共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
鼓泡塔内气液两相湍流实验研究 总被引:1,自引:0,他引:1
介绍了研究鼓泡塔气液两相流的实验装置、实验方法。液相用激光多普勒测速技术(LDV)测量,气相用粒子示踪测速技术(PIV)测量。实验表明,轴向液相速度的径向分布呈塔中心峰值、壁面附近倒流形式,且与气相表观速度大小有关,当液相表观速度一定时,随气相表观速度增大而愈加陡峭,返混也剧烈。当表观液速与表观气速之比小于19.6时,返混区总是存在,且返混区大小与高度有关:当表观液遣与表观气速之比大于19.6时,返混消失,含气率分布由塔中心峰值转向壁面峰值。径向液相速度既与气相表现速度有关又与位置高度有关,在塔底部呈现负值,这意味着向塔轴心方向流动。随着塔高增加。流动方向逐渐转变为向塔壁方向,且又有明显的峰值。 相似文献
3.
4.
应用确定性混饨分析技术,以气液两相鼓泡塔内的压力波动时间序列为分析对象,系统研究了鼓泡塔系统的混饨特性.结果表明,鼓泡塔内气液两相流动系统为混饨动力学系统,混饨特征参数最大Lyapunov指数、Kolmogorov熵和关联维数D2等可以有效地表征鼓泡塔的流区及其过渡.混沌分析为定量判别鼓泡塔的流区及其过渡提供了新途径.操作条件对鼓泡塔内气液两相流动的混沌特性影响显著,表现为混沌特征参数值随表观气速增加而增加,随表观液速增加而减小,但是,混沌特性随空间位置的变化不显著. 相似文献
5.
6.
引言 鼓泡床是一种重要的气液或气液固多相反应器.液体循环流动是鼓泡床的一个重要流体力学特征,从20世纪50年代人们就开始对此进行了比较系统的实验研究[1-6].这个特征对鼓泡床的流体返混行为、气含率、气液界面积以及传热传质系数都有很大影响,特别是液体返混行为可以由液体循环特性直接决定.如何准确地描述和预测鼓泡床中的液体流速沿径向的分布,关系到鼓泡床反应器的设计、放大和优化.因此,许多年来它一直是人们致力探讨的重要课题之一[7-8]. 相似文献
7.
8.
9.
不同分布器对鼓泡塔气液两相流影响的CFD模拟 总被引:1,自引:0,他引:1
对不同分布器的鼓泡塔反应器内的气液两相流体动力学行为进行了三维瞬态数值模拟.模型采用欧拉-欧拉双流体模型以及RNG κ-ε湍流模型,研究了不同分布器设计对鼓泡塔反应器气液两相流的影响.模拟得到了鼓泡塔内整体气含率、液相速度矢量分布、时均气含率以及时均轴向液速的径向分布等结果,并对部分模拟结果与文献实验结果进行了比较,其结果吻合得较好,证实了随着分布器开孔越均匀则有利于加强流形的非对称性,从而加剧了气液两相径向混合,但对整体气含率的影响不大. 相似文献
10.
通过实验研究,得到了非牛顿型浆液鼓泡塔内压力的轴向分布关联式,进而得到了塔内气含率的轴向分布式。为进一步研究非牛顿型浆液鼓泡塔流体力学行为打下基础。 相似文献
11.
12.
13.
针对鼓泡塔一维流动模型,应用新分析方法首次给出环流特征参数(如速度转折点、最大Reynolds剪应力及其位置以及最大回流速度点)的具有明确物理含义的理论表达式,并比较了该关系式与既有结果的异同,分析了气含率分布与Reynolds剪应力的相互关系,提出一种基于流体动力学相似的鼓泡塔放大准则,即以所导出的最大Reynolds剪应力作为特征量,若几何尺寸不同的两个塔满足流体动力学相似,则该剪应力近似相等或具有相同的量级,对比分析表明,该准则对直径介于0.14~5.5m的鼓泡塔近似成立。 相似文献
14.
15.
A new technique to measure gas phase dispersion in bubble columns is presented. This technique is fairly simple to implement, accurate and inexpensive as compared to conventional methods used in the literature. Nitrogen is used as a tracer and a step change is effected by switching from air to the tracer, nitrogen. The gas phase concentration of oxygen is monitored by means of a polarographic oxygen sensor. The system studied is air-water and the experimental results compare well with the literature data. The technique presents a simple way to measure gas phase axial dispersion in bubble columns and can also be applied to other types of reactors 相似文献
16.
