. Moreover, the material readiness rate is analyzed in statistics objective to evaluate the simulation result. The research is of significance for improving the efficiency of equipment maintenance and the promotion of material readiness rate.     

煤层瓦斯地段隧道施工中存在的问题及对策

结合贵州省西北部高原草堤I号隧道的施工实践,分析该隧道内瓦斯的性质以及释放方式,探讨煤层瓦斯地段隧道施工中存在的问题,并提出相应的对策。     

UML-HLA协同建模方法及其在多车仿真中的应用

针对复杂实时大系统分布式交互性特点,通过综合对比UML与HLA的特点,提出了基于UML-HLA的列控系统建模仿真方法.在传统建模方法的基础上,采用提出的UML-HLA建模方法,从多个不同的角度建立多车仿真系统的分析模型,包括用例建模、活动建模、结构建模、交互建模和状态建模等,构建起高层体系架构资源库.在分析模型的基础上,建立多车仿真系统体系结构,得到多车仿真系统的设计模型.从性能和功能上对多车仿真系统进行了仿真验证.仿真结果表明:基于UML-HLA的建模方法具有较强的可交互性和可操作性,通过对原有线程机制与定时器控制机制进行优化,采用线程管理机制将原有系统的CPU占有率由50％降低至15％以下,定时器误差控制在0.02 ms范围内,满足了列控系统的仿真要求.     

道路交通事故模拟再现的车辆动力学三维模型

应用动力学理论, 提出了用于道路交通事故模拟再现分析的车辆动力学三维模型, 并引用日本汽车研究所的16例车对车实车碰撞实验数据对该三维模拟模型的计算误差进行界定, 并与二维四轮模拟模型的计算精度进行了定量比较, 针对实际道路交通事故案例进行了模拟再现。实例证明车辆三维模型在计算车辆碰撞动力学问题时的总体平均相对误差值为6.65%, 虽然相对于车辆二维四轮模型其速度计算精度在总体水平上降低了1.43%, 但若考虑到其对道路交通事故形态的包容性和形象化方面的优势, 计算精度的适度降低是可以接受的。     

Rigid-flex coupling modeling and simulation on multistage gear transmission system

As multistage gear transmission systems are complex and precise, the flexibility of shaft can influence the dynamic response of system. In order to study dynamic response of the system, we build the rigid model of gear system and the finite element model of the gear shaft. The rigid-flex coupling model is established with the virtual prototype technology, and a contrast between rigid model and rigid-flex coupling model is constructed.With these methods, the dynamic responses with different rotation speeds and different loading magnitudes are examined. We also analyze the influence of shaft flexibility, rotation speeds and loading magnitudes on the vibration characteristics of gear transmission systems.     

蛇形流场PEM燃料电池膜中水传输的三维模拟

膜中水传输对质子交换膜燃料电池的性能具有极其重要的影响.文中建立了一个蛇形流场单电池的三维模型,研究了低电流密度下燃料电池运行温度、膜厚、过量系数、相对湿度、操作压力和电流密度等运行条件对膜中水含量的影响.计算结果表明:随着温度的升高,膜中的水含量先升高后降低;减小质子交换膜膜厚和过量系数.增大相对湿度、操作压力和电流密度.膜中的水含量增加.电导率就会增加,从而促进电池性能提高.     

Numerical modeling of dual-pulse shock test machine for simulating underwater explosion shock loads on warship equipments

In order to qualify shock resistance performance of shipboard equipments and simulate real underwater explosion environment, a novel dual-puise shock test machine is proposed. The new machine will increase testing capability and meet special shock testing requirement. Two key parts of the machine, the velocity generator and the shock pulse regulator, play an important role in producing the positive acceleration pulse and the succeeding negative acceleration pulse, respectively. The generated dual-pulse shock for test articles is in conformity with an anti-shock test specification. Based on the impact theory, a nonlinear dynamic model of the hydraulically-actuated test machine is established with thorough analysis on its mechanism that involves conversion of gas potential energy and dissipation of kinetic energy. Simulation results have demonstrated that the proposed machine is able to produce a double-pulse acceleration shock in the time domain or a desired shock response spectrum in the frequency domain, which sets up a base for the construction of the machine.     

