固液两相流下蝶阀的磨损特性研究与结构优化

基于Fluent软件提供的湍流模型与离散相模型,对中线蝶阀内部流场进行了数值模拟研究,考察了阀门开度对蝶阀壁面及蝶板磨损的影响。结果表明,随着阀门开度的减小,蝶阀的磨损量和磨损范围都在增大,其中,蝶板受到的磨损量最大,磨损区域主要集中在蝶板的边缘,而蝶板中心区域的磨损量基本为零。蝶阀内壁面受到的磨损程度与蝶板表面相比较小,磨损范围主要集中在过流截面的两侧。基于研究结果对蝶阀结构进行了优化,优化后蝶阀的磨损程度降低,磨损范围减小,流阻特性改善。     

阀杆可移动硬密封蝶阀

硬密封蝶阀一般采用双偏心及三偏心结构。由于蝶板是在旋转中密封 ,所以密封副易磨损。阀杆可移动蝶阀 (图 1 )通过蝶板特殊1 支承块　 2 蝶板　 3 斜块　 4 阀杆　 5 阀杆螺母6 限位块　 7 操纵装置　 8 定位销　 9 弹簧　 1 0 密封座图 1　阀杆可移动蝶阀的运动轨迹 ,降低了蝶板与阀座的摩擦 ,增加了密封的可靠性 ,延长了阀门的使用寿命。阀杆可移动蝶阀从关闭位置开启时 ,操纵装置先驱动阀杆螺母转动 ,在阀杆螺母的带动下阀杆上升。由于斜块固定在阀杆上 ,于是斜块也上升脱离蝶板斜面。受弹簧的作用 ,蝶板回缩 ,脱离与阀座的接触。…     

三偏心蝶阀蝶板性能分析

研究了三偏心蝶阀关键部件--蝶板的工作特点和规律,分析了蝶板的受力和变形的分布,并推导出相应的理论公式,得出蝶板边缘应力的分布直接影响三偏心蝶阀性能,而影响蝶板边缘应力主要因素之一是夹角γ的变化,利用有限元分析对结论进行了验证.提出了蝶阀结构的改进意见,对改进三偏心蝶阀设计、改善蝶板应力和变形分布、保证其操作及密封性能起到参考作用.     

超音速风洞大口径蝶阀流场分析及改进

介绍了超音速风洞大口径蝶阀的配置形式。运用COSMOSFloWorks软件分析了不同结构蝶板及蝶阀不同开度情况下的流场情况。通过在蝶板上增加蒙皮以及在蒙皮上开孔的方式改善了蝶阀的流场,蝶阀配置旁路阀的方式改善了蝶阀的使用工况,从而降低了蝶阀的故障率,延长了蝶阀的使用寿命。     

双偏心金属硬密封蝶阀蝶板修型方法研究

在研究双偏心金属硬密封蝶阀密封副结构特点的基础上,采用变半径方法给出了蝶板修型的数值计算方法,并结合实例给出蝶板加工余量曲线,使得双偏心硬密封蝶阀密封副存在完整密封线,降低了蝶板与密封圈磨损,延长了蝶阀寿命。     

三偏心蝶阀蝶板密封面的摩擦力矩分析

阀门类设备如三偏心蝶阀起着调节流量等作用,在煤制天然气行业广泛应用,因此对阀门设备的研究分析具有重要意义。在蝶阀的蝶板关闭或开启瞬间情况下,对蝶板密封面进行力学分析,利用椭圆微分方程和数值计算方法,在考虑蝶板厚度的情况下,推导出三偏心蝶板密封面的摩擦力矩的计算公式,并分析其与三偏心蝶阀三个偏心值之间的关系,对蝶阀驱动力矩的选取和结构的优化有着重大的意义。     

浮动蝶板式高压蝶阀

浮动蝶板式高压蝶阀为金属硬密封阀,阀杆既能作轴向移动,又能绕自轴转动。阀杆轴向移动时,推动蝶板槽内的凸轮驱动蝶板到达关闭位置。通过阀杆的旋转及凸轮和槽的共同作用,蝶板在开关位置旋转。蝶板被槽的夹持盖限制,作轴向移动,阀杆被限制在蝶板和夹持盖内（图１、...     

