翼型叶片精确参数化建模的研究及应用

从理论上分析了抛物线、单圆弧和双圆弧型翼型中心线方程,推导并更正了双圆弧中心线翼型的前、后缘方向角的取值规律。阐述了翼型叶片截面的参数化建模方法,利用微分的思想,通过中心线分割点的弧长值求得了对应横坐标,从而获得了更加精确的翼型叶片上、下轮廓控制点坐标参数化计算方法。在此基础上,开发了翼型叶片截面参数化绘图程序,实现了叶型截面的精确自动绘制。     

基于参数化技术的海流能水轮机三维设计

基于参数化CAD设计技术对海流能发电装置叶片结构进行了三维设计,将Wilson设计方法与MATLAB编程相结合,得到了相应的叶素弦长和扭转角。综合考虑加工和叶片翼型过渡等因素,对叶片参数进行了结构优化,并通过EXCEL软件转换成三维参数化坐标导入到Pro/E软件中,由此生成水轮机的叶片模型。     

基于UG/Open GRIP的汽轮机叶片夹具参数化设计

通过对UG二次开发工具及其工作原理分析,介绍了参数化设计原理.利用GRIP语言进行编程,实现了叶片夹具实体自动生成的程序.该程序采用简单的人机交互方式,在不需要手工绘图的情况下就能得到叶片夹具实体装配图,并具有通用性、系列化等特点.最后,以某汽轮机叶片夹具为例介绍了参数化设计中的关键技术.该三维参数化设计方法不仅可以应用于汽轮机叶片夹具,也可以应用于其它一些典型非标准结构件的参数化设计,可大大提高产品的设计效率.     

可逆翼型的应用现状与设计技术研究进展

可逆翼型是叶轮机械实现正反向可靠运行的主要途径,已经成为可逆式叶轮机械领域的重要研究课题之一。结合近年来有关可逆翼型的研究报道,详细综述了国内外可逆翼型设计技术及其在叶轮机械领域应用的研究进展。首先,介绍了可逆翼型在通风领域、水力机械领域和航空领域的应用,并指出目前基于可逆翼型设计的可逆式叶轮机械性能相对于常规单向叶轮机械还有较大差距,制约着可逆式叶轮机械的进一步推广应用。然后,分析了可逆翼型的设计方法,无论是S型可逆翼型还是完全对称翼型,其设计方法基本是一致的,主要有单独设计S型中弧线并叠加厚度分布、利用现有翼型对称或非对称拼接等。其次,详细介绍了不同的翼型参数化方法,并对其优缺点进行了总结分析,指出翼型参数化方法是翼型设计与分析的基础,合理选择参数化方法有助于设计出高性能的翼型。最后,对可逆翼型设计及应用技术在今后的发展方向进行了展望。     

基于钝尾缘翼型叶片的三维风力机性能分析

随着风力机向大型化发展,为有效提升风力机叶片的性能以及结构强度,将钝尾缘翼型应用于风力机叶片设计。以NACA639XX系列翼型为基准翼型,通过Hicks-Henne型函数和钝尾缘函数对翼型进行参数化拟合,使用多岛遗传算法优化得到层流钝尾缘翼型族(USST-XXX)。将此翼型族中相对厚度为21%的USST-211翼型与NACA63921层流翼型替换NREL PhaseVI叶片截面的S809翼型,建模得到两种三维风力机叶片,采用数值模拟的方法,对这两种叶片不同风速下的流场进行分析,并与NREL Phase VI风力机叶片的气动性能进行对比。数值模拟结果表明,在额定风速附近,采用层流钝尾缘翼型所构造的新叶片风力机的风能利用系数高于其他两种叶片。研究结果表明优化得到的层流钝尾缘翼型族可以有效提升风力机气动性能,在大型水平轴风力机叶片设计方面具有良好的应用前景。     

基于通用翼型的小型风力机叶片结构设计与性能分析

以风力机的通用集成翼型为对象,分析了通用翼型升力系数、升阻比等气动性能.选取了自主设计的相对厚度为18％风力机通用翼型,完成了小型风力机叶片的气动外形设计.以修正的风力机风轮空气动力学模型为基础确定了叶片弦长以及扭角的分布.根据叶片的形状参数,完成了叶片的三维实体以及有限元模型的建立,应用ANSYS软件分析了叶片的结构...     

基于气动性能与刚度特性的风力机翼型优化设计

结合翼型泛函集成理论与叶片截面刚度矩阵数学计算模型,提出了风力机中等厚度翼型气动性能与结构刚度特性的一体化设计方法,实现了翼型气动性能与叶片截面刚度特性的同时提高。对考虑叶片截面铺层参数变化设计的WQ-B300翼型与DU97-W-300翼型进行了气动性能与结构刚度特性对比分析,结果表明:相比于DU97-W-300翼型,WQ-B300翼型的气动性能与叶片截面刚度性能均有显著提高,其挥舞刚度和摆振刚度分别提高了6.2%和8.4%,验证了该设计方法的可行性,给风力机中等厚度及大厚度翼型设计提供了一种思路。     

一种基于Fluent与UG的风机叶片反求设计的方法

针对风机叶片进行反求设计.建立叶片坐标系,利用UG获取坐标数据,通过导入Gambit软件,建立空气动力学流场,对其进行网格划分和边界条件的定义等,利用Fluent软件进行CFD计算,得到升力系数和阻力系数的数据;运用Hicks- Henne参数化方法,建立翼型弯度和厚度函数表达式.该研究为叶片的理论研究和优化设计提供了基础.     

风力机叶片数学模型及叶片函数化设计法探讨

为实现叶片的函数化设计,经过对翼型函数进行坐标变换、扭角旋转变换和数学推导等步骤,建立了叶片的通用数学模型,且给出了具有2个参变量(翼展位置、弦长位置)的显式参数方程组;提出了叶片函数化设计法的初步设想,用叶片函数生成了叶片三维立体图像,给出了两组示例。研究表明,叶片数学模型由翼型函数、弦长函数和扭角函数3个子函数组成,且可用显式方程组表示;通过调整叶片子函数的结构或其中的常数值,可以方便、迅速地修改设计,且可随时显示最终效果图,在叶片函数与叶片图像之间可建立一一对应的随动关系,能方便设计分析工作。     

基于Solid Works的参数化工程图自动调整技术

SolidWorks参数化设计时,随着模型参数的改变,工程图会出现视图位置偏移、尺寸和注解错位等不符合工程图规范的现象。根据参数化设计中工程图的变化特点,提出一种模板式工程图自动调整的方法。通过提取模板图纸中的特征信息,来对参数化驱动后生成的实例工程图进行调整。包括SolidWorks工程图模板制定、视图位置调整、视图比例调整、尺寸调整及注解位置调整。经实例验证,该方法正确可行,实现了工程图的自动调整,显著提高了设计效率。     

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。     

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.     

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....     

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.