基于多智能体建模和蒙特卡洛仿真的跑道容量评估

分析了飞机编队动力学特性以及机场组织模式、管制方式和飞行方式等特征,建立了跑道容量计算模型和跑道运行模型;以中距平行双跑道半混合运行模式和混合运行模式作为典型场景,综合运用多智能体建模和蒙特卡洛仿真方法,计算了不同运行模式下跑道容量;设计正交仿真试验,研究了跑道容量与运行模式、起降比例、出动间隔、机型比例、编队数量和环境因素的关系。仿真结果表明：相比于半混合运行模式,混合运行模式的起飞容量平均增加了55.2%,着陆容量平均减小了6.2%,总容量平均增加了28.5%;随着出动间隔从60 s增加到180 s,半混合运行模式的总容量减小了27.2%,混合运行模式的总容量减小了24.9%;随着机型比例从0增加到1.0,半混合运行模式的总容量减小了29.7%,混合运行模式的总容量减小了29.2%;随着平均编队数量从1.9增加到3.2,半混合运行模式下的总容量增加了9.8%,混合运行模式的总容量增加了7.1%。可见,混合运行模式的性能整体优于半混合运行模式,跑道容量与任务出动方式密切相关,需要根据任务出动方式合理选择跑道运行模式。     

低速磁浮车辆动力学建模与导向机构仿真分析

在分析低速磁浮车辆结构及其运动学关系基础上, 利用SIMPACK软件, 建立了含主动悬浮控制的76个自由度的磁浮车辆虚拟样机模型, 开展了基于整车动力学的低速磁浮车辆导向机构仿真分析, 研究了T形臂、横向滑台及两者之间的运动学规律。仿真结果表明: 在300 m半径曲线和三转向架结构条件下, 为了保证磁浮车辆顺利通过曲线, 磁浮车辆导向机构前T形臂长度应大于后T形臂长度, 两者比值的优化区域在1.50和2.00之间; 车辆头尾T形臂相对于车体的转角幅值大小基本相同, 方向相反, 对应滑台的横向位移曲线形状与幅值基本相同; 同一转向架前后滑台的最大横移量之比等于前后T形臂长度之比。     

隧道过煤层瓦斯治理方案及安全策略

针对隧道过煤层的瓦斯治理方案以及安全策略加以分析,为确保煤层隧道施工的安全性,保证建设的有序进行提供参考资料。     

Experimental simulation on dynamic variation of the permeability of high-rank coal reservoirs

In terms of the coal reservoir permeability of effective stress, coal matrix shrinkage and gas slippage, we conduct the tests of gas permeability under constant confining pressure and effective stress, as well as illustrate the cumulating method of permeability increment caused by the effects of gas slippage and coal matrix shrinkage. The results show that under the constant confining pressure, gas slippage affecting coal permeability changes to effective stress affecting it mainly. The change point increases with the increase of the confining pressure. The gas slippage effect leads to high permeability under low confining pressure, but coal matrix expansion results in the low value as confining and gas pressures increase. Combined with the drainage process of coalbed methane (CBM) well, the permeability is divided into four change stages based on the above analysis about the three effects, which can improve the change regulation understanding. Four stages are the downward phase under effective stress, the conversion phase of effective stress-coal matrix contraction effect (mainly based on effective stress), the rising stage of the effective stress-coal matrix contraction effect (mainly based on coal matrix contraction effect) and the rising phase of coal matrix contraction-slippage effect (mainly based on slippage effect). Permeability of coal reservoir during the process of drainage and production goes through four stages.     

天然气发动机氧传感器故障模拟试验

在自行搭建的发动机试验台架上,以台架试验与排放分析法为基础,以NI采集卡、前端信号处理电路、信号丢失控制电路与信号异常控制电路等为硬件,以LabVIEW软件为技术支持设计了天然气发动机氧传感器故障模拟系统,分析了天然气发动机氧传感器故障对发动机动力性、经济性以及各项排放指标的影响.试验结果表明:当转速为2 500 r·min-1,节气门开度为25％,模拟信号电压低于0.5V时,过量空气系数变小,混合气变浓,转矩与正常值相比变化不大,CO排放上升,HC排放略有升高,但变化不大,NOx排放下降;当模拟信号电压高于0.5V时,过量空气系数变大,混合气变稀,转矩下降较大,CO排放下降,并低于正常值,HC排放上升,NOx排放基本为0.     

