共查询到20条相似文献,搜索用时 156 毫秒
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建立了脉动流诱发振动转子密封系统的振动模型的一次近似方程,分析了系统的平衡点稳定性问题。从脉动流诱发振动的角度,建立转子密封系统的振动模型的一次近似方程为线性周期系数系统的方程。脉动流诱发振动转子密封系统的振动模型的稳定性判别,采用微分方程稳定性理论当中的线性周期系数系统的稳定性判据,讨论了系统的平衡点稳定性问题。研究表明,系统满足一定情况时能实现零解稳定性。 相似文献
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采用流固耦合动力学数值仿真和气液两相流理论分析轻烃回收重沸器返塔管道振动机理,发现垂直管段中的段塞流是引起管道振动的主要原因。通过对比分析,结合现场实际情况,提出防止管道振动改进方案,用两相流—管道耦合分析软件计算管道振动响应,证明改进方案有效。 相似文献
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变传感器设定值的科氏质量流量管控制方法 总被引:3,自引:0,他引:3
在科氏质量流量计中,流量管的稳幅振动是准确测量的前提。当两相流发生时,科氏质量流量管无法维持在最佳幅值下振动,导致传感器输出信号幅值波动大。针对两相流下流量管幅值控制面临的问题,分析影响流量管振动幅值大小和稳定性的因素,提出跟踪传感器信号幅值、变传感器信号设定值的控制方法,在研制的数字式科氏质量流量变送器上实时实现,并在气-液两相流实验装置上进行2种设定值方法的对比实验。实验结果表明,在不同含气量和控制及时性的情况下,变传感器设定值的控制方法均具有良好的信号跟踪和幅值控制的性能,流量管振动较平稳,传感器信号幅值波动范围小,极大地减小了两相流测量过程中的波动性。 相似文献
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采用数值模拟方法,使用CFD软件FLUENT对管壳式冷凝器壳侧按两相流动及相变传热进行了模拟计算,选定合适的湍流模型、两相流模型为混合物模型,并根据汽水转化公式编写了自定义函数UDF来描述相变过程质和量的传递。针对壳侧流体介质为高温饱和水蒸汽情况下,分别对不同的介质入口速度和入口温度情况下换热器壳侧传热系数、湍流动能和压强变化的模拟结果进行了比较,得出了流体介质入口速度与温度对换热器壳侧传热特点和传热性能的影响规律。从而对冷凝器壳侧结构参数的优化及流动介质进行合理的选择起到指导作用。 相似文献
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通过对实际运行中发生振动的U型管换热器进行振动检测、并对管束振动进行计算及分析 ,判断管束因壳侧气体流经管束及折流板时 ,气流及声波所产生的振动诱发管束产生了共振 ,通过在折流板间加装纵向支撑板 ,有效地消除了换热器的振动 相似文献
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根据多元平行流冷凝器的特点,采用分布参数法对其建立了稳态数学模型.对不同流程数的多元平行流冷凝器的传热和流动性能进行了模拟计算和分析比较,发现了增加流程数对换热量和制冷剂侧压降影响的规律;得出了为保证冷凝器合适的压降,不宜使整体流程数过多的结论.同时,对多元平行流冷凝器的多种各流程扁管排数分配方式进行了模拟比较.结果表明:各种各流程扁管排数分配方式对冷凝器的换热量影响相对较小,主要影响制冷剂侧压降的变化;两相段应该作为冷凝器芯体的主体部分,以保证整个冷凝器有较高的换热性能;由于过冷段扁管排数对制冷剂侧压降影响较大,不宜过少. 相似文献
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起伏振动气液两相流型准确识别对漂浮核动力平台安全稳定运行有重要意义。通过对比静止和起伏振动管道的压差信号以及对应的频谱图发现,起伏振动管道内的压差信号波动幅度更大且包含更多的频率分量,两种流型均含有主频率,该频率为起伏振动频率。针对起伏振动状态气液两相流压差信号的复杂性,分别采用自适应白噪声的完备总体经验模态分解(CEEMDAN)和集合经验模态分解(EEMD)对小波降噪后的压差信号进行模式分解,发现CEEMDAN能够在减少模式分量的同时获得更多有效的分量。通过计算spearman相关系数选择具有表征意义的IMF分量进行Hilbert变换计算能量作为特征值,采用概率神经网络对流型进行识别。结果表明,采用CEEMDAN进行模式分解结合概率神经网络的识别方法准确率达到95.83%,能够用于起伏振动下气液两相流型识别。 相似文献
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Ukhwan Sur 《Journal of Mechanical Science and Technology》1998,12(5):773-781
This paper provides a combined thermal hydraulic and vibration analysis of the Yonggang Nuclear (YGN) 3/4 steam generators
using a developed ATHOS3 code model to calculate the multi-dimensional two-phase flow distribution, and ANSYS code to calculate
the free and forced responses of a specific U-tube. The local porosity idea has been used for the ATHOS3 step 1 model development
and the flow-induced vibration. The step 2 model development in the tube lane region was carried out to change into rectangular
modes which separated the hot and cold sides of inverted U-tubes and to enhance understanding of the difference between ATHOS3
and Flow 3 modeling. Stability ratios for the tube vibration has been calculated using the developed ATHOS3 model and ANSYS
code. The results of this analysis for YGN3/4 steam generators show that the design goals were met for all three critical
regions of cross flow, with the stability ratios much less than 1.0.
Halla Institute of Technology 相似文献
