화학공학소재연구정보센터
HWAHAK KONGHAK, Vol.32, No.1, 65-71, February, 1994
기체-액체-고체 유동층에서 압력변동 신호의 Fractal 해석
Fractal Analysis of Pressure Fluctuations in a Gas-Liquid-Solid Fluidized Bed
초록
기체-액체-고체 유동층에서 각 상들의 접촉과 흐름 현상을 고려한 수력학적 특성을 해석하고자 입력 변동신호를 fractal 해석하였다. 압력 변동 신호는 유동 입자의 크기가 1.0-6.0X10-3(m)의 범위에서, 기체유속은 0-10X10-2(m/s), 그리고 액체유속은 4-16X10-2(m/s)의 범위에서 측정되었으며 유동층으로는 직경 0.152(m), 길이 2.5(m)인 아크릴관을 사용하였다. 각 실험조건에서 유동층이 정상상태에 도달한 후 압력 변동 신호를 측정하였으며 측정된 압력 변동 신호 시리즈를 fractional Brownian 거동에 근거하여 rescaled range 해석으로 Pox diagram 을 얻었으며, 이 Pox diagram으로부터 Hurst 지수와 국부 fractal차원을 구하였다. 압력 변동 신호의 fractal 해석 결과 Hurst 지수는 기체-액체-고체유동층의 특성을 잘 나타내었는데, 이 값은 기체유속이 증가함에 따라 감소하였고, 액체유속이 증가함에 따라 최대값을 나타내었으며, 유동 입장의 크기가 증가함에 따라 증가하였다.
To investigate the hydrodynamic characteristics of gas-liquid-solid fluidized beds considering the phase contact and flow phenomena of individual phase, fractal analysis has been adopted to manipulate the pressure fluctuation signal from the fluidized bed. The pressure fluctuation signals were measured in a gas-liquid-solid fluctuation signal from the fluidized bed. The pressure fluctuation signals were measured in a gas-liquid-solid fluidized bed of 0.152m×2.5m acryle column. The size of fluidized particles was in the range of 0-6.0×10-3(m), and the gas and liquid flow rates were in the range of 0-10.0×10-2(m/s) and 4.0-16.0×10-2(m/s), respectively. The pressure fluctuation signals which were measured at a steady state were analyzed in terms of Rescaled Range analysis(R/S analysis) based on the concept of fractional Brownian motion, yielding the Pox diagram where the Hurst exponent and eventually local fractal dimension could be obtained. From the fractal analysis of the signals, the hydrodynamic charateristics of gas-liquid-solid fluidized beds could be described by means of the Hurst exponent; the Hurst exponent decreased with an increase in the gas flow rate, but it increased with an increase in the fluidized particle size. However, it exhibited a maximum with an increase in the liquid flow rate.
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