共查询到20条相似文献,搜索用时 218 毫秒
1.
为更好地揭示旋流静态混合器内竖直上升螺旋流中混沌动力结构突变规律,在湍流状态下(Re=1756~3512),基于动力指数分割算法,分析了混合器内不同区域的压力脉动时间序列在结构突变点左右两部分的动力学结构指数分布,研究了流量变化对压力波动时间序列的混沌动力学结构指数的影响,并利用动力学指数的最大统计值Tmax定量表征旋流静态混合器内复杂流动的混沌突变特性. 结果表明,当Re≤2107时,静态混合器压力波动信号的平均突变统计指数随Re增加而增大;当Re≥2458时,管壁尺寸对流体湍动约束增强使流体动力结构差异趋于稳定. 径向二次流使漩涡中心处的动力结构差异复杂程度是壁面处的2~3倍;轴向切割分流作用产生的动力结构是移位混合作用的8~10倍. 瞬态压力波动信号的动力学指数模型能较好地挖掘旋流静态混合器内流场瞬时突变结构. 相似文献
2.
3.
为揭示SK型静态混合器内非稳态流动特性,利用激光多普勒粒子分析仪对直径为0.04m、长径比为1.25的SK型静态混合器的切割区瞬时流场进行测量。采用功率谱和最大Lyapunov指数识别混合器内瞬时速度时间序列的混沌特性,利用湍流高阶矩参数分析混沌运动的统计特征。实验结果表明:SK型静态混合器切割区速度波动时间序列具有混沌特性;功率谱函数随频率的增加呈幂函数衰减,瞬时速度脉动主要能量集中在31.25Hz以下;湍流高阶矩分布揭示了切割区内的速度脉动存在非线性拟序结构,混沌运动的概率密度函数偏离高斯分布。 相似文献
4.
5.
为了探讨湍流状态下(雷诺数Re=1756~3512)旋流静态混合器内混沌拓扑结构演化规律,对采集的360组竖直上升螺旋流瞬态压力波动时间序列进行相空间重构,通过在其混沌吸引子域中放置参考截面,考察旋流静态混合器内瞬态流混沌吸引子形态特征量与雷诺数、轴向位置和径向位置之间的关系. 结果表明,轴截面内径向二次流为不同尺度强制涡和自由涡组合的兰金涡,在rm/R≤0.3和rm/R>0.8(rm为测量点到截面中心距离,R为混合管半径)处混沌吸引子特征量随Re增大而减小,而0.4≤rm/R≤0.8处主体区内压力波动信号混沌吸引子特征量随Re增大呈先增大后减小再变大的趋势. 瞬态压力波动信号混沌吸引子形态特征量对漩涡结构演化敏感,有助于理解竖直上升螺旋流的非线性混沌动力学机制. 相似文献
6.
7.
首先概括了静态混合的技术特色;其次,重点综述了近年来旋流静态混合器内脉动压力与速度波动的统计特征、多尺度分形和混沌混合特性等方面的研究进展;实验研究发现Kenics静态混合器各点压力最大波动幅值与进口流量呈二次函数关系,脉动功率谱随着频率的增加呈幂函数关系衰减;轴截面内壁面自由涡和主体区强制涡相互耦合诱导混沌流的产生,同时提高速度与温度梯度的场协同程度。最后,总结了静态混合器内螺旋元件的切割分流、改变流向和径向混合等功能在强化CO2水合物形成过程中的作用。指出将计算流体力学、映射法等方法同LIF、PIV、PFS有机结合可有效地分析静态混合器内多相流动混合机理。 相似文献
8.
9.
全书共204页(32开),正文178页,分4章,它以日本东丽型静态混合器为主介绍如下内容: 第1章为静态混合器基础,概要介绍各种静态混合器的构造及特点,日本及其它国家主要静态混合器产品的品种,流体在静态混合器中的流动状态,混合机理,混合形态及混合效果。 第2做静态混合器的压力损失。介绍一些计算压力损失的公式。 第3章介绍用静态混合器进行的各项单元操作。主要包括溶解、气体混合、粉粒体混合、乳化、液—液萃取、气体吸收、反应等。每一单元操作包括原理、装置、实验方法.实验结果(数据和图表)以及对实验结果所作的比较、分析。 第4章为应用实例介绍。包括排水处理及装置、pH调整装置、凝聚沉降装置、锅炉及燃烧装置、热变换器、树脂熔融装置,注塑成型 机混合喷嘴、树脂着色装置、双液混合装置、微混合器等内容。分别介绍了装置的原理及特点,主要流程,使用效果。并附有装置结构原理图或实物照片以及实际使用的技术参数等。 书末还附有东丽型静态混合器的压力损失数据表20页,可供查阅参考。 相似文献
10.
