순환유동층에서 기체-고체의 접촉과 흐름현상의 특성을 해석하고자 riser에서의 압력요동신호를 fractal 해석방법 및 상공간 투영방법을 도입하여 해석하였다. 유동고체입자는 평균입도가 0.454㎜이고 밀도가 920㎏/㎥인 폴리에틸렌을 사용하였으며 riser의 직경과 높이는 각각 0.102m와 3.5m이였다. 기체의 공탑속도 및 고체의 재순환속도 등의 변화가 riser 내부에서 고체입자의 실제속도, 기체와 고체의 slip속도, 고체입자의 체류량의 변화 등 수력학적 특성에 미치는 영향에 대한 검토를 하였으며, 이들 변수의 변화에 따른 Hurst지수의 변화와 상공간투영의 변화를 고찰하였다. 각 실험변수의 변화에 따른 Hurst지수값은 재조정된 구간해석에 의한 Pox diagram으로부터 얻었으며, 상공간투영은 다차원상공간 투영에 의한 자료의 재구성방법에 의해 얻었다. 본 연구의 결과 riser에서 고체입자의 choking속도와 수송속도는 같은 개념으로 해석할 수 있었으며, 이 조업조건에서 Hurst지수는 최대값을 나타내었고 상공간투영은 자료에 포함된 정보상호간의 연관성과의 의존성이 상대적으로 큰 것으로 나타났다.

Pressure fluctuations in the riser of a circulating fluidized bed have been analyzed by means of stochastic analysis such as fractal analysis and phase space portrait, to analyze the characteristics of gas-solid contact and flow behavior in the riser. Polyethylene whose mean diameter is 0.454mm and density is 920㎏/㎥ has been used as a solid. The diameter and height of the riser are 0.102m and 3.5m, respectively. Effects of superficial gas velocity and solid circulation rate on the hydrodynamic characteristics such as solid interstitial velocity, slip velocity between gas and solid, and solid holdup have been determined. Effects of operating variables on the Hurst exponent and phase space portrait have been also examined. The values of the Hurst exponent have been recovered from the Pox diagram obtained by the rescaled range analysis of the data. The phase space portraits have been obtained by means of rearrangement of the data by the multidimensional phase space portrait method. As a result of this study, the concept of choking velocity is very similar to that of transportation velocity in the riser. The Hurst exponent has exhibited its maximum value and the phase space portrait has focused its tracing within the limited boundary at the transition regime of gas-solid flow.

Circulating Fluidized Bed Stochastic Analysis Hurst Exponent Phase Space Portrait Gas/Solid Flow

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