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涡轮泵转子-迷宫密封系统的非线性稳定性和分岔 总被引:2,自引:0,他引:2
研究迷宫密封对某一工程涡轮泵转子系统动力特性的影响,迷宫密封力采用Muszynska非线性力模型,应用有限元法建立转子系统的动力学方程,采取系统动力学方程中包含的高阶线性自由度和低阶的非线性自由度进行分块处理的方法,有效地缩短了求解时间。根据Floquet理论,判别系统的临界失稳转速,并由Floquet乘子来确定系统失稳后分岔方式。采用分块-Newmark法数值模拟了转子二涡轮盘的轴心轨迹。最后分析了涡轮泵转子二涡轮盘的质量偏心同相位和存在90度相位差时对转子系统运动特性的影响。 相似文献
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研究了型孔形状和方向性对孔型阻尼密封泄漏特性的影响. 建立了孔型阻尼密封流场特性CFD数值模型,对比分析了不同转速和密封间隙下圆孔阻尼密封、蜂窝密封、迷宫密封和光滑面密封的泄漏特性,研究不同转速下型孔形状、超椭圆系数和倾斜角对广义孔型阻尼密封泄漏特性的影响规律,探讨了方向性型孔阻尼密封阻流控漏机制. 结果表明:紧密排列的孔型阻尼密封相较于迷宫密封和光滑面密封具有显著优异的密封性能;倾斜角为30°、超椭圆系数为2且边数为2的类椭圆型孔阻尼密封在静止时具有最小的泄漏率,且可通过减小周向或轴向排列间距进一步减小泄漏;一定倾斜角条件下,超椭圆系数较大的类椭圆型孔出口尖端附近能形成明显的低速阻流区,从而达到阻流控漏的效果. 相似文献
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迷宫密封是依靠节流间隙中的节流过程和迷宫空腔内的动能耗散过程来实现密封的,这两个流体流动过程从本质上规定了迷宫密封的密封性能。通过密封内部流动本质的研究,合理利用湍流流动的规律和特点,能够发挥密封内部湍流的增阻作用,提高密封性能。本文数值计算了一种锯齿型径向迷宫密封的内部流动,得到了密封内部的流动形态,揭示了密封内部流动与密封性能的关系。结果表示,密封存在一个最佳的齿插入长度。在最佳齿插入长度时,尽管节流间隙较大,但由于节流间隙内流动收缩和偏转,间隙的有效通流面积却很小,泄漏介质可以在间隙中获得较大的速度,在迷宫空腔内形成正确的耗散涡流,密封具有最佳的密封效果。所以,充分发挥湍流增阻的作用,可以突破节流间隙的微小尺寸限制,实现较大间隙下的良好密封。这不仅会给迷官密封的制造、安装及运行等带来很大的方便,而且可以为发展新的迷宫密封技术奠定理论基础。 相似文献
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蜂窝密封动力特性计算方法的改进及应用 总被引:1,自引:0,他引:1
针对蜂窝密封的转子动力学特性分析,本文由双控制体模型入手,建立相应的控制方程,将其无量纲化,并通过摄动分析分解为零阶及一阶无量纲方程。通过零阶方程求得定常流场,确定流场是否发生阻塞现象,继而求解一阶方程得到密封的动力特性系数。本文的双控制体模型在蜂窝密封静子和转子表面采用Blasius模型的摩擦系数,且舍弃转子轴心传统的圆轨迹小扰动假设,直接设定为椭圆轨迹小扰动,加之矩阵形式的表达,得到了更为清晰的模型及更为简洁的算法。随后与实验结果相比较,验证模型及计算结果的准确性,并比较一般气体密封的计算结果,体现蜂窝密封在稳定性方面的优越性。最后分析了几种密封参数对其动力特性的影响,揭示某些规律并给出一些建议。 相似文献
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研究了惯性效应和端面倾斜对超高速气膜端面密封稳动态特性的影响. 考虑气体惯性效应,建立了气膜端面密封稳动态特性数值分析模型,采用有限差分法求解稳态和微扰雷诺方程,获得端面膜压分布. 数值分析了惯性效应和端面倾斜度对开启力、气膜刚度和泄漏率等稳态性能参数以及刚度系数和阻尼系数等动态特性系数的影响规律,并以获得较大刚度系数为目标,获得了螺旋槽关键几何参数的优选值范围. 结果表明:在超高速条件下,考虑惯性效应后的干气密封泄漏率显著减小,刚漏比明显增大,而开启力、气膜刚度和动特性系数变化不大;倾斜端面气膜密封相较于平行端面气膜密封具有更佳的低频刚度和高频阻尼. 相似文献
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建立了不同偏心状态下迷宫密封三维数值分析模型,应用基于微元理论的密封动力特性系数识别方法计算密封静态和动态特性. 结果表明:转子偏心会降低密封抑制流体泄漏的效果;密封腔内周向压力高点随偏心率增大逐渐偏离最小间隙处. 低偏心率(≤ 0.5)下,静态直接刚度K与静态交叉刚度k变化较小,高偏心率(> 0.5)下K和k的绝对值减小. 随着偏心率的增大,密封小间隙侧流动黏性效应增强是产生负静态直接刚度的主要原因. 密封偏心涡动时,低偏心率(< 0.6)下刚度和阻尼系数变化较小,随偏心率和涡动频率的升高直接刚度逐渐变为负值;随偏心率的增大,交叉刚度在正交两个方向上大小不再相等,有效阻尼降低,高偏心率(≥ 0.6)下有效阻尼受偏心率影响更显著. 相似文献
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相对于有限元法,边界单元法在求解断裂问题上有着独特的优势,现有的边界单元法中主要有子区域法和双边界积分方程法.采用一种改进的双边界积分方程法求解二维、三维断裂问题的应力强度因子,对非裂纹边界采用传统的位移边界积分方程,只需对裂纹面中的一面采用面力边界积分方程,并以裂纹间断位移为未知量直接用于计算应力强度因子.采用一种高阶奇异积分的直接法计算面力边界积分方程中的超强奇异积分;对于裂纹尖端单元,提供了三种不同形式的间断位移插值函数,采用两点公式计算应力强度因子.给出了多个具体的算例,与现存的精确解或参考解对比,可得到高精度的计算结果. 相似文献