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为解决管束流致振动试验中,现有接触式振动测量方法的应用局限性,提出一种基于测量受激对象换热管两侧压差脉动频率原理的测振装置,即差压式测振装置。差压式测振装置解决了传统接触式传感器对换热管外部流场的干扰问题以及安装空间受限的问题。为了验证差压式测振装置的有效性,分别进行了单管和换热管束两类流致振动测试试验。试验结果表明,差压式测振装置能在复杂的流动环境中准确捕捉到换热管受到的各类激振形式的频率,而且单管流致振动试验结果表明差压式测振装置所测得的周期性涡激振动频率与理论值偏差在5%以内。因此,差压式测振装置的研制与应用对于流致振动试验的测试以及换热管振动的长期监测均有很重要的意义。 相似文献
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在对基于流态化技术的振动流化床气固两相流动的欧拉(Euler)方法的双流体模型研究的基础上,利用专业流体力学分析软件Fluent对褐煤颗粒床层进行数值模拟.研究振动、风速、褐煤颗粒粒度等参数对振动流化床床层中褐煤颗粒均匀流化的影响.实验结果表明:振动及气流的交互作用,可有效抑制褐煤颗粒在床层中的返混现象,使得振动流化床褐煤颗粒干燥均匀;选择双流体模型,将Fluent用于振动流化床气固两相流动数值模拟,是一种行之有效的数值模拟方法. 相似文献
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Woo-Gun Sim 《Journal of Mechanical Science and Technology》2006,20(1):125-132
To understand fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information
about the characteristics of two-phase flow. Stratified steady and unsteady two-phase flows between two parallel plates have
been studied to investigate the general characteristics of the flow related to flow-induced vibration. Based on the spectral
collocation method, a numerical approach has been developed for the unsteady two-phase flow. The method is validated by comparing
numerical result to analytical one given for a simple harmonic two-phase flow. The flow parameters for the steady two-phase
flow, such as void fraction and two-phase frictional multiplier, are evaluated. The dynamic characteristics of the unsteady
two-phase flow, including the void fraction effect on the complex unsteady pressure, are illustrated. 相似文献
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In refrigeration cycles, quality measurement of two-phase refrigerant flow is required to monitor the cycle operation. Although sectional void fraction of the two-phase flow can be detected in several ways, the quality of the two-phase flow is hardly obtained from the sectional void fraction since velocities of liquid- and gas-phase in the pipe are different from each other. In this study, a new quality measuring method was developed by installing multiple narrow tubes in a test section. By installing a gas bypass tube with the multiple narrow tubes, the quality measurement having an accuracy within 0.03 was achieved in the quality range from 0.05 to 0.8. In addition, the influence of oil contamination in the refrigerant flow on the flow pattern in the narrow tube was examined. It was found that the flow pattern in the narrow tube became bubble flow by the mixing of oil. 相似文献
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射流泵极限工况下空化流动 总被引:4,自引:0,他引:4
极限工况发生时,液体射流泵喉管中段至末端的汽液两相空化流动为均相泡状流。基于定常、等温及水平流动假设和Wood声速公式,导出极限工况发生时射流泵喉管中段至末端一维均相泡状流的控制方程组。依据该控制方程结合射流泵壁面沿程压力测试结果,计算喉管中段至末端液汽两相流动的马赫数。从喉管的中段至末端液汽两相流动的马赫数逐渐增加,在压力最低点附近达到最大,其最大值为0.94,十分接近1。进一步分析表明,极限工况发生时,射流泵喉管中段至末端液汽两相空化流表现为两相临界流动,其流速达到当地液汽两相流声速,流动出现臃塞,从而导致一定工作压力下吸入流量不再随出口压力的降低而增加,而是保持不变。揭示射流泵极限工况发生的机理,对其深入研究具有重要意义。 相似文献
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湍流激励是核蒸汽发生器换热管发生流致振动的重要机理之一,也是微振磨损的重要诱因。为计算换热管的微振磨损速率,需要首先获得湍流激励功率谱密度(PSD),其此前只能通过试验的方法获取。为利用CFD方法获得换热管上的湍流激励功率谱密度,建立了蒸汽发生器换热管束流场的数值模型,基于LES方法计算得到了管束内部的流场分布,提取了传热管上所受流体力并计算得到了其功率谱密度,计算结果与试验结果吻合良好。结果显示,管束内部传热管所受流体力为具有尖峰特征的宽频信号,其能量集中在一定带宽内。其结果为利用CFD方法计算传热管微振磨损建立了基础。 相似文献
