基于CFD的工程机械导风罩优化计算

针对某款新型工程机械须满足最新的法规标准的要求,本文从导风罩的角度对工程机械的冷却风扇气动噪声和风量进行优化。建立了冷却风扇与导风罩流场的CFD模型运用Fluent软件对其进行了数值模拟,探究了两种导风罩形状对风量大小和噪声水平的影响。优化结果表明,四周斜切角的导风罩可使流量提高0.08kg/s,噪声降低了0.02d B。结果表明,在新方案的基础上可以适当降低转速,从而降低风扇的气动噪声。     

某推土机发动机舱热管理性能分析及优化

本文计算了一款推土机的发动机舱内空气流动,发现设计中存在着风量较小,散热器散热量不足的问题,针对发现的问题,提出了移动风扇,改变风扇旋转方向,增加导风罩三种优化方案。在三种优化方案中,可以看到改变风扇的旋转方向可以有效的增加发动机舱的流量,但是对散热器散热效果提升不明显,增加导风罩会使得机舱空气流量变小,但是能有效地增加散热器散热。     

基于ANSYS的电动机风扇声场仿真分析

电动机径向离心式风扇可双向旋转,比轴流式风扇具有更高的稳定性。利用ANSYS软件对一款封闭式电动机的风扇进行网格划分及有限元分析,根据仿真得到的噪声频谱,对比分析优化前后风扇在不同转速下的空气噪声。结果表明,优化后的风扇有良好的降低空气噪声的效果,同时验证了优化手段的合理性。     

短尾挖掘机热平衡与噪声的分析与优化

某短尾挖掘机在样机试验时,热平衡与噪声未达到目标要求。基于在不影响整机大的布局下,仅改变部分零部件,对整机的改动工作量小的原则,首先对其热平衡进行分析与改进,通过对散热器水散和液压油散的面积对比,结合水温和液压油温的测试数值,优化水散和液压油散的散热面积后,液压油温下降6.0℃;进一步对机罩进风孔面积优化,增加进风孔面积20%后,热平衡满足目标值。然后对其噪声进行分析与改进,通过采集该挖掘机的噪声频谱,识别出主噪声源为风扇旋转噪声;通过降低风扇旋转转速和使用低噪声风扇两个措施,使噪声下降了3.5 dB(A)。在以上采用的优化措施中,机罩进风孔面积、发动机转速、风扇结构这三种因素会同时影响热平衡和噪声,验证改进效果时须对热平衡和噪声都进行测试。将全部改进措施在新的挖掘机上进行装机试验,测试数据与分析符合,热平衡和噪声均满足目标值。分析与优化方法对其他挖掘机特别是短尾挖掘机的性能优化,具有一定的参考和指导。     

基于FLUENT轴流风叶的气动性能分析

利用Fluent软件对空调室外机的轴流风扇进行仿真分析,分析风扇特征对风扇气动性能的影响,结果表明风扇不光滑表面可以增加吸力面的吸附能力,风扇外缘翻边有利于降低噪声。最后,利用有限元软件对风扇进行模态分析,选择优化方案并进行噪声测试,试验结果与仿真趋势一致。     

低噪声发动机冷却风扇结构改进设计

为在不牺牲气动性能的前提下降低发动机冷却风扇的气动噪声,提出了一种新型的冷却风扇结构改进方案,即在风扇叶片吸力面上增加若干沿径向规律分布的楔形结构.以风量及进风口处噪声值为评价指标,设计正交试验,借助CFD/CAA耦合仿真法对各风扇流场及声场进行数值模拟,探究楔形结构参数对冷却风扇性能的影响.根据正交试验结果选择出一组楔形结构优化方案,将其与原始方案仿真结果进行对比,风量略增加,噪声值降低了8.8%,有一定工程应用价值。     

基于耦合传热的涡轮增压器涡轮箱有限元分析

基于涡轮增压器涡轮箱传热机理,采用专业CFD软件和FEM软件分别建立了涡轮箱流体区域和固体区域网格仿真模型。在流体域建立多重旋转坐标系,精确计算出涡轮箱流场、壁面传热系数及温度。应用流固耦合的仿真方法对涡轮箱进行耦合传热分析,得到涡轮箱固体域的温度场并对其进行热应力分析。与实验结果对比发现,仿真模型的温度场符合实际涡轮箱温度分布,最大误差仅为3.3%。该涡轮箱耦合传热模型具有较高的精度,为涡轮增压器的设计优化提供了依据。     

大涡模拟在轴流风扇气动噪声仿真中的应用

随着高集成、大功率电子设备的应用越来越广泛,随之而来的气动噪声问题越来越受到人们的重视,对其主要气动噪声来源—风扇的研究也越来越深入。伴随着仿真计算方法以及计算机技术的发展,数值仿真已经成为气动噪声仿真、预测、降噪的新手段。在总结了前人在气动噪声仿真中的相关手段方法后、采用流体力学计算软件Fluent和LES大涡模型对轴流风扇气动噪声进行了数值模拟,分析了轴流风扇气动噪声产生机理,验证了仿真方法的正确性,结果表明LES湍流模型能够准确预测气动噪声,满足工程应用要求。     

无叶风扇绕环出口分析与优化

无叶风扇凭借其无叶片旋转,使用安全系数高,产生气流平稳、舒适,方便清洁,噪音低等特点得到社会的广泛认可,在国内的发展更如雨后春笋,然而作为无叶风扇关键部件的绕环出风口,并没有相应的设计理论指导。本文章在对绕环出风口建模的基础上采用Fluent流体分析软件,对出风口窄缝宽度以及出风口倾角和出风量大小进行模拟分析,最终寻找出最优宽度与倾角。对今后无叶风扇的设计与制造提供了参考。     

基于三维耦合热保护仿真技术的机舱热害分析及优化

针对某乘用车发动机舱内散热器的风扇罩受高温烤化问题,运用流体软件STARD CCM+和热分析软件Radtherm进行了三维耦合热保护仿真分析.通过优化前舱布置及隔热罩设计,有效地解决了风扇罩的热害问题.试验结果表明,优化方案的仿真误差在10％以内.     

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.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.