固液两相流离心泵内颗粒运动规律的数值研究

针对分析固相参数对颗粒在流道内运动规律影响的问题,对不同固相参数工况下流道内颗粒运动轨迹、固相速度分布和颗粒雷诺数分布规律进行了研究,对颗粒直径以及颗粒浓度对颗粒运动规律影响进行了归纳。应用RNG k-ε湍流模型以及离散相模型进行了离心泵内部固液两相流场数值模拟。研究结果表明,颗粒与蜗壳碰撞的次数随着直径和颗粒浓度的增大而减少;叶轮流道内,颗粒与叶片发生碰撞的位置在叶片工作面;流道内的固相速度随着直径的增大整体会有减小的趋势;蜗壳和叶轮流道内两相分离严重,两相滑移速度较大。     

大颗粒下螺旋离心泵内运动特性数值模拟与分析

以150×100LN-32型螺旋离心泵为模型,采用欧拉多流体、RNG k-ε模型对其内部进行三维数值模拟。对比不同颗粒粒径以及浓度情况下固液两相流场,分析了在大颗粒情况下,固体颗粒在螺旋离心泵内的运动情况。通过固相体积分数、压力以及速度分布,得出了大颗粒固液两相流在螺旋离心泵内的运动特性。并以此为参照,分析大颗粒情况下螺旋离心泵磨损情况。     

离心式通风机内稀疏气固两相流整机三维数值模拟

利用颗粒轨道模型对通风机内部稀疏气固两相流动进行了数值模拟,重点分析了最优工况下不同粒径粒子轨迹分布情况.模拟得到了不同直径的固体颗粒在风机中的运动轨迹,积尘分布.这些结果为研究风机磨损,延长使用寿命提供理论基础.     

小粒径固液两相流在旋流泵内运动的数值模拟

为了分析旋流泵内固液流动特性,采用Eulerian多相流模型,扩展的标准κ-ε湍流方程与SIMPLEC算法,应用流体动力学软件FLUENT对旋流泵叶轮内固液两相湍流进行了数值模拟。分析了多种粒径及浓度条件下的固相体积浓度分布规律。在旋流泵叶轮固液两相流动中,固体颗粒还是主要集中于叶轮工作面,因而会加剧叶轮工作面磨损破坏速度。数值结果表明,泥沙颗粒直径变大以及泥沙浓度的加大都会使旋流泵扬程和效率下降,其中浓度的变化对扬程和效率的影响更明显。     

双叶片螺旋离心泵固液两相流特性研究

为研究双叶片螺旋离心泵叶轮内固液流动特性,采用Eulerian多相流模型,扩展的标准k-ε湍流方程以及SIMPLE算法,应用流体动力学软件对双叶片螺旋离心泵叶轮内固液两相湍流进行了数值模拟。分析了多粒径及初始固相体积浓度条件下的固相体积浓度分布规律。通过分析可得到固体颗粒存在由叶片压力面向吸力面迁移的趋势,同时有从轮毂侧向轮缘侧运动的趋势;通过外特性分析得到了相同粒径下水泵扬程随固相浓度的升高而减小,相同固相浓度下水泵扬程随粒径的增大而减小的变化趋势。     

固液两相离心泵内部非定常流动特性研究

为研究固液两相流离心泵内部的非定常流动特性,基于滑移网格方法,采用RNGκ-ε湍流模型以及ASMM代数滑移混合物模型,对一台高比转速固液两相离心泵内部流场进行非定常流动的数值模拟,通过分析清水工况数值计算结果、外特性性能实验结果以及固液两相流非定常数值计算结果,获得了非定常条件下固液两相输送离心泵的瞬时外特性曲线和内部流动及磨损规律。研究结果表明:在一个转动周期内,离心泵的扬程、效率和轴功率均呈现正弦波动特征;动静干涉效应使得叶轮出口处的速度和静压分布均呈现周期性波动;模型泵叶轮前后盖板的磨损情况比蜗壳壁面的磨损严重。上述计算结果可为实现高比转速固液两相流离心泵的优化水力设计和减轻磨损提供一定的理论参考。     

大型轴流泵泥沙磨损特性研究

为探讨大型轴流泵的泥沙磨损特性,采用非均相流模型、Particle模型和Tabakoff磨损模型和滑移壁面边界条件,研究泥沙在轴流泵内部的流动规律及磨损机制。结果表明:叶片头部及叶片工作面的泥沙体积分数和磨损率最大,导致叶片头部、工作面磨损速度和程度大于背面;粒径对泥沙的运动轨迹有显著影响,而含沙量的改变对泥沙的运动轨迹影响不大;颗粒在叶轮中的运动速度与粒径呈正相关关系,粒径大的沙粒向叶片工作面运动的趋势更为明显,说明粒径为影响泥沙运动轨迹的一个主要因素,含沙量为一个次要因素;随着泥沙粒径的增大,磨损率范围增大,磨损强度也相应增大,随着含沙量的增大,叶轮内各处磨损率均增大,说明粒径和含沙量均是加快轴流泵磨损的重要因素。     

螺旋离心泵内固液两相流的数值模拟

以螺旋离心泵为对象,利用欧拉k-ε数学模型对其内部三维流动进行数值模拟,计算了颗粒直径相同和浓度不同、颗粒直径不同和浓度相同以及同一流体中含有两种不同直径颗粒等三种状况下螺旋离心泵的液固两相流场,比较了颗粒直径和浓度对计算结果的影响,分析了浓度、速度、压力等流动参数在泵内的分布规律及相互影响,为改善叶轮的性能和进一步深入研究泵内的液固两相流动机理提供了一定的参考.     

扫路机专用风机内部气固两相流场仿真分析

针对扫路机专用风机的磨损问题,采用RNG k-ε湍流模型结合欧拉-拉格朗日方法的颗粒轨道模型,对某型号扫路机专用风机内部气固两相流场进行了数值仿真研究。首先分析了扫路机专用风机叶片吸力面上的分离流动情况及颗粒在叶轮内的流动规律;然后结合颗粒运动轨迹,探究风机叶片的主要磨损位置、磨损形状及蜗壳的磨损情况,获得了专用风机内部气固两相流磨损机理及磨损规律。结果表明:在分离流动的作用下,固体颗粒偏向叶片压力面运动,导致叶片压力面磨损;压力面的磨损呈条带状分布,叶片磨损最严重区域位于叶片与后盘接触区的1/4处;蜗壳表面存在周期性磨损区。     

离心式污水泵叶轮磨损的数值模拟

针对离心污水泵内固液两相流动比较复杂的情况,用含沙水为工作介质,通过改变沙粒粒径和含沙水颗粒浓度的方法,对小粒径颗粒在离心污水泵内的流动进行了数值模拟。借助弄清内流场的速度、压力与颗粒分布,分析了粒径大小对泵内固体颗粒运动的影响和进口初始颗粒浓度对泵内压力和固相分布的影响,得出压力沿叶轮吸力面和压力面的分布规律以及固体颗粒沿叶片吸力面和压力面的分布规律,并在此基础上得出了离心污水泵叶轮的磨损特性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.