中低压轴流通风机最优流型气动设计方法

采用最优化理论和数值计算方法,应用VBA程序,进行中低压轴流通风机的最优化流型气动优化设计计算.运用孤立翼型和叶栅叶型相结合的理论,在保证通风机结构参数不变的情况下,通过改变变环量指数来调整叶片的扭曲规律,进行变环量流型的优化气动设计计算,进而找到通风机设计工况下的效率最高点.     

轴流风扇两种扭叶片设计方法及其气动性能的比较

"等密流型"与"变密流型"设计方法是轴流风扇扭叶片气动设计中的两种典型的方法,本文对这两种气动设计方法进行了深入的探讨,并以某型轴流风扇为例,分别采用这两种方法对其进行了扭叶片改型设计,详细比较了按这两种扭叶片设计方法所获得的扭叶片的几何特征。在此基础上,利用CFD技术数值研究了这两种扭叶片的气动性能在设计工况与变工况的差异,以此对这两种方法的设计效果作出评价。研究结果表明:"变密流型"扭叶片的气动性能受变环量指数影响较大,较大的变环量指数能明显地提高"变密流型"扭叶片的气动性能,而"等密流型"扭叶片的气动性能受变环量指数的影响较小;"变密流型"扭叶片具有较大的径向压力梯度,易于诱发径向串流而引起额外的二次流损失,这直接造成其静压效率明显低于相应的"等密流型"扭叶片;按"等密流型"方法设计的扭叶片,其叶道根部具有较小的扩压度,这使其在小流量工况下叶根部抗失速能力明显高于对应的"变密流型"扭叶片。     

微型轴流风扇中变环量指数对扭叶片气动性能的影响特点

对微型轴流散热风扇叶片扭曲规律进行研究,根据"径向平衡原理",通过引入一反映气动特性的参数-变环量指数α,建立轴流叶轮中通流速度沿径向分布的微分方程及其边界条件,提出在几类不同条件下该方程解的解析形式,并分析这些解所对应的物理意义及其叶片扭曲形式.在此基础上,根据微型轴流风扇实际运行工况的特点,提出其扭叶片设计中变环量指数α所须满足的约束条件,并指出该变环量指数α存在一个最小值,具体数值则确定于风扇的气动、几何等参数.运用"计算流体动力学"(Computational fluid dynamics,CFD)技术详细地数值研究变环量指数α对微型轴流风扇气动性能的影响,发现降低变环量系数能增加风扇气动性能.进而有助于提高其散热能力.因此,满足约束条件下的最小变环量指数是微型轴流风扇扭叶片气动设计中所须选取的最佳值.     

单叶轮轴流通风机的叶片扭曲规律研究及薄叶型设计

针对单叶轮轴流式通风机的特点,推导出全压沿着叶轮半径分布规律与环量指数取值之间的关系式,并讨论了叶片扭曲规律、叶片弦长沿半径方向的变化趋势.明确指出设计应采用变环量设计方法,并给出了环量指数的适合取值范围.还研究了薄叶型的单圆弧设计方法.应用这种叶型设计方法和扭曲规律设计了通风机的叶片,通过数值模拟和试验测试结果表明,采用这种扭曲规律和薄叶型设计方法是合理的.     

不同流型对轴流通风机性能影响的数值

本文采用Navier-Stokes方程和标准k-s湍流模型,对采用两种不同流型设计的低压轴流通风机进行三维稳态内流模拟,详细分析两种流型造成叶片根部安装角变化对轴流通风机性能的影响.并对采用改进型流型设计的样机采用大涡模拟和声学模型进行噪声预测分析.计算结果表明,改进型流型设计不仅能改善叶轮根部的流动,同时也有利于风机...     

大风量高效低噪喷雾轴流通风机的优化设计

将最优化方法应用于喷雾轴流通风机的气动设计及其结构参数的选择计算,应用电子表格进行风机叶轮流型的优化设计和最佳结构参数的确定.按最优化方法设计了JYPW-1型大风量喷雾轴流通风机,并给出了该风机的流量、全压、效率、噪声等气动性能实测数据与国内同类型风机的性能对比.     

环量分布控制轴流风扇气动性能的机理分析

采用数值模拟的方法,对比研究了不同环量指数的轴流风扇在设计工况下的气动性能,通过分析风扇内部流动结构,揭示了沿叶高变环量设计对气动性能影响的控制机理.结果表明:环量指数取适当的负值时,风扇叶顶通流能力较强,削弱了间隙处逆流对主流的影响,减小叶顶间隙泄漏带来的损失;但环量指数若取值过小,会使吸力面根部沿径向指向叶顶和沿轴向指向前缘的静压梯度较大,促进了附面层的分离,增大了二次流动损失本文的轴流风扇在环量指数取-0.2左右时气动性能最好.     

中低压轴流风机流型优化的数值模拟与试验分析

利用先进的CFD技术对不同环量指数(等环量指数、变环量指数和优化计算得到的环量指数)所设计的风机进行对比模拟。并对现有风机进行了数据实测,从而验证物理模型的正确性。结果表明,采用优化环量指数设计的风机的效率比采用另外2种环量指数设计的风机的效率高大约3%,但是优化环量指数的风机效率曲线相对较陡,当风机的实际运行工况与设计工况发生较大偏离时,优化环量设计的风机效率低于等环量法所设计的风机。     

前弯前掠低噪声纺织轴流通风机的优化设计

从提高纺织轴流通风机效率、降低风机气动噪声的目标出发,采用叶片前弯前掠技术,在叶轮叶片的重心线上各基元截面采用高效翼型的最优化流型成型。应用叶片前弯前掠和最优流型相结合的技术研制开发了JYFZ新型纺织轴流通风机,并与目前纺织行业应用量较大的FZ40(35)-11/12型纺织轴流通风机进行了对比性能测试。结果表明,JYFZ型纺织轴流风机具有效率高、噪声低、质量轻、结构简单及工作区域宽广等特点。     

低压轴流风机的气动设计及参数化建模

采用变环量流型对低压轴流风机进行了气动优化设计,同时利用Visual Basic6．0对三维建模软件SolidWorks进行二次开发,实现轴流风机的参数化建模,为后续气动性能和噪声分析奠定基础。     

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.