11.
Non‐intrusive characterization of particle size changes in fluidized beds using recurrence plots 下载免费PDF全文
Chiya Savari Rahmat Sotudeh‐Gharebagh Reza Zarghami Navid Mostoufi 《American Institute of Chemical Engineers》2016,62(10):3547-3561
An on‐line method is developed for monitoring of mean particle size in fluidized beds using pressure fluctuations (PFs) and acoustic emissions (AE) signal by recurrence plot (RP) and recurrence quantification analysis (RQA). PFs and AE signals of a lab‐scale fluidized bed were measured simultaneously at various superficial gas velocities and mean particle sizes. Although the AE signals are often very complicated due to many different acoustic sources in the bed, applying RP analyses showed that small changes in mean particle size can be detected by visual comparison of AE‐RP structures, while this cannot be distinguished by graphical RP analysis of PFs. Moreover, the hydrodynamics of the bed was inspected through RQA analysis of both signals. For this purpose, recurrence rate, determinism, laminarity, average length of diagonal and vertical lines were extracted from RPs showing the effect of an increase in the mean particle size. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3547–3561, 2016 相似文献
12.
隔板式内循环流化床中流化态及颗粒循环特性对压力脉动信号特征具有重要影响,其作用机制尚未完全清楚。测量了隔板式内循环流化床在不同气速比条件下的压力脉动信号,通过时域及递归分析,获得了压力脉动信号的标准差、递归率、确定性及香农熵等特征参数。结果表明,随着表观气速比的增加,内循环中颗粒循环状态存在未循环、鼓泡循环、过渡循环和湍动循环四个阶段;通过压力脉动信号的标准差、递归图黑白结构占比和递归特征参数可识别这四种循环状态,递归特征参数在不同循环区域内显示出良好的线性关系,可用于识别隔板式内循环流化床系统的循环状态。 相似文献
13.
Behzad Babaei Reza Zarghami Rahmat Sotudeh‐Gharebagh 《American Institute of Chemical Engineers》2013,59(2):399-406
A new method is presented for on‐line monitoring of fluidized beds hydrodynamics using pressure fluctuations signal by recurrence quantification analysis. The experiments were carried out at different gas velocities and sand types. A 95% confidence interval was computed for determinism (Det) of signals obtained from reference state as well as other operating conditions named as unideal states. Det of unideal states was compared with Det of the reference state to reject the null hypothesis that all the signals have been generated from the reference state. It was shown that Det is sensitive to small change in particles size whereas it is not sensitive to minor superficial gas velocity variations, indicating its ability for hydrodynamic on‐line monitoring. Furthermore, in this method it is no need for time series embedding, long‐term data sampling and time‐consuming numerical algorithms. © 2012 American Institute of Chemical Engineers AIChE J, 59: 399–406, 2013 相似文献
14.
The origin and coupling of pressure fluctuations in an internal loop airlift bioreactor are investigated. The pressure fluctuations in the reactor are divided into two categories: global pressure fluctuations and local pressure fluctuations. It is found that the coupling between global pressure fluctuations and local pressure fluctuations mainly focuses in the frequency region between 10 and 30 Hz. Local pressure fluctuations in the reactor are strongly affected by pressure waves originating from the air‐supply system, while pressure fluctuations caused by the bubble eruption at the liquid surface have less influence on local pressure fluctuations. Based on the coherence analysis, the pressure signal at a certain position in the reactor is decomposed into three different parts: coherent part, joint incoherent part and exclusive incoherent part. The energy ratios of these different parts are helpful to study the interaction among pressure fluctuations from different sources. Three flow regimes were identified from the evolution of the energy ratio of the joint incoherent part. © 2011 Canadian Society for Chemical Engineering 相似文献
15.
