空气-水两相流压差波动研究

FLUCTUATING DIFFERENTIAL PRESSURE FOR AIR-WATER TWO-PHASE FLOW

两相流的压差波动过程包含了关于流动的大量信息 ,是实现流动监测与控制的重要研究内容。该文研究了U形管垂直上升段空气 水两相流压差波动过程的统计和分形特征 ,着重分析了压差波动过程的均值、均方根、分维数随折算气速和液速的变化规律。结果表明这些特征参数都与流型有密切的联系 ,但据此识别流型缺乏实用性。均方根在低液速下随气速的变化体现了流型的转变 ,高液速时则不明显。相关研究根据概率密度分布函数识别流型的方法不具有普适性。实验发现环状流区高气速时的压差波动分维数大于1.5 ,在其它流型内都小于 1.5。同时 ,折算液速的大小强烈影响压差波动的混沌特性。

The differential pressure fluctuation appearing from the two phase flow contains much information about the mixture fluid flowing,which is one of important research work to realize the flowage measurement and automatic controlling.The statistical and fractal feature of fluctuating differential pressure for air water two phase flow in the upward section of U type tube was investigated in the present paper. Specially, the mean, the root mean square, the fractal dimension and their variety vs gas superficial velocity are emphasized. The results show that the features have close relationship with flow pattern, but they have less practicality to be used to identify the transitions of flow patterns. Whereas, the root mean square can be used as a criteria under the condition of low liquid superficial velocity, while it is invalid under the condition of high liquid superficial velocity. In addition, the referenced research results cannot be applied to the present work, which the flow patterns can be identified with the possibility density function. The fractal dimension of the fluctuations are lower than 1.5 in all flow regimes besides the annular flow with great gas superficial velocity. At the same time, the liquid superficial velocity influences the chaotic strongly. The future investigation is needed to understand the chaotic feature.