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2008年5月12日,汶川M80地震在四川省绵竹市清平乡文家沟内诱发一巨型滑坡。通过现场调查得知,滑坡前后缘高差455m,厚度20~30m,滑面为基岩层面,初始方量2750×107m3。滑体在运动中转化为碎屑流。滑坡-碎屑流总的水平运动距离为4022m,垂直运动距离为1443m,遗留的堆积物体积达5×107m3。滑坡距映秀—北川断裂仅36km,位于其下盘,地震烈度达XI度。滑坡导致文家沟中48人遇害,并形成一条完整的地震次生地质灾害链。初步分析表明滑坡启动速度快,滑坡向碎屑流转化过程明显、地点明确。碎屑流运动过程复杂,伴有强烈的“气垫效应”和“前缘气浪冲击效应”。作者认为,文家沟滑坡的高启动速度是长持时强烈地震动作用的结果,与山体的猛烈碰撞是导致滑体解体并转化为碎屑流的原因。 相似文献
2008年5月12日,汶川M80地震在四川省绵竹市清平乡文家沟内诱发一巨型滑坡。通过现场调查得知,滑坡前后缘高差455m,厚度20~30m,滑面为基岩层面,初始方量2750×107m3。滑体在运动中转化为碎屑流。滑坡-碎屑流总的水平运动距离为4022m,垂直运动距离为1443m,遗留的堆积物体积达5×107m3。滑坡距映秀—北川断裂仅36km,位于其下盘,地震烈度达XI度。滑坡导致文家沟中48人遇害,并形成一条完整的地震次生地质灾害链。初步分析表明滑坡启动速度快,滑坡向碎屑流转化过程明显、地点明确。碎屑流运动过程复杂,伴有强烈的“气垫效应”和“前缘气浪冲击效应”。作者认为,文家沟滑坡的高启动速度是长持时强烈地震动作用的结果,与山体的猛烈碰撞是导致滑体解体并转化为碎屑流的原因。 相似文献
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Junfeng Li 《Acta Mechanica Sinica》2014,30(3):281-281
One of the core issues in modern celestial mechanics is the orbital dynamics in the near-regime gravitational field of as- teroids, which provides deep insights into the mathematical nature of a class of nonlinear systems, and plays as a critical basis for in situ explorations of different science goals. Lots of efforts have been made to reveal the characteristics of orbital motion in the vicinity of asteroids, and to improve the skills of asteroid research in methodology. 相似文献
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Maxime Sauzay 《Comptes Rendus Mecanique》2006,334(6):353-361
Experimental studies of the plasticity mechanisms of polycrystals are usually based on the Schmid factor distribution supposing crystalline elasticity isotropy. A numerical evaluation of the effect of crystalline elasticity anisotropy on the apparent Schmid factor distribution at the free surface of polycrystals is presented. Cubic elasticity is considered. Order II stresses (averaged on all grains with the same crystallographic orientation) as well as variations between averages computed on grains with the same crystallographic orientation but with different neighbour grains are computed. The Finite Element Method is used. Commonly studied metals presenting an increasing anisotropy degree are considered (aluminium, nickel, austenite, copper). Concerning order II stresses in strongly anisotropic metals, the apparent Schmid factor distribution is drifted towards small Schmid factor values (the maximum Schmid factor is equal to 0.43 instead of 0.5) and the slip activation order between characteristic orientations of the crystallographic standard triangle is modified. The computed square deviations of the stresses averaged on grains with the same crystallographic orientation but with different neighbour grains