Wen-Hui Zhang 《Chemical engineering science》2009,64(5):1009-5235
The origin of pressure fluctuations in an internal-loop airlift reactor (ILALR) and its application in the flow transition detection are investigated. It is found that pressure fluctuations can be characterized as global pressure fluctuations and local pressure fluctuations by frequency domain analysis and wavelet analysis. The global pressure fluctuations generated by gas compression in the gas plenum and flow fluctuations in the gas-supply system have almost a linear attenuation in the downcomer and almost no attenuation in the riser, especially in heterogeneous flow regime. However, it is found that the pressure wave from bubble eruption at bed surface has little impact on the wall pressure fluctuations. The global pressure fluctuations may be explained by Sasic's model. The local bubble-induced pressure fluctuations generated by bubble passage, coalescence and breakage can be determined by bubble passage frequency bandwidth and lower coherence. After extracting the local bubble-induced pressure fluctuations from the origin wall pressure fluctuations, it is shown that the Hurst exponent of the local pressure fluctuations increases faster in the homogeneous flow regime than in the heterogeneous flow regime, which can be employed to indicate the flow regime transition. 相似文献
16.
混沌递归分析在油水两相流流型识别中的应用 总被引:6,自引:3,他引:3
采用由Lorenz方程生成的时间序列验证了递归定量分析的有效性及敏感性,并将该分析方法应用于油水两相流流型识别.研究结果表明:对油水两相流过渡流型,在递归图上表现为分散点或线条纹理两种纹理结构特征;而对同一种水包油流型,仅表现为线条纹理结构特征.表明混沌递归图纹理结构特征对油水两相流流型变化敏感,混沌递归定量分析是一种流型识别的有效辅助诊断工具. 相似文献
17.
18.
采用递归分析方法对流化床内的压力脉动信号进行分析,研究了不同工况下石英砂与柱形生物质颗粒混合双组分颗粒的流动特性。柱形生物质颗粒尺寸为10 mm×10 mm(直径×长),石英砂粒径为0.8 mm。在鼓泡床阶段,随着生物质含量的增加,系统的周期性呈现先减弱再增强的变化趋势;该阶段确定性与层流率均表现为随气速的增加而增大,其值在生物质含量低时会明显减小,系统熵则随着气速的增大而减小。在腾涌阶段,生物质添加前后系统信号的递归图呈现相似的纹理特征,确定性与层流率变化较小,此时熵随着气速的增加而减小,与单组分流动呈现相反的趋势。 相似文献
19.
在双喷嘴对置气流床气化炉热模平台上,对炉内压力波动特性进行了试验研究。把小波变换和FFT相结合,验证了R/S分析方法是测量气化炉压力波动周期性的有力工具。采用R/S分析计算出Hurst指数,说明气流床气化炉内的压力波动具有分形特征,同时发现压力波动存在周期成分,从统计意义上计算出压力波动频率为0.067 Hz。用小波变换进行滤波后,再对低频信号进行FFT,得出主频约为0.053 Hz,二种方法结果吻合得比较好。用高速摄像仪对气化火焰拍照,并用“乘法串级过程”思想,解释了压力波动产生机理。 相似文献
20.
The characteristics of pressure drop fluctuation in a 5.0 cm I.D.×250cm high circulating fluidized bed with fine polymer particles
of PE and PVC were investigated. The measurements of time series of the pressure drop were carried out along the three different
axial locations. To determine the effects of coarse particles and relative humidity of air on the flow behavior of polymer
powders-air suspension in the riser, we employed deterministic chaos analysis of the Hurst exponent, correlation dimension
and phase space trajectories as well as classical methods such as standard deviation, probability density function of pressure
drop fluctuation. From a statistical and chaos analysis of pressure fluctuations, the upper dilute region was found to be
much more homogenous flow compared to that in the bottom dense region at the same operating conditions. It was also found
that the addition of coarse particles and higher humidity of air reduced the pressure fluctuations, thus enhancing flow stability
in the riser. The analysis of pressure fluctuations by statistical and chaos theory gave qualitative and the quantitative
information of flow behavior in the circulating fluidized bed. 相似文献