叶轮损失模型对离心压缩机性能预测的影响

针对目前离心压缩机损失模型的差异性,在总结离心压缩机叶轮损失模型的基础上,提出在计算各截面参数时采用多变系数替换绝热指数的方法.并利用MATLAB编写程序计算压缩机在不同流量和不同转速下的压比和效率.通过和单级离心压缩机性能实验数值比较,分析叶轮损失模型对压缩机性能的影响,得出了采用简化的叶轮损失模型对压缩机效率影响较大而对压比影响较小的结论.     

离心压缩机变比热性能预测方法

在对离心压缩机损失进行分类的基础上给出了相应的损失计算模型。为了使计算过程更加真实地模拟实际流动过程,采用了变比热计算方法。运用模型对两台离心压缩机进行了性能预测:一台为单级、低转速离心压缩机,另一台为三级、高转速离心压缩机。通过分析预测结果表明:(1)采用变比热计算方法的计算结果优于采用定比热计算方法的计算结果;(2)本模型可用于多级离心压缩机的性能预测。     

离心式压缩机性能预测模型研究

本文在广泛收集有关离心式压缩机各部件模型的基础上，编制了单级离心式压缩机性能预测的计算机程序。以有叶扩压器进口角度可调离心式压缩机的级性能试验曲线为例，分析讨论了现有模型预测结果与实验数据的偏差，并提出了改进措施。     

离心压缩机圆截面外蜗壳型线改进的数值研究

基于数值方法,以一台单级离心压缩机为研究对象,对其圆截面外蜗壳的型线进行了改进研究。主要措施有:改进蜗壳横截面积沿圆周角的变化规律,以改善蜗壳入口流场的均匀性,降低蜗壳截面最大通流速度;减小蜗舌处蜗壳的横截面积,从而减少蜗壳内通流气体总量,减小蜗壳总流动损失。数值计算结果表明,改进后蜗壳自身气动性能得到明显提升,蜗壳入口流场得到改善,在设计流量下,蜗壳多变效率提高了8.04%,压缩机级多变效率提高了1.26%。     

变频滚动转子式压缩机热力性能分析

考虑工质及润滑油的泄漏、吸气加热损失、残余气体膨胀等,采用有限元方法对排气阀建立模型,完善了滚动转子式压缩机的数学模型。利用模型计算和分析了压缩机在变频运行时的响应,并对其变频运行作出性能预测,指出样机合适的变频范围。     

离心式压缩机吸气室设计改进

吸气室是离心式压缩机的重要静止元件之一,其结构对压缩机整机性能有较大影响。本文基于数值计算的方法,对一台离心式压缩机吸气室内的流场进行分析,认为其进气通道与螺旋通道交界处的结构是引起压缩机级效率下降的主要原因之一,并对该处结构进行改进。将吸气室风筒由直筒形式改为渐扩形式,并对比分析了不同渐扩结构模型的流场。结果表明,改进后吸气室内的流场明显改善,吸气室出口截面流场均匀性提高,总压损失系数降低,吸气室后级多变效率提高5.6%。     

大型离心压缩机性能预测的混合建模方法研究

提出了一种核函数非线性偏最小二乘(PLS)与机理模型相结合的多级离心压缩机性能预测混合建模方法,用以预测离心压缩机的输出压比.通过分析大型离心压缩机多级压缩过程的机理,利用能最守恒关系,在压缩机各级气流损失计算和等熵效率定义的基础上建立了多级离心压缩机性能预测机理模型;利用核函数非线性PLS对机理模型的误差进行了修正.实验结果验证了该方法相比于机理模型的有效性,将其应用于实际生产过程中,取得了满意的效果.     

离心压缩机小流量级叶片扩压器的改进研究

采用数值模拟方法对某一离心压缩机小流量级内部全三维有粘流场进行了详细的分析,得到了内部各元件主要气动参数的分布情况.通过减小D4/D2值,减小叶栅稠度,增大当量扩张角等方法有效减小了叶片扩压器内的摩擦损失.数值计算结果表明,改进后计算模型多变效率提高约1.02％,效果显著.     

润滑油对涡旋压缩机压缩过程的影响

提出了考虑到润滑影响的压缩腔和背压腔工作过程数学模型，并对压缩过程进行了计算模拟，得到了流入压缩腔内的润滑油量与涡旋压缩机容积效率、压缩功率损失，背压和排气温度的关系曲线。在此基础上，进行了一定运行条件下的实验研究，验证了计算模型的准确性。研究结果表明：压缩腔内油－气质量百分比为５％－１２％时，涡旋压缩机的性能较为理想。     

多级单轴离心式空压机选型及性能预测软件开发

为了快速且准确地对大型多级离心空压机进行性能预测以及开展选型工作，方便选购用户在购买产品之前，选择合适的压缩机型号，满足其使用预期。本文基于Python编程语言，设计并开发了多级单轴空压机性能预测和选型软件，深入研究了空压机性能预测的影响因素，分析了气体物性参数的影响及其获取接口，考虑了段间冷却水析出对计算结果的影响，将WMO手册推荐使用的改进Goff-Gratch公式用于段间冷却水析出计算，优化了段间参数计算模型。软件可根据用户需求计算整机不同工况条件下的性能参数，以及整机的性能曲线。软件界面简洁，计算速度快且结果准确，并能以Excel文档格式输出各段、级的各项性能参数，提高用户的选型效率。     

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.     

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....     

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.     

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.