A new technique to measure gas phase dispersion in bubble columns is presented. This technique is fairly simple to implement, accurate and inexpensive as compared to conventional methods used in the literature. Nitrogen is used as a tracer and a step change is effected by switching from air to the tracer, nitrogen. The gas phase concentration of oxygen is monitored by means of a polarographic oxygen sensor. The system studied is air-water and the experimental results compare well with the literature data. The technique presents a simple way to measure gas phase axial dispersion in bubble columns and can also be applied to other types of reactors 相似文献
17.
Mean gas holdup, lateral distribution of gas holdup and axial mixing of gas and liquid were measured in bubble columns of 12 and 19cm i.d. The lateral distribution of gas holdup was strongly dependent on the flow regimes in the column. The axial mixing of liquid in the homogeneous bubble flow regime was much smaller than that in the heterogeneous bubble flow regime, and was not expressed by existing correlations. The axial mixing of liquid in the homogeneous bubble flow and the intermediate flow regime was simulated with a flow model based on the lateral distribution of buoyancy force and the effective viscosity. The axial mixing of gas was larger than that of liquid. 相似文献
18.
A. Borole B. G. Joshi K. Wisecarver Y. T. Shah 《Chemical Engineering Communications》1993,126(1):189-203
This paper describes the results of an experimental study to evaluate phase holdups and RTD for a jet bubble column. The experimental data were obtained in a 61 cm diameter jet bubble column with a conical inlet. Air and water were used as a two-phase system. The ranges of gas and liquid velocities examined were 0 to 9 cm/sec and 0 to 0·6 cm/sec respectively, both based on the cylinder diameter. The experimental data indicate that in the conical section of the column, the gas holdup first decreases with an increase in distance away from the cone inlet, achieves a minimum and then increases until it reaches a somewhat constant value within the cylinder. Gas holdup varies radially with the maximum at the center and the minimum near the wall. Radially-averaged gas holdup increased with gas velocity and remained essentially unchanged with liquid velocity. The RTD measurements were correlated by a two-dimensional dispersion model. The axial dispersion coefficient increased linearly from the cone inlet to the cylinder. It also increased with the gas velocity. The radial dispersion coefficients were considerably smaller than the axial dispersion coefficients. 相似文献
19.
The multi-value phenomenon of correlation dimension appearing in chaos analysis of time series of pressure fluctuation obtained from gas-liquid bubble columns was studied. Its relationship with multi-scale flow behavior and possible application in the identification of flow regime and regime transition in bubble columns were investigated. The results indicated that the multi-value phenomenon of correlation dimension results from the multi-scale behavior existing in the heterogeneous churn flow regime in bubble columns. When a bubble column is in the homogeneous flow regime, only one correlation dimension is found at a specified superficial gas velocity, indicating that single-scale behavior is dominant in the system. When a bubble column is in the heterogeneous churn flow regime, multi- (generally three) correlation dimensions can be obtained, showing the appearance of multi-scale behavior. Therefore, the formulation of an effective flow model depends on an appropriate multi-scale analysis for bubble columns. Flow regime and regime transition can be characterized by the structure and structure variation of the plot of the correlation integral versus radius of the hyper-sphere. On the basis of the above analysis, a complementary potential methodology called correlation integral analysis for the identification of flow regime and regime transition in gas-liquid bubble columns is recommended. 相似文献
20.
The multi-value phenomenon of correlation dimension appearing in chaos analysis of time series of pressure fluctuation obtained from gas-liquid bubble columns was studied. Its relationship with multi-scale flow behavior and possible application in the identification of flow regime and regime transition in bubble columns were investigated. The results indicated that the multi-value phenomenon of correlation dimension results from the multi-scale behavior existing in the heterogeneous churn flow regime in bubble columns. When a bubble column is in the homogeneous flow regime, only one correlation dimension is found at a specified superficial gas velocity, indicating that single-scale behavior is dominant in the system. When a bubble column is in the heterogeneous churn flow regime, multi- (generally three) correlation dimensions can be obtained, showing the appearance of multi-scale behavior. Therefore, the formulation of an effective flow model depends on an appropriate multi-scale analysis for bubble columns. Flow regime and regime transition can be characterized by the structure and structure variation of the plot of the correlation integral versus radius of the hyper-sphere. On the basis of the above analysis, a complementary potential methodology called correlation integral analysis for the identification of flow regime and regime transition in gas-liquid bubble columns is recommended. 相似文献