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Flow regime identification based on local parameters of axial upward two-phase flow in vertical tube bundles, at high-temperature and high-pressure, was performed using optical probes. A staggered arrangement of the tube bundles was simulated inside a non-circular test channel, the tube size and pitch are same as that in a real steam generator of a PWR under design. Optical probes were utilized to acquire the void fraction, interface frequency, and fluctuation characteristics of the local void fraction at two typical locations (centroid of the three tubes, named op-1, and centre of the minimum gap between two tubes, named op-2). The system pressure ranged from 5 to 9 MPa, mass flux from 100 to 350 kg m−2 s−1, thermodynamic steam quality from 0 to 1, and inlet fluid temperature from 263.9 to 303.3 °C, depending on the saturation pressure. This study investigated local parameters and flow pattern characteristics of high-pressure steam-water two-phase flow in vertical tube bundles using optical probes, with the measurement error of less than 2%. Results showed that local void fraction at op-1 was much larger than that at op-2, and the local void fraction difference between op-1 and op-2 increased first and then gradually decreased, which was primarily affected by the transition in flow regimes. The flow pattern characteristics of steam-water two-phase flow were described based on three aspects, namely, variation in interface frequency with local void fraction, fluctuation characteristics of local void fraction, and statistical analysis of local void fraction deviating from the average. Additionally, the flow regime identification criteria, applicable to the steam-water two-phase flow in vertical tube bundles, were proposed based on local parameters. 相似文献
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Byeong Rog Shin 《Journal of Mechanical Science and Technology》2011,25(5):1373-1379
A high resolution numerical method for solving high speed gas-liquid two-phase flow is proposed and applied to the two-phase
shock tube problem. The present method employs a finite-difference 4th-order Runge-Kutta method and Roe’s flux difference
splitting approximation with the MUSCL TVD scheme. A homogeneous equilibrium gas-liquid two-phase model that takes account
of the compressibility of mixed media is used. Therefore, the present density-based numerical method permits simple treatment
of the whole gasliquid two-phase flow field, including wave propagation, large density changes and incompressible flow characteristics
at the low Mach number. The speed of sound of above two-phase media has been derived on the basis of thermodynamic relations.
By this method, a Riemann problem for the Euler equations of a one-dimensional shock tube was computed. Numerical results
such as detailed observations of shock and expansion wave propagations through the gas-liquid two-phase media at thermal and
isothermal conditions, and some features related to computational efficiency are made. Comparisons of predicted results with
exact solutions are provided and discussed. 相似文献