are a bit higher than the second order ones (inter-orientation scatter). Our numerical evaluations agree quantitatively with several observations and measures of the literature concerning stress and strain distribution in copper and austenite polycrystals submitted to low amplitude loadings. Hopefully, the given apparent Schmid factor distributions could help to better understand the observations of the plasticity mechanisms taking place at the free surface of polycrystals. To cite this article: M. Sauzay, C. R. Mecanique 334 (2006). 相似文献
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Tuan Hung Le Luc Dormieux Laurent Jeannin Nicolas Burlion Jean-Franois Barthlmy 《Comptes Rendus Mecanique》2008,336(8):670-676
This paper is devoted to a micromechanics-based simulation of the response of concrete to hydrostatic and oedometric compressions. Concrete is described as a composite made up of a cement matrix in which rigid inclusions are embedded. The focus is put on the role of the interface between matrix and inclusion which represent the interfacial transition zone (ITZ). A plastic behavior is considered for both the matrix and the interfaces. The effective response of the composite is derived from the modified secant method adapted to the situation of imperfect interfaces. To cite this article: T.H. Le et al., C. R. Mecanique 336 (2008). 相似文献
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A. N. Rozhkov 《Fluid Dynamics》2005,40(6):835-853
The phenomena of hydrodynamic breakup of liquid jets, drops, films, bridges, and filaments are reviewed for liquids with viscoelastic properties. The reasons for breakup are capillary instabilities, collisions with rigid obstacles, and other forms of dynamic action. The relationship between the properties of the liquids and the features of the breakup process is discussed. 相似文献
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Flow stability analysis and excitation using pulsating jets 总被引:1,自引:0,他引:1
Classical flow stability applied to transition from laminar to turbulent flow may also describe the behavior of vorticity fluctuations created by a pulsating jet placed along a solid boundary. A numerical laminar flow experiment involving a pulsating jet placed along the surface of a duct with flow separation downstream, resulted in eliminating most part of the separated flow region. Applying the same approach to a turbulent flow, it was possible to develop a turbulent stability flow formulation and apply successfully turbulent pulsating jet flow separation control. To cite this article: D. Skamnakis, K. Papailiou, C. R. Mecanique 333 (2005). 相似文献