Study On Fractal Scale Characterization Of Inclined And Vertical Upward Gas/Liquid Two Phase Flow Patterns

The flow pattern identification is an important aspect of the two-phase flow measurement. So in this paper fractal scale algorithm is used to deal with the gas/liquid two-phase flow conductance fluctuation signals which have been gathered in dynamic experiments. The results show that the characteristic quantities of different flow patterns have great distinctness, which reflects the rule of the flow character in two-phase flow. Hence, corresponding characteristic quantities can be used as the effective indicator to characterize the two-phase flow patterns.In this paper, firstly the Weierestrass function, fgn function and fbm function are taken as an example to produce nonlinear time series, and the applicability of fractal scale algorithm to the presence of Gauss noise, stochastic noise, periodic noise and pulse noise is discussed. The study shows that the detrended fluctuation analysis algorithm is strong robustness. Based on the conductance fluctuating signals of gas/liquid two phase flow in vertical upward pipe and inclined upward pipe, the characterization of two phase flow patterns are obtained. The result of two phase flow in vertical upward pipe indicates when the range of the superficial water velocity is 0.0453ms^-1 to 0.226 ms^-1 and the range of the superficial gas velocity is 0.0043ms^-1 to 3.43 ms^-1 the values of the fractal scale of bubble flow are lowest and show very random complex dynamic behavior, the values of slug flow are highest and show oscillating motion behavior of gas slug and liquid slug, and the values of churn flow are between bubble flow and slug flow and show comparable complex dynamic behavior. The result of two phase flow in inclined upward pipe indicates that the values of the fractal scale of bubble flow are very high and change little with superficial gas velocity increasing, and show very simple dynamic behavior. The values of slug flow appear descenging trend and show attenuated periodic motion behavior of gas slug and liquid slug. The study shows that the flow pattern variations of gas/liquid two phase flow can be characterized by the fractal scale of conductance fluctuating signals, and it has a significant value for understanding the dynamics evolution characteristic of gas/liquid two phase flow pattern.