电厂天然气锅炉富氧燃烧数值模拟

对传统燃烧方式下和应用富氧燃烧技术（O2/CO2燃烧技术）时电厂天然气锅炉内的燃烧特性进行数值模拟研究.结果表明随着氧气浓度的增大,整个炉膛的高温区分布趋于集中,烟气温度增加,火焰分布更为集中,充满度也越来越差.当氧气浓度为25%时,炉膛内的温度分布和烟气辐射特性与传统燃烧方式下最接近.当氧气浓度由21%上升到40%时,炉膛内烟气温度得到较大幅度的提高,燃烧器所在截面温度上升300 K以上,火焰充满度变差.     

Feature extraction and modeling of welding quality monitoring in pulsed gas touch argon welding based on arc voltage signal

Arc sensing plays a significant role in the control and monitoring of welding quality for aluminum alloy pulsed gas touch argon welding （GTAW）. A method for online quality monitoring based on adaptive boosting algorithm is proposed through the analysis of acquired arc voltage signal. Two feature extraction algorithms were developed in time domain and frequency domain respectively to extract six statistic characteristic parameters before removing the pulse interference using the wavelet packet transform （WPT）, based on which the Adaboost classification model is successfully established to evaluate and classify the welding quality into two classes and the classified accuracy of the model is as high as 98.81%. The Adaboost algorithm has been verified to be feasible in the online evaluation of welding quality.     

气液环簧组合式缓冲器非对称拉压特性动力学建模及冲击仿真

为解决气液环簧组合式缓冲器呈现非对称拉压动态特性问题,构建了气液环簧组合式缓冲器动力学模型,基于MATLAB/Simulink软件编制了考虑不同吸能元件特性的车辆冲击动力学模型程序,研究了两辆单车冲击及两列动车组冲击的动态特性。研究结果表明：组合式缓冲器动力学模型既能有效地模拟拉伸状态下环簧缓冲器的线性加载特性,又能较好地模拟压缩状态下气液缓冲器随冲击速度变化的非线性加载动态特性,即组合式缓冲器动力学模型体现了明显的非对称拉压特性;低速与中高速冲击过程中,组合式缓冲器动力学模型及车辆冲击模型可依次完整有效地模拟缓冲器-压溃管-防爬器-车体结构变形产生的缓冲吸能动态过程及磁滞拉压特性曲线;列车冲击速度为5 km·h^-1时,最大车钩力及组合式缓冲器最大行程均小于缓冲器阻抗力和行程限值,其压缩加载特性曲线仅呈现出气液缓冲器的加载特性;冲击速度为20 km·h^-1时,最大车钩力为2 900 kN,最大行程为534 mm,防爬器已经触发,其压缩加载特性曲线呈现出了气液缓冲器-压溃管-防爬器组成的连续力学特性,此时车体结构未发生破坏;冲击速度达到25~30 km·h^-1时,列车开始发生结构破坏,车钩力陡升;全自动车钩与半永久车钩参数选型能够满足冲击速度20 km·h^-1以内的列车车体结构安全性。     

Numerical simulation of thermal and iron ore reduction conditions in pre-reduction shaft furnace based on reducing gas composition and temperature

Based on the principles of mass, momentum and heat transfers between the reducing gas and the iron ore solid, a two-dimensional mathematical model for above two phases is established to study the influences of reducing gas composition on thermal and reduction conditions in pre-reduction shaft furnace with the temperature ranging from 1 023 to 1 223K. Due to the strong endothermic effect of iron ore reduction participated by hydrogen (H₂), increasing the ratio of carbon monoxide (CO) to H₂ enlarges high temperature zone under present calculation conditions, thus improves reduction efficiency inside the furnace. In addition, replacing of the reducing gas with an appropriate proportion of nitrogen (N₂) featuring the same temperature has a potential to reduce fuel consumption by as much as 6.5% while the products of similar quality are yielded.