双偏心斜板式蝶阀密封结构的设计

介绍了双偏心斜板式蝶阀锥面密封蝶板的位置和结构的设计方法，并给出了其函数表达式和蝶板自由启闭的条件。     

三偏心金属密封蝶阀蝶板密封圈结构分析与研究

根据三偏心金属密封蝶阀蝶板的特点,利用有限元分析软件分别对加弹性槽的金属密封蝶板和未加弹性槽的金属密封蝶板进行了应力分析,优化设计。得出了蝶板弹性槽结构形式及其介质流向对阀门密封性能的影响因素和相关数据。     

三偏心金属蝶阀的干涉分析

通过对蝶板的运动分析,从三偏心蝶阀密封副发生干涉的根本原因介绍了一种判断干涉问题的方法。通过程序分析了蝶板与阀座密封面之间的干涉状况,进而能够很方便地判定不同结构的三偏心蝶阀的干涉情况。     

Vehicle Detection Method with Sub-stretching Based on Light Contrast in Fog Road Image

In this paper,detection of a vehicle from a road image with fog is focused to detect an vehicle from a foggy image.Because of the fog in the image,a shape of an object is vague.Therefore an obstacle may occur on the vehicle detection.Thus,features from a foggy road image are surveyed through experiments,and a histogram is calculated with the bright value.The stretching method is then applied with the specific weight as the centre to detect a vehicle smoothly.If the high density area,from the view point of histogram,is applied with the stretching method,the definition of the image can be increased.On this fact,this paper proposed a method to divide the histogram and to determine applicable range of the stretching method.The improved results by the proposed methods are proved with the comparison tests between the proposed and previous methods.     

单螺杆压缩机星轮的周向力分析

星轮磨损速度快,使机器容积效率下降迅速,是单螺杆压缩机发展的主要技术障碍。对大量失效星轮的齿面检测结果表明：星轮齿前侧的磨损比齿后侧严重。这与当前技术文献所持观点不符,且刚好相反。对气体力作用在星轮上形成的周向力进行了分析,结果表明该周向力扭矩是导致星轮齿快速磨损,且齿前侧易于齿后侧磨损的根本原因。对星轮齿的磨损行为进行了定性分析,并提出在星轮前、齿后侧分别采用不同的型线以减小周向力矩,提高星轮寿命。     

The representative topography of worn hot rolling mill cylinders

In this paper, a method is proposed to extract the most representative surface topography from n surfaces. A criterion is proposed that allows rejecting irrelevant topographical maps. Then, this methodology is applied on the hot rolling process, on replicas of industrial surfaces. These analyses have shown the major difference between ICDP and HSS roll behavior in terms of topography. Carbides oxidation observations correlates lab studies from bibliography. We confirm that this methodology is relevant to industrial investigations, especially on phenomena requiring non-destructive protocol.     

自动上下料机械手运动学分析及仿真

基于数控机床-机械手加工系统的布局及功能,详细分析了上下料机械手的结构,并运用D-H参数法建立了该机械手的运动学方程。与此同时,对该机械手进行了正运动学和逆运动学分析,通过计算验证了,经运动学正解所求得的机械手末端位姿表达式T是正确的。最后,基于用Solid-Works软件建立的机械手三维立体模型,用ADAMS软件对机械手完成自动上下料的过程进行仿真,得到上下料轨迹曲线。仿真结果符合工作过程的实际情况,说明该机械手运动学方程是有效的。     

基于小波分析的交流伺服电流中摩擦影响信息特征提取的研究

由于交流伺服电动机的伺服电流受到很多干扰,难以从中直接得到有用的信息。为此,利用霍尔传感器测量了交流伺服电动机控制器输出的伺服电流,将小波变换的理论用于提取反映摩擦力动态特性的伺服电流的有用信息。在这一过程中,对它进行多分辨率分析,即把伺服电流信号分解成多个层次细节部分和平滑部分,从中识别出静摩擦力到动摩擦力过程中信息特征。通过和位移输出信号对比分析,说明在伺服电流中能提取出摩擦影响的信息。此外,还发现突变发生时刻总是早于工作台宏观运动时刻,这一提前量还需要进一步研究。     

Isolability of faults in sensor fault diagnosis

A major concern with fault detection and isolation (FDI) methods is their robustness with respect to noise and modeling uncertainties. With this in mind, several approaches have been proposed to minimize the vulnerability of FDI methods to these uncertainties. But, apart from the algorithm used, there is a theoretical limit on the minimum effect of noise on detectability and isolability. This limit has been quantified in this paper for the problem of sensor fault diagnosis based on direct redundancies. In this study, first a geometric approach to sensor fault detection is proposed. The sensor fault is isolated based on the direction of residuals found from a residual generator. This residual generator can be constructed from an input-output or a Principal Component Analysis (PCA) based model. The simplicity of this technique, compared to the existing methods of sensor fault diagnosis, allows for more rational formulation of the isolability concepts in linear systems. Using this residual generator and the assumption of Gaussian noise, the effect of noise on isolability is studied, and the minimum magnitude of isolable fault in each sensor is found based on the distribution of noise in the measurement system. Finally, some numerical examples are presented to clarify this approach.     

Reconstruction of off-axis electron holograms using a neural net

In off-axis electron holography, the information about the specimen contained in amplitude and phase of the image wave is recorded by superimposing a reference wave to the image wave and recording the resulting interference pattern, called a hologram. The image wave is usually retrieved from this hologram by a filtering process in Fourier space. An alternative approach is to calculate the image wave pixel by pixel from the intensities in the hologram. In this paper, we describe a neural network that performs this step. As neural networks can represent nonlinear relations between the input and output data, this reconstruction process can use the nonlinear part of the information contained in the hologram and is thus less sensitive to noise.     

Data mining algorithm for manufacturing process control

In this paper, a new data mining algorithm based on the rough sets theory is presented for manufacturing process control. The algorithm extracts useful knowledge from large data sets obtained from manufacturing processes and represents this knowledge using “if/then” decision rules. Application of the data mining algorithm developed in this paper is illustrated with an industrial example of rapid tool making (RTM). RTM is a technology that adopts rapid prototyping (RP) techniques, such as spray forming, and applies them to tool and die making. A detailed discussion on how to control the output of the manufacturing process using the results obtained from the data mining algorithm is also presented. Compared to other data mining methods, such decision trees and neural networks, the advantage of the proposed approach is its accuracy, computational efficiency, and ease of use.     

Water in malignant tissue,measured by cell refractometry and nuclear magnetic resonance

It has long been known that tumour-bearing tissues often have a significantly higher water content than the normal tissues from which they have been derived. Most of the evidence suggesting this in recent years has been obtained from methods employing nuclear magnetic resonance (NMR), which, although undoubtedly indicative of hydration, cannot at present be precisely quantified. Furthermore it has not been possible by these means to determine whether this overall increase in the water content of the tissue is principally an increase in the extracellular fluid or whether the water content of the tumour cells and the cells immediately adjacent to the tumours increases also. In this investigation, which is the first of its kind, a combination of NMR and immersion refractometry techniques have been used to examine the water content of normal and tumour bearing tissues. NMR measurements were made on pieces of normal and tumour bearing tissue from rat livers: intact living cells were also isolated from these pieces and their refractive indices measured by immersion refractometry from which the water content of their cytoplasm was calculated. It was found that all the cells so measured obtained from hepatomas had more water in their cytoplasm (usually over 5% more water) than any of the cells from normal livers; and that normal-looking cells taken from the vicinity of hepatomas also all had more water in them than those of normal liver cells, although the differences in this case were less. These results were closely parallel to those obtained by NMR measurements. It is therefore concluded that an appreciable proportion of the increase in the water content of the tissue as a whole that occurs during carcinogenesis, must, in this tissue, be an increase in intracellular water.     

Comments on the shortcomings of predicting the precision of Cavalieri volume estimates based upon assumed measurement functions

It is well known that the estimation of an object's volume by means of serial cross-sections, the so-called Cavalieri method, yields an unbiased estimate. But by itself it provides no means by which to estimate how precise this estimate is unless the shape of the volume is fully known beforehand. This knowledge can only be partially determined from the serial section information that is collected. Methods have been developed that claim to surmount this difficulty by using the serial section data to create a mathematical model of the volume's shape properties. The model then is used to estimate (predict) the precision of the volume estimate (its CE) from the single set of data available. Unfortunately, the theory underlying the model is flawed and so the model itself amounts to no more than an unsubstantiated guess about the shape of the volume. Therefore, the precision of the volume estimates that one obtains from the method is only as good as the model and this cannot be ascertained from the single set of acquired data. In this letter I explain the inadequacies of the modelling method. I suggest that it be used only with caution, if at all. Instead I suggest two alternative ways to predict the CE, one that is based upon a rule-of-thumb approach to the object's shape, and another that is based upon spectral analysis of the measurement function and that is easy to implement with available computer software.